PATENT APPLICATION

TITLE

Sensor for Continuous Measurement of Hydration and Fatigue

CROSS REFERENCE TO RELATED APPLICATIONS: This application claims the benefit of U.S. Provisional Application No. 62/380,924 filed August 29, 2016.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT: Not Applicable. THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT: Not Applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC: Not

Applicable.

FIELD OF THE INVENTION

[0001] The invention is directed to sensors and systems for measuring hydration. More particularly, the invention is directed to orally-deployed sensors and systems to monitor hydration trends, fatigue and other physiological parameters.

BACKGROUND

[0002] Dehydration occurs in an individual when free water loss exceeds free water intake, usually due to exercise, performance of work, lack of potable water, disease, and high environmental temperature. Fatigue can be directly tied to dehydration, exhibiting symptoms of tiredness, muscle soreness, lapses in memory and difficulty concentrating. Dehydration occurs when water intake is insufficient to replace free water lost due to normal physiologic processes (e.g. breathing or urination) and other causes (e.g. diarrhea or vomiting). Studies indicate that most people can tolerate a three to four percent decrease in total body water (TBW) without difficulty or adverse health effects. A five to eight percent decrease, however, can cause fatigue and dizziness. Loss of over ten percent of TBW can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of TBW.

[0003] Mild dehydration is characterized by thirst and general discomfort and is usually resolved with oral rehydration. Hypovolemia is a related condition specifically meaning a decrease in volume of blood plasma, not of TBW. Both (TBW and plasma volume) are regulated through independent mechanisms in humans. However, dehydration can affect each individual in a different manner, depending on other various factors such as age, weight, health status, activity level, fluid replenishment rate, other diseases, etc.

[0004] Due to the continuing inability of athletic coaches to accurately monitor and act on signals indicating harmful dehydration and heat stress, there have been various efforts to develop methods for tracking an athlete's hydration status or trends. A hydration trend can be directed toward dehydration or rehydration, based upon fluid and electrolyte replenishment. In one effort, researchers at the University of Cincinnati developed a wearable patch in an attempt to measure chloride and sodium levels in sweat and small iconic solutes that may be released when an individual is dehydrated.

[0005] In US Pat. App. Pub. No. US 2015/0088002 Al, 2015, by Ronald Podhajsky et al (hereinafter, "Podhajsky"), entitled, "HYDRATION MONITORING," having a filing date of September 19, 2014, a hydration monitoring technology is described which measures changes in vascular volume caused by pulsatile pressure waves and in tissue volume in response to pulsatile pressure. The disclosure specifies placement of the monitoring technology on an in individual's wrist, fingertip, earlobe, or forehead for measurement of "tissue pressure area" and "vessel pressure area" defined as measurement of areas associated with monitored wave forms. Podhajsky describes a hydration metric based upon the ratio of "tissue pressure area" to "vessel pressure area". Further, Podhajsky suggests a separate hydration monitoring system based upon electrodes in contact with the surface of a user's skin at the wrist to measure impedance or resistance. As noted by Podhajsky, skin contact integrity and surface moisture may cause impediments to measurement. Podhajsky also identifies issues associated with interference from ambient light. Consequently, it would be desirable to have a sensor to measure hydration that was less impacted by issues associated with skin contact integrity, surface moisture or ambient light. Further, Podhajsky does not propose or suggest a

correlation of core body temperature, respiratory temperature, humidity and other parameters as additional confirmatory physiologic parameters upon which to determine a hydration metric. Podhajsky further suggests the use of multiple sensors at multiple locations, e.g., ear lobe, wrist, forehead, to determine a preferred location for generating the best output. In particular, Podhajsky does not contemplate, propose or suggest placement of a sensor in an oral cavity.

[0006] In US Pat. App. Pub. No. US 2013/0261468 Al, by Herbert J. Semler et al (hereinafter, "Semler"), entitled, "NON-INVASIVE PORTABLE DEHYDRATION DIAGNOSTIC SYSTEM, DEVICE AND METHOD," having a filing date of December 20, 2011, Semler describes a non-invasive portable dehydration diagnostic system, device and method which leverages a

photoplethysmographic (PPG) sensor placed on an extremity, such as a finger, toe or penis, with an infrared transceiver to measure blood perfusion or circulation in an extremity. The disclosure of Semler describes the use of perfusion data to determine an individual hydration state. The disclosure of Semler emphasizes monitoring of intravascular fluid volume and comprises a sensor operatively connected to a cell phone or other device. The sensor is placed on an individual's fingertip to collect data about blood flow and volume. The data is processed via an algorithm on the cell phone to calculate dehydration status. The representative algorithm relies on an existing empirically-derived data store for a given individual or population. Semler does not describe the content of specific algorithms associated with development of either a circulation index or a resulting hydration index. Although cited as a resource, Semler further does not provide detail associated with look-up tables that might be used to arrive at a resulting hydration index. Semler likewise does not discuss issues associated with application of the PPG sensor on the various extremities. In particular, Semler does not contemplate or suggest placement of the sensor in an oral cavity, and instead, focuses on attachment to a finger, toe or other extremity. Likewise, the disclosure of Semler does not address correlation between core body temperature and a PPG wave form to assist in arriving at a confirmed hydration status.

[0007] It is a standard safety precaution in many athletic activities for participants to wear mouth guards. Ranging from baseball, to gymnastics, to martial arts, mouth guards are designed to protect the wearer from impacts that would otherwise cause injury to the mouth. Mouth guards are shaped to take the brunt of the impact and shield the teeth, gums, and tongue from trauma.

[0008] With the advent of sensorized wristbands like the MICROSOFT BAND, the FITBIT, and the JAWBONE, athletes and doctors have begun to explore the potential benefit of using wearables for collecting physiologic data. Due to the pre-existence of mouth guards within athletic use, various attempts have been made to integrate certain sensors with standard mouth guards. Most prominently, certain companies are developing and promoting mouth guards having sensors to measure acceleration and impact to an athlete's head to assess whether a concussion may have occurred. In a market survey performed by Massachusetts Lincoln Laboratory under contract to the United States Army, forty-six physiological monitoring devices were identified which measured heart rate, breathing rate, skin temperature and accelerometry. Placement of these devices included arm, chest, shirt, ear, earlobe, fingertip, forearm, forehead, headset, and wrist. None of these devices were designed for placement and operative use in an individual's oral cavity.

[0009] In certain sports, e.g., boxing, wrestling, football and mixed martial arts, mouth guards are a desirable and sometimes required protective device. However, in other sports, e.g., baseball, track and field, soccer and basketball, among others, the use of a mouth guard may be discretionary. Hence, the inclusion of a protective mouth guard as a foundation to support data collection intra-o rally is not a necessity.

[0010] Data recorded from an athletic sensor can be frequently most useful if the data is available and actionable in real time. For example, a coach may rely upon data from a sensor to know if an athlete shows signs of being concussed, creating an opportunity for the athlete to be immediately removed from the game. Additionally, a coach might rely on data from one or more biometric sensors to know when to rotate out an athlete from play to reduce the risk of injury. To access this information, there exists an unmet need for a component that can enable real-time, reliable transmission of an athlete's physiologic data across an entire playing field to an external receiver where coaches, trainers and other personnel may act on the physiologic information in a meaningful manner.

[0011] There exist many challenges associated with delivering data externally from a sensor deployed within an athlete's body, including intra-orally. For example, a wireless transmitter would acquire electrical power from a battery incorporated with the sensor. Due to the small size of the battery, power availability would be low. Hence, associated radio transmission signals would be of the low-energy type. Due to the low energy of a radio signal, excessive attenuation of wireless signals transmitted from within an oral cavity would need to be addressed. Further, a wireless transmitter would need to be sufficiently robust to withstand the rigors of athletic activity. In certain instances, the wireless transmitter must be able to operate and withstand the same blunt-force impact against which a mouth guard is designed to protect, e.g., as in football.

[0012] Some sensorized mouth guard designs include sensors and a wireless transceiver that extend outside a user's oral cavity. For example, ilBIOMETRICS sells a mouth guard under the brand name, VECTOR, that measures the magnitude of head impacts and transmits the data to a wireless receiver. The VECTOR mouth guard addresses wireless signal attenuation by incorporating electronics including accelerometers, battery, processor, and transmitter in a segment that rests entirely outside the individual's mouth. The electronics package is connected via a bridge to a "standard" mouth guard.

[0013] Although the VECTOR design may solve the problem of signal attenuation by placing the antenna outside the mouth, it creates additional elements of concern. First, the entirety of the electronics package rests outside of the user's mouth, where it is prone to impact and damage. Second, the addition of a large block in front of the mouth will likely prove to be distracting to the athlete and possibly hinder performance. Third, the design does not allow for sensors to be easily incorporated inside a player's mouth as the power supply rests entirely in the exterior block. Given external placement, an impact on the protruding block could cause corresponding impact on the wearer's mouth. Consequently, a mouth guard having a protruding block may be subjected to other failure modes associated with impact.

[0014] Due to the challenge of communicating data from oral sensors, some have attempted to use visual cues to indicate a physiological status, e.g., a concussion. In other instances, to access the data collected by an oral sensor, a user may be required to remove the device from his or hers mouth. For example, the FITGUARD (produced by FORCE IMPACT TECHNOLOGIES) includes a mouth guard having LED's that will change colors as certain acceleration thresholds are breached. However, the device must be removed from the user's mouth to download collected data to an application on a smart phone via BLUETOOTH ^® . The system does not provide real-time continuous tracking of physiologic symptoms that can be immediately communicated to a player, coach, trainer, parent or other interested party.

[0015] Due to the naturally moist microclimate present in the oral cavity, the oral cavity has not lent itself to serving as an appropriate location for measuring physiologic parameters, particularly concerning hydration. Some research institutions are expending efforts in an attempt to develop sensors that rely on creation of electrical charge by chemical interaction. However, the challenges associated with biofouling of these sensors from deployment in the oral cavity creates issues for both short term and longer term use. Additionally, since these sensors have only been shown to work with an initial salivary substance in a batch mode, it is unclear whether these chemically-driven oral biosensors will prove practical for continuous measurement.

[0016] There are two primary technologies for measuring heart rate metrics: ECG

(electrocardiography) and PPG (photoplethysmography). ECG measures the bio-potential generated by electrical signals that control the expansion and contraction of heart chambers, while PPG uses a light-based technology to sense the rate of blood flow as controlled by the heart's pumping action. ECG-based solutions rely directly on electrical signals produced by heart activity and do not directly address changes in vascular volume or flow. The PPG uses electrical signals derived from changes in reflected light due to changes in blood flow during heart activity.

[0017] PPG sensors are typically used to measure heart rate and oxygen saturation.

Challenges with PPG technology include cancelling the effects of ambient light, accommodating different skin conditions and colors, and dealing with physical motion artifacts. In the past, PPG has been used on external parts of the body that have a high concentration of blood vessels (for example, it can be difficult to get a good PPG signal from the wrist).

[0018] Consequently, there exists an unmet need for a device, e.g., a hydration or fatigue sensor having wireless communication and an antenna that enables the hydration sensor to effectively and continuously transmit data to an exterior transceiver or receiver that is not placed on a user's immediate body, e.g., as in a smart phone. Further, there is a need for such a device that minimizes or eliminates projection of components of the device from the wearer's mouth or other body locations during use. Still further, there is a need for a device that is safe and resilient against impacts and other events that may routinely occur during athletic activities. Even further, there is a need for such a device wherein the device need not be removed from a user's mouth or from another location on the user's body to continuously communicate data to a hand-held device, e.g., a smart phone, or for example, an external base station associated with the field of play. Further, there is a need for such a device that need not rely on visual cues, e.g., lighting different colored LED's to provide alerts when certain physiologic thresholds may be met. Further, there is a need for such a device that can measure physiologic and biometric signals and parameters such that these signals and parameters may be collected and processed to effectively deduce a user's hydration and fatigue status. SUMMARY

[0019] The inventive subject matter is directed to a device comprising means for measuring and tracking physiological parameters which are used to determine the hydration status and hydration trend of an individual and means for continually communicating the hydration status and hydration trend data to an external receiver. Means for communicating to an external receiver may be accomplished using a transmitter. In addition, the transmitter may be integrated with a receiver, in the form of what is generally known as a transceiver. Hydration and other physiological parameters are aggregated and analyzed by one or more processors embedded in the device to create an assessment of fatigue. In one embodiment, the device may be located in a user's mouth. With intra-oral placement, the hydration sensing device may comprise a flexible printed circuit board mounted on a semi-flexible scaffolding structure. A rechargeable battery may be supported in a pocket on the scaffolding structure along with an inductive charging coil for recharging the battery. Electronic components supporting the various functions of the device may be mounted on the flexible circuit board. For intra-oral placement, the flexible circuit board includes an antenna segment configured to slightly protrude between a user's lips. The circuit board, antenna, scaffold, embedded electronics and sensors, are preferably sealed within a housing, preferably, an absorptive shell shaped for intraoral placement. The absorptive shell serves to help protect the electronic components and the user's teeth from impact. When worn intra-orally by a user, the antenna segment rests between the user's lips, holding the lips slightly open and exposing the antenna segment to the external environment, thereby minimizing attenuation of transmitted radio signals. The wireless implementation associated with the sensor supports over-the-air wireless software updates and communication to the user. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0020] These and other features, aspects and advantages of various embodiments of the inventive subject matter will become better understood with regard to the following description, appended claims, and accompanying drawing where:

[0021] FIG. 1 shows a perspective view of a first embodiment of an intra-oral hydration sensor according to an aspect of the inventive subject matter;

[0022] FIG. 2 is a side elevation view of the hydration sensor of FIG. 1 according to an aspect of the inventive subject matter, as worn within a user's mouth;

[0023] FIG. 3A and FIG 3B are views of the hydration sensor of FIG. 1 in use, according to an aspect of the inventive subject matter;

[0024] FIG. 4 is a front elevation view of the three primary components of the hydration sensor of FIG. 1;

[0025] FIG. 5 is a rear exploded view of the hydration sensor of FIG. 1;

[0026] FIG. 6 is a perspective view of the absorptive shell of the hydration sensor of FIG. 1, according to an aspect of the inventive subject matter;

[0027] FIG. 7 is a rear elevation view of the absorptive shell of FIG. 6;

[0028] FIG. 8 is a front elevation view of the absorptive shell of FIG. 6;

[0029] FIG. 9 is a side view of the absorptive shell of FIG. 6;

[0030] FIG. 10 is a top view of the absorptive shell of FIG. 6;

[0031] FIG. 11 is a perspective view of the hydration sensor scaffolding according to an aspect of the inventive subject matter;

[0032] FIG. 12 is a front elevation view of the hydration sensor scaffolding; [0033] FIG. 13 is a bottom view of the hydration sensor scaffolding;

[0034] FIG. 14 is a perspective view of the hydration sensor flexible printed circuit board and antenna segment according to an aspect of the inventive subject matter;

[0035] FIG. 15 is a view of the hydration sensor flexible printed circuit board and antenna in a flattened state, including various electrical components, according to an aspect of the inventive subject matter;

[0036] FIG. 16 is a view of the hydration sensor flexible printed circuit board and antenna in a partially folded state, including various electrical components, according to an aspect of the inventive subject matter;

[0037] FIG. 17 is a view of one version of the hydration sensor antenna segment according to an aspect of the inventive subject matter;

[0038] FIG. 18A is a chart illustrating the attenuation of a radio signal from an antenna in free space;

[0039] FIG. 18B is a chart illustrating the attenuation of a radio signal from an antenna situated intra-orally;

[0040] FIG. 18C is a chart illustrating the attenuation of a radio signal from an antenna positioned intra-lip according to an aspect of the inventive subject matter;

[0041] FIG. 19 is a diagram illustrating the enhanced communication range of the hydration sensor having an intra-lip antenna according to an aspect of the inventive subject matter;

[0042] FIGS. 20A, B, C and D are illustration of antenna geometries suitable for use in an intra- lip configuration according to an aspect of the inventive subject matter; [0043] FIGS. 21A and 21B are charts of PPG signal intensity vs time with PPG measurement in the cheek and tongue, respectively, for a 50-year-old male test subject in a specific test protocol with exercise, and eventual fluid replenishment;

[0044] FIG. 22A is a chart of PPG signal intensity vs time with PPG measurement in the cheek for a 50-year-old male test subject in a specific test protocol with exercise, and eventual fluid replenishment;

[0045] FIG. 22B is a chart of PPG signal intensity vs time with PPG measurement in the cheek for a 20-year-old male test subject in a specific test protocol with exercise, and eventual fluid replenishment;

[0046] FIG. 22C is a chart of PPG signal intensity vs time with PPG measurement in the cheek for a 25-year-old male test subject in a specific test protocol with exercise, and eventual fluid replenishment, but with pre-test exertion in shoveling of snow;

[0047] FIG. 23 is a chart of PPG signal intensity vs time with PPG measurement in the cheek for a 20-year-old male test subject in a specific test protocol with exercise, and eventual fluid replenishment;

[0048] FIG. 24 is a front elevation view of the three primary components of a second embodiment of a hydration sensor, according to the inventive subject matter;

[0049] FIG. 25 is a rear elevation view of the absorptive shell of FIG. 24;

[0050] FIG. 26 is a front elevation view of the absorptive shell of FIG. 24;

[0051] FIG. 27 is a side view of the absorptive shell of FIG. 24;

[0052] FIG. 28 is a top view of the absorptive shell of FIG. 24;

[0053] FIG. 29 is a front elevation view of the scaffolding of the hydration sensor of FIG. 24; [0054] FIG. 30 is a bottom view of the scaffolding of the hydration sensor of FIG. 24;

[0055] FIG. 31 is a perspective view of the flexible printed circuit board and antenna of the hydration sensor of FIG. 24 in a flattened state, including various electrical components, according to an aspect of the inventive subject matter;

[0056] FIG. 32 is a view of the second embodiment of the flexible printed circuit board and antenna of the hydration sensor in FIG. 24, in a flexed or folded state, including various electrical components, according to an aspect of the inventive subject matter;

[0057] FIG. 33 is a view of the antenna segment of the hydration sensor of FIG. 24, according to an aspect of the inventive subject matter;

[0058] FIG. 34 is a chart illustrating output of the capacitive sensor associated with the hydration sensor of FIG. 24, according to an aspect of the inventive subject matter;

[0059] FIG. 35 is a chart illustrating the output of the respiratory and humidity sensor, according to aspects of the inventive subject matter; and,

[0060] FIG. 36 is an image of a user's tongue produced by the imaging module, according to aspects of the inventive subject matter.

[0061] These and other features, aspects and advantages of various embodiments of the inventive subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

OBJECTS

[0062] It is one object of the inventive subject matter to provide a sensor for tracking hydration and assessing fatigue that may detect biometric, physiologic and other relevant parameters associated with the activity of an individual while placed inside the user's mouth. [0063] It is an additional object of the inventive subject matter to provide a sensor for tracking hydration and assessing fatigue that is sufficiently safe to use in athletic events without being damaged or destroyed.

[0064] It is an additional object of the inventive subject matter to provide a sensor for tracking hydration and assessing fatigue that may be worn comfortably and avoid hindering a user's performance.

[0065] It is an additional object of the inventive subject matter to provide a sensor for tracking hydration and assessing fatigue having effective wireless communication to an external receiver, which may comprise a transmitter/receiver (transceiver).

[0066] It is an additional object of the inventive subject matter for the sensor to communicate with an external transceiver on the side-lines of an athletic field while the user and hence, the sensor, are at any location on the athletic field.

[0067] It is an additional object of the inventive subject matter for the wireless signal transmission method to use low power to communicate with an external transceiver/receiver.

[0068] It is a further object of the inventive subject matter to provide an antenna

configuration associated with the sensor to transmit signals concerning biometric, physiologic and other data gathered via sensors deployed intra-o rally without having to remove the intraoral sensors or intra-oral device from the user's mouth.

[0069] It is still a further object of the inventive subject matter to provide a system wherein a subject may maintain euhydration (a normal state of body water content)within a preferred variance between dehydration, rehydration and over-hydration/hyperhydration, (abnormally increased water content in the body). DETAILED DESCRIPTION

[0070] A set of embodiments provides methods, systems, devices and software that can be used to quickly and accurately assess the state of hydration and effectiveness of rehydration of an individual. Such an assessment can include, without limitation, an estimate of the effectiveness of rehydration efforts at a current time, a prediction of the effectiveness at some point in the future, an estimate and/or prediction of a volume of fluid and electrolytes necessary for effective rehydration, an estimate of the probability an individual requires fluids/electrolytes to adequately rehydrate, and, an estimate that an individual has consumed or may consume an excessive amount of fluid which might result in hyperhydration. In a particular set of embodiments, a device, preferably worn within an individual's oral cavity, can include one or more sensors that monitor an individual's physiological parameters. The device (or a computer in communication with the device) can analyze the data captured by the sensors and compare such data with a model (which can be generated in accordance with other embodiments) to assess and present a hydration trend, to present a hydration status, to assess the effectiveness of rehydration, and to assess level of fatigue, as described in further detail below.

[0071] The terms, "individual," "person," "subject," "patient," and "athlete" are used herein for convenience. However, these descriptors should not be considered limiting, because various embodiments can be employed in many settings, such as by an athlete before, during, or after an athletic contest or training, a person during daily activities, a soldier on the battlefield, a worker in a construction operation, an individual in a clinical setting, a senior citizen in a care facility, a patient in a hospital, etc. Thus, the term, "individual," as used herein, should be interpreted broadly and should be considered to be synonymous with "person."

[0072] The tools provided by various embodiments include, without limitation, methods, systems, and/or software products. Merely by way of example, a method might comprise one or more procedures, any or all of which are executed by a computer system. Correspondingly, an embodiment might provide a computer system configured with instructions to perform one or more procedures in accordance with methods provided by various other embodiments. Similarly, a computer program might comprise a set of instructions that are executable by a computer system (and/or a processor therein) to perform operations associated with assessment of biometric and physiologic parameters. In many cases, such software programs are encoded on physical, tangible and/or nontransitory computer readable media (such as, to name but a few examples, optical media, magnetic media, and/or the like).

[0073] For example, an embodiment may provide one or more methods. An exemplary method might comprise monitoring, with one or more sensors, physiological and biometric data of an individual. The method might further comprise analyzing, with a computer system, the physiological data. Many different types of physiological data can be monitored and/or analyzed by various embodiments, including without limitation, blood pressure waveform data, photoplethysmograph ("PPG") waveform data (such as that generated by a pulse oximeter), and/or the like. In an aspect of some embodiments, analyzing the physiological data might comprise analyzing the data against a pre-existing model. For example, the pre-existing model may consist of empirical data gathered from prior monitoring of an individual. In some cases, the method can further comprise assessing the hydration status or trend of an individual, and/or displaying (e.g., on a display device) an assessment of the hydration status or trend. Such an assessment can include, without limitation, an estimate of hydration status at a current time, a prediction at some point in the future, an estimate and/or prediction of a volume of fluid necessary for effective rehydration, an estimate of the probability an athlete requires fluids, an estimate that an individual has consumed or may consume an excessive amount of fluid which might result in hyperhydration, an assessment of the level of fatigue of the individual, and, a recommendation for changing the work load or activity of an individual. [0074] A system, in accordance with yet another set of embodiments, might comprise one or more processors and a computer readable medium in communication with the one or more processors. The computer readable medium has encoded thereon a set of instructions executable by the computer system to perform one or more operations, such as the set of instructions described above, to name one example. In some embodiments, the system might further comprise one or more sensors and/or a therapeutic device, either or both of which might be in communication with the processor and/or might be controlled by the processor. Such sensors can include, but are not limited to, a blood pressure sensor, a cardiac monitor, a transthoracic impedance plethysmograph, a pulse oximeter, an ear infrared spectrometer, a ventilator, an accelerometer, a gyroscope, an electrolyte sensor, and an electronic stethoscope.

[0075] The inventive subject matter comprises one or more sensors that collect data associated with the physiological aspects of bodily fluids, both extracellular fluids and intracellular fluids. An understanding of dehydration affords an ability to ensure that appropriate physiological parameters are used to assess hydration. In addition to describing the present invention, the following discussion provides a framework for understanding the mechanics of dehydration and other related physiological parameters, as they relate to the inventive subject matter described herein.

[0076] Dehydration refers to a deficit of total body water (TBW) with an accompanying disruption of metabolic processes. Early symptoms of dehydration may include a strong feeling of thirst, weakness, nausea, and loss of appetite. Severe symptoms may include confusion, muscle twitching, and bleeding in or around the brain.

[0077] Dehydration can also be a proximate cause of hypernatremia. Hypernatremia is a high sodium level in the blood, generally cause by a relative deficit of free water in the body as opposed to excess sodium. Normal serum sodium levels are 135 - 145 mEq/liter. Hypernatremia is generally defined as a serum sodium level of more than 145 mEq/L. Severe symptoms typically only occur when serum sodium levels are above 160 mEq/L.

[0078] The term, dehydration, is distinct from hypovolemia (loss of blood volume, particularly plasma). Dehydration, in the present sense, refers to a loss of TBW producing hypertonicity, wherein the sodium concentration of the extracellular fluid increases, causing the movement of of intracellular fluid to extracellular spaces. The term, dehydration, is often used

interchangeably, but incorrectly, with volume depletion, which refers to a deficit in extracellular fluid volume. The distinction between these two conditions is important as the type of fluids used for therapy and their rate of administration differs for each. Hypertonicity is the primary pathophysiologic feature of water deficiency and is preferred terminology over the use of the term, dehydration. However, throughout the remainder of this disclosure, we will refer to dehydration and hypertonicity as equivalents.

[0079] TBW represents about 45-60% of body weight depending on age, gender, and race. TBW may be characterized and further divided into an intracellular fluid compartment (ICF; about 55% of TBW) and an extracellular fluid compartment (ECF; about 45% of TBW), which are proportional to the ratio of osmotically-active intracellular K+ to extracellular Na+. The clinical term, volume, is bedside shorthand for ECF volume (ECFV). ECF can be subdivided into plasma volume representing 17% of the ECF, interstitial volume encompassing 50-60% of the ECF, and the remainder consisting of bone and connective tissue water. Blood volume is the sum of the extracellular plasma volume and the red blood cell volume.

[0080] Neurohormonal homeostatic mechanisms sense and defend effective circulating blood volume (ECBV), a measurable quality of arterial filling determined primarily by blood volume, cardiac output, and vascular tone. Plasma volume, as a component of blood volume, represents the common link between ECFV and ECBV. Thus, ECFV and ECBV parallel one another normally, but diverge in many pathologic states; for example, edematous states such as congestive heart failure or cirrhosis, often exhibit diminished ECBV with expanded ECFV.

[0081] The defense of ECBV classically involves vasoconstriction, tachycardia, and improved myocardial contractility to maintain circulatory pressure and flow to vital organs. A less commonly appreciated response is transcapillary refill, which involves movement of interstitial fluid into the vascular space to replenish lost intravascular volume. Transcapillary refill is observed routinely during dialytic ultrafiltration particularly using hemoconcentration-based blood volume monitoring. Kinetic studies after phlebotomy or ultrafiltration (10-20% blood volume loss) suggest the vascular refill rate is maximal immediately after a volume loss, recouping about 50% of lost fluid within 2 hours with an eventual plateau at 24 hours after about 75-80% of lost vascular volume is recovered. Rapid losses of blood volume draw primarily from blood volume alone, while slower losses recruit from about 75% of the ECF (plasma volume plus interstitial fluid volume) requiring 3 to 4-fold greater deficits to produce equivalent hemodynamic compromise.

[0082] When net fluid loss is isotonic, it draws completely from the ECF and thus the volume of fluid loss exactly equals the volume deficit. Conversely, when there is pure water loss, ECF tonicity rises causing rapid translocation of water from the larger intracellular compartment to establish a new elevated level of body tonicity. Thus, pure water loss leads to hypertonicity and contraction of all body water compartments proportional to their share of TBW. Theoretically, the concept of isotonic or pure water loss is attractive, but such losses rarely occur in isolation. Most non-hemorrhagic fluid losses are hypotonic, but can be partitioned into isotonic and pure water components to apply the theoretical framework. Moreover, considering hypotonic losses as part isotonic and part pure water distinguishes volume depletion from hypertonicity, helps recognize a predominant abnormality, and allows for an appropriate intervention combining isotonic saline and free water repletion at safe rates for therapy. [0083] With pure water loss, extracellular tonicity rises and draws fluid from the intracellular compartment which, given its larger size, bears more of this loss. Thus, hypertonicity in many respects requires intracellular volume contraction, while volume depletion is a disorder of blood volume contraction. Brain cell function is particularly sensitive to crenation and neurologic symptoms predominate following hypertonicity.

[0084] A rationale approach to therapy for dehydration begins with estimation of the volume and water deficits, as these deficits are replenished with rapid isotonic saline administration and slow free water repletion, respectively. The inventive subject matter comprises an oral hydration sensor 10 supporting one or more biosensors capable of measuring one or more physiological parameters to assess both volume and water deficits, and thus, determine trends of hydration, including dehydration, rehydration, euhydration and over-hydration, which may then be correlated along with one or more other parameters to assess individual fatigue.

[0085] As discussed, dehydration has been used to either mean true dehydration or as a proxy for hypovolemia; only the former is the proper use of this term. This is important because TBW is not controlled via sodium regulation, only intravascular volume is so controlled, and this distinction is important to guide therapy and recommendations for fluid replenishment as determined by the hydration sensor 10. Dehydration can be life-threatening when severe and lead to seizures or respiratory arrest.

[0086] Dehydration also carries the risk of osmotic cerebral edema if rehydration is overtly rapid. Cerebral edema is excess accumulation of fluid in the intracellular or extracellular spaces of the brain. The hydration sensor 10 is intended to provide sufficient monitoring to avoid overtly rapid hydration. For example, during a high school football game in a hot and humid environment, a player may actually consume excess water. The sensor will enable tracking in a manner that allows a recommended amount of fluid/electrolyte to be consumed based on each player's individual physiology, including exertion, size, gender, age, and height. [0087] For routine activities, an individual's level of thirst may serve as an adequate guide to maintain proper hydration. With exercise, exposure to hot environments, or a decreased thirst response, additional water may be required above and beyond what a person's level of thirst may indicate. Consequently, there is a need for an intra-oral hydration sensor capable of tracking relevant physiological parameters to determine an individual's hydration trend and status, and, to provide accurate guidance for fluid intake and replenishment in real-time.

[0088] Insensible water loss is defined as the amount of fluid lost on a daily basis from the lungs, skin, and respiratory tract, as well as water excreted in the feces. Insensible water loss is defined as loss that cannot be sensed. In contrast, sensible water loss is loss that can be sensed by an individual. Therefore, sensible water loss includes both urination and sweat. In assessing trends of hydration, algorithms associated with the hydration sensor 10 consider aspects of both insensible and sensible water loss to provide a hydration assessment and suggest recommendations for therapeutic intervention, e.g., fluid replenishment, rest or activity reduction.

[0089] In resting, thermoneutral individuals, whole-body insensible water loss is widely accepted to occur at about .03L/h and approximately 50% of this passes through the skin. The remaining 50% of normal insensible water loss occurs through the lungs as water vapor.

Additional sensible losses throughout the day occur through the kidneys as urine (some of which is obligatory water excretion that gets rid of solutes) and some water, in the absence of diarrhea, is also lost through the feces. According to the inventive subject matter,

embodiments of the hydration sensor 10 may include one or more sensors to measure temperature and moisture of respiration to provide predictive analytics concerning respiratory water losses.

[0090] In warm or humid weather or during heavy exertion, sensible water loss can increase markedly, because humans have a large and widely variable capacity for the active secretion of sweat. For example, whole-body sweat losses in men can exceed 2 L/h during competitive sport, with rates of 3-4 L/h observed during short-duration, high-intensity exercise in the heat. When such large amounts of water are being lost through perspiration, electrolytes, especially sodium, are also being lost.

[0091] The hydration sensor 10 continuously collects data over time to determine whether an individual is acclimatizing to the environment, e.g., altitude, humidity, temperature. The hydration sensor 10 includes components to locally register environmental conditions or receive external data feeds addressing ambient environmental conditions including air quality, cloud cover, wind velocity and precipitation along with the other mentioned parameters. The external data feeds including current meteoroglogical conditions, and in particular, predictive weather forecasts, are collected and processed in conjunction with a person's physiological data, including activity, to provide a predictive and anticipatory approach to fluid intake recommendations. This predictive approach will allow a person's activity to be monitored much more closely rather than simply responding to urgent issues that could have been avoided.

The hydration sensor 10 includes instructions configurable for operation on one or more processors to allow ingestion of relevant data applicable to an assessment of a person's health status. For example, with the addition of more complete weather information, the hydration sensor 10 may be configured to provide early alerts to persons known to suffer from various levels of asthma but still participating in athletic endeavors.

[0092] The hydration sensor 10 is likewise configured to help health care professionals to differentiate between symptoms that may or may not actually be caused by dehydration. The hydration sensor 10 will also provide guidance to assist in determining which types of fluids should be used for replenishment. For example, individuals presenting with orthostatic hypotension and normal plasma sodium concentrations are frequently admitted to the hospital with a diagnosis of dehydration. Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or dizzy spell, is a form of low blood pressure in which a person's blood pressure falls when suddenly standing up or stretching. If fortunate, the individual receives fluids containing sodium chloride instead of free water to correct obvious extracellular fluid volume depletion. Confusing this diagnosis highlights the growing and pernicious habit of using the terms dehydration and volume depletion interchangeably at the bedside when the two describe clearly different disturbances, requiring two different therapeutic approaches.

[0093] Referring now to FIG. 1, according to the inventive subject matter, a hydration sensor 10 collects PPG data from a PPG sensor 124 (see FIG. 15 and Fig. 16) and tracks correlative points from a PPG waveform generated based on the PPG data. For example, in one instance, the hydration sensor 10 continually tracks peak measurements from the PPG waveform. In another instance, the hydration sensor 10 continually tracks the location of a dicrotic notch associated with the waveform. In another version, the hydration sensor 10 continually tracks a lowest amplitude value of the PPG waveform. In still another version, the hydration sensor 10 tracks two or more parameters, e.g., peak measurements and dicrotic notch location, associated with the PPG waveform to create a holistic hydration trend index.

[0094] Measurement of these parameters by the hydration sensor 10 supports the production of a hydration trend line that illustrates whether an individual is in a dehydrating, rehydrating or stable and balanced hydration mode, i.e., in a state of euhydration. The sensor 10, in one instance, derives a value for the current state of hydration, e.g., a hydration status index, based on a cumulative assessment of a hydration trend over time. In one version, an individual may input a subject assessment of hydration and the device will then proceed to calculate trends from the initial subjective assessment baseline. As hydration trend data is collected, the hydration processor 10 will continually process the data to compare initial hydration assessment with current system hydration status and deliver updates to the user. The hydration sensor 10 produces user feedback and presents the individual with information indicating hydration status to allow the individual to gather empirical experience that can be used to correlate determined system hydration status with the individual's subjective assessment of hydration status. The information can be presented to the individual via a separate display, e.g, in a cell phone, or via intra-oral vibratory signals coded to alert the individual to changes in hydration.

[0095] The hydration sensor 10 correlates hydration trend data with fluid replenishment volumetrics and work performed by an individual to create a personalized profile and algorithm to describe the individual's trending hydration status. Further, the hydration sensor 10 provides data that is processed to generate recommendations for fluid replenishment based on the observed hydration trend data. The fluid replenishment recommendations and subsequent measured hydration trends may be correlated by the hydration sensor 10 to create an optimized hydration status for the user. An optimized hydration status is identified to maximize performance and maintain a healthy hydration level, whether athletic or otherwise, and stabilize an individual's physiological parameters. The hydration sensor 10 processes and correlates collected data to recommend fluid intake replenishment amounts to move the individual to a preferred hydration state and on a preferred rehydration trend, thereby, minimizing fatigue caused by inadequate water or electrolyte intake during performance of any task or athletic activity. A hydration trend based on PPG measurement is conjunctively assessed and integrated with additional algorithms comprising core body temperature assessment driven by the collection of respiratory temperature trends, respiratory rate and heart rate. In a preferred embodiment, each of the measurements are collected from orally- deployed sensor components embedded with the hydration sensor 10.

[0096] The hydration sensor 10 also collects data that may be used to identify hydration states more likely to precipitate concussions during athletic activity. For example, where an athlete becomes dehydrated, there can be a corresponding reduction in cerebrospinal fluid (CSF) encased with the brain within the protective shell of the skull. A reduction in CSF will reduce the fluid cushioning effect provided to the brain, and hence, increase the likelihood of concussion when an impact is experienced.

[0097] In contrast, where an athlete may overhydrate, i.e., drink an excessive amount of water, particularly without proper electrolyte balance, the over-hydration may lead to a dilution of the sodium concentration in blood plasma. This condition is known as

hyponatremia. Hyponatremia is a water-electrolyte imbalance often seen in athletes after an endurance sporting event. Additionally, athletes such as football players or basketball players can inadvertently experience hyponatremia due to overdrinking during the athletic activity. The symptoms of hyponatremia may be misinterpreted as symptoms of concussion. Thus, the hydration sensor gathers and processes data to determine whether an athlete has

overhydrated with the intent to differentiate between a diagnosis of concussion vs

overhydration. Mild hyponatremia, or even a more marked hyponatremia that develops very slowly, may be considered relatively harmless, but a large and rapid fall in the plasma sodium level will lead to an influx of water into the body's cells to balance osmotic forces. Increasing the water content of the brain can lead to an increase of pressure within the skull: at its most serious, this can lead to seizures and coma and, very occasionally, it can prove fatal. Just as a reduction in cerebrospinal fluid volume in the skull, caused by dehydration, may cause a reduction in the cushioning effect for an athlete's brain and tend to result in concussions during an impact, an overly-hydrated athlete may likewise be susceptible to concussion through impact due to excessive pressure in the brain and skull. In one version, a sensor component deployed with the hydration sensor 10 uses electromagnetic frequencies, including narrow band and ultrawideband, to measure analogues to fluid volume in the skull to assess pressure and dehydration.

[0098] The hydration sensor 10 collects and processes physiological data from one or more sensor components to assist in determining whether presented symptoms are indicative of concussion, over-hydration, and dehydration. The hydration sensor 10 provides monitoring capability that helps to stabilize an individual's hydration in a manner that is volumetrically and electrolytically-balanced.

[0099] Determining a hydration trend for an individual, e.g., an athlete in play or practice, provides an important set of physiological information that may be used to assess other physiologic parameters, such as the fatigue of an individual. An individual's hydration trend, which may also be considered the individual's personalized hydration profile, may be incorporated in and help drive other instructions to calculate and perform assessments to determine an individual's ability to perform certain work or activities under specific conditions or a range of conditions. For example, the hydration sensor 10 may collect and contribute data to a "thermal-work strain index." The thermal-work strain index ("TWSI") is an index that combines scaled heart rate and scaled core body temperatures with equal weights into an index from 0 to 10+. The TWSI is calculated according to Moran et al (1998) from measures of heart rate and core body temperature. Additionally, an estimated TWSI may be calculated using an estimated core body temperature calculated from measurements of heart rate.

[0100] According to the inventive subject matter, with one emphasis on application in athletic endeavors, a Sports Monitoring and Response Technology index (hereinafter, the "SMRT" index), is established which includes elements of the TWSI described beforehand, but may also include parameters and variables driven by hydration trending information and other physiological parameters and environmental conditions. The SMRT index may likewise incorporate measures of respiration rate, respiration temperature, oxygen saturation, heat flux, user motion, and, other biometric and physiological parameters.

[0101] In one version, the SMRT index comprises an algorithm which creates a personalized profile incorporating assessment of individual characteristics for each user based on estimates or actual measurements of: (a) individual height, (b) body fat, (c) body shape/circumference, (d) age, (e) gender and (f) race. Further, the SMRT index may incorporate environmental and geospatial information to support predictive analysis for the anticipated rehydration or dehydration trend associated with a particular activity or task. These additional environmental and geospatial data may include, but are not limited to: (a) geographic location, (b) surface gradient, (c) load carried by athlete/individual, (d) altitude, (e) air temperature, (f) air quality, (g) wind speed, (h) humidity, (i) solar radiation and (j) thermal information concerning clothing worn by the individual.

[0102] For example, the SMRT index may incorporate additional variables based on the type of clothing, manufacturer, insulation factor and vapor permeability for each athletic or work activity, e.g., running gear, baseball uniform, football uniform and gear, soccer gear, skiing outfit, work clothes, and other types of garments. The inclusion of garment thermal information supports the calculation of a physiology-based thermoregulatory model that may be correlated against observed hydration trends to provided predictive assessment of the need for fluid replenishment and rest. The SMRT index determined by the system comprises the use of instructions configured to run on one or more processors in software or firmware deployed on a smart phone or other computing processors that collect the relevant data and generate real-time SMRT index values. Hence, the hydration sensor 10 is able to provide feedback to each user and trainers or coaches concerning appropriate exertion and need for replenishment of water and electrolytes.

[0103] The hydration sensor 10 intelligently refines variable coefficients associated with one or more algorithms contributing to the SMRT index to enhance ability to recommend steps and parameters to optimize individual performance via continual collection and aggregation of empirical data for individuals and groups of individuals which may be used to develop physiological models of hydration. The hydration sensor 10 generates predictive assessments of allowable individualized and personalized thermal-work strain hydration-fatigue guidelines to help ensure that each individual is able to perform within an acceptable and safe operational envelope, whether engaged in an athletic or work activity. The hydration sensor 10 collects data to generate a predictive safe operational envelope that may be determined for any task, whether applicable to athletes, roofers, ditch diggers, agricultural workers, military personnel, weekend warriors and others.

[0104] Referring again to FIG. 1, the SMRT index is determined based on input from one or more sensor components deployed with the hydration sensor 10 for placement in an individual's oral cavity and input from one or more local and external databases. A printed flexible circuit board 100 of the hydration sensor 10 is adaptable to and is supported by a semi- flexible scaffolding 200. The printed flexible circuit board 100 and the scaffolding 200 are shaped to follow the curvature of a user's mouth. The flexible circuit board 100 includes an antenna segment 140 configured to rest between a user's lips such that the energy from an antenna 150 is not attenuated by facial tissue.

[0105] In addition to enabling wireless communication between an intra-oral device and other external devices, the inventive subject matter delivers numerous safety advantages. First, since the antenna and respiratory sensor extends only slightly between a user's lips, there is a reduced chance that the hydration sensor 10 will be impacted directly during an athletic activity or during a fall. The hydration sensor 10 comprises, in one instance, a housing, preferably an shell 20 made from absorptive material which will serve to lessen the impact on the hydration sensor 10 and the wearer's teeth. The absorptive shell 20 likewise protects the electrical components on the circuit board 100 and the antenna 140 of the hydration sensor 10. The scaffolding 200 and flexible printed circuit board 100 are likewise flexible and able to withstand levels of mechanical stress that might otherwise damage conventional rigid printed circuit boards. Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. [0106] The inventive subject matter supports the deployment of an orally-placed hydration sensor 10 to track dehydration, rehydration, euhydration and over-hydration. The hydration sensor 10 is adaptable to communicate with consumption information provided in conjunction with an external water resource or electrolyte fluid reservoir. The hydration sensor 10 provides data that allows a coach or trainer to guide those under their care to avoid moving into that portion of the hydration spectrum that can negatively affect health or performance. The ability to gather hydration trend information and coalesce that information with other physiological parameters and trends creates an actionable resource and tool to help prevent an individual from entering a dehydrated state or electrolyte-deficient state that can cause serious risks to health, well-being and performance.

[0107] Now in greater detail, and having described above various relevant physiological aspects of hydration, referring to FIG. 1, a perspective view of one embodiment of a hydration sensor 10 according to the inventive subject matter is shown. In a first configuration, the hydration sensor 10, encased within an absorptive shell 20, may provide a level of protection for a user's teeth, tongue, and gums against impact-related injuries. The absorptive shell 20 is a semi-rigid, yet absorptive enclosure capable of absorbing external forces and impacts via elastic deformation, thereby minimizing strain on objects encased within the absorptive shell 20. When worn, the absorptive shell 20 rests within a user's mouth between a front surface of the teeth and a rear surface of the lips and adjacent the inner surface of the cheeks. An interior of the absorptive shell 20 accommodates and encapsulates several components, including a wireless charging coil 60, a rechargeable battery 70, a flexible printed circuit board 100, and support scaffolding 200. Extending from a front of the absorptive shell 20 is an absorptive shell protrusion 40. When the hydration sensor 10 is worn, the absorptive shell protrusion 40 resides between the user's upper and lower lip, separating them slightly. While the flexible printed circuit board 100 rests mostly within the absorptive shell 20, an antenna segment 140 of the flexible printed circuit board 100 extends into and is enveloped and encapsulated by the absorptive shell protrusion 40. The thickness of the absorptive shell protrusion 40 may be adjusted to adapt to the preferences of a user.

[0108] Referring now to FIG. 2, a side elevation view of the hydration sensor 10 as worn within a user's mouth is shown. With a predetermined geometry and level of flexibility, the hydration sensor 10 conforms to the shape of the user's teeth and gums. The antenna segment 140, encased within the absorptive shell protrusion 40, extends forward between the user's lips, separating the lips slightly. Since the hydration sensor 10 is captured within a user's mouth and placement and retention is enhanced by the shape of the absorptive shell 20, an individual need not think about maintaining separation between the lips since the hydration sensor 10 causes the separation to occur as an inherent outcome of the design and configuration of the absorptive shell 20 and the protrusion 40.

[0109] Referring now to FIG. 3A, a lateral view of an individual wearing a hydration sensor 10 according to the inventive subject matter is shown. In this view, the hydration sensor 10 is substantially enclosed within the user's mouth, while the absorptive shell protrusion 40 is barely visible yet exposed between the user's upper lip U and lower lip L.

[0110] Referring now to FIG. 3B, a diagram of the hydration sensor 10 from a lateral perspective revealing its placement in the mouth of an individual is shown. The hydration sensor 10 rests within the user's mouth between the user's teeth and cheeks. The absorptive shell protrusion 40, which fully envelopes the antenna segment 140, rests between the upper lip U and the lower lip L, separating them slightly. Since the lips are separated slightly, the antenna segment 140 is exposed to the outside environment, enabling less impeded transmission of radio signals. The absorptive shell protrusion 40, in one version, does not extend past the front of the user's lips. Thus, the hydration sensor 10 is less awkward for an individual to wear and removes critical elements of the hydration sensor 10 from a frontal placement. Hence, there is a lower likelihood of damage to the hydration sensor 10 from a direct impact and a significantly lower probability that any of the force of the impact will be delivered to the user's teeth and gums. The design and placement of the antenna segment 140 of the hydration sensor 10 reduces attenuation of wireless transmissions.

[0111] Referring now to FIG. 4, a front elevation view of three components of a first embodiment of the hydration sensor 10 according to the inventive subject matter is shown. The hydration sensor 10 comprises an absorptive shell 20 having an absorptive shell protrusion 40, which extends from a front surface 35 of the absorptive shell 20. The absorptive shell 20 is configured to encapsulate both a flexible printed circuit board 100 and hydration sensor scaffolding 200. The flexible printed circuit board 100 contains several regions configured to enable, in one version, a monopole antenna to extend into the absorptive shell protrusion 40, including a ground plane segment 130 and an antenna segment 140. The flexible printed circuit board 100 is supported by a semi-flexible hydration sensor scaffolding 200. The hydration sensor scaffolding 200 contains support structures including a ground plane scaffold 230 and an antenna scaffold 240 to support the ground plane segment 130 and antenna segment 140, respectively.

[0112] Referring now to FIG. 5, a rear exploded perspective view of the hydration sensor 10 is shown. The absorptive shell 20 may be described as having an absorptive shell left side 22, an absorptive shell right side 24, an absorptive shell rear surface 30, and an absorptive shell front surface 35. Extending from the absorptive shell front surface 35 is the absorptive shell protrusion 40, which houses the antenna segment 140 further supported by the antenna scaffold 240.

[0113] Extending from the absorptive shell rear surface 30 is a bite shelf 50. The bite shelf 50 is positioned for placement between a user's upper and lower teeth, and an individual may clamp down on the bite shelf 50 to further secure the hydration sensor 10 in place during use. In the present embodiment, the bite shelf 50 can be adapted and sized to fit an individual user's bite size or bite profile. Additionally, in one version, the bite shelf 50 is configured without having been molded to a user's teeth, as with a standard mouth guard, such that the hydration sensor 10 may be quickly removed from or replaced within a user's mouth. Other

embodiments according to the inventive subject matter may include a molded bite shelf 50 intended to provide further protection to a user's teeth and gums, wherein the bite shelf 50 comprises a thicker shelf that can be molded to fit a user's bite. The bite shelf 50 of the hydration sensor 10 may be sized for different users based upon mouth size, age, and gender, from a young athlete to a mature adult user/athlete. Still further, other versions may include a hydration sensor 10 wherein the bite shelf 50 may be positioned at different elevations or angles along the absorptive shell rear surface 30. In still other versions, the bite shelf 50 may be removable from the absorptive shell rear surface 30. Additionally, in other versions, the hydration sensor 10 may include multiple slots along the absorptive shell rear surface 30 to allow an individual to experiment with different positions of the bite shelf 50 to determine which is most comfortable. Such variable positioning may also be used by a technician optimizing fit of the hydration sensor 10 to ensure that any sensory components of the hydration sensor 10 are placed effectively to optimize signal quality and data collection.

[0114] In manufacturing, the absorptive shell 20 may be molded about the electrical components. Different sizes and shapes of the absorptive shell 20 may be created to customize or adapt fit to different mouth shapes, profiles, and circuit board configurations. Additionally, although shown herein as having a flat profile, the bite shelf 50 may be adjusted in thickness or shape to accommodate various user preferences and requirements. For example, the bite shelf 50 might extend along the entire length of absorptive shell rear surface 30 from a left end 22 of the hydration sensor 10 to its right end 24. Further, the bite shelf 50 might be substantially truncated and provide only a small bite shelf 50 for engagement with a user's teeth. Still further, the bite shelf 50 might be thinner closer to the rear absorptive shell surface 30 and thicker further away from the rear absorptive shell surface 30 to create a means for the user to retain placement by closing teeth without having to actually clamp down on the bite shelf 50. A biosensor window 37 may be located along the front surface 35.

[0115] Referring still to FIG. 5, the absorptive shell 20 encapsulates a wireless charging coil 60, a rechargeable battery 70, the flexible printed circuit board 100, and the hydration sensor scaffolding 200. The flexible printed circuit board 100 may be described as having a flexible printed circuit board rear surface 102 and a flexible printed circuit board front surface 104. Likewise, the hydration sensor scaffolding 200 may be described as having a scaffolding rear surface 202 and a scaffolding front surface 204. In this first embodiment, the flexible printed circuit board 100 is supported by the hydration sensor scaffold 200 such that the flexible printed circuit board rear surface 102 rests against the scaffolding front surface 204, and the antenna segment 140 rests in front of the flexible printed circuit board front surface 104 and on top of the antenna scaffold 240.

[0116] Additionally, the hydration sensor scaffolding 200 contains a battery pocket 270 to receive and hold the rechargeable battery 70 and provide connectivity from the battery 70 to power electrical components, and, to receive current from the wireless inductive

charging/receiving coil 60 to recharge the battery 70. The wireless inductive charging/ receiving coil 60 rests in front of the flexible printed circuit board front surface 104 adjacent to the antenna segment 140, but may be positioned at other locations. An extracorporeal power sending system (not shown herein) generates an appropriate wireless frequency to feed energy to the external coil of the power sending system. The external coil generates magnetic fields within some distance. The inner inductor receiving coil 60 is positioned perpendicularly to the external coil and within range such that the magnetic flux makes current flow through the inner inductive receiving coil 60 and induces uniform electrical voltage by rectification and regulation. Then, the rechargeable battery 70 is replenished by the voltage from the inductor

charging/receiving coil 60. For charging purposes, the distance between the inner and outer coils cannot be excessive or proper inductive coupling will not occur. Consequently, in a preferred embodiment, the hydration sensor 10 is mateable to an external charging, sterilization and data transfer housing (not shown herein) wherein the placement of the inductive coupling from the housing with the inner inductive charging coil 60 of the hydration sensor 10 is optimized and tuned to charge the battery 70 at a reasonable power transfer rate based on total power requirements and intended duration of use. In athletic and other activities, the battery 70 of the hydration sensor 10 shall be sized to have adequate power capacity to support the duration of the athletic activity, with adequate reserves, whether in training or actual play. Extended use may be accomplished by tuning operation of the various electronic components and modifying battery type.

[0117] The shape and size of the scaffolding 200 is adaptable and configurable to optimally integrate with the absorptive shell 20. Hence, thinner material and lower profiles may be included in the design of the scaffolding 200 to support the various electrical components and allow differentiation of shape and thickness to accommodate different use cases and users. In other versions, the scaffolding 200 may be integrated with and embedded on the flexible printed circuit board 100. In still another version, the scaffolding 200 may not be included in the structure of the hydration sensor 10. Support for the flexible printed circuit board 100 and other electrical components is then provided primarily by the encapsulating absorptive shell 20. For example, in another version, the absorptive shell 20 may comprise a flexible strength membrane, e.g., a nylon mesh, that provides sufficient inner support.

[0118] The battery pocket 270 in the scaffolding 200 is oriented such that the rechargeable battery 70 will be positioned between a front cheek and the teeth/gums of the individual. This orientation and placement of the battery 70 according to the inventive subject matter places the battery 70 in a preferred location wherein the likelihood of the battery 70 being crushed by a user's teeth is unlikely. Additionally, the absorptive shell 20 serves to reduce damage to the battery 70 by absorbing any impacts from external forces. [0119] The rechargeable battery 70 is preferably non-cytotoxic and biocompatible even if crushed while in use. In one instance, the battery 70 is a rechargeable biocompatible solid state battery that is hermetically sealed and isolated from the oral environment. In another aspect, the battery 70 further comprises energy harvesting means to deliver charge to the battery 70 while in use. Energy harvesting means may include piezoelectric, thermal and chemical and are likewise preferably biocompatible. The battery 70 may be coated with silicone to provide additional separation from the oral environment.

[0120] In another version, housing materials for the rechargeable battery 70 comprise ceramics and titanium to protect the battery components from the oral environment and to protect the individual from potentially toxic elements in the battery 70. In this version, the battery 70 comprises packaging within a laser-welded titanium enclosure 72 to provide mechanical hardness, resistance to corrosion from oral fluids, biocompatibility, and durability. Electrical connections between the battery 70 and electronics mounted on the printed circuit board 100 and the inductive charging coil 60 may be addressed using polymer and ceramic- based electrical feed through 74 to ensure separation between the internal portions of the battery 70 and the oral environment.

[0121] Polymer encapsulation of various electrical components on the printed circuit board 100 through conformal coatings may be accomplished using, among other substances, epoxies, silicones, polyurethanes, polyimides, silicon-polyimides, parylenes, polycyclic-olefins, silicon- carbons, benzocyclobutenes, and liquid crystal polymers, or their equivalents. The selected conformal coating preferably has sufficient elasticity to allow some flex while avoiding any breach of the conformal coating.

[0122] Referring now to FIGS. 6-10, additional views of the absorptive shell 20 are shown. FIG. 6 is a perspective view of the absorptive shell 20 of the hydration sensor 20, emphasizing a view of bite shelf 50. FIG. 7 is a rear elevation view of the absorptive shell 20. Fig. 8 is a front elevation view of the absorptive shell 20. FIG. 9 is a side view of the absorptive shell 20. Fig. 10 is a top view of the absorptive shell 20. The absorptive shell 20 may be described as having an absorptive shell left side 22, an absorptive shell right side 24, an absorptive shell rear surface 30, and an absorptive shell front surface 35. Extending from the absorptive shell front surface 35 is absorptive shell protrusion 40. Extending from the absorptive shell rear surface 30 is bite shelf 50.

[0123] The absorptive shell 20 is preferably made from a biocompatible absorptive material. Absorptive herein describes the ability of the shell material to absorb impacts, not fluids. The absorptive shell 20 can be made from various materials including poly (vinyl acetate-ethylene) copolymer clear thermoplastic; polyurethane; and laminated thermoplastic. In one version, the bite shelf 50 may be comprised of thermally moldable material such that the bite shelf 50 better conforms to the user's actual bite profile, while the remainder of the absorptive shell 20 need not be molded due to inherent flexibility that allows conformation with the shape of the user's mouth and teeth. Although shown herein as having some thickness that might be perceived as uncomfortable while worn by a user, the absorptive shell 20 is preferably of sufficient but minimal thickness. Consequently, material selection can be used to adapt the performance features of the absorptive shell 20. For example, the absorptive shell may be made from a material known as POLYSHOK™, which may increase shock-absorption and provide a softer material for a more comfortable fit for the user.

[0124] Referring now to FIG. 11, a perspective view of the hydration sensor scaffolding 200 is shown. The scaffolding 200 may be described as having a scaffolding rear surface 202 and a scaffolding front surface 204. Protruding forward from the scaffolding front surface 204 is a ground plane scaffold 230. In one version, the ground plane scaffold 230 comprises a somewhat "S-shaped" support structure that extends from the scaffold front surface 204 at a bottom slightly off-center location. [0125] In a preferred embodiment, a bottom of the ground plane scaffold 230 curves upwardly such that, a flat section 234 of the ground plane scaffold 230 is oriented substantially parallel to the scaffolding front surface 204. A top 236 of the ground plane scaffold 230 curves forward away from the scaffolding front surface 204. Extending forward from the top 236 of the ground plane scaffold 230 is the antenna scaffold 240. When enveloped within the absorptive shell 20, the scaffolding rear surface 202 and scaffolding front surface 204 are positioned in a general vertical orientation such that when deployed within a user's mouth, the scaffolding 200 is positioned vertically in front of the user's teeth. A rechargeable battery pocket 270 is shaped to receive and secure the rechargeable battery 70 which delivers power to the electrical components. The battery pocket 270 may be shaped and sized to hold various sized and shaped batteries 70 as required to support the energy requirements of the various electrical components associated with the hydration sensor 10.

[0126] Referring now to FIGS. 12 and 13, additional views of the hydration sensor scaffolding 200 are shown. FIG. 12 is a front elevation view of the scaffolding 200. The ground plane scaffold 230 is shown as being slightly offset from a midpoint of the scaffolding 200, along the front surface 204 of the scaffolding 200, extending from a bottom edge 206 of the scaffolding 200. The ground plane scaffold 230 extends to an approximate midpoint between the bottom edge 206 and a top edge 208 of the scaffolding 200, placing the antenna scaffold 240 at an approximate midpoint of the scaffolding 200. The antenna scaffold 240 is slightly offset from the ground plane scaffold 230, placing the antenna scaffold 240 in an approximate centralized location in relation to the width of the overall hydration sensor 10, which corresponds to a centralized location between a user's lips. FIG. 13 is a bottom view of the hydration sensor scaffolding 200, further illustrating the slightly offset position of the scaffold ground plane 230 and corresponding offset of the antenna scaffold 240 to cause the antenna scaffold 240 to be somewhat centrally located along the width of the scaffolding 200. [0127] Referring now to FIG. 14, a perspective view of the flexible printed circuit board 100 and antenna segment 140 are shown. The flexible printed circuit board 100 may be described as having a flexible printed circuit board rear surface 102 and a flexible printed circuit board front surface 104. Extending upward from a lower edge 106 of the flexible printed circuit board front surface 104 is a ground plane segment 130. The ground plane segment 130 extends upward to position the antenna segment 140 in an approximate centralized position between the lower edge 106 and a top edge 108 of the flexible printed circuit board 100 to correspond to the position of the antenna scaffold 240. When folded into position, the antenna segment 140 extends perpendicularly from the front surface 104.

[0128] The flexible printed circuit board 100 may be made using polyimides as a base material with the application of silicone coatings to ensure biocompatibility by encapsulating the circuitized polyimide substrate and its metal layers. Other conformal coatings described in this disclosure may likewise be used to encapsulate the flexible printed circuit board 100 and its mounted components. The conformal coating comprises a thin polymeric film that conforms to the contours of the printed circuit board and its components to protect against moisture, dust, chemicals and other potentially harmful substances, including saliva and sugar or other corrosive fluids encountered via an intra-oral placement.

[0129] Referring now to FIG. 15, an exemplary view of the flexible printed circuit board 100 in a flattened state, including various electrical components placed on the flexible printed circuit board front surface 104, is shown. The flexible printed circuit board 100, in one version, comprises various segments, including a central segment 110, a sensor segment 120, a ground plane segment 130, and an antenna segment 140. Situated between the central segment 110 and the sensor segment 120 is a first hinge segment 160 configured to allow easier bending of the circuit board 100. Between the central segment 110 and the ground plane segment 130 is a second hinge segment 170. Situated between the ground plane segment 130 and the antenna segment 140 is a third hinge segment 180. The first hinge segment 160, second hinge segment 170, and third hinge segment 180 exist to provide regions on the flexible printed circuit board 100 that are flexible and bendable so as to allow the flexible printed circuit board 100 to be mounted upon the hydration sensor scaffolding 200. In another version, the printed circuit board 100 need not be flexible and instead, is manufactured to conform to the shape of the scaffolding 200.

[0130] Referring still to FIG. 15, each of the segments 110, 120, and 130 may serve a specific purpose. In the present embodiment, the central segment 110 provides an electronic footprint to mount various electronic components. The sensor segment 120 provides an electronic footprint to mount various sensors, including but not limited to one or more

accelerometers/gyroscopes 122, one or more biosensors 124, and one or more impedance sensors 126. Biosensors 124 may measure a plurality of vital signs, including heart rate, respiration rate, body temperature, oxygen consumption and saturation, hydration, and saliva chemical analysis, among others. The first hinge segment 150 is bendable to conform to the shape of the hydration sensor scaffolding 200 so that the scaffolding 200 and the flexible printed circuit board 100, encased in the absorptive shell 20, may be placed within a user's mouth. In this instance, the sensor segment 120 wraps around a right side of the mouth. Note that, in other versions, the flexible printed circuit board 100 may be reversed to cause the sensor segment 120 to wrap about a left side of the mouth instead of the right side.

[0131] In a preferred embodiment, biosensor 124 comprises a photoplethysmographic (PPG) sensor. A plethysmograph is an instrument for measuring changes in volume within an organ or whole body, resulting from fluctuations in the amount of oxygenated blood contained within the organ or whole body. One such sensor is the AS7000 biosensor produced by AMS. The AS7000 biosensor comprises, in one function, a PPG sensor that uses optical techniques. For example, a pulse oximeter, which is based on PPG methodology, measures oxygen saturation level (Sp02). Reflectance-based pulse oximetry is a technique used for noninvasively monitoring the oxygen saturation (Sp02) and pulse rate (PR), typically with sensor placement on the finger or toe.

[0132] Through testing, we have been able to measure and develop a correlation between the measurement of oxygen saturation from an intra-oral placement of the hydration sensor 10 and predicted trends in hydration. In particular, we have determined that oxygen saturation is negatively correlated relative to dehydration. Therefore, by measuring oxygen saturation based on PPG signals, we have established a measurable and calculable correlation between measured oxygen saturation and hydration status. In particular, we have established an ability to measure hydration trends to determine whether an individual is either dehydrating, rehydrating or in a state of euhydration. The hydration sensor 10 collects data that is processed to develop a baseline hydration level for an individual that may be used as a reference to determine whether an individual is dehydrating, rehydrating or in a state of euhydration.

[0133] Other PPG sensors and configurations are available and could be substituted for the AS7000 biosensor. Consequently, the following discussion with regard to the AS7000 biosensor is likewise applicable to other biosensors having PPG capability.

[0134] The AS7000 includes an optical sensor module with light emitting diodes, integrated circuity, an analog front end and a processor. The AS7000 solution incorporates software to provide optical heart rate measurements (HRM) and heart rate variation (HRV) readings. The AS7000 may also enable skin temperature and skin resistivity measurements by providing interfaces to other external sensors. The AS7000 is housed in a 6.1mm x 4.1mm x 1.0mm package and mounted on the flexible printed circuit board 100.

[0135] Now, in greater detail, a description of the operation of AS7000 is provided. The AS7000 is based on photoplethysmography (PPG), a heart rate measurement method which measures the pulse rate by sampling light modulated by the blood vessels, which expand and contract as blood pulses through them in correlation with the cardiac cycle. The AS7000 comprises a digital processor which is capable of implementing various digital algorithms to process raw PPG data. In one instance, the digital algorithms convert PPG readings into digital HRM and HRV values. When the AS7000 is paired with an external accelerometer, these algorithms may also filter out motion artifacts attributable to the beating of the heart which may interfere with PPG readings. The AS7000 provides low noise and high sensitivity to maintain high accuracy whether the user is resting or exercising. Further, in a preferred embodiment, a low-power design is preferable for application in an oral device wherein circuit board space is limited and power is limited to smaller batteries.

[0136] Referring still to FIG. 15, the central segment 110 of the flexible printed circuit board 100 provides a footprint to affix additional electronic components, while other electronic components may be alternatively affixed to the sensor segment 120 or ground plane segment 130. In the illustrated first embodiment of the inventive subject matter, the central segment 110 supports a processor 111, a power supply 112, a battery gauge 113, and a wireless charging circuit 114, while a flash memory chip 115 may be mounted on the ground plane segment 130. The ground plane segment 130 provides an electronically reflective surface to support, in one version, a monopole antenna 150 embedded on the antenna segment 140. In other embodiments, certain of the electrical components may aggregated and consolidated in a fewer number of microchips. Additionally, in other embodiments, the flash memory chip 115 may be eliminated and replaced with memory associated with other of the electrical components.

[0137] As illustrated in FIG. 15 and FIG. 16, in addition to PPG, the inventive subject matter further comprises a bioelectrical impedance sensor 126 that uses low amperage current in single or multiple frequencies passed between one or more electrodes to measure current resistance of tissue water and electrolyte content. As an athlete dehydrates, salivary osmolality generally tracks changes in hydration brought on by sweating. The impedance data collected from the impedance sensor 126 is processed by one or more algorithms operable on the processor 111 with the hydration sensor 10 to provide further refinement of the assessed hydration status and trend. By incorporating these various measures into the core algorithms and functions associated with the hydration sensor 10, the hydration sensor 10 is capable of determining when one or more of the sensor data feeds may be providing consistent, conflicting or inaccurate data. In addition, the aggregation of the physiological signals from each of the sensors allows the independent algorithms for each sensor to be aggregated in a weighted algorithm to refine and improve assessment of dehydration and hydration trends.

[0138] Referring still to FIG. 15, the flexible printed circuit board 100 supports a plurality of computer processing chips and components. A processor 111 executes software and instructions necessary to operate the hydration sensor 10, including collecting data from one or more sensors mounted on the sensor segment 120. In the embodiment shown in FIGS. 15 and 16, the processor 111 may be an integrated system on a chip that is capable of driving the antenna 150 directly. In an alternative embodiment, radio signal processing may be managed by a separate chip. A power supply 112 draws power from the battery 70 and delivers power to other electronic components. A battery gauge 113 measures the current charge available from the battery 70 and communicates that information to the processor 111 for use in power management and to relay status of the battery 70 via wireless signal to the user or another external station. A charging circuit 114 provides electrical connectivity between the battery 70 and the wireless charging coil 60, enabling wireless recharging of the battery 70 via induction. The flexible printed circuit board 100 supports a flash memory chip 115 that provides active memory storage to the processor 111.

[0139] Referring now to FIG. 16, a front perspective view of the flexible printed circuit board 100 and antenna segment 140 in a folded state, including various electrical components, is shown. The first hinge segment 160, interposed between the sensor segment 120 and the central segment 110, may be flexed to bend the sensor segment 120 to curve around to one side of the mouth to effectively position one or more sensors at preferred locations. The second hinge segment 170, interposed between the central segment 110 and the ground plane segment 130 and extending from a bottom edge 106 of the central segment 110, may be flexed to bend approximately 180 degrees, causing the ground plane segment 130 to be positioned parallel to, and in front of, the plane of the central segment 110. The third hinge segment 180, interposed between the ground plane segment 130 and the antenna segment 140, may be flexed to bend approximately 90 degrees, causing the antenna segment 140 to extend horizontally from the ground plane segment 130 away from the front surface 104 of the flexible printed circuit board 100. In this configuration, the base of the antenna 150 extends orthogonally from the ground plane segment 140, enabling a monopole antenna configuration. In the embodiment shown, the antenna is sized to serve as a 1/4-wave monopole antenna in the frequency range of 2.4GHz, in one instance to support BLUETOOTH ^® communications protocol. The antenna 150 may be modified in both its length and pattern to accommodate a range of signal wavelengths and protocols.

[0140] Referring still to FIG. 16, the flexible printed circuit board 100 in a flexed configuration is shaped to fit and be supported by the hydration sensor scaffolding 200. In particular, the central segment 110, first hinge segment 160, and sensor segment 120 are flexible to allow conformation with the curvature of the scaffolding front surface 204. Additionally, the curvature of the second hinge segment 170, ground plane segment 130, and third hinge segment 180 conform with the curvature of the ground plane scaffold 230 such that the ground plane segment 130 is positioned between the central segment 110 and the ground plane scaffold 230. Thus, the antenna segment 140 is positioned on the antenna scaffold 240 and within the absorptive shell protrusion 40.

[0141] Referring now to FIG. 17, a view of one embodiment of the antenna segment 140 is shown. The antenna segment 140 enfolds an antenna 150 in a monopole configuration. The antenna 150 extends from an antenna base 152 on a back edge 141 of the antenna segment 140 near a first side edge 143. The antenna 150 extends from the antenna base 152 towards a front edge 142 before turning ninety degrees to extend toward a second side edge 144. In one version, the change in direction of the antenna geometry is accomplished via a miter that will tend to conserve the signal energy. Other geometric shapes may be used to make the desired turn.

[0142] The antenna segment 140, in one version, comprises the antenna 150, a top antenna layer 145, and a bottom antenna layer 146. The antenna 150 is sandwiched between the top antenna layer 145 and bottom antenna layer 146, which protect the antenna 150 from deformation and from coming into electrical contact with other objects. In one version, the top antenna layer 145 and bottom antenna layer 146 may be made from KAPTON ^® to provide electrical and thermal insulation for the antenna 150.

[0143] It will be understood that the present invention is not limited to the method or detail of construction, fabrication, material, application or use described and illustrated herein.

Indeed, any suitable variation of fabrication, use, or application is contemplated as an alternative embodiment, and thus is within the spirit and scope, of the invention.

[0144] Further, the depicted hydration sensor 10 of FIG. 1 is not intended to be limiting;

different and additional embodiments can employ any sensor that captures suitable data, including without limitation sensors described elsewhere in this disclosure. The illustrated hydration sensor 10, is designed to be worn within an individual's mouth and can be used both in clinical settings and in the field, e.g., on any person for whom monitoring might be beneficial, for a variety of reasons, including without limitation, assessment of hydration trend, heart rate, respiration rate, and work performed during athletic competition or training, daily activities, military training or action, etc. In one aspect, the hydration sensor 10 may serve as an integrated hydration monitor, which can assess hydration as described herein, display an indication of the assessment via multiple external devices, and recommend therapeutic action based on the assessment, or the like, in a form factor that can be worn during athletic events and/or daily activities.

[0145] In different embodiments, the processing unit 111 can have different types of functionality. For example, in some cases, the processing unit 111 might simply act to store and/or organize data prior to transmitting the data to a monitoring computer, which might perform data analysis and recommend certain actions based on that data analysis. In other cases, however, the processing unit 111 might act as a specialized computer (e.g., with some or all of the components described below and/or some or all of the functionality ascribed to the computer), such that the processing unit 111 can perform data analysis onboard, e.g., to estimate and/or predict an individual's current and/or future hydration trend and status. As such, the hydration sensor 10 may communicate to an external display, such as a wrist mounted device, base station or smart phone, which can display any output described herein, including without limitation estimated and/or predicted values of heart rate, hydration status, and, data captured by the sensor (e.g., heart rate, oxygen saturation, hydration status, and/or the like).

[0146] The hydration sensor 10 might further comprise analyzing, with a computer system (e.g., a monitoring computer and/or a processing unit of a sensor unit, as described above), the physiological data. In some cases, the physiological data is analyzed against a preexisting model (which might be generated as described above and which in turn, can be updated based on the analysis).

[0147] To assess the hydration status of an individual, the hydration sensor 10 aggregates various measurements to create an assessment of change of hydration, i.e., either dehydration or rehydration. In a first assessment, the hydration trend is correlated with oxygen saturation and the amplitude of a blood volume pulse waveform (BVP) generated by the PPG sensor 124. The BVP waveform is assessed to measure circulatory function that can be obtained noninvasively through the PPG biosensor 124.

[0148] Historically, PPG sensors have been applied to the finger or the earlobe of human subjects. However, the use of a PPG sensor on the finger or earlobe provides very limited information. Various devices have been developed which deploy PPG sensors in wrist bands as well. However, in the present inventive subject matter, the PPG sensor 124 is applied in an intra-oral location to obtain one or more physiological signals which are processed to measure oxygen saturation and to create a cardiac and respiratory waveform for additional analysis to correlate aspects of the cardiac and respiratory cycle and waveform with hydration trends. The cardiac waveform is analyzed to determine a degree of cardiovascular change undergone by a subject through an exercise or athletic session. In one instance, the cardiovascular change (CC) is applied to determine a hydration level by assessing the individual's TBW based upon a reduction in amplitude of the cardiac waveform as an individual dehydrates. Conversely, as the amplitude of the cardiac waveform increases, the individual is determined to be in a mode of rehydration.

[0149] In an additional version of the hydration sensor, the CC, oxygen saturation and analogues of the core body temperature are assessed to determine both a level of hydration, a hydration trend, a level of fatigue and a fatigue trend. As the CC indicates a trend in dehydration, the core body temperature is likewise assessed based on analysis of the trend in the cardiac waveform via an algorithm that correlates heart rate with core body temperature.

[0150] In a further version, the hydration sensor 10 collects data via the PPG and a separate respiratory temperature probe. The respiratory temperature probe, in one instance, comprises a thermistor to measure respiratory rate and respiratory temperature. An increase in respiratory rate and respiratory temperature is correlated with the cardiac waveform, CC and oxygen saturation to assess a trend in hydration, either dehydration or rehydration. [0151] The PPG sensor 124 comprises a matched infrared LED - phototransistor. The PPG sensor 124 is small enough to be applied to the flexible printed circuit board 100 in the sensor segment 120. The placement of the PPG 124 within an individual's oral cavity, where there is minimal ambient light, substantially eliminates problems associated with ambient light interference as with other PPG placement locations. The PPG sensor 124, in a preferred embodiment, is placed so as to direct the light output toward a user's cheek. However, in other versions, the PPG sensor 124 may be directed inward toward an individual's gums or tongue to likewise obtain PPG data. In other versions, the PPG sensor 124 may be directed both outwardly and inwardly to collect PPG data, such that the multiple streams of PPG data may be juxtaposed for confirming accuracy.

[0152] Now, in greater detail, we describe features associated with dehydration relevant to the inventive subject matter described herein. In medicine, intravascular volume status refers to the volume of blood in an individual's circulatory system, and is essentially the blood plasma component of the overall volume status of the body, which otherwise includes both

intracellular fluid and extracellular fluid. Still, the intravascular component is usually of great interest, and volume status is sometimes used synonymously with intravascular volume status. Volume status is related to the individual's state of hydration, but is not identical to it. For instance, intravascular volume depletion can exist in an adequately hydrated person if there is loss of water into interstitial tissue (e.g. due to hyponatremia or liver failure). Intravascular volume depletion, (volume contraction of intravascular fluid (blood plasma) is termed hypovolemia. Signs of hypovolemia include, in order of severity: a fast pulse, infrequent and low volume urination, dry mucous membranes (e.g. a dry tongue), poor capillary refill (e.g. when an individual's fingertip is pressed, the skin turns white, but upon release, the skin does not return to pink as fast as it should - usually >2 seconds), decreased skin turgor (e.g. the skin remains "tented" when it is pinched), a weak pulse, orthostatic hypotension (dizziness upon standing up from a seated or reclining position, due to a drop in cerebral blood pressure), orthostatic increase in pulse rate, cool extremities (e.g. cool fingers).

[0153] In contrast, signs of intravascular volume overload (high blood volume) include: an elevated jugular venous pressure. There exists a standard norm or correlation for intravascular blood volume base on an individual's ideal height and weight.

[0154] In one instance, the hydration sensor 10 includes one or more digital signal processing algorithms for removing a respiratory trend from photoplethysmographic signals. Removal of the respiratory trend from the PPG data helps avoid distortion potentially introduced by low- frequency respiratory trend contaminating the PPG signals recorded for the purpose of exercise evaluation. Removal of the respiratory trend can preserve the morphology of the PPG signals for determination of one or more indices as derived from the PPG signals.

[0155] The SMRT index comprises an integration of algorithms tied to each monitoring sensor incorporated with the hydration sensor 10. For example, dehydration may be calculated using one or more algorithms that integrate the myriad sensor inputs into a single SMRT hydration index, HSMRT. In one embodiment, HSMRT may be calculated using a weighted average equation:

HSMRT (xi, X2, ·.., Xn) = Fi(xi) + F ₂ (x ₂ ) + ... + F n(Xn)

= ± ki(xi - ai) ± k ₂ (x ₂ - a ₂ ) ± ... ± k _n (x _n - a _n ) wherein HSMRT is a total hydration function, F is a specific hydration function, x is a physiological input signal, a is a physiological input offset, k is a weight, and n is the total number of physiological input signals.

[0156] HSMRT may be calculated using a plurality of physiological input signals, including but not limited to core body temperature, oral impedance, pulse rate, pulse regularity, respiration rate, respiration volume, oxygen saturation, and PPG intensity.

[0157] The physiological input offsets, a, may be constant values, or they may vary between individuals. For example, while everyone shares a resting, hydrated body temperature of 37 degrees Celsius, resting heart rate will vary from one person to the next. When an

individualized physiological input offset, a, is used, the custom value may be determined based on an initial value measured at a known hydration level. Alternatively, the custom value may be determined and adjusted based on prior use sessions. In another embodiment, any of the specific hydration functions F(x) in the total hydration function may be replaced with their time derivatives F'(x).

[0158] For example, in one embodiment the hydration function describes a hydration index wherein the value 100 represents full hydration, and a decrease in the index represents a decrease in hydration. Additionally, the hydration function may be used to measure overhydration in which case, the hydration index would exceed a value of 100. Clearly, at a value of 0, the hydration index indicates severe dehydration. In this embodiment, the specific hydration function Fi calculates hydration based on the individual's core body

temperature xi wherein an increase in body temperature of 0.1 degrees Celsius corresponds to a reduction in the hydration index by 1 point, and that the core body temperature specific hydration function is weighted at 10 percent of the total hydration function. The specific hydration function for core body temperature Fi may then be derived as Fi(xi) = 0.1*(100 - [0159] In the present inventive subject matter, placement of the hydration sensor 10 having a PPG sensor 124 within an individual's oral cavity allows the amount of blood in the capillaries of the cheeks or gums at any given time to be indirectly measured by the amount of infrared radiation sensed by a phototransistor after being emitted by a constant source and reflected in either the cheeks or gums. In spite of its monitoring potential, the applicability of

photoplethysmographic measurements to the evaluation of cardiovascular changes during an exercise session has been limited by the presence of motion artifacts in PPG signals measured from exercising subjects. Indices derived from the PPG signals waveform and designed to reflect changes through an exercise and recovery session can be severely distorted by motion artifacts that arise in the condition described above. Elimination of the motion artifact through fixed filtering techniques is applicable but may compromise analysis of the PPG signals due to both the in-band nature of the interference (overlapping the most important spectral components of the signal), and expected frequency variations according to the exercise type or pace. As such, the application of an adaptive noise canceler is a viable approach for the reduction of the interference. Application of an adaptive noise canceler requires the availability of a "noise reference signal", correlated with the additive noise polluting the signal of interest. A suitable reference signal can be obtained directly from the mechanical elements of the exercise apparatus.

[0160] The hydration sensor 10 is configured specifically to enhance wireless signal transmission from an intra-oral placement. In use, the hydration sensor 10 is positioned such that the antenna 150 will be positioned distally between a user's upper lip U and lower lip L. The distal intra-lip placement of the antenna 150 allows variation in antenna length and geometry. In an embodiment of the inventive subject matter using the BLUETOOTH ^® communications protocol at a frequency of 2.4 GHz, a 1/4-wave monopole antenna is sized to be approximately 32 mm in length. The preferred length is established by calculating the wavelength of a 2.4 GHz radio wave signal traveling at the speed of light (2.99 x 10 ^s meters per second) and dividing by a factor of 4. However, the wavelength of light at a given frequency decreases as it travels through a dense medium. While the density of air is negligible, the density of tissue in a user's lips will attenuate a radio signal transmitted by an antenna 150 located between the lips. Therefore, in the present case, the antenna 150 is configured to compensate for attenuation. In one embodiment, the correction is made by designing an antenna 150 with a reduced physical length equal to 1/4 of the target radio signal's wavelength through tissue. In another embodiment, the antenna length remains unmodified but the processor 111 used to generate a radio signal includes a tuning circuit to compensate.

[0161] Referring now to FIG. 18A, 18B and 18C, the benefit of intra-lip placement of the antenna 150 according to the inventive subject matter is illustrated. Three comparative illustrations are provided. In FIG. 18A, performance of a standard 2.4 GHz signal in air (free space) is illustrated; in FIG. 18B, performance of a 2.4 GHz signal attenuated by intra-oral impediments (cheek) is illustrated. In FIG. 18C, performance of a 2.4 GHz signal driven from the hydration sensor 10 and through the intra-lip antenna 150 is illustrated. Now, in greater detail, in FIG. 18A, chart 1000 illustrates the attenuation of a radio signal from an antenna in free space (air). The communication between a hydration sensor 10 and a third party transceiver is dependent on the effective range of the antenna 150. When a radio signal is traveling through free space, the calculation of effective range is based solely on the initial signal strength. The chart 1000 of radio signal strength through unimpeded air is shown with distance 1010 on the x-axis and signal strength 1020 on the y-axis. A minimum signal detection strength 1030 is represented by a horizontal dotted line, wherein the y-value corresponds to the minimum signal strength necessary for a receiver to detect the signal. A first free space curve segment 1040 of distance vs signal strength is at a maximum value when distance is zero, and decays as distance increases. A free space maximum range 1050 is represented by a vertical dotted line with an x value matching the intersection point of the first free space segment 1040 intersecting the minimum detection strength 1030. The second free space curve segment 1060 of distance vs signal strength represents signal strength as a function of distance wherein the distance is greater than the unimpeded maximum range 1050 and below the minimum detection strength 1030.

[0162] Referring now to FIG. 18B, chart 1100 illustrates attenuation of a radio signal from an antenna situated intra-orally (fully enclosed within a user's mouth). Chart 1100 illustrates signal attenuation as a function of distance of the same transceiver as described in FIG. 18A, only placed inside a user's mouth. The graph of radio signal strength from the intra-oral transceiver is formatted with the same distance 1010 on the x-axis, signal strength 1020 on the y-axis, and minimum detection strength 1030 as previously shown in FIG. 18A. A first intra-oral attenuated curve segment 1110 graphs the signal strength as a function of distance within the mouth. An intra-oral attenuation line 1120 is a vertical dotted line representing the distance from the transceiver at which the radio signal must cross through tissue in order to reach unimpeded air and continue travel towards an external receiver. A second intra-oral attenuated curve segment 1130 shows attenuation in signal strength caused by the oral cavity as the signal travels across the intra-oral attenuation line 1120. In an embodiment utilizing a 2.4 GHz signal, the second intra-oral attenuated segment 1130 shows a drop in signal strength of approximately -16 decibel. The third intra-oral attenuated segment 1140 represents signal strength as a function of distance between the intra-oral attenuation line 1120 and the intra-oral attenuated maximum range 1150, analogous to the first free space curve segment 1040 and the free space maximum range 1050, respectively. Due to the attenuation observed in the second intra-oral attenuated curve segment 1130, the intra-oral attenuated maximum range 1150 will be significantly lower than the free space maximum range 1050 for the same initial signal strength. In applications envisioned in association with the inventive subject matter, the reduced range represented by the intra-oral attenuated maximum range 1150 causes wireless communication between a hydration sensor 10 and a third party external receiver to be impracticable or impossible. The fourth intra-oral attenuated curve segment 1160 represents signal below the minimum detection strength 1030 and above the intra-oral attenuated maximum range 1150.

[0163] Referring now to FIG. 18C, chart 1200 illustrates the attenuation of a radio signal from an antenna positioned intra-lip according to the inventive subject matter. Chart 1200 illustrates signal attenuation as a function of distance of the same transceiver of FIG. 18A and FIG. 18B. However, in this third instance, the antenna 150 is configured such that it is positioned between a user's lips during use, according to the inventive subject matter in the manner previously shown in FIG. 2, FIG. 3A and FIG. 3B. The graph of radio signal strength from the intra-lip antenna 150 is formatted with the same distance 1010 on the x-axis, signal strength 1020 on the y-axis, and minimum detection strength 1030 as previously shown in FIG. 18A. The first intra-lip attenuated curve segment 1210 graphs signal strength as a function of distance between the antenna 150 and the exterior of the lips. An intra-lip attenuation line 1220 is a vertical dotted line representing the distance from the antenna 150 at which the radio signal is partially attenuated by the user's lips. The second intra-lip attenuated curve segment 1230 shows the attenuation in signal strength caused by the lips as the signal travels across the intra- lip attenuation line 1220. The magnitude of the attenuation shown by the second intra-lip attenuated curve segment 1230 is less than that observed by an intra-oral transceiver as previously shown by the second intra-oral attenuated curve segment 1130 in FIG. 7B. The third intra-lip attenuated curve segment 1240 represents signal strength as a function of distance between the intra-lip attenuation line 1220 and the intra-lip attenuated maximum range 1250, analogous to the first free space curve segment 1040 and the free space maximum range 1050, respectively. Due to the attenuation observed in the second intra-lip attenuated curve segment 1230, the intra-lip attenuated maximum range 1250 will be lower than the free space maximum range 1050 for the same initial signal strength, but greater than the intra-oral attenuated maximum range 1150 for the same initial signal strength. In applications contemplated in association with the inventive subject matter, the signal range represented by the intra-lip attenuated maximum range 1250 enables effective communication between a hydration sensor 10 and an external receiver. The fourth intra-lip attenuated curve segment 1260 represents signal below the minimum detection strength 1030 and above the intra-lip attenuated maximum range 1250.

[0164] FIGS. 18B and 18C describe signal attenuation as a function of distance wherein the wearer of the hydration sensor 10 is directly facing the receiver. However, signal attenuation can be greater when the user is not directly facing the receiver because of additional tissue through which the signal must travel. For example, a signal from an antenna placed intra-orally that is communicating with a receiver directly in front of the user must only travel through teeth and lips. However, in order to communicate with a receiver directly behind the user, the signal will be greatly attenuated since it must travel through the tissues of the user's brain and skull. Consequently, an intra-oral antenna will have extremely limited range.

[0165] Referring now to FIG. 19, a range diagram 1300 describing the communication range of a hydration sensor 10 is shown. For an antenna situated intra-orally, the intra-oral attenuated maximum range 1150 is shown as it varies radially around an individual 1310. The intra-oral attenuated maximum range 1150 shows the range of an intra-oral transceiver with properties described by the exemplary graph of radio signal strength from an intra-oral transceiver 1100 as shown in FIG. 18B. For the sake of scale, a sample athletic field 1320 is also shown. The sample athletic field 1320 is shown with dimensions of 160 feet by 300 feet, as utilized by standard football games. The intra-oral attenuated maximum range 1150 is highest in the direction where the intra-oral transceiver user 1310 is facing, represented by a first intra-oral detection point 1330. The intra-oral attenuated maximum range 1150 decays as the angle from the first intra-oral detection point 1330 increases. The intra-oral attenuated maximum range 1150 is lowest directly behind the intra-oral transceiver user 1310, represented by a second intra-oral detection point 1340. Due to the extreme attenuation experienced when transmitting through the back of a user's head, the second intra-oral detection point 1340 may be as close as five feet from the user.

[0166] Referring still to FIG. 19, an intra-lip attenuated maximum range 1250 is shown. The intra-lip attenuated maximum range 1250 varies radially around an individual 1310. The intra- lip attenuated maximum range 1250 shows the range of an intra-lip transceiver with properties described by the exemplary graph of radio signal strength from an intra-lip transceiver 1200 as shown in FIG. 18C. The intra-lip attenuated maximum range 1250 is highest in the direction where the user 1310 is facing, represented by a first intra-lip detection point 1350. The intra-lip attenuated maximum range decays as the angle from the first intra-lip detection point 1350 increases. The intra-lip attenuated maximum range 1250 is lowest directly behind the user 1310, represented by a second intra-oral detection point 1360. Because of the reduced signal attenuation of an antenna segment 140 placed between a user's lips, the intra-lip attenuated maximum range 1250 is higher than the intra-oral attenuated maximum range 1150 at all angles. The improved range is most noticeable at the second intra-lip detection point 1360 behind the user 1310, as the placement of the antenna 150 between the lips allows the radio signal to propagate around the user 1310 rather than through the user's skull.

[0167] The hydration sensor 10 may leverage other wireless protocols and standards to be accommodated by the intra-lip antenna 150. These additional wireless protocols include, but are not limited to, ultra-wideband (UWB), ZIGBEE ^® , Z-WAVE ^® , low power wide area network protocols (LPWAN), SIGFOX ^® , LORA ^® and various cellular protocols including 5G.

[0168] For example, ZIGBEE ^® supports wireless personal area networks for short range, low data rate applications. As with BLUETOOTH ^® , in many jurisdictions, ZIGBEE ^® operates in the 2.4 GHz frequency band. Other counties, e.g., China, Europe, USA, and Australia operate ZIGBEE ^® within the 900 MHz frequency band. Generally, ZIGBEE ^® transmission distances are between thirty and three hundred feet line of sight. However, ZIGBEE ^® allows transmission of data over longer distances by passing data through a mesh network of intermediate devices to reach more distance devices. The pairing of the ZIGBEE ^® protocol on the hydration sensor 10 in conjunction with the intra-lip antenna 150 creates a novel implementation where a plurality of sensorized intra-oral devices 10 may communicate with other more distant hydration sensorslO. Thus, this integrated implementation substantially extends the reach and accessibility of intra-oral devices leveraging mesh network communication protocols and the intra-lip antenna 150 according to the inventive subject matter.

[0169] Another wireless protocol example, Z-WAVE ^® , is based on the concepts of ZIGBEE ^® and operates at 908.42 MHZ in the United States. Z-WAVE ^® supports a low data rate and transmission distances in free space of approximately 100 feet. As with ZIGBEE ^® , Z-WAVE ^® devices can communicate to one another by using intermediate nodes, and, can transmit between two nodes that are not within range of each other via the mesh capability of Z- WAVE ^® . Z-WAVE ^® is frequently used for smart home implementation. Deployment of Z- WAVE ^® as a wireless protocol supportive of mesh communication in conjunction with the benefits of the intra-lip antenna 150 according to the inventive subject matter hereof will further extend the range and capability of communication between one or more sensorized intra-oral devices 10 and other external transceivers.

[0170] Other wireless protocols may be deployed in conjunction with the hydration sensor 10 and its intra-lip antenna 140, particularly those described as being applicable in the low power wide area network space (LPWAN). Examples include SIGFOX ^® and LORA ^® , which are based on a star-topology rather than a mesh topology. SIGFOX ^® employs a cellular style system using ultra-narrow band (UNB) technology, and is targeted at low cost machine to machine applications where wide area coverage is required. Currently, SIGFOX ^® transmits using the 900 MHz band. Once again, the inclusion of SIGFOX ^® with the hydration sensor 10 and its intra-lip antenna 150 allows the benefits of SIGFOX ^® to be leveraged for extended on-person intra-oral device communications. LORA ^® (Long Range) is another wireless protocol that leverages spread spectrum, chirping and a star topology that can be effectively integrated with the hydration sensor 10 and its intra-lip antenna 150 to provide even greater range for orally- deployed sensors.

[0171] Another wireless protocol that will significantly benefit from the application of the inventive subject matter, particularly the use of the intra-lip antenna 150, is the evolving 5G (fifth generation mobile networks/wireless systems) protocol. The 5G network protocol is expected to deliver enhanced connectivity but with certain benefits and limitations.

[0172] Benefits will include: (a) data rates of tens of megabits per second for tens of thousands of users; (b) data rates of 1 gigabit per second simultaneously to a plurality of persons or devices on the same level, e.g., an office floor; (c) capacity to support several hundreds of thousands of simultaneous connections for a massive wireless sensor network; (d) enhanced spectral efficiency; (e) improved coverage; (f) enhanced signaling efficiency; and (g) significantly reduced latency as compared to existing cellular protocols.

[0173] In the delivery of 5G, shorter wavelengths will be used with higher signal frequencies. Consequently, there will be greater attenuation through any medium, including the

atmosphere. The implementation of the intra-lip antenna 150 according to the present inventive subject matter will serve as an offset to the increased attenuation associated with the higher frequencies and shorter wavelengths of the 5G network protocol.

[0174] Irrespective of the wireless standard deployed for use with the oral hydration sensor 10, the intra-lip antenna 150 provides a common thread for overall improvement of range and therefore, overall effectiveness, with lower power consumption. Although described herein as supportive of communication for an intra-oral sensor device 10, the intra-lip antenna 150 may also serve as a communication enhancement for other on-body data collection and gathering. For example, other sensors worn on the body may communicate data to a repository worn in the user's mouth where the purpose is to collect all associated data from the on-body sensors and relay that data to other transceivers, base stations and interested parties.

[0175] Further, the intra-lip antenna 150 can serve as a more reliable receiver to relay alerts to the user via vibration. For example, in applications where it might be preferable to avoid audible alerts and allow the user to communicate in a non-audible hands free method, a hydration sensor 10 dedicated to communication would be useful. Such applications might include communications between military or other teams where connectivity is important but silence is required for a particular mission. The implementation of the inventive subject matter would provide a method where communication might occur silently, as with using hand signals, where all team members are in sight of each other. However, the inventive subject described herein matter would allow team members to communicate silently even where they are not in sight of each other, simply by the use of an oral communication protocol, e.g., a simplified Morse code tied to specific actions generated by clenching of the jaws on the mouthpiece to generate a signal. Additionally, the intra-lip antenna 150 would allow real-time monitoring of team member physiologic and biometric parameters to determine their status while engaged in a mission, and, allow for emergency personnel to be directed to priority team members via real-time triage.

[0176] Although shown herein as using a monopole antenna 150 in the antenna segment 140, the hydration sensor 10 may also use other antenna configurations. FIG. 20A - 20D are illustrations of other antenna geometries suitable for use in the hydration sensor 10. FIG. 20A is an illustration of an inverted "F" antenna geometry that may serve as an option to a monopole antenna. FIG. 20B is an illustration of a fractal antenna geometry, which is based on reiteration of a geometric generator. Variations of the fractal antenna geometry include a Peano-Gosper curve based antenna and a Koch fractal based antenna. FIG. 20C and FIG. 20D are examples of other applicable antenna geometries. Other antenna designs may likewise be incorporated with the hydration sensor 10 as long as the geometry of the antenna is such that it will fit within the framework and size of the antenna support platform 240 of the scaffolding structure 200.

[0177] Referring to FIGS. 21A and 21B, an illustration of empirical data gathered by testing the PPG sensor 124 in the oral cavity of an approximately 50-year-old male subject exercising on a treadmill is shown. In the treadmill test, the male subject first exercised without replenishing any fluids, indicating a drop in signal intensity for PPG measurement on both the cheek (FIG. 21A) and tongue (FIG. 21B), indicating a dehydration trend. After completion of exercise, the male subject replenished fluids and a corresponding increase in PPG signal intensity was observed, indicating that the male subject had entered a rehydration trend. Eventually, the male subject's hydration trend leveled, suggesting that fluid replenishment had been sufficient to bring the male subject back to a baseline normal and stabilized hydration status, i.e., euhydration.

[0178] Referring now to FIGS. 22A through 22C, additional charts illustrating PPG signal intensity vs time for three different test subjects is shown. Each of these test subjects followed the equivalent treadmill exercise protocol and fluid replenishment protocols. As can be seen, in each case, the test subject generally experienced a decrease in PPG signal intensity while exercising and not replenishing any fluid. Upon completion of exercise, and the replenishment of fluids, each subject likewise reversed a trend of dehydration and began trending in a rehydration mode with, in some cases, evidence of hydration stabilization.

[0179] During the course of testing, an additional correlation was observed due to an inadvertent and unintended change in protocol. Referring to FIG. 23, the chart illustrating change in PPG signal intensity for a 25-year-old male subject who had previously been shoveling snow before engaging in exercise on the treadmill is shown. In this case, after completion of shoveling snow, the male subject did ingest fluids for replenishment.

Consequently, although additional energy and sweat was being expended during the treadmill exercise protocol, the initially ingested fluids provided sufficient replenishment to cause the "snow shoveler" to maintain a rehydration trend throughout the exercise and fluid

replenishment protocol.

[0180] The inventive subject matter described herein, in one aspect, focuses on the determination of the appropriate physiological indices extracted from the

photoplethysmographic cardiac and respiratory waveforms, PPG signal intensity and other associated parameters to reflect the extent of physiological changes induced by exercise and cessation thereof, along with fluid replenishment. With the combination of sensors and physiological parameters, one or more indices may be determined. It is important to emphasize that, by measuring the change of parameters, the potential difficulty of calibrating PPG measurements is bypassed. In other words, the analysis can focus on changes over time rather than establishing a specific value at a point in time. However, the hydration sensor 10 described herein includes functionality to collect continuing data streams which may be iteratively analyzed to develop baseline trends and stabilization norms for each individual's hydration trend response and other physiological parameters.

[0181] Second Embodiment 900

[0182] Referring now to FIG. 24, an exploded view of a second embodiment 900 of the inventive subject matter is illustrated. The hydration sensor 900 comprises the features and sensors of the first embodiment of the hydration sensor 10 and includes additional sensors and features. In the following discussion, those features and elements having reference numerals in the 900 range are associated with the second embodiment 900.

[0183] The absorptive encapsulating shell 20 of the second embodiment 900 includes a respiratory flow orifice 910 to allow a controlled flow of air to pass through the hydration sensor 10 during use. The flexible printed circuit board 100 includes an ovular penetration 920 to accommodate the respiratory flow orifice 910. The scaffolding 200 likewise includes an appropriately sized passageway 930 to accommodate the respiratory flow orifice 910.

[0184] Referring now to FIG. 25 through FIG. 28, the hydration sensor 900 comprises one or more additional sensors. Hydration sensor 900 further comprises a capacitive sensor 950 placed along the bite shelf 50 to measure moisture content of the surface of oral mucosa on the basis of electrostatic capacity. The capacitive data collected by the capacitive sensor 950 is processed by one or more digital algorithms operable with the hydration sensor 900 to provide further refinement of the assessed hydration status and trend, e.g., the HSMRT index.

[0185] Referring to FIG. 25, hydration sensor 900 further comprises an imaging module 960 configured with the hydration sensor 900 to image a surface of an individual user's tongue. The imaging module 960 may receive both infrared and visible light images of the individual's tongue. The imaging module 960 comprises an LED 962 for illumination within the oral cavity and a photodiode 964 for collection of imagery. The imaging module 960 is electronically connected to the printed circuit board 100. Software associated with the hydration sensor 900 will identify various visual cues suggesting the development or presence of dehydration based on image recognition of the tongue. In one aspect, the imaging module 960 will take periodic pictures that will be assessed by edge detection or pattern recognition algorithms incorporated with the software of the hydration sensor 900.

[0186] Referring to FIG. 28, hydration sensor 900 further comprises an electrochemical sensing strip 980 to measure one or more components of saliva within the individual's mouth, including the ions, sodium and potassium, which may be indicative of a level of dehydration, euhydration or over-hydration. The electrochemical sensing strip 980 is electronically connected to the printed circuit board 100. Software associated with the hydration sensor 900 will identify various signals from the electrical chemical sensing strip 980 suggesting the development or presence of dehydration. The data collected by the electrochemical sensing strip 980 is processed by one or more digital algorithms operable with the hydration sensor 900 to provide further refinement of the assessed hydration status and trend, e.g., the HSMRT index. The chemical sensing strip 980 is shown as being placed on a top side of the bite shelf 50 but may be placed at other locations on the bite shelf 50.

[0187] The electrochemical sensing strip 980 correlates saliva components, e.g., changes in concentration of sodium or potassium ion levels, with other indicators of hydration status. The main cations of saliva are known to be sodium and potassium and the main anions are chloride and bicarbonate. Changes in the levels of these ions are primarily responsible for any significant change in the osmolality of saliva. Changes in osmolality correlate to changes in hydration. Further, increased salivary flow rate positively correlates with sodium concentration in the saliva, which subsequently may correlate with hydration.

[0188] Referring now to FIG. 29, the scaffolding 200 includes an ovular penetration 920. The ovular penetration 920 allows an individual to direct respiration through the respiratory flow orifice 910 which also passes through the passageway 930 in the flexible printed circuit board 100.

[0189] As illustrated in FIG. 31, in addition to measurements obtained via PPG methods, the inventive subject matter further comprises a humidity sensor 940 to measure relative humidity (RH). The humidity sensor 940 measures actual respiratory vapor density and compares that measure to saturated vapor density to determine RH. Typically, oral mucous membranes show symptoms of dehydration and will be recognized to produce less moisture, creating a dryer oral environment. Consequently, the RH of exhaled air from an individual undergoing dehydration should measure less than a baseline measurement of RH from when the individual is determined to be better dehydrated. [0190] In one instance, the humidity sensor 950 comprises a thermistor 952 placed downstream of a respiratory flow orifice 910 in the hydration sensor 900. The thermistor 952 is used to measure temperature changes which are used to determine a differential RH between inspiration and expiration. In a second instance, a sensor comprising nanofibers is mounted downstream of a breathing orifice 910 in the hydration sensor 10 to monitor the humidity, temperature and respiratory flow. This data from the nanofiber sensor is processed by one or more algorithms operable with the hydration sensor 10 which may be aggregated to further refine the HSMRT index, which will provide enhanced measures of the assessed hydration status and trend.

[0191] As illustrated in FIG. 32, when the printed circuit board 100 is placed in a flexed or folded state for mounting on the scaffolding 200, the respiratory orifice 910 is generally aligned with placement of the respiratory sensor 950, such that when in use, a partial respiration stream will flow over the respiratory sensor 950. FIG. 33 is an illustration of the antenna segment 140 further comprising the respiratory sensor 950.

[0192] Referring now to FIG. 34, exemplary output of the capacitive sensor 950 is illustrated. Referring to FIG. 35, exemplary humidity readings from the respiratory cycle are illustrated. Referring to FIG. 36, exemplary illustrations of images of the tongue indicating certain features associated an assessment of potential dehydration are shown.

[0193] Referring to FIG. 36, imaging module 960 assists in the assessment of the presence of dehydration based on various oral mucosa symptoms as evidenced by images of the tongue. For example, in one aspect, an image showing the absence of lateral furrows on the surface of the tongue may suggest a mild state of dehydration or no dehydration. An image wherein the indentation of teeth is visible along the lateral edges of the tongue may indicate mild to moderate dehydration. An image wherein indentation of teeth is visible on the surface of the tongue indicates severe dehydration. An image wherein lateral cracks and furrows are present on the surface of the tongue indicate moderate to severe dehydration. An image wherein deep lateral furrows and cracks are present on the surface of the tongue indicate severe

dehydration. The software supporting the imaging module 960 collects data suggesting various stages of hydration and correlates that data against other indicators from other biosensors employed by the hydration sensor 900, e.g., a capacitance/impedance sensor, a PPG sensor, a humidity sensor, a temperature sensor, et al.

[0194] Finally, those of skill in the art will appreciate that the invention described and illustrated herein, specifically, various electrical and logic components, may be implemented in part in either software, firmware or hardware, or any suitable combination thereof. Thus, those of skill in the art will appreciate that elements of embodiments of the invention may be implemented by a computer or microprocessor process in which instructions are executed, the instructions being stored for execution on a computer-readable medium and being executed by any suitable instruction processor.

[0195] An embodiment of a computer system that can perform the methods provided by various other embodiments, as described herein, and/or can function as a monitoring computer, processing unit of the hydration sensor 10. The following discussion is meant only to provide a generalized illustration of various components, of which one or more (or none) of each may be utilized as appropriate. This discussion broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner.

[0196] The computer system comprises hardware elements that can be electrically coupled via a bus (or may otherwise be in communication, as appropriate). The hardware elements may include one or more processors, including without limitation one or more general purpose processors and/or one or more special purpose processors (such as digital signal processing chips, graphics acceleration processors, and/or the like) ; one or more input devices, which can include without limitation a mouse, a keyboard and/or the like; and one or more output devices, which can include without limitation a display device, a printer and/or the like.

[0197] The computer system may further include (and/or be in communication with) one or more storage devices, which can comprise, without limitation, local and/or network accessible storage, and/or can include, without limitation, a disk drive, a drive array, an optical storage device, solid state storage device such as a random access memory ("RAM") and/or a read only memory ("ROM"), which can be programmable, flash updateable and/or the like. Such storage devices may be configured to implement any appropriate data stores, including without limitation, various file systems, database structures, and/or the like.

[0198] The computer system might also include a communications subsystem, which can include without limitation, a modem, a network card (wireless or wired), an infrared

communication device, a wireless communication device and/or chipset (such as a

BLUETOOTH™ device, an 802.11 device, a Wi-Fi device, a WiMAX device, a wireless WAN device, cellular communication facilities, etc.), and/or the like. The communications subsystem may permit data to be exchanged with a network (such as the network described below, to name one example), with other computer systems, and/or with any other devices described herein. In many embodiments, the computer system will further comprise a working memory which can include a RAM or ROM device, as described above.

[0199] The computer system also may comprise software elements, in one instance, located within the working memory, including an operating system, device drivers, executable libraries, and/or other code, such as one or more application programs, which may comprise computer programs provided by various embodiments, and/or may be designed to implement methods, and/or configure systems, provided by other embodiments, as described herein.

[0200] Merely by way of example, one or more procedures described with respect to the method(s) discussed above might be implemented as code and/or instructions executable by a computer (and/or a processor within a computer) ; in an aspect, then, such code and/or instructions can be used to configure and/or adapt a general purpose computer (or other device) to perform one or more operations in accordance with the described methods.

[0201] A set of these instructions and/or code might be encoded and/or stored on a non- transitory computer readable storage medium, such as the storage device(s) described above. In some cases, the storage medium might be incorporated within a computer system, such as the system. In other embodiments, the storage medium might be separate from a computer system (i.e., a removable medium, such as a compact disc, etc.), and/or provided in an installation package, such that the storage medium can be used to program, configure and/or adapt a general purpose computer with the instructions/code stored thereon. These instructions might take the form of executable code, which is executable by the computer system and/or might take the form of source and/or installable code, which, upon compilation and/or installation on the computer system (e.g., using any of a variety of generally available compilers, installation programs, compression/decompression utilities, etc.) then takes the form of executable code.

[0202] Thus, specific compositions of a hydration sensor 10 have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the disclosure. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms, "comprises" and

"comprising" should be interpreted as referring to elements, components, or steps in a nonexclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.