FIELD OF THE INVENTION [0001] The present invention relates to a vital sign monitoring system, particularly adapted for children and, in particular, for infants, for monitoring vital signs of a patient. The vital signs include oxygen saturation in blood (= Sp02), cardiac rhythm (HR), and breathing rhythm of the patient. The present system comprises two sets of sensors, including, hand sensors coupled to a hand of the patient, for sensing the vital signs thereof, and

• external sensors, located in the same environment as, albeit separate from, the hand sensors, and configured for measuring external data including the temperature, relative humidity, and optionally air quality of the environment surrounding the external sensors and hand sensors.

[0002] The system comprises also a processing unit configured for, · monitoring the vital signs instantly (in real time) and triggering an alarm in case a vital sign deviates from predefined boundaries, and for

• correlating the vital signs and the external data over a longer monitoring period, for optimising the living conditions of the patient such as to maintain the vital signs within agreeable boundaries.

BACKGROUND OF THE INVENTION

[0003] Symptoms such as hypoxia or bradycardia can be indicative of cardiorespiratory pathologies including asthma, sleep apnea, or even in extreme cases, sudden infant death syndrome (SIDS). Asthma is an inflammation of the bronchial tubes, which bring air into and out of the lungs, rendering breathing more difficult. It is difficult to diagnose asthma in infants and toddlers, and yet, since they have much smaller airways than adults, even small blockages caused by viral infections, tight airways or mucus can make breathing difficult for a child.

[0004] Sleep apnea is a sleep disorder where a person has pauses in breathing of a few seconds to a few minutes or periods of shallow breathing during sleep. Sleep apnea may be either obstructive sleep apnea (OSA) in which breathing is interrupted by a blockage of air flow, central sleep apnea (CSA) in which regular unconscious breath simply stops, or a combination of the two.

[0005] The foregoing symptoms can be monitored by measuring vital signs including the oxygen saturation in blood (= SpQ2) and the cardiac rhythm of a patient. Since asthma and sleep apnea are breathing disorders, monitoring the breathing rhythm would also be a valuable information for monitoring, understanding, and possibly curing or preferably preventing such diseases.

[0006] Monitoring these vital signs on a patient with low invasive monitoring devices excludes the use of face masks for monitoring the breathing rhythm. Sensors must be used which do not interfere, or at least as little as possible, with the freedom of movements of a patient. This is particularly true for children and infants. Infants are of particular interest since about 80% of children with asthma have symptoms, that started before they turned 5. For these reasons, wearable monitoring sensors have been developed for monitoring vital signs on patients during their daily activities and, in particular, during their night sleep.

[0007] US8140143 describes a washable, wearable biosensor that can gather sensor data, communicate the sensed data by wireless protocols, and permits the analysis of sensed data in real-time as a person goes about their normal lifestyle activities. The biosensors are supported on a textile, wearable device, which can be worn in multiple positions, and can be put on or removed quickly. The sensors may include multiple photoplethysmographs (PPG) and/or one or more electrodes for measuring electrodermal activity (EDA), i.e., skin conductance, and can also include temperature sensors. The sensor data may be sent by wireless transmission and received by a digital device or a computer.

[0008] US29199956886 describes a portable vital sign monitor which has a palm vital sign monitor unit carried by the patient. The unit comprises an optical probe positioned in the palm of the patient which measures at least one vital sign including Sp02 and pulse rate but not exclusively and only those vital signs. The detected vital signs are stored in memory and transmitted by wireless inter-connection to a communication base unit, which transmits the vital signs by a phone line, LAN, Internet, serial interface or the like to a data processing device/centre.

[0009] US9955877 describes a wearable, wireless, non-invasive device and system applicable to the hand or foot, comprising a sensor and a computing algorithm. The device is worn on the hand or foot of a user. Part of the device may be placed on the proximal phalange of a finger or a foot, or even in the palm. The electronics of the device may be placed inside gloves or booties of different sizes to accommodate the hands or feet of different wearers. The device measures blood oxygen saturation and heart rate through a sensor that is preferably a pulse oximeter.

[0010] EP3453319 describes a device including a pliable membrane, a sensor module and a communication module. The membrane is configured to conform to a tissue surface including the palm of a hand. The sensor module is coupled to the membrane. The sensor module comprises sensors configured for monitoring the Sp02 (pulse oximetry), and sensors for monitoring the heart rate and heart rate variability (HVR). The communication module is coupled to the membrane. The communication module is configured to receive the electrical signal and wirelessly communicate data corresponding to the electrical signal with a remote device.

[0011] US8929967 describes a flexible sensor pad includes a cavity to hold a sensor unit supported on a flexible, adhesive support. The sensor unit comprises light sources and light detectors configured for measuring oxygen saturation levels in blood (Sp02).

[0012] There are no or little wearable monitoring devices available on the market allowing the monitoring of the breathing rhythm, which is the parameter of highest relevance to follow up the upcoming and evolution of diseases like asthma and sleep apnea. Furthermore, none of the foregoing references give any solution for understanding the causes of such symptoms, which is a pre-requisite for finding a way of preventing them, or at least reducing the risk of their occurrence. The present invention proposes a solution (a) for monitoring the breathing rhythm of a patient in a non-invasive way, and (b) for establishing a causal link between said symptoms and the direct environment surrounding the patient. These and other advantages are discussed more in details in the following sections.

SUMMARY OF THE INVENTION

[0013] The objectives of the present invention have been reached with a kit of parts for monitoring vital signs of a patient, preferably of an infant, comprising

(a) a hand-monitoring unit devoid of any wire communication means with an external unit, and comprising,

• hand-sensors including optical sensors comprising one or more light emitting sources for emitting an emitted light and one or more photodetectors, configured for measuring optical data including a reflected light signal intensity representative of a proportion of reflected light from the emitted light measured by the one or more photodetectors, and

• a flexible support comprising an inner surface and an outer surface and supporting the hand-sensors, wherein the optical sensors are all on the inner surface, wherein the flexible support is configured for being coupled to a hand of the patient, with the optical sensors contacting a palmar region of the hand at the level of a thenar eminence,

(b) an external monitoring unit, separate from the hand-monitoring device and comprising external sensors for monitoring external data, including

• a temperature sensor for monitoring the temperature of an atmosphere surrounding the external monitoring unit,

• a relative humidity (RH) sensor for monitoring a relative humidity (RH) of the atmosphere surrounding the external monitoring unit, and

(c) a processing unit (40) configured for,

• processing data measured by the hand-sensors, including the optical data, and for generating a photoplethysmogram (PPG) and configured for determining therefrom consolidated data including. o a cardiac rhythm of the patient, and o a breathing rhythm of the patient, and, o an oxygen saturation in blood (= SpC>2) of the patient, and for • correlating the consolidated data with the external data.

[0014] The correlation of the consolidated data with the external data opens the door to a better understanding of the influence the direct environment of a patient can have on the occurrence and evolution of symptoms representative of a cardiorespiratory disease.

[0015] The kit-of-parts preferably comprises a data storage unit in communication with the processing unit for storing the consolidated data and the external data. This allows the establishment of such correlations over statistically representative amounts of data collected over several patients, and over an extended cumulated monitoring period. The data storage unit can be located either,

• in the external monitoring unit, or

• in a separate unit which is separate from both external monitoring unit (20) and hand-monitoring unit, or

• in the hand-monitoring unit.

[0016] The processing unit can comprise a first processing unit element and a second processing unit element, wherein the first processing unit element is located in the hand-monitoring unit and is provided with wireless communication means with the second processing unit element. The second processing unit can be located in the external monitoring unit or in a separate unit. Alternatively, the processing unit is located in the hand monitoring unit (10) or is located in the external monitoring unit or in a separate unit. In these cases, the processing unit comprises wireless communication means with the hand-monitoring unit for transferring data measured by the hand-sensors, including the optical data.

[0017] The processing unit can be configured for triggering an alarm in case values of one or more vital signs measured by the hand-sensors falls out of predetermined boundaries.

[0018] Beside the optical sensors, the hand-sensors can comprise,

• a skin temperature sensor for monitoring a skin surface temperature of the patient, and located in the inner surface of the flexible support (12), and/or

• an accelerometer (11a) for monitoring movements of a hand of the patient, and/or

• an outer temperature sensor for measuring the temperature in a close environment surrounding the hand-monitoring unit, and/or

[0019] If the hand-sensors comprise an accelerometer, the processing unit is preferably configured for correcting artefacts in the data measured by the optical sensors due to movements of the hand as measured by the accelerometer, including ignoring a series of data measured during a period of intense movements as revealed by the accelerometer.

[0020] The kit of parts can comprise a quality sensor for monitoring the quality of air and configured for measuring in the atmosphere surrounding the quality sensor one or more of a concentration in fine and/or ultra-fine particulate and/or a concentration of selected gases; the quality sensor can be an external sensor located in the external monitoring unit or it can be a hand-sensor located in the hand-monitoring unit.

[0021] The flexible support can comprise,

• a main strap configured for surrounding the hand of the patient,

• reversible fastening means for fastening a portion of the inner surface to a corresponding portion of the outer surface of the main strap for forming a closed loop configured for surrounding the hand of the patient over at least the palmar region, preferably without covering any fingers, thus securing the flexible support to the hand with the optical sensors pressed against a skin of the hand in their respective positions at the thenar eminence, wherein the reversible fastening means are preferably selected among a hook and loop fastener, a zipper, a hook and eye fastener, press studs, button and buttonhole and combinations thereof

• a thumb strip configured for joining a palmar portion and a back portion of the main strap by passing between the thumb and first finger of the hand, wherein the palmar portion is configured for being positioned in the palmar region, and wherein the back portion is configured for being positioned on a back of the hand, and

• fastening means selected among permanent fastening means or reversible fastening means for fastening the thumb strip to the main strap.

[0022] The optical sensors preferably comprise,

• a green light emitting source, preferably a light emitting diode (LED) emitting light, the green light emitting source emitting light in a wavelength range comprised between 510 and 570 nm, preferably between 520 and 560 nm,

• a red light emitting source, preferably a light emitting diode (LED) emitting light, the red light emitting source emitting light in a wavelength range comprised between 600 and 700 nm,

• an IR-light emitting source (11 L), preferably a light emitting diode (LED), the IR light emitting source emitting light in a wavelength range comprised between 700 and 1000 nm,

• an IR-cut photodetector (11 p) configured for detecting light in a wavelength range comprised between 340 and 740 nm, and a broad band photodetector (11 p) configured for detecting light in a wavelength range comprised between 600 and 1100 nm

[0023] In one embodiment, the hand-monitoring unit comprises the processing unit or a first processing unit element as defined supra. The processing unit or first processing unit element of this embodiment preferably comprises

• an analog front end (= AFE) recording and managing parameters of light beams emitted by the one or more light emitting sources and received by the one or more photodetectors (11 p), and

• a wireless communication device for communicating with the data storage unit and preferably with the external monitoring unit.

[0024] The cardiac rhythm of a patient, an inter-beat interval (IBI) and a variation with time of the IBI (d IBI / dt) of the patient can be determined by measuring the time intervals separating two maxima or two minima of a magnitude of the optical data, wherein the optical data is preferably measured in a wavelength range comprised between 495 and 600 nm or between 600 and 1000 nm. In reflection mode, a wavelength range comprised between 495 and 600 nm is preferred. The breathing rhythm of the patient can be determined as a function of the variation (d IBI / dt) with time of the IBI thus determined.

[0025] The oxygen saturation in blood (= SpC>2) of the patient can be determined by calculating the ratio, R = (ACred / DCred) / (ACIR / DCIR), and correlating the result with a pre-established correlation curve or by calibration to determine the corresponding value of SpC>2. The optical data comprises

• constant contributions (DC) to the reflected light signal intensities measured by one or more photodetectors in the red wavelength range (DCred), and in the IR wavelength range (DCIR), respectively, which are constant in time, and

• pulsatile average contributions (AC) to the reflected light signal intensities measured by one or more photodetectors in the red wavelength range (ACred), and in the IR wavelength range (ACIR), respectively, which vary with time, wherein the red wavelength range is comprised between 600 and 700 nm, and the IR-wavelength range is comprised between 700 and 1000 nm.

The kit of parts according to any one of the preceding claims, wherein the processing unit (40) is configured for triggering an alarm in case values of one or more vital signs measured by the hand-sensors falls out of predetermined boundaries.

BRIEF DESCRIPTION OF THE FIGURES [0026] On the following figures, Fig. 1 illustrates (a) a hand with the thenar eminence thereof, (b) to (d) various views of different embodiments of hand-monitoring units.

Fig. 2 shows (a) an external monitoring unit, (b) a processing unit, (c) a data storage unit, and (d) a single device comprising the external monitoring unit, the processing unit, and the data storage unit.

Fig. 3 shows. an embodiment of hand-monitoring unit (a) inner surface, (b) outer surface.

Fig.4 shows the deviation from reference measures of the Sp02 and cardiac rhythm (HR) measured with optical sensors as defined herein applied on the wrist and on the thenar eminence.

Fig.5 shows an example of possible correlation between relative humidity (RH) in a room and breathing rhythm (BR) of an infant sleeping in that room.

Fig.6 shows a PPG and an ECG showing equal peak to peak periods corresponding to inter-beat intervals (IBI).

DETAILED DESCRIPTION.

[0027] As illustrated in Figures 1(b)-1(d) and 2(a), 2(b) & 2(d), a monitoring system for monitoring of vital signs of a patient according to the present invention is formed by a kit-of-part comprising,

• a hand-monitoring unit (10) comprising hand sensors (11 L, 11 p) supported on a flexible support (12),

• an external monitoring unit (20) comprising external sensors (211, 21 rh) for monitoring the temperature and relative humidity of the atmosphere surrounding the external monitoring unit, and

• a processing unit (40) configured for processing data measured by the hand-sensors to yield consolidated data, and for correlating the consolidated data with the external data.

[0028] The foregoing components (and others) and their functions are discussed in detail in the following sections.

HAND-MONITORING UNIT (10)

[0029] The hand-monitoring unit (10) is devoid of any wire or any optical fibre communication means with an external unit in order to preserve freedom of movements of the patient hands. The hand-monitoring unit comprises hand-sensors including optical sensors comprising,

• one or more light emitting sources (11 L) for emitting an emitted light and

• one or more photodetectors (11 p), configured for measuring optical data including a reflected light signal intensity representative of a proportion of reflected light from the emitted light measured by the one or more photodetectors. [0030] The hand sensors are supported on a flexible support (12) comprising an inner surface (12i) and an outer surface (12o) separated from the inner surface by a thickness of the flexible support. The optical sensors are all located on the internal surface. The flexible support is configured for being wrapped around a hand (1) of the patient, with the optical sensors contacting a palmar region (1 p) of the hand at the level of a thenar eminence (cf. Figures 1 (a) and 1 (b)).

[0031] In one embodiment illustrated in Figures 1 (b) to 1 (d) and in Figures 3(a) and 3(b), the flexible support (12) can comprise a main strap (12m) configured for surrounding the hand of the patient. The flexible support can also comprise reversible fastening means (12f) for fastening a portion of the inner surface to a corresponding portion of the outer surface of the main strap for forming a closed loop configured for surrounding the hand of the patient over at least the palmar region, preferably without covering any fingers. The flexible support can thus be firmly secured to the hand with the optical sensors pressed against a skin of the hand in their respective positions on the thenar eminence. The reversible fastening means can be selected among a hook and loop fastener, a zipper, a hook and eye fastener, button and buttonhole, press studs, and combinations thereof.

[0032] It is important for the reliability of the measures, that the optical sensors maintain as constant as possible their position relative to the skin of the hand during the whole duration of the monitoring (e.g., a full night), in spite of movements of the hand. In order to more firmly couple the flexible support and optical sensors to the hand of the patient, the flexible support is preferably provided with a thumb strip (12s) configured for joining a palmar portion and a back portion of the main strap by passing between the thumb and first finger of the hand. The palmar portion is configured for being positioned in the palmar region (1 p), and the back portion is configured for being positioned on a back of the hand, when the main strap is fastened around the hand. The thumb strip prevents the main strap (12m) from rotating around the hand, and thus contributes to maintaining the optical sensors over the thenar eminence. The thumb strip (12s) can be secured to the main strap (12m) by fastening means (12f) selected among permanent fastening means or reversible fastening means. Permanent fastening means are preferably stitches, glue, welding, rivets, and the like. Reversible fastening mean can be selected among a hook and loop fastener, a hook and eye fastener, button and buttonhole, press studs, and combinations thereof.

[0033] The flexible support (12) can be made of a fabric. Fabrics have the advantage that they allow breathing of the skin, which is advantageous for long monitoring periods. Alternatively, the flexible support can be in the form of a film, typically a polymeric film, preferably an elastomeric film, such as a silicon film, or a rubber film. The film can also be in the form of a foam, preferably with open porosity or the film can be provided with openings to allow the passage of air and moisture to and from the skin of the patient.

[0034] The optical sensors comprise one or more light emitting sources (11 L) and one or more photodetectors (11 p), In a preferred embodiment, the one or more light emitting sources (11 L) comprise,

• a green light emitting source (11 L), preferably a light emitting diode (LED) emitting light in a wavelength range comprised between 510 and 570 nm, preferably between 520 and 560 nm, · a red light emitting source (11 L), preferably a light emitting diode (LED) emitting light in a wavelength range comprised between 600 and 700 nm, and

• an IR-light emitting source (11 L), preferably a light emitting diode (LED) emitting light in a wavelength range comprised between 700 and 1000 nm,

[0035] The one or more photodetectors (11 P) can comprise at least, · an IR-cut photodetector (11 p) configured for detecting light in a wavelength range comprised between 340 and 740 nm, and

• a broad band photodetector (11 p) configured for detecting light in a wavelength range comprised between 600 and 1100 nm

[0036] The one or more light emitting sources (11 L) are located such that the light beam emitted by a light emitting source propagates through the skin of the thenar eminence to a depth depending on the intensity, angle, and wavelength of the emitted light beam, as well as on the nature of the tissues traversed by the light beam. The one or more photodetectors (11 p) are located such that they intercept at least a portion of the emitted light reflected by the skin and tissues crossed by the emitted light beam. This means that the photodetectors are positioned side- by-side or even enclosed within or surrounding the corresponding light emitting sources, on the same side of the hand. The reflected light detected by the photodetectors comprises a constant component (DC) and a variable or pulsatile component (AC). The pulsatile component (AC) results mainly from the reflexion of light against blood vessels and any tissue transporting fluids in movement. The intensity of the AC varies with the pulsations of fluids (mostly blood), affecting the amount, composition, and density of the fluids, in particular blood. The constant component (DC) is the fraction of light reflected against tissues which reflectivity does not vary substantially during the monitoring period. These include skin, fat, muscles, bones, and the like.

[0037] The reflected lights measured by the photodetectors (11 p) from the sources of light emission (11 L) described supra can be processed for generating a photoplethysmogram (PPG). A PPG can be used for determining a cardiac rhythm (HR) and oxygen saturation (Sp02). In the present invention, the PPG is also used for determining the breathing rhythm (BR) of the patient. Positioning the reflection optical sensors on the thenar eminence yields PPG-results which correlate considerably better with reference values than positioning the reflection optical sensors elsewhere, such as on the wrist, the foot, the ear lobe or the like. In the present tests, a portable PPG pulse oximeter working in transmission of the type Nellcor PM10N (= PM10N) was used to determine the reference values of Sp02 and HR. The PM10N is currently used in many hospitals to monitor Sp02 and HR of patients and is considered as reliable and accurate so that it can safely be used as reference measuring method. The reference values for determining Sp02 and the cardiac rhythm (HR) are obtained with state-of-the-art PPG measured in transmission at a tip of a finger, foot, ear lobe, etc. Figure 4 plots the relative difference (APPG-R) between the PPG signal measured with optical sensors according to the present invention compared with the foregoing state-of-the-art reference oximeter PN10N. The reflection optical sensors were positioned on the wrist (W), represented on the left-hand side, and on the thenar region (TR) according to the present invention, represented on the right-hand side. The white columns represent the Sp02 values and the shaded columns the HR values. Both sets of values are compared with results obtained with the transmission sensors of the PM10N oximeter, clipped at a finger of adults. It can be seen that deviations of 18.6% and 6.2% compared with the state-of-the-art PM10N-reference device are obtained when applying the reflection optical sensors on the wrist (W), whilst excellent correlation with the state-of-the-art PM10N-reference device are obtained with reflection optical sensors located on the thenar region (TR), with deviations of less than 1%. It is therefore important to position the optical sensors on the thenar region of the hand of a patient.

[0038] The hand sensors can also comprise additional sensors. For example, they can comprise a skin temperature sensor (11st) for monitoring a skin surface temperature of the patient and located in the inner surface (12i) of the flexible support (12). It can comprise an outer temperature sensor (11 ot) for measuring the temperature surrounding the patient. Such outer temperature sensor (11 ot) is useful for monitoring the temperature of the close environment surrounding the hand of the patient, which can be, e.g., over or under a blanket or exposed to heat generated by the electronics of the hand monitoring unit. This information is important with respect with the skin temperature sensor, in that a higher skin temperature can be an indicator of fever unless the outer temperature is high too.

[0039] The hand sensors can also comprise an accelerometer (11a) for monitoring movements of a hand of the patient. The accelerometer can be provided either on the inner or outer surface (12i, 12o) of the flexible support (12). An accelerometer (11a) measures proper acceleration, which is the acceleration it experiences relative to freefall and is the acceleration felt by people and objects. The proper acceleration is popularly denoted g-force, in comparison with standard gravity. An accelerometer at rest relative to the Earth's surface indicates approximately 1 g upwards, because the Earth's surface exerts a normal force upwards relative to the local inertial frame (the frame of a freely falling object near the surface). To obtain the acceleration due to motion with respect to the Earth, this "gravity offset" must be subtracted and corrections made for effects caused by the Earth's rotation relative to the inertial frame. The accelerometer suitable for the present invention is configured for measuring proper accelerations along the three axes defining a space. Modern accelerometers are often small micro electro-mechanical systems (MEMS) and comprise a cantilever beam with a proof mass. An accelerometer is advantageous, because the reflected light measured by the photosensors is strongly dependent on the positions of the source of light emission and of the photosensors relative to the surface of the skin. These positions are likely to be altered by movements of the hand, more so depending on the briskness of the movements. An accelerometer serves to identify and quantify such movements. An algorithm can be used to correct signals measured by the photosensors during such movements, or even to ignore such signals if the movements are particularly brisk.

[0040] The flexible support (12) can also support a hand communication unit (12c) for transferring data measured by the hand sensors to a processing unit (40) or to a data storage unit (30). Alternatively, or concomitantly, the flexible support can also support a data storage unit (30) to store the data measured during a monitoring session (e.g., during a night sleep). In this case, a communication unit (12c) is not essential, as the data can be transferred at a later stage from the data storage unit to a processing unit via a cable. Wireless communication remains, however, a preferred option, regardless of whether data transfer occurs during a monitoring session or after the monitoring session is over. Bluetooth is a preferred communication system, but other communications systems can be envisaged, including WiFi, radio frequency (RF), or optical communication.

[0041] the hand-monitoring unit (10) can comprises a processing unit (40) or a first processing unit element (401). The processing unit (40) or first processing unit element can comprise,

• an analog front end (= AFE) (13) recording and managing parameters of light beams emitted by the one or more light emitting sources (11 L) and received by the one or more photodetectors (11 p), and

• the wireless communication device (12c) for communicating with the data storage unit and preferably with the external monitoring unit.

[0042] A battery (12b), preferably a rechargeable battery, can also be supported by the flexible support for supplying the energy required for actuating the various sensors, communication unit, processing unit (element) (40, 401), and AFE.

[0043] Figures 3(a) and 3(b) show an example of hand monitoring unit (10). Figure 3(a) shows the inner surface (3i) which contacts the skin of the hand when worn for monitoring vital signs, and Figure 3(b) shows the outer surface (12o) facing the environment surrounding the patient when in use. The components illustrated with solid lines face the corresponding inner or outer surfaces (12i, 12o) of Figures 3(a) and 3(b), respectively, and the ones with dashed lines face the other of the inner and outer surface illustrated in Figures 3(a) and 3(b), respectively. Most important are the optical sensors (11 L, 11 p) located such as to face the thenar eminence of the hand of a patient. Since the optical sensors are configured to function in reflection mode, they are all located side-by-side on the same inner surface (12i) of the flexible support. A wireless hand communication unit (12c) is also illustrated, which can be located at the outer surface (12o). Similarly, a sensor for measuring ambient temperature can be positioned at the outer surface (12o- of the flexible support. A battery (12b) can also be provided to power the hand sensors. For comfort of the patient, it preferably protrudes out of the outer surface (12o) rather than out of the inner surface (12i). Finally, fastening means (12f) are provided as discussed supra. The fastening means must be configured for firmly coupling the optical sensors to the thenar eminence when worn properly by a patient.

EXTERNAL MONITORING UNIT (20)

[0044] The external monitoring unit (20) is separate from the hand-monitoring device and comprises external sensors for monitoring external data. The external sensors include at least,

• a temperature sensor (211) for monitoring the temperature of an atmosphere surrounding the external monitoring unit,

• a relative humidity (RH) sensor (21 rh) for monitoring a relative humidity (RH) of the atmosphere surrounding the external monitoring unit.

[0045] In use, the external monitoring unit (20) must be positioned in the same room as the patient (infant) being monitored, possibly at a relative proximity from the patient, preferably within a radius of not more than 3 m from the patient, preferably not more than 2 m, more preferably of not more than 1 m.

[0046] The external monitoring unit (20) can also comprise additional external sensors, such as a quality sensor (21 q) for monitoring the quality of air and configured for measuring in the atmosphere surrounding the quality sensor one or more of a concentration in fine and/or ultra-fine particulate and/or a concentration of selected gases. The quality sensor could alternatively be a hand-sensor instead, located in the hand-monitoring unit (10). Depending on the size of such quality sensor, it is preferably an external sensor to reduce the size and weight of the hand-monitoring unit (10).

[0047] The external monitoring unit can also host the processing unit (40) or a second processing unit element (402) in wireless communication with a first processing unit element (401) located in the hand-monitoring unit (10). Locating the whole of the processing unit (40) or a second processing unit element (402) in the external monitoring unit (20) is advantageous in that there are not the same constraints of space, volume, and weight as in the hand-monitoring unit (10). Furthermore, the external monitoring unit (20) normally stands still in its position and is less likely to be shaken as the hand-monitoring unit (10). This is especially true with children and infants, which are most likely to move their hands.

[0048] The external monitoring unit can also host a data storage unit (30), which can be in communication with the processing unit (40) for storing consolidated data and the external data. Locating the data storage unit (30) in the external monitoring unit (20) is advantageous for the same reasons as discussed with respect to the processing unit (40) or the second processing unit element (402). Additionally, being located adjacent to both processing unit and external sensors makes transfer of data easier between these three components (processor, external sensors, and data storage unit), and can be performed via cables or optical fibres, as well as wireless. [0049] The external sensors of the external monitoring unit (20) can be very helpful in finding a correlation between a pathological pattern measured by the hand sensors and the direct environment surrounding the patient. It is preferred to reduce or even eliminate a pathological state by optimizing the humidity, temperature, and preferably air quality of the environment where the patient lives, rather than curing it with medicine whilst maintaining sub-optimal environmental conditions.

PROCESSING UNIT (40)

[0050] The processing unit (40) is configured for processing data measured by the hand sensors, including the optical data, and for generating a photoplethysmogram (PPG). From the PPG, the processing unit is configured for determining consolidated data including.

• a cardiac rhythm of the patient, and

• a breathing rhythm of the patient, and,

• an oxygen saturation in blood (= Sp02) of the patient, and for

The processing unit is also configured for correlating the consolidated data with the external data measured by the external sensors located in the external monitoring unit (20). This provides a powerful tool for possibly removing the causes, or at least the conditions responsible for or enhancing a pathological condition.

[0051] The processing unit (40) can be entirely located in the external monitoring unit (20) or in a separate unit which could be a server or the cloud. It should comprise wireless communication means with the hand communication unit (12c) of the hand-monitoring unit (10) for transferring data measured by the hand-sensors, including the optical data. This solution is interesting in that there are less constraints on the size of the processing unit, which could be substantial depending on the calculation power required for running the algorithms for determining the consolidated data.

[0052] Alternatively, the processing unit (40) can be entirely located in the hand monitoring unit (10). This has the advantage of a more compact system. For ergonomic reasons, however, the dimensions of the processing unit should be reduced to ensure comfort of the patient, in particular in case of infants, with their small hands.

[0053] In yet an alternative embodiment, the processing unit can comprise a first processing unit element (401) and a second processing unit element (402), wherein the first processing unit element (401) is located in the hand-monitoring unit (10) and, as discussed supra, is provided with wireless communication means with the second processing unit element (402). The second processing unit element (402) can be located in the external monitoring unit (20) or in a separate unit which could be a server or the cloud. [0054] In the embodiment wherein the hand-monitoring unit (10) comprises an accelerometer (11a), the processing unit (40) is preferably configured for correcting artefacts in the data measured by the optical sensors due to movements of the hand as measured by the accelerometer (11a). Correcting the artefacts can include ignoring the data measured during a period of active movements.

[0055] The processing unit is configured for comparing and correlating the consolidated data determined from the optical data and from data measured by any other hand-sensor, including e.g., a skin temperature sensor, with the external data, including temperature, relative humidity and, preferably, air quality of the environment surrounding the patient. For example, Figure 5(a) illustrates schematically external data, including temperature (T) and relative humidity (RH) of a room as a function of time. Figure 5(b) illustrates schematically breathing rhythm (BR) and cardiac rhythm (HR) of a patient located in said room. Figure 5(c) shows an example of correlation between BR as a function of RH (the data has not been measured and is congectural and only for illustrative purposes). The system may comprise a graphical interface (e.g., a screen) for plotting various parameters as a function of time or as a function of one another, with an indication of the correlation coefficients.

[0056] The processing unit (40) can also be configured for triggering alarms in case the values of one or more vital signs measured by the hand-sensors falls out of predetermined boundaries. For example, an acoustic alarm and/or optical or vibrating alarm can be triggered in a smartphone of a third person, for example a nurse or a parent of an infant being monitored in a separate bedroom. The third person can then check on the patient being monitored. Alternatively, the alarm can wake up the patient being monitored to resume breathing after an apnea. For example, a device supported in the flexible support can vibrate against the hand of the patient. An acoustic or optical alarm can be triggered at the external monitoring unit (20), to wake up the patient.

[0057] For its functioning, the processing unit (40) runs one or more algorithms to establish the consolidated data. In a preferred embodiment, the processor also uses artificial intelligence to learn and identify with increasing accuracy patterns of the consolidated data thus established which are representative of a pathology. The accuracy and fineness of the machine learning is enhanced with an increasing size of consolidated data measured over a large number of patients and over extended monitoring periods, on which the processing unit can base its learning.

DATA STORAGE UNIT (30)

[0058] As described supra, the processing unit can generate the consolidated data directly as the optical data are being transferred to the processing unit. This is essential in case the monitoring system is to trigger an alarm upon deviation of any vital sign from predefined boundaries. The monitoring system of the present invention can also comprise a data storage unit (30), wherein consolidated data, and external data can be stored. The data storage unit is in communication with the processing unit,

• for transferring from the processing unit to the data storage unit the consolidated data generated by the processing unit, and

• for the processing unit to retrieve consolidated data and external data to establish a case history and correlations between data. This operation needs not be carried out in real-time, during monitoring of a patient and can be carried out any time.

[0059] The data storage unit can be located at different places. The data storage unit (30) is preferably located in the external monitoring unit. Alternatively, it can be located in a separate unit which is separate from both external monitoring unit (20) and hand monitoring unit (10) and which could be a server or the cloud. Finally, the data storage unit can be located in the hand-monitoring unit.

[0060] Figure 2(a) shows an external monitoring unit (20) comprising external sensors, and an external communication unit (20c) for communicating with the processing unit (40), with the data storage unit (30), and preferably with the hand-monitoring unit (10). Figure 2(b) shows a processing unit (40) or a second processing unit element (402) separate from all other elements of the kit-of-parts. Finally, Figure 2(c) shows a data storage unit (30) separate from all other elements of the kit-of-parts. In a preferred embodiment, the external monitoring unit (20) houses all the units of the kit-of-part except the hand-monitoring unit. The external sensors and data storage unit can be coupled to the processing unit (40) by means of wires or optical fibres, but of course can also be coupled thereto wireless. With this embodiment, the kit-of-parts comprises two separate components only, namely the hand monitoring unit (10) and the external monitoring unit (20) housing all other external sensors and units (30, 40). To summarize, beside the temperature sensor (211) and the relative humidity sensor (21 rh), the external monitoring unit (20) can comprise one or more, or all of the processing unit (40), the data storage unit (30), and any additional external sensor.

DETERMINATION OF THE CONSOLIDATED DATA

[0061] The processing unit is configured for generating a photoplethysmogram (PPG) from the optical data measured by the optical sensors. A PPG is obtained by illuminating the skin with a light beam from a source of light emission (11 L) such as a LED, and then measuring the amount of light reflected to a photodetector (11 p). The PPG detects the change in volume caused by the pressure pulses as each cardiac cycle appears as a peak. The PPG is then used to determine consolidated data including a cardiac rhythm of the patient (HR), a breathing rhythm of the patient (BR), and an oxygen saturation in blood (Sp02) of the patient.

OXYGEN SATURATION IN BLOOD (SP02)

[0062] Oxygen is transported in blood by haemoglobin and oxygen saturation (Sp02) can be defined as,

Sp02 = HbO / (HbO + Hb) 100% wherein HbO is oxygenated haemoglobin and Hb is non-oxygenated haemoglobin.

[0063] Oxygenated haemoglobin (HbO) absorbs light at different wavelengths than non- oxygenated haemoglobin (Hb). This phenomenon is used to determine oxygen saturation levels (Sp02) by generating a PPG with a red light (red) and an infrared light (IR). The red light preferably is comprised between 600 and 700 nm, typically 660 nm, and the IR light is preferably comprised between 700 and 1000 nm, typically 940 nm. The ratio of absorption (R) at the two wavelengths is used to determine the fraction of saturated haemoglobin, wherein

Sp02 = K R = K (ACred / DC red) / (ACIR / DCIR) wherein AC and DC are the pulsatile and constant components of the reflected light (as defined supra), and K is a constant which can be determined by calibration results. Pre-established correlation curves are also available to determine the value of Sp02 corresponding to a given value of R.

[0064] To simplify the calculations, Sp02 can be determined by applying the foregoing equation only to the maxima and minima of the PPG’s of each of the IR light and red light, thus considerably reducing the required number of calculations and the computing capacity thus required.

CARDIAC RHYTHM (HR)

[0065] Since the PPG can detect variations caused with each cardiac cycle the heart pumps blood to the periphery, there is a direct correlation between PPG and ECG, within a small deviation of less than 1% (cf. Figure 4, shaded column (TR)). Figure 6 shows a PPG with an electrocardiogram (ECG). It can be seen that there is a delay, D, between a peak of the ECG and a peak of the PPG, which is ascribed to the time required for a blood pressure wave to reach the location of the PPG measurement. Though the ECG and PPG peaks are offset by a delay, D, the inter-beat intervals (IBI) measured between two successive peaks are substantially equal for both ECG and PPG. The PPG is preferably measured in a wavelength range comprised between 495 and 600 nm or between 600 and 1000 nm. A wavelength range comprised between 495 and 600 nm is preferred because it yields better results in reflection mode than red or infrared light. [0066] The cardiac rhythm (HR) of the patient can thus be determined by measuring the number (n) of PPG-peaks comprised within a given time interval (At), such that HR = n / At [min]. The inter-beat interval (IBI) is determined by measuring time intervals separating two maxima or two minima of the PPG.

[0067] The variation with time of the IBI (d IBI / dt) of the patient can be calculated by the processing unit (40) by running a fast Fourrier transform (FFT) on the conditioned data representative of the cardiac rhythm of the patient.

BREATHING RHYTHM (BR)

[0068] processing unit (40) is configured for determining a cardiac related breathing rhythm of the patient from the variation (d IBI / dt) with time of the IBI determined as explained supra. [0069] The present invention therefore offers a compact and ergonomic (especially for infants) monitoring system which not only monitors vital signs including Sp02, cardiac rhythm (HR) and breathing rhythm (BR) but is also configured for correlating the evolution of the vital signs thus measured with environmental conditions surrounding the patient being monitored, including temperature, relative humidity, and optionally air quality. The monitoring system of the present invention allows both instant detection of a faulty vital sign, with immediate triggering of an alarm, and subsequent analysis of data over a longer period, as the consolidated data are stored in a storage unit. Thanks to the ergonomic design of the hand-monitoring unit, each monitoring session can last long hours, e.g., a whole night, with both adults and children, in particular infants of less than 1 year of age. This affords the collection of a number of vital signs and external data over long periods of time which can be used for determining statistical correlations between them. It is of course much more advantageous to prevent a disease by optimizing the environment of the patient, rather than giving medicine whilst maintaining the patient in nonoptimal environmental conditions.