Field of the Invention

[0001] The present disclosure is directed generally to methods and systems for detecting disconnect of a patient care device using electrical impedance measurements.

Background

[0002] Critical care patients on ventilation are always at risk of becoming disconnected from the ventilator. This disconnect can occur anywhere along the flow path, including at tube junctions, at the interface with the ventilator, and/or at the patient's face or mouth. As a result, ventilators typically include a mechanism to automatically and quickly detect a disconnection event and provide a reliable trigger for an alarm so that the disconnect can be remedied.

[0003] Traditionally, ventilators configured to detect a ventilator disconnect utilize algorithmic methods that evaluate measured flows, pressures return volumes, and/or timing and sequences of these events. But the accounting of gas flow does not always provide a reliable mechanism to detect disconnect. And the algorithms utilized by ventilators, depending on how they are biased, can result in false disconnect alarms or undetected disconnects. Another approach to detect disconnect is the use of one or more interlock switches between the tubing, fittings, and components such that if the patient circuit is disconnected, the electrical circuit is opened and an alarm is triggered. However, this approach has at least two drawbacks: (1) the concern that an electrical disconnect in the presence of an oxygen rich environment could cause fire, and (2) that an extubation (disconnect at the patient) would be undetected since the method does not include the patient as part of the electrical circuit. Indeed, extubation can be especially difficult to detect when the tube flow resistance is high and when leaks are expected, as in the case of neonatal patients.

Summary of the Invention

[0004] Accordingly, there is a need in the art for ventilator systems that automatically and reliably detect disconnect from the ventilator, including extubation disconnect events. [0005] The present disclosure is directed to inventive methods and systems for detecting disconnect from a ventilator using electrical impedance measurements. Various embodiments and implementations herein are directed to a ventilator system comprising a conductive breathing circuit connecting the breath delivery unit of the ventilator to the patient. A high frequency signal is fed into the conductive breathing circuit and a sensing electrical circuit detects a responding signal affected by the intact circuit which includes the patient. A disconnect event results in loss of or changes to the high frequency signal and triggers an alarm. According to an embodiment, the sensing electrical circuit can be automatically or manually adjusted to a predetermined threshold to provide effective detection while avoiding false alarms.

[0006] Generally, in one aspect, a method for detecting disconnect in a patient care system comprising a conductive circuit formed at least in part by tubing between a patient care device and a patient is provided. The method includes the steps of: (i) inputting, by a signal generation circuit of the patient care device, an excitation signal to the conductive circuit; (ii) detecting, by a monitoring circuit of the patient care device, a responding signal from the conductive circuit; (iii) comparing the detected responding signal to a predetermined threshold or impedance signature to determine whether a disconnect of the tubing exists; and (iv) generating, if a disconnect of the tubing exists, an alarm by an alarm circuit of the patient care device.

[0007] According to an embodiment, the method further includes the step of calibrating the patient care system by testing the conductive breathing circuit. According to an embodiment, the predetermined threshold or impedance signature is based at least in part on the calibrating step.

[0008] According to an embodiment, the excitation signal is a high frequency AC signal.

[0009] According to an embodiment, the monitoring circuit performs the detecting step continuously.

[0010] According to an embodiment, the alarm is one or more of an audible alarm, a visual alarm, a tactile alarm, and a text alarm.

[0011] According to an embodiment, the patient care device is a ventilator.

[0012] According to an embodiment, the tubing comprises a first conductive portion configured to communicate the excitation signal from the patient care device to the patient, and a second conductive portion configured to communicate the responding signal from the patient to the patient care device.

[0013] According to an embodiment, the tubing comprises composed alternating layers of a plastic material and electrically insulated layers of a conductive material.

[0014] According to an embodiment, the tubing is conductive and at least partially translucent.

[0015] Generally, in one aspect, a patient care device configured to detect disconnect in a conductive circuit between the patient care device and a patient is provided. The patient care device includes: a tubing connecting the patient care device to a patient, wherein at least a portion of the tubing is conductive to facilitate the conductive circuit; and a controller comprising: (i) a signal generation circuit configured to input an excitation signal to the conductive circuit; (ii) a monitoring circuit configured to detect a responding signal and compare the detected responding signal to a predetermined threshold or impedance signature to determine whether a disconnect of the tubing exists; and (iii) an alarm circuit configured to generate, if a disconnect of the tubing exists, an alarm.

[0016] Generally, in one aspect, a controller of a patient care device is provided. The controller includes: (i) a signal generation circuit configured to input an excitation signal to a conductive circuit formed at least in part by tubing between the patient care device and a patient; (ii) a monitoring circuit configured to detect a responding signal and compare the detected responding signal to a predetermined threshold or impedance signature to determine whether a disconnect of the tubing exists; and (iii) an alarm circuit configured to generate, if a disconnect of the tubing exists, an alarm.

[0017] As used herein for purposes of the present disclosure, the term "controller" is used generally to describe various apparatus relating to the operation of a ventilator apparatus, system, or method. A controller can be implemented in numerous ways (e.g., such as with dedicated hardware) to perform various functions discussed herein. A "processor" is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform various functions discussed herein. A controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).

[0018] In various implementations, a processor or controller may be associated with one or more storage media (generically referred to herein as "memory," e.g., volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM, floppy disks, compact disks, optical disks, magnetic tape, etc.). In some implementations, the storage media may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein. Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects of the present invention discussed herein. The terms "program" or "computer program" are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

[0019] The term "user interface" as used herein refers to an interface between a human user or operator and one or more devices that enables communication between the user and the device(s). Examples of user interfaces that may be employed in various implementations of the present disclosure include, but are not limited to, switches, potentiometers, buttons, dials, sliders, track balls, display screens, various types of graphical user interfaces (GUIs), touch screens, microphones and other types of sensors that may receive some form of human-generated stimulus and generate a signal in response thereto.

[0020] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0021] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. Brief Description of the Drawings

[0022] In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

[0023] FIG. 1 is a schematic representation of a patient care system, in accordance with an embodiment.

[0024] FIG. 2 is a schematic representation of a conductive breathing circuit of a patient care system, in accordance with an embodiment.

[0025] FIG. 3 is a schematic representation of a patient care system, in accordance with an embodiment.

[0026] FIG. 4 is a schematic representation of a conductive breathing circuit of a patient care system, in accordance with an embodiment.

[0027] FIG. 4 is a schematic representation of a conductive breathing circuit of a patient care system, in accordance with an embodiment

[0028] FIG. 6 is a flowchart of a method for detecting disconnect in a patient care system, in accordance with an embodiment.

[0029] FIG. 7 is a schematic representation of a conductive breathing circuit experiencing a disconnect, in accordance with an embodiment.

[0030] FIG. 8 is a schematic representation of a conductive breathing circuit experiencing a disconnect, in accordance with an embodiment.

Detailed Description of Embodiments

[0031] The present disclosure describes various embodiments of a ventilator system and method. More generally, Applicant has recognized and appreciated that it would be beneficial to provide a ventilation system that automatically and reliably detect disconnect from the ventilator. The ventilator system includes a conductive breathing circuit connecting the breath delivery unit of the ventilator to the patient. According to an embodiment, the impedance of the conductive circuit may be such that the circuit is more conductive at specific frequencies, and these frequencies can shift or change in amplitude depending on whether the circuit is fully intact and connected to the patient, or is otherwise being broken at any point in the connection (i.e, a disconnect). Thus, the electrical impedance of the circuit changes depending on whether the circuit patient connection is fully intact or is disconnected at one or more of a number of points of connection.

[0032] To produce a conductive breathing circuit that allows transmission of the high frequency excitation signal through the circuit and patient, the components of the circuit must be conductive at least over some range of bandwidth in which the excitation frequency or frequencies operate, and can include, for example, plastics doped with conductive material. The conductive material can be, for example, coated, layered, or completely homogeneous in construction. A sensing circuit monitors the patient circuit electrical response to the excitation signal, i.e., the response defined as a responding signal, and detects changes in the responding signal resulting from impedance changes (capacitive-inductive effects) caused by any part of the tubing coming apart or an extubation. The system can then compare the responding signal to a threshold or a frequency signature to determine whether an alarm should be triggered.

[0033] Referring to FIG. 1, in one embodiment, is a representation of an example ventilator system 100. Ventilator system 100 may be either an invasive or non-invasive ventilator system. In this embodiment, the system is a dual limb ventilator with an inspiratory limb 102 and an expiratory limb 104 connected at their distal ends to the ventilator 106 via an inhalation port 103 and an exhalation port 105. The proximal ends of inspiratory limb 102 and expiratory limb 104 optionally combine at a Y-piece that ends in an interface with patient 108, although many other embodiments are possible. The patient interface can be, for example, a face mask that covers all or a portion of the patient's face, mouth, and/or nose. There may be masks of many different sizes to accommodate patients or individuals of different sizes, and/or the mask may be adjustable. As another alternative, the patient interface may fit within or on, or otherwise interact with, a tracheostomy tube. According to another embodiment, the patient interface is an intubation tube for invasive ventilation. [0034] System 100 includes a controller 110, which can be a conventional microprocessor, an application specific integrated circuit (ASIC), a system on chip (SOC), and/or a field- programmable gate arrays (FPGA), among other types of controllers. A controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. The controller 110 can be coupled with or otherwise in communication with any needed memory, power supply, I/O devices, control circuitry, and/or other devices necessary for operation of the system according to the embodiments described or otherwise envisioned herein. For example, in various implementations, a processor or controller may be associated with one or more storage media 112. In some implementations, storage media 112 may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein. Storage media 112 may be fixed within controller 110 or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects of the present invention discussed herein. The terms "program" or "computer program" are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.

[0035] According to an embodiment, ventilator system 100 also includes a user interface (UI) 114. UI 114 includes graphical, textual and/or auditory information that the system presents to the user, such as a clinician, as well as the control sequences - such as keystrokes, computer mouse movements or selections, and/or touchscreen movements or selections, among other control sequences - that the user utilizes to control the system. In one embodiment, the UI 114 is a graphical user interface. For example UI 114 may include a display screen. The display screen may include, for example, a touchscreen enabling the user to change one or more settings of the ventilator system 100, as well as a graphical output that displays breathing and ventilation information to the user.

[0036] According to an embodiment, a conductive breathing circuit 200 is formed by and between the ventilator 106 and the patient 108, as shown in FIG. 2. Ventilator 106 comprises a signal generation circuit 116 configured to generate a high frequency AC excitation signal for input to the breathing circuit. The circuit can generate and introduce the signal at any point along the conductive path, but is most commonly situated to introduce the signal at or near the inhalation port 103. The high frequency AC excitation signal is input into conductive breathing circuit 200, and comprises frequency and amplitude sufficient to excite the conductive breathing circuit. The parameters of the excitation signal will depend on numerous factors, and could include, for example, the size of the patient circuit, the components of the patient circuit, the material(s) from which the patient circuit is composed, and many other factors. According to one embodiment, the parameters of the excitation signal may be determined or programmed during a configuration stage.

[0037] According to an embodiment, a conductive breathing circuit can be thought of as impedance having an equivalent circuit of lumped parameters comprising DC resistance, capacitance, and inductance. For example, if a patient circuit were to comprise an impedance characteristic that was primarily capacitive, it could be modeled with an approximate 10 picofarad (10 pF) capacitance when the patient circuit is complete, and approximately 5 pF when the path is broken.

[0038] When an excitation signal is input into conductive breathing circuit 200 as described or otherwise envisioned herein, the system will respond to that excitation with a responding signal. According to an embodiment, one formula for the magnitude of the electrical impedance |Z| of a primarily capacitive circuit is given by |Z| = l/(2*pi*f*C) where f is the excitation frequency in Hertz and C is the capacitance in Farads. Similarly, one formula for the magnitude of the resulting responding signal, defined as an electrical current |i| in amperes, would be |i| = |V| / |Z|, where |V| is the magnitude of the voltage of the exciting signal in volts. Accordingly, the resulting magnitude of the impedance of the circuit at 10 MHz excitation frequency would be 1591 ohms with circuit intact, and 3183 ohms with circuit opened. If an excitation voltage 10 MHz frequency and 3 Volts rms amplitude were applied to this impedance, the sensor circuit would detect approximately 1.9 milliamperes (mA) of current with the patient circuit intact, and 0.9 mA with the patient circuit open, or interrupted.

[0039] Accordingly, the responding signal is dependent upon both the parameters of the excitation signal and the configuration state of the conductive breathing circuit, including all of the conducting components. A monitoring circuit 118 monitors breathing circuit 200 for the responding signal, and can be configured to detect changes in the signal resulting from impedance changes (capacitive-inductive effects) caused by any part of the tubing coming apart or an extubation.

[0040] The conductive breathing circuit 200 is formed, for example, by components that are electrically conductive to a high frequency AC excitation or responding signal along their length between the inhalation port 103 to the patient 108 interface back to the exhalation port 105, and a current path that that flows through the patient 108, forming a multipath electrical circuit. The patient circuit portion of the electrical circuit includes the tubing and any intermediate plastic fittings or devices that provide the flow of gas from the inhalation port 103 to the exhalation port 105. The patient circuit portion of the electrical circuit also includes the patient connecting device such as the patient mask and the ET tube, as well as the patient to ground. As described or otherwise envisioned herein, the components of the conductive path, including the tubing and any intermediate plastic fittings, can be coated, impregnated, and/or otherwise provided with conductive material to enable conduction of the high frequency AC excitation and responding signal. According to an embodiment, one or more components of the conductive path are generally speaking electrically insulating to any DC current along the length of the conductive path between the attachment point on the ventilator and the attachment point on the patient, including any intermediate plastic fittings.

[0041] Although the conductive breathing circuit 200 in FIG. 2 is shown with the ventilator 106 connected to ground, the ventilator will not be connected to ground when running on battery power. In that scenario, for example, the ventilator 106 will have a capacitance (not shown in the figures) relative to itself and the ground, just as the patient 108 does.

[0042] According to an embodiment, the return circuit for an excitation signal can flow through these capacitances between one or more of the following circuit nodes, among others: (i) between the patient and ground through the capacitance formed by the patient's body area and proximity to the surrounding room or bedframe ground; (ii) between the ventilator and ground through either or both of a direct ground connection and the capacitance formed by the patient's body area and proximity to the surrounding room or bedframe ground; and (iii) between the ventilator and patient through the mutual capacitance formed by the respective surface areas of the patient and ventilator and the proximity between them.

[0043] Referring to FIG. 3, in one embodiment, is a representation of an example ventilator system 300. Ventilator system 300 may be either an invasive or non-invasive ventilator system. In this embodiment, the system is a single limb ventilator with a single tube 320 connected at the distal end to the ventilator 106 via a tube port 310 and connected at their proximal end to an interface with patient 108. The patient interface may be any interface, including a mask, a tracheostomy tube, an intubation tube, or any other interface. Similar to the ventilator system depicted in FIG. 1, the system can comprise a controller 110 with storage media or database 112, and a user interface 114, among many other possible components.

[0044] According to an embodiment of ventilator system 300, a conductive breathing circuit 400 is formed by and between the ventilator 106 and the patient 108, as shown in FIG. 4. The conductive breathing circuit 400 is formed, for example, by components that are electrically conductive to a high frequency AC excitation and responding signal along their length between the tube port 310 to the patient 108 interface back to the tube port 310, forming a circuit. As described or otherwise envisioned herein, the components of the conductive path, including the tubing and any intermediate plastic fittings, can be coated, impregnated, and/or otherwise provided with conductive material to enable conduction of the high frequency AC excitation and responding signal. According to an embodiment, one or more components of the conductive path are electrically insulating to any DC current along the length of the conductive path between the attachment point on the ventilator and the attachment point on the patient, including any intermediate plastic fittings.

[0045] According to an embodiment of system 300, the tube 320 may be configured to form multiple paths of the circuit. For example, one side or portion 330 of the tube 320 may be configured to communicate the high frequency excitation AC signal from the tube port 310 to the patient interface, and another side or portion 340 of the tube 320 may be configured to communicate the responding signal from the patient interface to the tube port 310, which is or comprises an electrical circuit node. The tube may be designed, for example, with a first conductive portion on one side of the tube, and a second conductive portion on the other side of the tube, where each of the conductive portions are electrically isolated from each other. Although this design may result in some coupling capacitance between the two conductive sides or portions of the tube 320, this coupling capacitance could be accounted for during calibration and/or design of the system.

[0046] According to another embodiment of ventilator system 300, a conductive breathing circuit 500 is formed by and between the ventilator 106 and the patient 108, as shown in FIG. 5. The tube 320 is configured to offer a single conductive path 510 between the signal generation circuit 116 of the ventilator and the patient 108. For example, the signal generation circuit 116 may communicate a high frequency voltage excitation signal into the tube 320 at the tube port 310 and the monitoring circuit 118 of the ventilator would be configured to communicate the responding high frequency current signal at an electrical circuit node, which can be, for example, tubing port 310 or a component of the tubing port.

[0047] In this manner, the combination of signal generation circuit 116 and monitoring circuit 118 function as an impedance analyzer, which detects the high frequency electrical impedance Z of an electrical path that is affected by the physical configuration of the breathing circuit. The electrical impedance Z can be viewed as a complex frequency dependent parameter which embodies the relationship (such as phase, amplitude) between an applied excitation voltage from signal generation circuit 116 applied to the electrical circuit node 310 and the resulting detected current flow, detected by monitoring circuit 118, into the circuit node 310.

[0048] Conversely, the parameter Z may also be viewed as a complex frequency dependent parameter which embodies the relationship (such as phase, amplitude) between an applied excitation current applied to the circuit of interest and the resulting detected voltage at the circuit node 310 as observed at the signal junction node of an antenna. This view of parameter Z is intended to show that no explicit return path is required as a closed electrically conductive circuit in order for the excitation signal to result in a useable responding signal. For example, according to an embodiment, the means of detecting a circuit disconnect can in this manner be viewed as the following process: 1) the combination of excitation and responding signal provides a calculation of impedance parameter Z the values of which depend on the physical geometry of the electrical circuit comprised of electrical circuit path elements 310, 320 and 108; 2) any change or interruption of the connection between of electrical circuit path elements 310, 320 and 108 result in a corresponding change in the parameter Z; and 3) the change in this parameter Z can be detected by observing the change in the relationship between excitation and responding signals.

[0049] According to another embodiment, the functions of signal generation circuit 116 and monitoring circuit 118 can be combined. For example, an active high frequency electronic circuit may be connected to electrical circuit node 310. This active electronic circuit may be an electronic oscillator or similarly acting circuit such as that used in an electronic musical instrument called a "theremin," which generates an oscillatory signal with characteristic oscillation frequency, phase and amplitude, all of which depend on the complex impedance characteristics Z. A detectable change in the characteristic oscillation frequency, phase or amplitude result in a change in the complex impedance characteristics Z in response to a change in the physical configuration of the patient circuit, which can be used to detect any change or interruption of the connection between of electrical circuit path elements 310, 320 and 108, and therefore detect a patient pneumatic circuit interruption.

[0050] According to an embodiment of either system 100, 300, or any other system described or otherwise envisioned herein, any portion of the conductive breathing circuit between the ventilator and the patient may be composed of alternating layers of plastic laminated with offset but electrically insulated layers of conductive material, providing a capacitive electrical path between the ventilator 106 and the patient 108. The capacitive electrical path provides the desired frequency/impedance characteristic, which can pass sufficient signal for detection. The capacitive electrical path also maintains sufficiently low leakage current at the typical 60 Hz mains supply voltage that two means of patient protection are provided in satisfaction of safety regulatory requirements.

[0051] According to another embodiment of system 100, 300, or any other system described or otherwise envisioned herein, the conductive breathing circuit between the ventilator and the patient does not require absolute continuity, since the system can operate using impedance signature. For example, instead of having a single or dual limb circuit that provides two separate conductors between the patient and ventilator, the circuit can comprise a single conductor, as shown in FIG. 5. In this embodiment, the system analyzes changes in the structure or signature of the impedance as described above. Notably, the ventilator in FIG. 5 may be connected directly to ground, or may be capacitively coupled to ground.

[0052] According to another embodiment, one or more components of the conductive breathing circuit may be configured to be both conductive and translucent or transparent. For example, the tubing between the ventilator and the patient may be configured to be translucent or transparent for safety and/or to satisfy regulatory requirements. The tubing between the ventilator and the patient may also be configured to be conductive.

[0053] According to another embodiment, the ventilator systems could be configured to combine an inductive with a capacitive path by distributing a capacitive and inductive deposition or lamination of conductive material within the tube plastic material. This would also provide two means of patient protection in satisfaction of safety regulatory requirements, while advantageously providing very high frequency selectivity to an appropriate excitation and sensing frequency for means of detecting pneumatic circuit continuity.

[0054] According to an embodiment ventilator 106 comprises a signal generation circuit 116 configured to generate a high frequency AC signal for input to the breathing circuit. Signal generation circuit 116 is any circuit or component configured to generate a high frequency AC signal. The circuit can generate and introduce the signal at any point along the conductive path, but is most commonly situated to introduce the signal at or near the inhalation port 103.

[0055] According to an embodiment, the impedance of the tubing and any plastic fittings along the conductive path decreases with frequency such that a high potential test voltage applied between the ventilator 106 and the patient 108 of a frequency of 100 cycles/second or less will meet the criteria for leakage current for means of patient protection. Further, the impedance of the tube at a chosen test frequency will be such that a test voltage signal applied by the ventilator between the signal input portion of the ventilator and the ground potential of the ventilator enclosure or surrounding room will result in a detectable responding signal current. This detectable current will vary with electrical continuity and contact all along the pneumatic circuit and all its fittings. This serves as an indication of adequate pneumatic coupling between the patient 108 and the ventilator 106. Furthermore, the detectable current will vary with the electrical impedance due to direct contact with the patient attachment and the patient body capacitive coupling 122 between the patient and surrounding room ground.

[0056] According to an embodiment, ventilator 106 comprises a signal monitoring circuit 118 configured to sense and monitor the detectable current from the high frequency signal input into the breathing circuit. In a dual limb configuration as shown in FIG. 1, the signal monitoring circuit 118 and/or a sensor for the signal monitoring circuit 118 can be located in, on, or in communication with the ventilator exhalation port 105. In a single limb configuration as shown in FIG. 3, the signal monitoring circuit 118 and/or a sensor for the signal monitoring circuit 118 can be located in, on, or in communication with the tubing port 310. Alternatively, the signal monitoring circuit 118 and/or a sensor for the signal monitoring circuit 118 could be located anywhere that the detectable current from the responding signal can be detected. According to an embodiment, the signal monitoring circuit 118 could be used by itself or together with pressure and flow measurements and pneumatic circuit models to provide consensus measures, further reliability, and accurate diagnosis of disconnect.

[0057] According to an embodiment, ventilator 106 comprises an alarm circuit 120 configured to raise an alarm if a disconnect is detected by the system. This alarm alerts the caregiver of any loss of connectivity of pneumatic circuit between the tubing connect point and the patient lungs. The alarm circuit 120 is in communication with the signal monitoring circuit 118, which is configured to sense and monitor the detectable current from the high frequency signal input into the breathing circuit. The signal monitoring circuit 118 and/or alarm circuit 120 can, for example, compare the responding signal return to a predetermined threshold, which may be preprogrammed or may be obtained during a calibration step. If the responding signal return falls below the predetermined threshold, indicating a disconnect somewhere between the ventilator and patient, then the alarm circuit 120 will trigger an alarm. According to an embodiment, the threshold may be stored in database or memory 112.

[0058] The alarm triggered by alarm circuit 120 can be any alarm sufficient to provide a notification to a system or individual that there is a disconnect situation. For example, the alarm may be an audible alarm, a visual alarm, a tactile alarm, a textual alarm, or any other alarm. As examples, the alarm may be a sound and/or flashing light emitted from the ventilator. As another example, the alarm may be a message transmitted by wired and/or wireless communication away from the ventilator, such as a central station. The alarm may be a text message sent to a device of a caregiver. Many other alarms are possible.

[0059] According to an embodiment, the system could coordinate two signal monitoring circuits 118 and two alarm circuits 120 in a dual limb ventilator system in order to prevent interference between the inhalation and exhalation sensed currents. For example, the circuits could utilize different sense frequencies or time division multiplexed test signals, taking turns, in order to differentiate between the signals and provide additional information about the disconnect situation. Furthermore, according to an embodiment, the system could comprise modulated carriers for excitation voltages and coding means to prevent interference between adjacent ventilators.

[0060] Referring to FIG. 6, in one embodiment, is a flowchart of a method 600 for detecting disconnect in a patient care system. At step 610, a patient care system is provided. The patient care system is configured with a conductive breathing circuit formed by and between the ventilator and the patient. For example, the patient care system may be ventilator system 100, ventilator system 300, and/or any of the ventilator or patient care systems described or otherwise envisioned herein. For a ventilator system, for example, the ventilator can include any of the components and circuits described herein, including but not limited to a signal generation circuit 116, a monitoring circuit 118, and an alarm circuit 120. Other embodiments are also possible.

[0061] At optional step 615 of the method, the system is calibrated. This calibration may be performed at any point of operation and any number of times after the patient is connected and stabilized. According to an embodiment, the calibration is performed prior to every use, or with every new patient. The calibration may be performed by transmitting a test signal when the system is fully connected and transmitting a test signal when the system is intentionally disconnected by a caregiver or prior to connecting the system to the patient. The responding signal detected during the connect and/or disconnect phase could then be utilized to create a threshold for the alarm circuit as described herein. Many other forms of calibration are possible.

[0062] At step 620 of the method, a high frequency AC excitation signal is introduced into the conductive breathing circuit by the signal generation circuit 116. The high frequency AC signal may be constant or may vary in frequency. According to another embodiment, the signal may be broadband noise. The high frequency AC signal may be any of the signals described or otherwise envisioned herein, and can be configured to ensure patient protection in satisfaction of safety regulatory requirements. The high frequency AC signal can be introduced at one of the tube ports of the patient care device or system, although many other embodiments and points of introduction are possible.

[0063] At step 630 of the method, the monitoring circuit 118 detects the responding high frequency AC signal from the conductive breathing circuit. The monitoring circuit can be configured to constantly monitor the responding signal return, or can periodically monitor the signal. The monitoring circuit 118 can comprise a sensor, for example, which may be located at one of the tube ports of the patient care device or system, although many other embodiments and locations are possible.

[0064] At step 640 of the method, the system compares the responding signal to a predetermined threshold, which may be pre-programmed, generated during calibration, or received from and/or generated by other sources. This step may be performed by monitoring circuit 118 and/or alarm circuit 120. Based on the comparison to the threshold, the system will determine whether a disconnect is likely to exist. According to an embodiment, the system may also use the information to determine what type of disconnect exists.

[0065] Referring to FIG. 7, for example, is a conductive breathing circuit 700 formed by and between the patient care device 106 and the patient 108. In this example, there is a disconnect in conductive breathing circuit 700, at the patient. For example, the patient may have been extubated or may have removed the mask, among other disconnect possibilities. Although there is a disconnect, the high frequency AC signal may still be transmitted by the tubing, but it will no longer be affected by the patient's coupling capacitance, and the characteristics of the signal will be significantly different either in terms of frequency, phase or magnitude. The monitoring circuit 118 can detect this difference, which will indicate that the system is in a disconnect state. Due to the specific change in the signal, and because there was not complete loss of the signal, the system may determine that the disconnect is likely at the patient. [0066] In other disconnect scenarios, such as a tubing disconnect as shown in FIG. 8, the conductive breathing circuit 800 is broken, and the high frequency AC signal will not be transmitted by the tubing. The monitoring circuit 118 can detect the total loss of signal, which may indicate that the system is experiencing a tubing disconnect versus a patient disconnect.

[0067] At step 650 of the method, the alarm circuit 120 generates a disconnect alarm in response to a determination that a disconnect exists or is likely to exist. The alarm may be an audible alarm, a visual alarm, a tactile alarm, a textual alarm, or any other alarm. As an example, the alarm may be a message transmitted by wired and/or wireless communication away from the ventilator, such as a central station. The alarm may be a text message sent to a device of a caregiver. Many other alarms are possible.

[0068] According to an embodiment, the alarm is configured differently depending on the predicted or detected type of disconnect. For example, an alarm of a first sound may be generated and emitted for a first type of disconnect, while an alarm of a second sound may be generated and emitted for a second type of disconnect. Alternatively, a message alarm may contain a description or listing of the possible type(s) of disconnect.

[0069] Although the disclosure is described in conjunction with critical care ventilation where a disconnect could be seriously harmful or fatal to the patient, the systems and methods described or otherwise envisioned herein can be utilized for any setting where tubing connects a device to a patient, including but not limited to venous and arterial catheterization. For example, many homecare and sleep products connect a device to a patient, including tubing used to deliver medications to a patient via IV tubing, or more generally any application requiring the conveyance of either liquid or gas between one point and another, and that requires a means of detecting disconnect. Although disconnect may not be immediately harmful or fatal to a patient in many of these other applications, it can lessen the efficacy of treatment, delay treatment, or have other undesirable side-effects, thereby further highlighting the value of the systems described or otherwise envisioned herein.

[0070] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. [0071] The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one."

[0072] The phrase "and/or," as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and/or" should be construed in the same fashion, i.e., "one or more" of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the "and/or" clause, whether related or unrelated to those elements specifically identified.

[0073] As used herein in the specification and in the claims, "or" should be understood to have the same meaning as "and/or" as defined above. For example, when separating items in a list, "or" or "and/or" shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as "only one of or "exactly one of," or, when used in the claims, "consisting of," will refer to the inclusion of exactly one element of a number or list of elements. In general, the term "or" as used herein shall only be interpreted as indicating exclusive alternatives (i.e. "one or the other but not both") when preceded by terms of exclusivity, such as "either," "one of," "only one of," or "exactly one of."

[0074] As used herein in the specification and in the claims, the phrase "at least one," in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified.

[0075] It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. [0076] In the claims, as well as in the specification above, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "composed of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of and "consisting essentially of shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0077] While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.