Patent Description:
In order to make respiratory clinical decisions for a patient, a clinician needs as much information as possible about the patient's current and historical medical status. For example, there are several methods available for measuring breathing, but many do so indirectly by looking at changes to the patient's heart rate, blood, or muscle movement. Conventionally, breath sensing measurements are available for patients receiving respiratory therapies that use a sealed mask, such a CPAP, BiPAP, mechanical ventilator, or other therapies. With a mask, accurate sensing is straightforward, because the mask seal delimits a closed system. But with high flow and high velocity nasal cannula systems, these measurements become more challenging, as the patient's nares are open to the environment. The flow rate from the cannula may exceed the patient's breathing flow rate and obscure the signal of pressure or temperature. Due to the open nature of the cannula interface, the pressure changes are very small, for example, on the order of <NUM> to <NUM> Pa, which are difficult to detect. Additionally, issues related to patient comfort are more problematic in the open nasal cannula systems and in systems which provide humidified breathing gas.

In <CIT>, a nasal cannula ventilation system is described for treating lung disease or for exercise conditioning, incorporating a Venturi system. The ventilation cannula comprises unique positioning features to positively locate a gas delivery nozzle in an optimal location to optimize Venturi performance, patient comfort and fitment to the patient. <CIT> describes a system for delivering oxygen on demand to a user, comprising a pressure transducer for sensing pressures during the breathing cycle of a user and for creating an electrical signal proportional to said sensed pressures, an electronic amplifier for amplifying the signal to at least <NUM>,<NUM> times the original signal strength, electronic filters for regulating the amplitude of the signal and for correcting the point of the signal where expiration stops and inspiration begins to correspond to zero respiratory pressure, an on/off switching circuit and cooperating valve drive circuit for switching to an on condition in response to a preselected first pressure and to an off condition in response to a preselected second pressure, and a valve driven by the valve drive circuit means for directing oxygen from an oxygen source to a user. <CIT> describes a nasal cannula, for supplying a respiratory gas to a patient, a respiratory therapy system incorporating the nasal cannula, a method of treating a patient with sleep disorder by using the nasal cannula, a diagnostic tool for measuring nasal cavity pressure of a patient, and a method of using the diagnostic tool for measuring nasal cavity pressure of a patient. <CIT> describes a method, system and apparatus for determining respiratory volume flow rate of a subject and associated parameters such as tidal volume, minute volume, and respiratory rate. The method for determining respiratory volume flow rate of a subject can include selecting an airway cavity of the subject, measuring delivery volume flow rate of respiratory gas delivered to the airway cavity, measuring pressure within the airway cavity and calculating a respiratory volume flow rate of the subject using the measured delivery volume flow rate of respiratory gas delivered to the airway cavity and the measured pressure within the airway cavity. <CIT> describes a high flow therapy system including a microprocessor, a heating element a non-sealing respiratory interface and a sensor. The sensor is disposed in electrical communication with the microprocessor and is configured to measure pressure in an upper airway of the patient. <CIT> describes a device, system and method for providing high flow therapy interfaces for use in the treatment of respiratory conditions and in assisted respirations. A nasal cannula for delivery of respiratory gases can include at least one nasal insert and at least one flange coupled to the at least one nasal insert where the at least one flange is configured to partially impede the egress of respiratory gasses delivered to an upper airway of a patient is provided. An oral interface for delivery of high flow therapy to the upper airway of a patient can include a gas diffuser that includes a terminus housing having a plurality of holes to allow the delivery of respiratory gases. <CIT> describes an apparatus that conserves oxygen delivered from a supply to a patient through a cannula by providing oxygen delivery selectively in accordance with the physiological requirements and current breathing pattern of the patient. An oxygen conserving unit includes a controller that operates responsive to timed relationships among pressure signals determined by a fuzzy logic program to deliver oxygen to the patient by opening a valve when a sensed pressure in the patient's nasal passage reaches a threshold level and when the controller determines that the reaching of the threshold is indicative of an inhalation cycle. <CIT> describes a method of forming a cannula from a cannula mandrel assembly comprising a pair of mouthpiece/nasal mandrels and a mating facepiece mandrel.

Devices and methods are provided herein for sensing and monitoring of patient breathing during high flow respiratory therapy. According to one aspect, there is provided a breath sensing device according to claim <NUM>. This aspect may also provide an apparatus according to claim <NUM>. The device includes a nasal cannula having a sensing lumen and pressure sensor for breath sensing that can provide an accurate and clear signal while high flow rates of breathing gas are delivered from the nasal cannula, for example, at a high exit velocity. A length of tubing may be used to consistently convey the pressure changes to the pressure sensor from near the nares. The pressure sensor may be located remotely, and the tubing may be used to convey the pressure change between the nares and the remotely positioned sensor. From the pressure measurements, certain characteristics of the patient, such as breathing pattern or efficiency of breathing, can be determined and used to track the clinical status of the patient or to adjust the therapy.

Directly measuring air flow of patient breathing is preferable relative to conventional methods that indirectly assess or detect patient breathing via other physiological indicators. By locating the pressure sensor away from the nares of the patient, for example, at the end of a small-bore sensing lumen, pressure changes in the lumen that result from patient inspiration and expiration are reduced to lower frequencies that are more easily detected by the sensor, avoiding significant signal noise due to gas turbulence. Furthermore, condensation can be removed from the sensing lumen by applying a constant, pulsatile, or burst flow of purge gas. This can be beneficial in systems where the tubing is prone to occlusion by condensation, especially when the therapy is humidified. Capillary action tends to draw water into the tubing where it can mask the small pressure changes and damage the sensor.

The breath sensing apparatus can be integrated in a respiratory system with a breathing gas source or can be packaged as a separate device capable of adapting to a variety of systems. Information about a patient's breathing can be useful in several ways. A high flow or high velocity nasal cannula therapy device could make use of this data to report the information, adjust therapy, or ensure proper use of the device.

The nasal cannula for breath sensing of a patient being provided high flow respiratory therapy includes a cannula body having a first connector configured to receive a first flow of breathing gas and a second connector configured to receive a second flow of breathing gas; a first nasal prong configured to deliver the first flow of breathing gas to a nare of the patient; a second nasal prong configured to deliver the second flow of breathing gas to a nare of the patient; and a pressure sensor system positioned on the cannula, on or near one or more of the nasal prong exits such that, during patient inspiration and expiration, the pressure of gas flowing in and out of the nare can be detected. The nasal cannula is configured with a first sensing lumen with a first sensing tip positioned along the first nasal prong, such that gas flows entering and exiting the nares flow over the first sensing tip to create a pressure change within the first sensing lumen. A first pressure sensor is also provided in the nasal cannula, the sensor being configured to detect a first pressure in the first sensing lumen. The pressure sensor is positioned at a proximal end of the first sensing lumen opposite the first sensing tip. A cannula configured with such a pressure sensor system can provide the advantage of deriving information about a patient's breathing while functioning with high velocity or high flow nasal cannula therapy. The remote positioning of the pressure sensor and use of a sensing lumen with distal tip allows for detection of pressure changes without substantial turbulence, noise, or high frequency pressure fluctuations at the pressure sensor, thus overcoming obstacles resulting from the open nature of nasal cannula therapy.

In some implementations, multiple pressure sensor systems may be used. For example, the nasal cannula may further include a second sensing lumen having a second sensing tip positioned along the second nasal prong such that, during patient inspiration and expiration, gas flows over the second sensing tip to create a second pressure change within the second sensing lumen; and a second pressure sensor configured to detect a second pressure in the second sensing lumen and positioned at a proximal end of the second sensing lumen opposite the second sensing tip. In some implementations, the first sensing lumen includes a housing mounted on the cannula body, and a tube configured to enable fluid communication between the first sensing tip and the pressure sensor, wherein the tube is in fluid communication with the pressure sensor at the proximal end of the first sensing lumen, and wherein the housing is fluidically connected to the tubing. The tube may have a length between about <NUM> and about <NUM> and an internal diameter between about <NUM> and about <NUM>.

In some implementations, a control gas flows from a flow generator through at least a portion of the pressure sensing tube in a direction from the proximal end to the sensing tip. The control gas collides with patient breath at a boundary region adjacent to the first sensing tip. The control gas may be delivered continuously or intermittently as a bolus flow. In some implementations, the control gas has a flow rate between about <NUM>/min and about <NUM>/min. The flow generator may be one of a fan, a syringe pump, a blower, a compressor, a bellows, or a wall air source. In some implementations, the nasal cannula is configured with the control gas so as to purge condensation from one or more sensing lumens. In some implementations, a sensing lumen includes a tee joint positioned along the tube and configured to convey the control gas into the tube from the flow generator. In some implementations, control gas is provided for first and second sensing lumens. In some implementations, the nasal cannula further includes a temperature sensor configured to measure a breath temperature.

In some implementations, the detected pressure by the pressure sensing system indicates a difference between an internal pressure within the first sensing lumen and ambient pressure of the surrounding environment. The difference may be about <NUM> Pa to about <NUM> Pa. The difference may be at least about <NUM> Pa or at least about <NUM> Pa. In some implementations, the first pressure sensor is configured to output a pressure signal indicative of the detected first sensing lumen pressure. A second pressure sensor may be similarly configured.

In some implementations, the first sensing tip has an exit port that is angled relative to a longitudinal axis of the first sensing lumen. The exit port may include a tip face at an angle other than <NUM> degrees relative to the longitudinal axis of the sensing lumen. For example, the angle may be between about <NUM> degrees and about <NUM> degrees. In some implementations, the angle is about <NUM> degrees. In some implementations, the angle is about <NUM> degrees or about <NUM> degrees. In some implementations, the tip face has rounded, beveled, or chamfered edges. In some implementations, the sensing tip is positioned on an exterior surface of the first nasal prong. In some implementations, the sensing tip is positioned on a dorsal side of the exterior surface of the first nasal prong. In some implementations, the sensing tip is positioned proximally to a prong tip of the first nasal prong. In some implementations, the sensing tip is positioned on the nasal cannula such that the sensing tip resides within the nare of the patient while the cannula is in use. The sensing tip may have an internal diameter between about <NUM> and <NUM>. In some implementations, the first nasal prong has an internal diameter of about <NUM> to about <NUM>. For example, the ratio of sensing tip diameter to nasal prong diameter is between about <NUM> and about <NUM>.

The breath sensing device includes a controller configured to receive a pressure signal from the first pressure sensor indicative of the first sensing lumen pressure and convert the pressure signal into data. In addition to the advantages of the nasal cannula recited above, the breath sensing device is advantageous as an adaptable device that can provide breath sensing and monitoring capabilities to existing respiratory therapy systems.

In some implementations, the device is configured to couple to a respiratory therapy system. The controller may be configured to send instructions to the respiratory therapy system to change an operating parameter of the respiratory therapy system, or the controller may be configured to send the data to the respiratory therapy system for determining a change to an operating parameter of the respiratory therapy system. The respiratory therapy system is configured to provide the first flow of breathing gas to the nasal cannula.

In some implementations, the controller is configured to determine periods of patient inspiration and/or expiration based on the data from the first pressure sensor. The controller may be configured to determine and display at least one of patient expiratory/inspiratory ratio, a current breath rate, or a patient breathing pattern based on the data from the first pressure sensor.

The controller is configured to apply an algorithm to the data. The algorithm is configured to determine an average pressure in the data, determine maximum and minimum peaks in the data and/or filter the data, determine an average maximum peak over a period of time, determine an average minimum peak over a period of time, and determine a pressure threshold as a percentage of the average maximum peak. The algorithm is configured to identify a breath when the pressure crosses from below the average pressure to above the average pressure, then exceeds the average pressure by at least the pressure threshold, then reaches a maximum peak, then crosses from above the average pressure to below the average pressure, then reaches a minimum peak, and then crosses from below the average pressure to above the average pressure. In some implementations, the algorithm is configured to identify and exclude non-breathing periods from the data.

In some implementations, the nasal cannula further includes a second sensing lumen having a second sensing tip positioned along the second nasal prong such that, during patient inspiration and expiration, gas flows over the second sensing tip to create a second pressure change within the second sensing lumen. In some implementations, the nasal cannula further includes a second pressure sensor configured to detect a second pressure in the second sensing lumen and positioned at a proximal end of the second sensing lumen opposite the second sensing tip. The controller may be configured to average data from the first pressure sensor and the second pressure sensor to generate an average sensing lumen pressure. The controller may be configured to receive data from only one of the first pressure sensor or the second pressure sensor when one of the nares of the patient is blocked.

Where provided, the respiratory therapy system may include a capital unit including a pressurized gas source, and a delivery tube configured to convey the first flow of breathing gas from the capital unit to the first connector of the nasal cannula. The respiratory therapy system may further include a controller configured to receive a pressure signal from the first pressure sensor indicative of the first sensing lumen pressure and convert the pressure signal to data. In addition to the advantages of the nasal cannula recited above, the respiratory therapy system is advantageous by allowing for feedback control of the respiratory therapy provided by the capital unit based on the information derived from the breath sensing data.

In some implementations, the controller is configured to change an operating parameter of the capital unit based on the received data. In some implementations, the controller is configured to determine periods of patient inspiration and/or expiration based on the data from the first pressure sensor. In some implementations, the controller is configured to determine and display a patient expiratory/inspiratory ratio, current breath rate, and/or a patient breathing pattern based on the data from the first pressure sensor.

In any of the above aspects, the first flow of breathing gas may be heated and humidified (e.g., by a vapor transfer unit or a hotpot humidifier). The first flow of breathing gas may be configured to exit the first nasal prong at a high velocity, for example, at an exit velocity of at least about <NUM>/s and/or to be delivered at a flow rate between about <NUM>/min and <NUM>/min.

In another aspect, there is provided a method according to claim <NUM>, for sensing patient breathing when the patient is provided with high flow respiratory therapy. The method includes the step of detecting a pressure in a sensing lumen of the nasal cannula using a pressure sensor positioned at a proximal end of the sensing lumen opposite a tip of the sensing lumen. The sensing lumen is positioned such that, during patient inspiration and expiration, gas flows over the tip of the sensing lumen to create a pressure change within the sensing lumen. The remote positioning of the pressure sensor and use of a sensing lumen with distal tip allows for detection of pressure changes without substantial turbulence, noise, or high frequency pressure fluctuations at the pressure sensor, thus overcoming obstacles resulting from the open nature of nasal cannula therapy.

The method further includes transmitting a signal indicative of the detected pressure from the pressure sensor to a controller, and processing the signal using an algorithm stored in a memory of the controller. Processing the signal includes determining a current breath rate, and the method further includes displaying the current breath rate. The signal is indicative of a plurality of pressures detected by the pressure sensor over a period of time, and processing the signal includes identifying peaks in the plurality of detected pressures over time. The method may further include determining an increase or decrease in pressure over time. The method may further include identifying an apnea event based on the signal and logging the apnea event.

The method further includes determining an average pressure in the data. The method further includes determining maximum and minimum peaks in the data and/or filtering the data. The method further includes determining an average maximum peak over a period of time, determining an average minimum peak over a period of time, and determining a pressure threshold as a percentage of the average maximum peak. The method further includes determining a breath when the pressure crosses from below the average pressure to above the average pressure, then exceeds the average pressure by at least the pressure threshold reaches a maximum peak, then crosses from above the average pressure to below the average pressure, then reaches a minimum peak, and then crosses from below the average pressure to above the average pressure.

the method may further include operating the controller to alter an operating parameter of the respiratory therapy based on the detected pressure. The operating parameter may be at least one of a breathing gas flow rate, an oxygen percentage of the flow of breathing gas, a breathing gas temperature, a breathing gas humidity, or an aerosolized medicament flow rate. In some implementations, the detected pressure is a differential pressure between a pressure within the sensing lumen and an ambient pressure. In some implementations, the method further includes conveying a control flow of gas through the sensing lumen from a flow generator. The method may further include purging condensation from the sensing lumen with the control flow of gas. In some implementations, the method further includes humidifying the flow of breathing gas using a vapor transfer unit or a hotpot humidifier.

In another aspect, outside the scope of the claims, there is provided a method of manufacturing a nasal cannula for respiratory therapy and breath sensing. The method includes the step of maintaining a first mandrel, a second mandrel, and a third mandrel in a fixed arrangement with respect to each other, wherein the third mandrel is positioned along at least a portion of the first mandrel at a distance from the first mandrel; coating the arrangement with a material, The method includes the step of curing the coated arrangement; trimming at least one coated mandrel to create an opening in the coating of the trimmed mandrel. The method includes the step of removing the cured coating from the arrangement, wherein the coating on the first, second, and third mandrels form a first nasal prong, a second nasal prong, and a sensing lumen, respectively.

The step of coating may include immersing the arrangement in the material and removing the arrangement from the material. In some implementations, the step of coating includes spraying the material onto the arrangement. In some implementations, the first, second, and third mandrels are fixedly held on a substrate.

To provide an overall understanding of the assemblies and methods described herein, certain illustrative implementations will be described. These illustrative implementations are described for high velocity respiratory therapy, which can be understood to mean that breathing gas is delivered to the patient at a velocity of at least about <NUM>/s, for example, exiting from a nasal cannula prong. Although the implementations and features described herein are specifically described for high velocity respiratory therapy, it will be understood that all the components and other features outlined below may be combined with one another in any suitable manner and may be adapted and applied to other respiratory therapy systems and devices, including low flow oxygen therapy, continuous positive airway pressure therapy (CPAP), mechanical ventilation, oxygen masks, Venturi masks, or Tracheostomy masks, or combinations thereof. Although the features are described within regard to over-ear lariat-type nasal cannula securement systems, it will be understood that the components and other features outlined below can be applied to other nasal cannula (or tracheostomy mask) securement systems, including head gear, adhesive-based systems, or braces. The term "about," as used herein, should be understood to mean plus or minus <NUM>%. For example, "about <NUM>" should be understood to mean <NUM> ± <NUM>.

<FIG> shows a system <NUM> including a nasal cannula <NUM> and breathing gas supply tubes <NUM> and <NUM>. Nasal cannula <NUM> includes a cannula body <NUM> having connectors <NUM> and <NUM> adapted to couple to breathing gas supply tubes <NUM> and <NUM>, respectively, to receive flows of breathing gas. Nasal cannula <NUM> further includes nasal prongs <NUM> and <NUM> adapted to convey the flows of breathing gas into the nares of a patient. A sensing lumen <NUM> is disposed along nasal prong <NUM>. Sensing lumen <NUM> includes a tip <NUM> and a housing <NUM> adapted to couple to a tube (not shown). Tip <NUM> may be disposed at a distal end of sensing lumen <NUM>. As breathing gas is delivered to the patient via prongs <NUM> and <NUM>, inhaled or exhaled gas flows past tip <NUM> or into sensing lumen <NUM> and changes the pressure within sensing lumen <NUM>. A pressure sensor (not shown) may be disposed at a proximal end of sensing lumen <NUM> and detect the pressure changes within sensing lumen <NUM>.

The pressure sensor is configured to output a pressure signal indicative of the detected pressure. By locating the pressure sensor away from cannula and, for example, at the end of the tube extending from the proximal end of sensing lumen <NUM>, the pressure at the pressure sensor is conditioned to reduce noise in the signal. The pressure signal outputted by the pressure sensor may be communicated to a controller, for example, as described below in relation to <FIG>. A pressure sensor capable of resolving pressure differences as small as about <NUM> Pa to about <NUM> Pa may be suitable. Such a high sensitivity pressure sensor allows detection of very small changes in pressure, for example, changes of about <NUM> Pa to about <NUM> Pa, or changes of less than <NUM> Pa. The pressure sensor may be configured to measure or determine absolute pressure within sensing lumen <NUM> or to measure or determine differential pressure relative to atmospheric pressure of the surrounding environment. In the latter implementation, the pressure sensor has a high resolution and includes an additional probe configured to measure the atmospheric pressure of the surrounding environment.

When the patient breathes, air flows past tip <NUM>. Depending on whether the patient has their mouth open or closed and what the therapy flow rate is, the direction of flow past tip <NUM> may reverse during each breath or may only increase and decrease while maintaining the same direction. Either event causes pressure changes within sensing lumen <NUM>, which may be detected or measured using the pressure sensor. The pressure may always be less than the environmental pressure (typically the case with open mouth breathing where the flow does not reverse) or may swing from positive to negative (typical with closed mouth breathing). When a patient stops breathing or removes cannula <NUM>, the pressure changes stop and may be detected as an absence of pressure change.

In some implementations, cannula <NUM> includes a second sensing lumen having a second sensing tip positioned along the second nasal prong such that, during patient inspiration and expiration, gas flows over the second sensing tip to create a second pressure change within the second sensing lumen. In some implementations, cannula <NUM> includes a second pressure sensor configured to detect a second sensing lumen pressure in the second sensing lumen and positioned at a proximal end of the second sensing lumen opposite the second sensing tip. When two sensing lumens and two pressure sensors are used, the two detected pressures may be averaged to generate an average sensing lumen pressure. Alternatively, one of the two pressure sensors may be chosen, for example, using a controller as described herein and configured to receive a pressure signal from each pressure sensor, for example, if one nare becomes occluded such that inhaled or exhaled gas only or mostly flows over one of the two sensing tips.

Housing <NUM> is mounted on cannula body <NUM>. For example, housing <NUM> may be integrally formed with cannula body <NUM>. Alternatively, housing <NUM> may be detachably affixed to cannula body <NUM> via a clip-on connector, a magnet, a sliding lock, or another suitable form of attachment. A tube may be attached to the housing <NUM>, for example at a proximal end of housing <NUM>. The tube enables fluid communication between tip <NUM> and the pressure sensor. The tube and housing <NUM> define a fixed volume between tip <NUM> and the pressure sensor, and the pressure within this fixed volume changes as inhaled or exhaled gas flows toward tip <NUM> from the nare. The fixed volume is partially determined by the tube length and the tube inner diameter. Microbore tubing may be used such that the inner diameter is small, e.g., about <NUM> to about <NUM>. The small inner diameter minimizes the volume of air flow needed to conduct the pressure change along to the pressure sensor at the proximal end (of the tube). A flexible tube may be used in order to facilitate movement and repositioning of the pressure sensor while cannula <NUM> is in use. The tube may have a length between about <NUM> and about <NUM>. As discussed above, the length of tube can serve to condition the pressure signal by reducing high frequency pressure fluctuations.

Tip <NUM> may be positioned on an exterior surface of prong <NUM>. For example, tip <NUM> is positioned on a dorsal side of prong <NUM>, for example, as shown in <FIG>. For example, tip <NUM> may be positioned on a side of prong <NUM> farthest from the patient or on a top side of prong <NUM>. Alternatively, tip <NUM> may be spaced from the tip of prong <NUM>. Longitudinally, tip <NUM> may be flush with the tip of prong <NUM> or located proximally relative to the tip of prong <NUM>, such that prong <NUM> extends farther into the nare than tip <NUM>. In some implementations, tip <NUM> is set back from the tip of prong <NUM> such that tip <NUM> is outside of the nare while prong <NUM> extends at least partially into the nare.

Tip <NUM> may be angled relative to a longitudinal axis of sensing lumen <NUM>. As noted previously, breath sensing with a high flow nasal cannula can be particularly difficult due to the high flow rates and open nature of the system, leading to high noise in the pressure signal. Constructing sensing lumen <NUM> with an angled tip <NUM> may reduce turbulence of the inhaled and/or exhaled gas, improving the pressure signal. For example, tip <NUM> may include a tip face at an angle other than <NUM> degrees relative to the longitudinal axis, such that the tip face is angled away from the outlet of prong <NUM>. In some implementations, the angle is between about <NUM> degrees and about <NUM> degrees. In some implementations, the angle is between about <NUM> degrees and about <NUM> degrees. In some implementations, the angle is about <NUM> degrees. In some implementations, the angle is about <NUM> degrees or about <NUM> degrees. In some implementations, the angle is about <NUM> degrees or about <NUM> degrees. The tip face may have rounded, beveled, or chamfered edges, for example, to further reduce turbulence and prevent irritation or discomfort to the patient. Tip <NUM> may have an internal diameter between about <NUM> and about <NUM>. Tip <NUM> may have an internal diameter between about <NUM> and about <NUM>. In some implementations, tip <NUM> may have an internal diameter of about <NUM> or about <NUM>. In some implementations, tip <NUM> may have an internal diameter of about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>.

In some implementations, a control gas flows from a flow generator through at least a portion of the tube and/or sensing lumen <NUM>. The control gas flows in a direction from the proximal end (e.g., of the tube) toward tip <NUM>. In some implementations, the control gas flows in a direction from the proximal end of the sensing lumen <NUM> toward tip <NUM>. The control gas may be introduced into the tube at a point near the pressure sensor, for example, via a tee joint in the tube that is fluidically connected to the flow generator. The control gas prevents liquids from entering sensing lumen <NUM> or the tube. The flow of control gas may be continuous or intermittent (e.g., as a pulse or single bolus of flow). A continuous flowrate of about <NUM>/min to about <NUM>/min can be effective to both prevent liquid ingress and maintain a stable, low pressure at the pressure sensor. The control gas may be supplied by a low pressure source (e.g., at <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa or any other suitable gauge pressure). For an intermittent pulse or single bolus, a volume of about <NUM> to about <NUM> can clear liquid near tip <NUM> or elsewhere in sensing lumen <NUM>. The control gas exits sensing lumen <NUM> at tip <NUM> and collides with inhaled or exhaled gas at a boundary region adjacent to tip <NUM>, such that changes in pressure due to patient breathing are still detectable by the pressure sensor via sensing lumen <NUM>. Suitable flow generators include a fan, a syringe pump, a blower, a compressor, a bellows, a wall air source, a pressurized tank, a piezo pump, or any other suitable source of pressurized gas. The flow generator may be incorporated in a respiratory system in use with cannula system <NUM> or may be separately configured with system <NUM> in a breath sensing device configured to adapt to various respiratory systems. For certain flowrates of control gas that lead to a high pressure at the pressure sensor, a pressure sensor with a larger pressure range may be used.

Suitable sources of pressurized breathing gas will be known to one of ordinary skill in the art. For example, the source may be the Vapotherm Flowrest System, Vapotherm HVT2. <NUM> System, Precision Flow unit, or the Vapotherm 2000i, all of which are provided by Vapotherm, Inc. of Exeter, New Hampshire, USA. For example, the source may be the respiratory therapy systems described in <CIT> (<CIT>), and <CIT> (<CIT>). Other suitable sources of breathing gas will be known to one of ordinary skill in the art from the description herein, such as a blower, a compressor, a pressurized tank, a wall air outlet, or any other suitable gas source capable of generating high flow rates.

The source of breathing gas may be fluidically connected to first and second gas supply tubes <NUM> and <NUM> via a delivery tube (not shown) including an inlet configured to receive breathing gas from the source and a split outlet configured to divide and transmit breathing gas into the flows of breathing gas to the first and second gas supply tubes <NUM> and <NUM>, respectively. The delivery tube may be insulated by an air or water jacket, or may be heated by an internal heated wire so as to maintain/regulate a temperature of the breathing gas provided to the patient. The tube providing the pressure to the pressure sensor is maintained separately from the delivery tube and external to any insulating means. In some implementations, the sensing lumen <NUM>, tube, and/or pressure sensor are integrated into the delivery tube. For example, the tube conveying the pressure to the pressure sensor may be enclosed within a lumen of the delivery tube or embedded in a wall of the delivery tube, or the pressure sensor may be embedded in or affixed to the wall. The delivery tube may also serve to enclose any wires needed to connect the pressure sensor to a controller as described herein or the respiratory therapy system. The system <NUM> and delivery tube can be provided as a single unit to be attached to a variety of respiratory systems.

System <NUM> may be integrated in a respiratory therapy system having a breathing gas source and, optionally, a humidifying device (e.g., a vapor transfer unit or hotpot humidifier). Alternatively, system <NUM> may be implemented as an add-on unit configured to couple to a compatible respiratory therapy system with a breathing gas source and, optionally, a humidifying device (e.g., a vapor transfer unit or hotpot humidifier). System <NUM> may be used with a system that provides heated and humidified breathing gas. System <NUM> may be integrated into system <NUM> of <FIG> as nasal cannula <NUM>, described below.

Suitable flowrates of breathing gas range from about <NUM>/min to about <NUM>/min. In some implementations, the flowrates of breathing gas is between about <NUM>/min and about <NUM>/min. In some implementations, the flowrates of breathing gas is between about <NUM>/min and about <NUM>/min. In some implementations, the breathing gas flowrate and nasal prong inner diameter are chosen such that the exit velocity of breathing gas from nasal prongs <NUM> and <NUM> is at a high velocity, for example, at least about <NUM>/s. In some implementations, the exit velocity is between about <NUM>/s and about <NUM>/s for a balance effective flushing of CO<NUM> from the patient airway and patient comfort or noise reduction. In some implementations, an exit velocity between about <NUM>/s and about <NUM>/s is used. In some implementations, nasal prongs <NUM> and <NUM> have an internal diameter of about <NUM> to about <NUM>. In some implementations, nasal prongs <NUM> and <NUM> may have an internal diameter of about <NUM> to about <NUM>. In some implementations, nasal prongs <NUM> and <NUM> may have an internal diameter of about <NUM> to about <NUM>. For example, the ratio of sensing tip diameter to nasal prong diameter is between about <NUM> and about <NUM>.

In some implementations, a temperature sensor is used in addition to or in place of the pressure sensor. A temperature sensor can be applied in this context by measuring changes in temperature of the air near tip <NUM>, because exhaled gas will have a higher temperature coming from within the patient's body than inhaled air from the atmosphere, presumed to be at or around room temperature, or possibly higher than room temperature due to heating of the delivered breathing gas. When using a temperature sensing in conjunction with the pressure sensor, the temperature sensing reading may be used to verify correlation between pressure signals and breathing patterns.

<FIG> shows a flowchart outlining an example method <NUM> for breath sensing while providing respiratory therapy to a patient. Method <NUM> includes steps <NUM> and <NUM>. Step <NUM> involves delivering a flow of breathing gas to a nare of the patient via a nasal cannula. The nasal cannula includes a sensing lumen in fluid communication with a pressure sensor. Step <NUM> involves detecting a pressure within the sensing lumen of the nasal cannula using the pressure sensor. The sensing lumen is positioned such that gas inhaled or exhaled by the patient flows over a tip of the sensing lumen while the cannula is in use. The cannula may be cannula <NUM> described in relation to <FIG>.

Method <NUM> may further include transmitting a signal indicative of the detected pressure from the pressure sensor to a controller, such as controller <NUM> of <FIG>. The signal may indicate a detected pressure at a time point or a plurality of detected pressures over a period of time. The controller may be or may include a processor. The controller may be operatively coupled to a memory configured to store the signal, data based on the signal, and/or one or more algorithms for processing the signal. Method <NUM> may further include processing the signal using an algorithm stored in the memory. In some implementations, processing the signal includes determining a current breath rate or inspiratory/expiratory ratio of the patient. In some implementations, processing the signal includes identifying peaks in detected pressures over time. In some implementations, processing the signal includes determining an increase or decrease in pressure over time. In some implementations, processing the signal includes identifying an apnea event or a breathing pattern. In some implementations, processing the signal includes filtering, averaging, or smoothing the pressure data.

In some implementations, the algorithm is configured to determine an average pressure in the signal/data. The algorithm may determine maximum and minimum peaks in the data. The algorithm may determine the average maximum peak and/or the average minimum peak over a period of time. A pressure threshold may be determined as a percentage (e.g., between about <NUM>% and about <NUM>%) of the average maximum peak. This may allow the algorithm to identify a single breath of the patient based on when the pressure signal follows the following pattern: crosses the average pressure from below the average to above the average, then exceeds the average by at least the pressure threshold, then reaches a maximum peak, then cross the average from above the average to below the average, then reaches a minimum peak, and then crosses the average from below the average to above the average. The above steps may be based on a positive pressure swing, meaning that the pressure change is positive when the patient inhales. Alternatively, the pressure threshold may be determined as a percentage of the average minimum peak, and the algorithm steps are based on a negative pressure swing such that the pressure change is negative when the patient inhales. The pressure sensor used herein can be a relative pressure sensor, measuring the difference in pressure between two ports with one port positioned within the sensing lumen and one outside (measuring pressure of the surrounding environment), so the ports can be swapped to switch between the bases of positive and negative pressure swings.

Data representing information such as pressure signal, current breath rate, inspiratory/expiratory ratio, identified peaks, identified apnea events, or breathing patterns may be stored in the memory, for example, as an additional method step. The method may further include generating for display any of the above-listed information.

The above data and/or signal can be used to inform users, for example, clinicians, particularly as support for making clinical decisions related to respiratory therapy. For example, any of the above data can be displayed for informing a user or clinician. The data can also be transmitted to the gas source or another device to inform feedback-based control decisions. For example, information like breathing pattern or inspiratory/expiratory ratio determined from the pressure signal can be used to make adjustments to the provided therapy in a control loop or determine recommendations for therapy or treatment. Adjustments may include changing the breathing gas flowrate, breathing gas humidity, breathing gas temperature, oxygen percentage, oxygen flow rate, or aerosol concentration. These functionalities are described further in relation to <FIG> below.

In some implementations, the method includes conveying a control gas through the sensing lumen from a flow generator. As discussed above, the control gas prevents liquids from entering the sensing lumen. This feature is particularly helpful when the breathing gas is humidified, which leads to a higher likelihood of condensation buildup at the cannula. The flow of control gas may be continuous or intermittent (e.g., as a pulse). The control gas may be introduced into the tube at a point near the pressure sensor, for example, via a tee joint in the tube that is fluidically connected to the flow generator. A continuous flowrate of about <NUM>/min to about <NUM>/min can be effective to both prevent liquid ingress and maintain a stable, low pressure at the pressure sensor. In some implementations, a continuous flowrate can be between about <NUM>/min and about <NUM>/min, or between about <NUM>/min and <NUM>/min. The control gas may be supplied by a low pressure source (e.g., at <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa, <<NUM> kPa or any other suitable gauge pressure). For an intermittent pulse, a volume of about <NUM> to about <NUM> can clear liquid near the tip of the sensing lumen. The control gas exits the sensing lumen at the tip and collides with inhaled or exhaled gas at a boundary region adjacent to the tip, such that changes in pressure due to patient breathing are still detectable by the pressure sensor via the sensing lumen. Suitable flow generators include a fan, a syringe pump, a blower, a compressor, a bellows, a wall air source, a pressurized tank, or any other suitable source of pressurized gas. The flow generator may be incorporated in a respiratory system in use with the cannula or may be separately configured with the in a breath sensing device configured to adapt to various respiratory systems. For certain flowrates of control gas that lead to a high pressure at the pressure sensor, a pressure sensor with a larger pressure range may be used.

<FIG> shows a flowchart describing a method <NUM>, not claimed, for manufacturing a nasal cannula for respiratory therapy and breath sensing. Method <NUM> includes steps <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Step <NUM> involves maintaining a first mandrel, a second mandrel, and a third mandrel in a fixed arrangement with respect to each other. In the fixed arrangement, the third mandrel is positioned along at least a portion of the first mandrel at a distance from the first mandrel. Step <NUM> involves coating the arrangement with a material. Step <NUM> involves curing the coated arrangement. Step <NUM> involves trimming at least one coated mandrel to create an opening in the coating of the trimmed mandrel. Step <NUM> involves removing the cured coating from the arrangement. The coating on the first, second, and third mandrels form a first nasal prong, a second nasal prong, and a sensing lumen, respectively, of the nasal cannula. For example, the cured coating may be a flexible plastic that is in the shape of the nosepiece shown in <FIG>.

In some implementations, in step <NUM>, coating the arrangement includes immersing the arrangement in the material and removing the arrangement from the material (e.g., dip molding). The relatively low monetary cost of the dip molding material allows for discarding the excess material without significantly affecting the production cost. In some implementations, in step <NUM>, coating the arrangement includes spraying the material onto the arrangement. In an example, the first, second, and third mandrels are fixedly held on a substrate. This may keep the mandrels in the desired arrangement for the step of coating. The third mandrel may be held at a distance from the first mandrel in the arrangement. All of the first, second, and third mandrels may be fixed in the arrangement with a spacing between each other. By leaving a small distance between the mandrels, the material that flows around the mandrels will separate the structures formed by the mandrels with a thin layer of material.

For example, the coated arrangement may be cured at room temperature, or at a temperature or set of temperature (such as those determined by the material's curing temperature profile) determined to accelerate the curing time. For example, the coating may be cured using a heat lamp, oven, UV radiation, or any other suitable means. After curing, at least one coated mandrel may be trimmed to create an opening in the coating of the trimmed mandrel.

The mandrels may be made of, for example, steel, aluminum-bronze alloys, stainless steel, or any other suitable material, such as those resistance to curing methods and which will not permanently adhere to the flexible material used in forming the nosepiece. The materials used to manufacture the cannula in general may also be selected so as to facilitate smooth flow within the tubing and appropriate durability and connectivity on the outside of the tubing. In some implementations a material of the outer surface includes at least one of: polyvinyl chloride (PVC) plastic, plastisol, vinyl, silicone, non-latex rubber, an elastomer, ethylene vinyl acetate (EVA), styrene-butadiene copolymer (SBC), polyether ether ketone (PEEK), a polyether block amide (such as PEBAX), a polyethylene material, a high-density polyethylene (HDPE) material, a medium-density polyethylene (MDPE) material, a low-density polyethylene (LDPE) material, a crack-resistant material, a material with a low coefficient of friction, a material less than <NUM> Durometer Shore A, and flexible plastic. Flexible plastics and the other material examples listed above may be chosen to provide customized comfort to a patient. For example, an infant patient may require a more flexible nosepiece than an adult patient. In such an example, a more flexible material may be chosen.

<FIG> shows a block diagram of a system <NUM> including nasal cannula <NUM>, capital unit <NUM>, pressure sensor <NUM>, controller <NUM>, and memory <NUM>. Capital unit <NUM> includes a pressurized breathing gas source (not shown) configured to deliver a flow of breathing gas to nasal cannula <NUM>. Nasal cannula <NUM> is configured to convey the flow of breathing gas at a high velocity (e.g., at least at about <NUM>/s) into the nares of a patient. In some implementations, the exit velocity is between about <NUM>/s and about <NUM>/s. In some implementations, an exit velocity between about <NUM>/s and about <NUM>/s is used. As the patient breathes, a sensing lumen of nasal cannula <NUM> conveys pressure changes to pressure sensor <NUM>, wherein the pressure changes result from patient inspiration and expiration. Pressure sensor <NUM> is configured to detect the pressure changes and output a signal indicative of the detected pressure to controller <NUM>. Controller <NUM> is operatively coupled to pressure sensor <NUM> and memory <NUM>. Controller <NUM> is configured to receive and process the signal from pressure sensor <NUM>. Memory <NUM> is configured to store information such as the received signal and an algorithm for signal processing. Controller <NUM> is optionally operatively coupled to capital unit <NUM>. In an example, nasal cannula <NUM> is cannula <NUM> of <FIG>.

In some implementations, processing the signal includes determining a current breath rate or inspiratory/expiratory ratio of the patient. In some implementations, processing the signal includes identifying peaks in detected pressures over time. In some implementations, processing the signal includes determining an increase or decrease in pressure over time. In some implementations, processing the signal includes identifying an apnea event or a breathing pattern. In some implementations, processing the signal includes applying a filter to the signal to remove noise. In some implementations, processing the signal includes identifying and excluding non-breathing periods (e.g., swallowing, sneezing, talking, or coughing) from the data. By ignoring non-breathing artifacts, controller <NUM> may more accurately calculate breathing parameters.

Processing the signal involves determining an average pressure in the signal/data. Maximum peaks, minimum peaks, the average maximum peak over a period of time, and the average minimum peak over a period of time are also determined. A pressure threshold is determined as a percentage (e.g., between about <NUM>% and about <NUM>%) of the average maximum peak. This allows controller <NUM> to identify a single breath of the patient based on when the pressure signal follows the following pattern: crosses the average pressure from below the average to above the average, then exceeds the average by at least the pressure threshold, then reaches a maximum peak, then cross the average from above the average to below the average, then reaches a minimum peak, and then crosses the average from below the average to above the average. The above steps may be based on a positive pressure swing, meaning that the pressure change is positive when the patient inhales. Alternatively, the pressure threshold may be determined as a percentage of the average minimum peak, and the algorithm steps are based on a negative pressure swing such that the pressure change is negative when the patient inhales. The pressure sensor used herein can be a relative pressure sensor, measuring the difference in pressure between two ports with one port positioned within the sensing lumen and one outside (measuring pressure of the surrounding environment), so the ports can be swapped to switch between the bases of positive and negative pressure swings.

In some cases, the patient's breathing pattern may change, resulting in breathing that does not reach the threshold for breath detection that has been established from previous average peaks. This can occur if the patient switches to shallow breathing after a period of deep breathing or when a patient switches from closed-mouth to open-mouth breathing. In these cases, an algorithm can detect that there is sufficient pressure change (e.g., one pressure change or multiple pressure changes) to indicate that breathing is occurring even though it is not reaching the minimum threshold of breath detection. The averages are reset and new average peaks are determined from the pressure data.

The above-identified signal processing, with or without any of the optional processing steps discussed above, is executed by an algorithm stored in memory <NUM>. Data representing information such as pressure signal, current breath rate, inspiratory/expiratory ratio, identified peaks, identified apnea events, or breathing patterns may be stored in memory <NUM>. System <NUM> may further include a screen or display configured to display any of the above information.

When controller <NUM> is operatively coupled to capital unit <NUM>, controller <NUM> may be configured to transmit information or data to capital unit <NUM>. For example, controller <NUM> is configured to notify capital unit <NUM> of a non-breathing period or apnea event, and in response capital unit <NUM> may vary the flow of breathing gas and/or generates an alarm. Controller <NUM> may transmit a pressure signal, current breath rate, inspiratory/expiratory ratio, identified peaks, identified apnea events, or breathing patterns to capital unit <NUM>. Capital unit <NUM>, in response to receiving any of the above information, may adjust one or more operational parameters. For example, capital unit <NUM> increases or decreases one or more of breathing gas flow rate, breathing gas humidity, breathing gas temperature, oxygen percentage, oxygen flow rate, or aerosol concentration. This feature may allow a caretaker to wean the user off of respiratory therapy when they demonstrate improved breathing. Capital unit <NUM>, in response to receiving any of the above information, may generate an alarm to notify a user or caretaker. This feature may be beneficial for compliance monitoring.

Capital unit <NUM> includes a pressurized breathing gas source that may be one of a blower, a compressor, a pressurized tank, a wall air outlet, or any other suitable gas source capable of generating high flow rates (e.g., between about <NUM>/min and <NUM>/min, or greater). In some implementations, capital unit <NUM> is configured to output a heated and humidified flow of breathing gas. For example, capital unit <NUM> contains a vapor transfer unit or hotpot humidifier configured to evaporate water into the flow of breathing gas. In some implementations, capital unit <NUM> includes a port for oxygen titration. For example, an oxygen tank, oxygen concentrator, or oxygen wall outlet is coupled to capital unit <NUM>, and a flow of oxygen is added to the breathing gas to reach a target oxygen concentration or oxygen flow rate. In some implementations, an aerosolized medicament is entrained in the flow of breathing gas and delivered simultaneously to the patient. For example, a nebulizer is mounted to nasal cannula <NUM>, to capital unit <NUM>, or to a disposable unit on capital unit <NUM>, and the nebulizer emits aerosol medicament particles into the flow of breathing gas.

In some implementations, capital unit <NUM>, nasal cannula <NUM>, pressure sensor <NUM>, controller <NUM>, and memory <NUM> are parts of one system <NUM>. In other implementations, capital unit <NUM> is a respiratory system, and a breath sensing device separately houses pressure sensor <NUM>, controller <NUM>, and memory <NUM>, and is adapted to couple to capital unit <NUM> and nasal cannula <NUM>. The breath sensing device may be packaged and adapted to couple to existing respiratory therapy systems having a suitable pressurized breathing gas source. In some implementations the system <NUM> includes additional medical monitoring devices such as a pulse oximeter device or transcutaneous carbon dioxide sensor, and the breath sensing data detected by the pressure sensor <NUM> is displayed at the capital unit <NUM> with additional parameters detected at the other monitoring devices.

The foregoing is merely illustrative of the principles of the disclosure, and the apparatuses can be practiced by other than the described implementations, which are presented for purposes of illustration and not of limitation. It is to be understood that the apparatuses disclosed herein, while shown for use in high flow therapy systems, may be applied to systems to be used in other ventilation circuits.

Variations and modifications will occur to those of skill in the art after reviewing this disclosure. The disclosed features may be implemented, in any combination and subcombination (including multiple dependent combinations and subcombinations), with one or more other features described herein. The various features described or illustrated above, including any components thereof, may be combined or integrated in other systems. Moreover, certain features may be omitted or not implemented.

Claim 1:
A breath sensing device (<NUM>) configured to monitor patient breathing, the device comprising:
a nasal cannula (<NUM>,<NUM>) for breath sensing of a patient being provided high flow respiratory therapy, the nasal cannula comprising:
a cannula body (<NUM>) having a first connector (<NUM>) configured to receive a first flow of breathing gas and a second connector (<NUM>) configured to receive a second flow of breathing gas;
a first nasal prong (<NUM>) configured to deliver the first flow of breathing gas to a nare of the patient;
a second nasal prong (<NUM>) configured to deliver the second flow of breathing gas to a nare of the patient;
a first sensing lumen (<NUM>) having a first sensing tip (<NUM>) positioned along the first nasal prong such that, during patient inspiration and expiration, gas flows over the first sensing tip to create a pressure change within the first sensing lumen; and
a first pressure sensor (<NUM>) configured to detect a first pressure in the first sensing lumen, the first pressure sensor being positioned at a proximal end of the first sensing lumen opposite the first sensing tip; and
a controller (<NUM>) configured to:
receive a pressure signal from the first pressure sensor indicative of the first sensing lumen pressure;
convert the pressure signal into data; and
apply an algorithm to the data,
characterized in that, the algorithm is configured to:
determine an average pressure in the data;
determine maximum and minimum peaks in the data and/or filter the data;
determine an average maximum peak over a period of time;
determine an average minimum peak over a period of time;
determine a pressure threshold as a percentage of the average maximum peak; and
identify a breath when the pressure:
crosses from below the average pressure to above the average pressure, then
exceeds the average pressure by at least the pressure threshold, then
reaches a maximum peak, then
crosses from above the average pressure to below the average pressure, then
reaches a minimum peak, then
crosses from below the average pressure to above the average pressure.