Patent Description:
<CIT>, <CIT> and <CIT> are hereby acknowledged.

Certain aspects, advantages and novel features of the present disclosure are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the present disclosure. Thus, the features, aspects, and advantages of the present disclosure may be embodied or carried out in a manner that achieves or selects one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

According to the present invention there is provided a respiratory assistance system according to claim <NUM>. Preferred features are set out in the dependent claims.

In certain embodiments, a respiratory assistance system can include a patient interface that can deliver a gas flow to a patient. The respiratory assistance system can also include a gas source that can drive the gas flow to the patient interface at an operating flow rate. The respiratory assistance system can also include a hardware processor. The hardware processor can apply a plurality of test flow rate values in a range as the operating flow rate. The hardware processor can further measure at least one patient parameter corresponding to each of the plurality of test flow rate values. The hardware processor can also determine a new flow rate value based at least in part on the measured at least one patient parameter. In some embodiments, the hardware processor changes the operating flow rate to the new flow rate value. The hardware processor determines a rate of change in the measured at least one patient parameter as a function of the change in the applied plurality of test flow rate values.

The system of the preceding paragraph can have any sub-combination of the following features: wherein said determining the new flow rate further includes determining where in the range of the plurality of test flow rate values does the rate of change approach zero; wherein said determining the new flow rate can further include determining a minimum or a maximum value of the at least one patient parameter measured for each of the plurality of test flow rate values; wherein the at least one patient parameter comprises a respiratory rate and wherein the hardware processor can measure the respiratory rate based at least in part on one or more of the following sensor measurements: pressure fluctuations, flow rate fluctuations, blower fans speed, blower motor power, blower motor torque, expired CO<NUM> fluctuations, transcutaneous CO<NUM> fluctuations, expired patient temperature, EMG signals, Edi signals, impedance pneumography, respiratory inductance plethysmography, acoustic sensing; wherein the at least one patient parameter can include a work of breathing indicator; wherein the patient parameter can include an expiratory CO<NUM> concentration indicator; wherein the patient parameter can include a thoracoabdominal asynchrony indicator; wherein the hardware processor can wait a predetermined time period after the change in the operating flow rate before measuring the patient parameter; wherein the range can include one of the following: <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; and <NUM>-<NUM> (in L/min/kg) ; wherein the range can include one of the following: <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; and <NUM>-<NUM> (in L/min) for patients; wherein changing the operating flow rate can include changing an amount of power delivered to the gas source; wherein the gas source can include a blower; wherein the hardware processor can generate an alarm value based at least in part on the measured at least one patient parameter; wherein the hardware processor is can determine that the measured at least one patient parameter is insensitive to the change in flow rate and generate an alarm based on said determination; wherein the patient interface includes an unsealed nasal interface; wherein the gas source comprises a flow meter, a blender, or a flow mode from a ventilator; and wherein the plurality of test flow rates are applied responsive to a user input. Also described is wherein the patient interface can include any of the following: unsealed nasal cannula, sealed nasal cannula, sealed nasal mask, or a full face mask.

Also described is a method for delivering gas to a patient that can include delivering a gas flow to a patient via a patient interface. The method can further include driving the gas flow from a gas source to the patient interface at an operating flow rate. The method can also include applying a plurality of test flow rate values in a range as the operating flow rate. Further, the method can include measuring at least one patient parameter corresponding to each of the plurality of test flow rate values. The method can further include determining a new flow rate value based at least in part on the measured at least one patient parameter. In some embodiments, the method can include changing the operating flow rate to the new flow rate value.

The method of the preceding paragraph can have any sub-combination of the following features: determining a rate of change in the measured at least one patient parameter as a function of the change in the operating flow rate; determining where in the range of the plurality of test flow rate values that the rate of change approaches zero; wherein the at least one patient parameter can include a respiratory rate; wherein the at least one patient parameter can include a work of breathing indicator; wherein the patient parameter can include a thoracoabdominal asynchrony indicator; wherein the range comprises one of the following: <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; and <NUM>-<NUM> (in L/min/kg); wherein the range can include one of the following: <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; and <NUM>-<NUM> (in L/min); wherein the patient interface can include any of the following: unsealed nasal cannula, sealed nasal cannula, sealed nasal mask, or a full face mask; wherein said plurality of test flow rate values are received from a user; generating an alarm based on the measured at least one patient parameter; and wherein the gas source comprises any of the following: a blower, a flow meter, a flow mode from a ventilator, and a blender.

These and other features, aspects, and advantages of the present disclosure will be described with respect to the following figures, which are intended to illustrate and not to limit the preferred embodiments.

A respiratory assistance system including a humidification apparatus may be used to deliver heated and humidified respiratory gases to a patient through a conduit and a patient interface. The respiratory assistance system can provide a number of therapies for patients requiring respiratory support. One of the therapies includes providing a high flow therapy. In high flow therapy, the respiratory support system delivers relatively high flows of gases through a nasal interface, which may be unsealed. The flow of gases can be in the range of <NUM>/min to <NUM>/min. In some embodiments, the flow of gases can be in the range of <NUM>/min to <NUM>/min. In some embodiments, the flow of gases can be in the range of <NUM>/min to <NUM>/min. In some embodiments, the flow of gases is in the range of <NUM>/Min to <NUM>/min. In some embodiments, the flow rate of gases can be as high as <NUM>/min. In some embodiments, the flow rate is greater than <NUM>/min, but less than <NUM>/min. In other embodiments, the flow rate is <NUM>/min or higher. The respiration assistance system can adjust the flow rate of gases during the treatment through a control system. A discussion of high flow therapy and how the flow rate can be changed in a respiratory assistance system can be found in <CIT>, titled "Improvements to Flow Therapy".

The flow rate in the high flow therapies may be a function of patient condition and can vary during the treatment. A clinician or patient may not be able to determine the set value of the flow rate for the respiratory assistance system to provide the optimal therapy and comfort. Care providers often do not know proper flow rates for particular patients and tend to set flow rates too low or too high to be clinically optimal. Care provides also often do not know how to gauge the effectiveness of the therapy or how long they should wait to determine effectiveness. Many care providers also may not understand how and when to wean a patient off from high flow therapy.

Accordingly, the present disclosure provides methods and systems for determining an optimal flow rate for a given patient. The methods can be performed by a control system of the device, although certain steps can also be performed by a clinician in communication with the control system. In some embodiments, the respiratory assistance system discussed below includes a control system implemented using a controller for determining a set value for the flow rate. The control system can determine the set value of the flow rate and automatically update it over the time of therapy or based on change in patient conditions. Alternatively, the control system can provide an indication to a clinician to reevaluate the flow rate for the patient or perform one or more other steps to determine a flow rate. Thus, in some embodiments, the control system can advantageously improve the efficacy of the high flow therapy and reduce the probability of the patient requiring more invasive treatment such as invasive mechanical ventilation. A flowrate control method for high flow respiratory therapy may help in a patient spending less time with a flow rate set too high or too low for their immediate breathing support requirements over the course of the therapy.

Flow rate is likely to affect a number of physiological and clinical parameters including work of breathing, end tidal CO<NUM>, respiration rate, thoraco-abdominal phase, and other parameters of clinical relevance. In an embodiment, the control system discussed below can generate an indication of the set flow rate for display to a physician. The control system can also automatically change the flow rate. In some embodiments, the control system can warn the clinician if the therapy is not efficacious for the particular patient based on the sensitivity or insensitivity of clinical and physiological parameters to the flow rate. The control system described below can automatically control high flow respiratory therapy flow rates based at least on one or more of the following parameters: respiratory rate, end tidal CO<NUM>, thoraco-abdominal asynchrony, and work of breathing.

In some embodiments, the control system's automatic determination of the set value for the flowrate can improve weaning times and reduce hospital lengths of stay. Patients can spend less time at flow rates higher than what is necessary and discontinuation of therapy can be identified earlier. The control system can also assist in faster identification of therapy success or failure. For example, it may be advantageous to know that high flow therapy is not working on a particular patient earlier rather than later. In an embodiment, the control system can compare the physiological parameters of the patient as a function of flow rate to expected predetermined parameters for determining effectiveness of the therapy.

<FIG> shows a schematic of an example respiratory assistance system <NUM>. As illustrated, the respiratory assistance system <NUM> includes a humidification apparatus <NUM>, a gases source <NUM>, a patient interface <NUM>, and an inspiratory conduit <NUM> that can transport respiratory gases from the humidification apparatus <NUM> to the patient interface <NUM>. The patient interface <NUM> includes an unsealed nasal cannula (as shown). Other patient interfaces described herein include a sealed nasal cannula, sealed nasal mask, or a full face mask (with, for example, a castle port). Other examples of respiratory systems including nasal cannula are discussed more in detail in <CIT>, titled "Improvements to Flow Therapy". In some embodiments, the gases source <NUM> and the humidification apparatus <NUM> may be co-located, within the same housing, and/or comprise a single apparatus. In some embodiments, the humidification apparatus <NUM> may not be included in the respiratory assistance system <NUM>. Accordingly, gases may flow directly from the gases source <NUM> to the patient interface <NUM>. In some embodiments, a headgear <NUM> mechanically supports the patient interface <NUM> to the patient.

The gases source <NUM> may include a flow source <NUM> that can create a flow of respiratory gases to be provided to the humidification apparatus <NUM>. In an embodiment, the flow source <NUM> is a blower. However, the flow source <NUM> is not limited to a blower and can include a flow meter, a blender, flow mode from a ventilator, or any other flow generating device. Other flow sources known to those of skill in the art can also be used with any of the embodiments of the present disclosure as further discussed below. In an embodiment, the flow source <NUM> can include a fan and a motor. In some embodiments, the gases source <NUM> may comprise an inlet <NUM> through which ambient air is drawn into the gases source <NUM>. In some embodiments, instead of drawing ambient air, the inlet <NUM> can be connected to a dry gas source, for example, a gas canister or tank. In some embodiments, the gases source <NUM> may include a controller <NUM> that can control the operation of the flow source <NUM>. For example, the controller <NUM> can execute or implement a control system described more in detail below to control operations of the flow source and the associated flow rate of gases. The control system can, for example in some embodiments that use a blower as a flow source, determine an amount of power delivered to the blower. The fan or motor speed may depend on the amount of power. In some embodiments, the gases source <NUM> may comprise a user interface <NUM> configured to provide information regarding user input to the controller <NUM>. The controller <NUM> may be configured to control the operation of the blower or other flow source <NUM> based on information provided by the user interface <NUM> and/or based on other information, for example but not limited to, feedback from the flow source <NUM>, such as from a sensor associated with the flow source <NUM> as described more in detail below with respect to the control system. The user interface <NUM> may include buttons, knobs, dials, switches, levers, touch screens, speakers, displays and/or other input or output elements.

As discussed above, the humidification apparatus <NUM> may be optionally included in the respiratory assistance system <NUM> but is not necessary in every embodiment. The humidification apparatus <NUM> may include a humidification chamber <NUM> and a chamber heater <NUM>. The humidification chamber <NUM> may be configured to hold a volume of water W or other suitable liquid. The chamber heater <NUM> may be configured to heat the volume of water W and respiratory gases within the humidification chamber <NUM>, which may increase the temperature of the respiratory gases and may create vapor from the volume of water W that is taken up by the respiratory gases. In some embodiments, the humidification chamber <NUM> may comprise a chamber inlet (not shown) and a chamber outlet <NUM>. In some embodiments, the inspiratory conduit <NUM> may be configured to be connected to the chamber outlet <NUM>, such that heated and humidified respiratory gases may be transported by the inspiratory conduit <NUM> from the humidification chamber <NUM> to the patient interface <NUM> and then delivered to a patient P.

In some embodiments, the humidification apparatus <NUM> may comprise a controller <NUM> configured to control the operation of the chamber heater <NUM> and a flow generator, such as the flow source <NUM>. In the embodiments which do not include the humidification apparatus <NUM>, the respiratory assistance system <NUM> can use controller <NUM> instead of controller <NUM>. In some embodiments, the humidification apparatus <NUM> may include a user interface <NUM> to provide information regarding user input to the controller <NUM>. In some embodiments, the humidification apparatus <NUM> may include an ambient sensor <NUM>. The ambient sensor <NUM> may measure a characteristic of the ambient air near the location of the ambient sensor <NUM>, such as a temperature of the ambient air. The controller <NUM> may receive information regarding a characteristic of the ambient air near the location of the ambient sensor <NUM> from the ambient sensor <NUM>. The controller <NUM> or <NUM> can control the operation of the flow source <NUM> based on information provided by the user interface <NUM>, based on information provided by physiological sensors, and/or based on other information, for example but not limited to, feedback from the chamber heater <NUM>, such as from a sensor associated with the chamber heater <NUM>. In particular, the controller <NUM> may be configured to determine an amount of power, or a power duty cycle, to provide to the chamber heater <NUM> such that the chamber heater <NUM> delivers a desired amount of heat to respiratory gases and the volume of water W within the humidification chamber <NUM>.

In some embodiments, the respiratory assistance system <NUM> may include an outlet sensor <NUM> that is associated with the chamber outlet <NUM>. The outlet sensor <NUM> may be located at, in, or on the chamber outlet <NUM>, at, in, or on the inspiratory conduit <NUM> near the connection between the chamber outlet <NUM> and the inspiratory conduit <NUM>, or at, in, or on another suitable location. The outlet sensor <NUM> may measure a characteristic of respiratory gases flowing past the location of the outlet sensor <NUM>, such as a temperature of the respiratory gases. The controller <NUM> may receive information regarding a characteristic of respiratory gases flowing past the location of the outlet sensor <NUM> from the outlet sensor <NUM>. The controller <NUM> may be configured to control the operation of the chamber heater <NUM> based on information provided by the outlet sensor <NUM>, instead of or in addition to other sources of information as previously described.

<FIG> illustrates a block diagram of an embodiment of a control system <NUM> that can detect patient conditions and control operation of the respiratory assistance system <NUM> including the gas source <NUM>. In an embodiment, the control system <NUM> manages flow rate <NUM> of the gas flowing through the respiratory assistance system <NUM> as it is delivered to a patient. The control system <NUM> can increase or decrease the flow rate by controlling a motor speed of the blower or a valve in a blender. The control system <NUM> can automatically determine a set value or a personalized value of the flow rate for a particular patient as discussed below. In some embodiments, the flow rate can be optimized by the control system <NUM> to improve patient comfort and therapy.

The control system <NUM> can also generate audio and/or visual outputs <NUM>. For example, the respiratory assistance system <NUM> can include a display <NUM> (see <FIG>) which may further include a speaker. The display <NUM> can indicate to the physicians any warnings or alarms generated by the control system <NUM>. The display <NUM> can also indicate control parameters that can be adjusted by the physicians. For example, the control system <NUM> can automatically recommend a flow rate for a particular patient. The control system <NUM> can also generate recovery state of the patient and send it to the display.

In some embodiments, the control system <NUM> can change a temperature set point <NUM> of one of the heating elements, such as chamber heater <NUM>, to control the output conditions of the gas delivered to the patient. The control system <NUM> can also change the operation or duty cycle of the heaters described above.

The control system <NUM> can determine outputs <NUM>-<NUM> based on one or more received inputs <NUM>-<NUM>. The inputs <NUM>-<NUM> can correspond to sensor measurements received automatically by the controller <NUM> or <NUM>. In the illustrated embodiment, the control system <NUM> receives sensor inputs corresponding to thoraco-abdominnal asynchrony (TAA) sensor inputs <NUM>, respiration rate sensor inputs <NUM>, work of breathing sensor inputs <NUM>, and CO<NUM> sensor inputs <NUM> and or other sensors (pressure sensor, ambient sensor) in the respiratory assistance system <NUM> described above. In an embodiment, the control system <NUM> can also receive inputs from user <NUM> or stored values in a memory <NUM>. The control system <NUM> can dynamically adjust flow rate <NUM> for a patient over the time of their therapy. In an embodiment, the control system <NUM> can continuously detect system parameters and patient parameters.

In a healthy patient, the abdomen and the rib cage move in synchrony when breathing. Thoraco-abdominal asynchrony (TAA) occurs when there is asynchronous movement between the ribcage and abdomen during breathing. Accordingly, TAA is the non-coincident motion of the abdomen and rib cage and can be an indication of respiratory distress. Higher phase difference between the movement of the abdomen and rib cage can indicate a greater level of respiratory distress. In some embodiments, the control system <NUM> can change the set value of the flow rate of gases to reduce the phase difference. TAA sensor measurements can include measurements from any device or sensors that can detect movement or electrical signal from the abdomen and rib cage. For example, in an embodiment, sensor measurements can include measurements from a respiratory inductance plethysmography or skin mounted strain gauges. Further, the measurements can include electrical activity of the diaphragm and other muscles. This electrical activity can be measured by electromyography(EMG), sEMG, EDI, or electrical impedance tomography (EIT) sensors.

Work of breathing can correspond to a measure of the effort required to inspire air into the lungs and can be an indication of a number of different breathing disorders. A high work of breathing is uncomfortable for the patient, can lead to elevated CO2 levels, and can result in a patient being escalated to more invasive care such as invasive mechanical ventilation. Therefore, in some embodiments, the control system <NUM> can determine a flow rate that reduces work of breathing. WOB can be measured as energy in Joules spent by a patient to breath over a minute. WOB may be difficult to detect or measure directly from sensors. Accordingly, in some embodiments, the control system <NUM> may indirectly measure an indication corresponding to WOB from one or more sensor inputs <NUM>. For example, the control system <NUM> can indirectly measure WOB from EMG measurements, EDI measurements, respiratory inductance plethysmography (RIP), minute ventilation, expiratory time, pressure-rate product, respiration rate, TAA, pressure-time product or CO<NUM> measurements. EMG can correspond to the magnitude of the electrical signal from the brain to the diaphragm muscles. When the brain signals to breathe more or respiratory distress exists, the EMG signals can increase. RIP measures the movement of the chest wall and/or abdomen and outputs a voltage. Higher voltage can indicate a larger movement of the chest wall and/or abdomen and therefore indicate a higher WOB.

In an embodiment, the control system <NUM> can store EMG and RIP values across a large group of patients for comparison between a current patient and average values. The control system <NUM> can determine output parameters based on the average patient values. However, in some instances, patient conditions can vary substantially. Thus, in some embodiments, it may be advantageous to monitor a particular patient to determine output parameters for that patient. For example, the control system <NUM> can use changes in either EMG or RIP or both to determine whether a change in flow rate increases or decreases WOB. Further, changes in calculated parameters such as minute ventilation, expiratory time, pressure-rate product and/or pressure-time product can also be used to indicate a work of breathing response.

Respiratory rate can be an important indicator of patient condition. An abnormal respiratory rate has been shown to be a predictor of serious events such as cardiac arrests and escalation to high levels of care. Respiratory rate can thus provide an indication of deterioration or improvement in patient condition. Respiration rate may also be related to work of breathing.

Patient respiration can also be measured through the use of capnography to determine partial pressure of CO2 in the respiratory gases. The concentration or partial pressure of CO<NUM> in the gas exiting the airway at the end of expiration is called end tidal CO<NUM>. Measurement of CO<NUM> (capnography) is common during anaesthesia and intensive care and it is usually presented as a graph of expiratory CO<NUM> plotted against time, or, less commonly, expired volume. The gas expired at the end of expiration can be an indirect but relatively accurate measure of the CO<NUM> partial pressure in arterial blood. Capnography therefore provides information on patient condition, including, for example, CO<NUM> production, lung perfusion, breathing patterns (including respiration rate), alveolar ventilation, and CO<NUM> elimination.

In some embodiments, the control system <NUM> can use CO<NUM> measurements or indications of CO<NUM> measurements <NUM> to determine a set value of flow rate <NUM> for a particular patient. Direct measurements of end tidal CO<NUM> accurately during high flow therapy may be difficult because the cannula flow may dilute and flush the expiratory breath with fresh gas. A method of measuring content of gases from diluted measurements in exhaled breath is described in <CIT>". In some embodiments, the control system <NUM> can use relative values of CO<NUM> to determine a set value of flow rate as discussed below. The control system <NUM> can adjust the flow rate to lower the CO<NUM> volume in the expiration. In an embodiment, the control system <NUM> can adjust the flow rate until changing it any more results in an increase in the lower end tidal CO<NUM> volume. In some embodiments, the control system <NUM> can adjust the flow rate to maximize end tidal oxygen (O<NUM>) volume.

The control system <NUM> can include programming instructions for detection of input conditions and control of output conditions. The programming instructions can be stored in a memory <NUM> of the controller <NUM> and/or <NUM> as shown in <FIG>. In some embodiments, the programming instructions correspond to the methods, processes and functions described herein. The control system <NUM> can be executed by one or more hardware processors <NUM> of the controller <NUM> and/or <NUM>. The programming instructions can be implemented in C, C++, JAVA, or any other suitable programming languages. In some embodiments, some or all of the portions of the control system <NUM> can be implemented in application specific circuitry <NUM> such as ASICs and FPGAs.

As illustrated in <FIG>, the control system <NUM> can receive inputs from multiple components of the respiratory assistance system <NUM>. Not all of the inputs <NUM>-<NUM> shown in <FIG> may be present. The inputs <NUM> to <NUM> and the outputs <NUM> to <NUM> may not necessarily be present in all embodiments. For example, in some embodiments, the control system <NUM> may only receive the EMG input <NUM> and generate a flow control measurement <NUM>. Depending on the configuration, some of the components corresponding to the inputs may not be included in the respiratory assistance system <NUM>. Lack of input itself can be used by the control system <NUM> to determine the input or system conditions.

<FIG> illustrates a block diagram of an embodiment of a controller <NUM> or <NUM>. The controller can include a hardware processor <NUM> that can execute the instructions stored in a memory <NUM>. In an embodiment, the control system <NUM> is stored as programming instructions in the memory <NUM>. The controller can also include circuits <NUM> for receiving sensor signals. The controller can further include a display <NUM> for transmitting status of the patient and the respiratory assistance system. The display <NUM> can also show warnings. The controller can also receive inputs from the display.

<FIG> illustrates a flow chart of an embodiment of a method <NUM> for selecting a set value of a parameter of the respiratory assistance system. The parameter can include one or more of heater temperature, flow rate, heating element current. In some embodiments, the set value is selected by the control system <NUM> to optimize patient comfort and therapy. The method <NUM> can be implemented by any of the systems described herein. In an embodiment, the method <NUM> is implemented by the control system <NUM>.

In an embodiment, the method <NUM> begins at block <NUM>. The control system <NUM> can adjust a respiratory assistance system parameter over a predetermined range. As discussed above, one of the system parameters adjusted by the control system <NUM> can include a flow rate parameter. The control system <NUM> can, for example, increase the motor speed of the blower when a blower is used as the flow source124 to increase the flow rate of gases through the respiratory assistance system <NUM>. The control system <NUM> can measure one or more patient conditions in response to the change the system parameter.

In some embodiments, the control system <NUM> can wait for a predetermined time period before measuring the patient parameter. For example, the control system <NUM> can wait for the patient to reach steady state before measuring the patient parameter. The wait time can be less than <NUM> minutes or greater than or equal to <NUM> minutes. In an embodiment, the control system <NUM> waits until the patient parameter stops changing significantly after the change in flow rate. The patient parameter can be obtained from one or more sensor measurements discussed above. In an embodiment, the patient parameter is directly obtained from the sensors by the control system <NUM>. In other embodiments, the patient parameter is indirectly deduced or calculated by the control system <NUM> from the sensor measurements. The patient parameters can include work of breathing, end tidal CO<NUM> volume, respiration rate, phase synchrony, and any other parameters indicating a patient's physiological condition. At block <NUM>, the control system <NUM> can store the measured patient parameter in the memory. The control system <NUM> can also store additional parameters of patient and/or system in the memory and associate it with the measured patient parameter. Accordingly, the control system <NUM> can store the state of the patient and the respiratory assistance system <NUM> in conjunction with the measured parameter. The control system <NUM> can adjust the system parameter again and repeat the measurement and storing steps of blocks <NUM> and <NUM> respectively. Accordingly, the control system <NUM> can sweep through the values in a predetermined range for the system parameter and store the corresponding patient parameters in response to the change in the system parameter.

In some embodiments, the control system <NUM> selectively identifies values within the range. For example, the control system <NUM> can use a binary search, start from two end points and select in the middle and so on. The control system <NUM> can also start from previously stored set values and increase or decrease the system parameter from the stored set value. A patient may notice big changes in the system parameters. For example, the patient can notice the big changes in the flow rate. Accordingly, in some embodiments, the control system <NUM> changes the parameters gradually and may start from the stored set value. The stored set value may also correspond to statistical average over time.

At block <NUM>, the control system <NUM> can analyse the stored patient parameters as a function of the change in the system parameter. Based on the analysis, the control system <NUM> can determine a set value for the system parameter. In an embodiment, the control system <NUM> can determine a derivative of a function corresponding to the stored patient parameter versus system parameter. The control system <NUM> can determine a point where the derivative of the function is zero. This point can be used as the set value for the patient parameter. Depending on the patient parameter, the point may correspond to either maximum or minimum values of the function. The control system <NUM> can also determine boundary conditions so that the set value does not fall outside of a predetermined range. In some embodiments, at block <NUM>, the control system <NUM> can receive additional parameters corresponding to the patient conditions and/or system conditions. Additional parameters may include patient characteristics, such as age, sex, weight, awake or asleep and the like. System parameters may include time of day, type of therapy selected, and the like. The control system <NUM> can use these additional parameters in determination of the set value.

At block <NUM>, the control system <NUM> can change the respiratory assistance system parameter to the determined set value. For example, the control system can adjust the flow rate using the process <NUM> discussed above. The process <NUM> can, in some embodiments, advantageously optimize system parameters for improved patient comfort and therapy. The control system <NUM> can run the process <NUM> periodically to adjust the system parameter. The period may be adjusted by the control system <NUM> based on changes in the patient condition. For example, a child with bronchitis may go from severe to normal in a matter of days while a patient with a chronic lung disease may need therapy for a month, or indefinitely with gradual improvement or decline and thus gradual adjustments in flow rate. The control system <NUM> can also run the process <NUM> in response to detecting a change in the patient condition or system condition. For example, the control system <NUM> can run the process <NUM> when the patient falls asleep or wakes up. In some embodiments, the control system <NUM> can run the process in response to an input from a user, such as a physician or a patient. The control system <NUM> can run the process until the patient can come off the respiratory assistance system <NUM>.

<FIG> illustrates a flow chart of an embodiment of a process <NUM> for optimizing flow rate to minimize a patient's work of breathing. The process <NUM> extends process <NUM> discussed above for a particular system parameter (flow rate) with respect to a particular patient parameter (work of breathing). Accordingly, some of the discussion above with respect to the process <NUM> can also apply to process <NUM>. The process <NUM> can be implemented by any of the systems described herein. In an embodiment, the process <NUM> is implemented by the control system <NUM>.

The process <NUM> can begin at block <NUM> during system initialization. The control system <NUM> can set the initial flow rate of the respiratory assistance system <NUM>. The initial flow rate may be stored in the memory. The initial flow rate can be a function of the age and/or weight of a patient. For example, in adults, the initial flow rate may be somewhere in the range of <NUM> to <NUM>/min. In an embodiment, the initial flow rate is <NUM>/min for an adult patient. For children or neonatal patients, the initial flow rate may be <NUM>/min/kg of the child's weight. In some embodiments, the initial flow rate may be greater than <NUM>/min/kg, but less than or equal to <NUM>/min/kg. In some embodiments, the initial flow rate is greater than <NUM>/min/kg. The initial flow rate may also be less than <NUM>/min/kg. The initial flow rate can also be received by the control system <NUM> as a user input. The initial flow rate may be estimated by the control system <NUM> based on comparing a patient characteristic with predetermined values stored in the memory. As discussed above with respect to the process <NUM>, the process <NUM> can be initiated by the control system <NUM> periodically or based on an event. Accordingly, the process <NUM> can also begin at block <NUM> for a periodic measurement.

At block <NUM>, the control system <NUM> can receive sensor measurements to determine the patient's work of breathing corresponding to the current flow rate of the respiratory assistance system <NUM>. The sensor measurements may correspond to electrical signals from EMG probes or NAVA probes attached near the chest of the patient as discussed above. The control system <NUM> can determine a direct value of work of breathing based on the received sensor measurements at block <NUM>. In some embodiments, the control system <NUM> does not have to directly or accurately measure the work of breathing. As discussed above, the control system <NUM> can determine set value from the derivative of a function representing the relationship between the patient parameter and the system parameter. Thus, accurate or direct values may not be necessary as long as the values are relatively comparable. Accordingly, the control system <NUM> can use voltage measurements from the EMG sensors as a proxy for work of breathing. Since these measurements are from the same patient and the configuration is likely to not change between measurements, it may be advantageous in some embodiments to compare relative measurements as a function of a change in system parameter. Comparing relative measurements may require less processing power. Furthermore, in some embodiments, proxy measurements like voltage or current can be used by the control system <NUM> instead of directly measuring patient condition.

At block <NUM>, the control system <NUM> can store work of breathing measurements or the corresponding proxy measurements. The control system <NUM> can determine if an additional measurement needs to be made at block <NUM>. The determination may be based on whether there are more flow parameters that need to be checked by the control system <NUM>.

For example, in some embodiments applicable to Neonatal patients or children, the control system <NUM> starts with an initial flow rate of <NUM>/min/kg and applies a range of flow rates up to <NUM>/min/kg starting from <NUM>/min/kg. In some embodiments, the control system <NUM> can apply any one of the following range of flow rates depending on the patient (in L/min/kg): <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; <NUM> - <NUM>; and <NUM>-<NUM>. In some embodiments, the ranges discussed above include the initial or operating flow rate. In some embodiments, the range of flow rates scanned may not include the initial or operating flow rate. The control system <NUM> can increase the flow rate by <NUM>/min/kg for each check at block <NUM>. The control system <NUM> can wait for a predetermined time period before changing the flow rate. The control system <NUM> can also wait for a predetermined time period after the changing the flow rate and before taking the measurement. Other increments, for example, <NUM>, <NUM> or <NUM>, are also possible. Increments may also be a function of patient condition or system parameters. For each increment, the control system <NUM> can perform steps <NUM> to <NUM>. When the control system <NUM> has reached <NUM>/min/kg, it can stop the loop and proceed to block <NUM>. In some embodiments, the control system <NUM> can stop the loop if it determines an increasing or decreasing trend in the patient parameter. For example, the control system <NUM> can stop the loop when the derivative is zero or close to zero. The derivative can correspond to the rate of change of the patient parameter with respect to the system parameter.

As another example, for an adult patient, the control system <NUM> can start from <NUM>/min and increase from that starting point. The control system <NUM> can also start from <NUM>/min. In an embodiment, the control system <NUM> can start from a flow rate between <NUM>/min and <NUM>/min. The control system <NUM> can increase the flow rates incrementally as discussed above until a predetermined limit or any other condition as discussed above has been satisfied. The predetermined limit can be a flow rate of <NUM>/min or lower. In an embodiment, the predetermined limit is <NUM>/min. The ranges and the initial rates discussed herein may also be a function of patient characteristics, such as age and weight. In some embodiments, the control system <NUM> can apply any one of the following range of flow rates (in L/min) for adults: <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; <NUM>-<NUM>; and <NUM>-<NUM>. In some embodiments, the ranges discussed above include the initial or operating flow rate. In some embodiments, the range of flow rates scanned may not include the initial or operating flow rate. Further, the flow rate parameters may also depend on a physiological parameter, such as a respiration rate, or the illness. In some embodiments, whether a patient is classified as an adult or a child may depend on age, weight, therapy, or illness. Some children may be classified as adults and administered the adult flow rates depending on their age and/or weight. The flow rates may also be changed by a clinician or a patient using the user interfaces.

After the control system <NUM> collects all the patient measurements, it can analyse the measurements at block <NUM>. The control system <NUM> can select a set value of the flow rate from the measurements by identifying a flow rate with the smallest work of breathing measurement. An example set of collected measurements is illustrated in a graph format in <FIG>. The control system <NUM> can select the flow rate <NUM> corresponding to the minimum point for work of breathing <NUM> as shown in <FIG>. The control system <NUM> can set boundary conditions and not select a flow rate below a minimum rate <NUM> The control system <NUM> can also cap flow rate at a maximum rate <NUM> that may be set by the clinician or stored in the controller. This limit may be based on a flow above which the patient may feel discomfort, for example <NUM>/min for adults and <NUM>/min/kg for neonatal patients and children. Higher flow rates can also increase noise and pressure. Accordingly, based on the data collected by the control system <NUM>, it can select a set value of the flow rate at block <NUM>. The control system <NUM> can change the current value of the flow rate to the determined set value at block <NUM>. Accordingly, the control system <NUM> can optimize flow rate to reduce work of breathing and improve patient comfort. In some embodiments, the control system <NUM> can reduce work of breathing by <NUM>% by determining a set value for the flow rate particularized for a patient.

<FIG> illustrates a flow chart of an embodiment of a process <NUM> for optimizing flow rate to minimize thoraco-abdominal asynchrony (TAA). The process <NUM> extends process <NUM> discussed above for a particular system parameter (flow rate) with respect to a particular patient parameter (TAA). Accordingly, some of the discussion above with respect to the processes <NUM> and <NUM> can also apply to the process <NUM>. The process <NUM> can be implemented by any of the systems described herein. In an embodiment, the process <NUM> is implemented by the control system <NUM>.

At block <NUM>, the control system <NUM> can set an initial flow rate. The control system can measure TAA at block <NUM> for the current flow rate. TAA can correspond to the phase angle between the chest and abdominal motion. As discussed above, the control system <NUM> can use relative measurements as indications of TAA. Relative measurements can include phase difference in the voltage recorded from the electrodes attached to the different parts of the body of the patient. Accordingly, the control system <NUM> can receive voltage measurements from sensors at block <NUM>. The control system <NUM> can identify the phase difference from the voltage measurements between two different sites of the patient's body at block <NUM>. The control system <NUM> can store the phase difference at block <NUM> in the memory. The control system <NUM> can determine if an additional measurement is necessary for a new flow rate at block <NUM>. If necessary, the control system <NUM> can change the flow rate at block <NUM> and repeat step <NUM> to <NUM>. If the control system <NUM> determines that it does not require additional data, it can proceed to block <NUM>.

The control system <NUM> can analyse the stored phase measurements at block <NUM>. As discussed above with respect to the work of breathing, the control system <NUM> can identify a flow rate for which the phase difference is the lowest in the stored measurements. The control system <NUM> can used the identified value as the set value of the flow rate at block <NUM>. Furthermore, the control system <NUM> can change the current value of flow rate of the respiratory assistance system <NUM> to the set value. Accordingly, the process <NUM> can be used by the control system <NUM> to optimize flow rate for reduced asynchrony.

<FIG> illustrates a flow chart of an embodiment of a process <NUM> for optimizing flow rate to respiration rate (RR). The process <NUM> extends process <NUM> discussed above for a particular system parameter (flow rate) with respect to a particular patient parameter (RR). Accordingly, some of the discussion above with respect to the processes <NUM>, <NUM>, and <NUM> can also apply to the process <NUM>. The process <NUM> can be implemented by any of the systems described herein. In an embodiment, the process <NUM> is implemented by the control system <NUM>.

Respiration rate can indicate a patient condition or a work of breathing. Accordingly, the control system can use the respiration rate to determine a set value of a system parameter, such as a flow rate. Furthermore, respiration rate is easier to measure than some of the patient parameters discussed above. However, a function corresponding to respiration rate versus flow rate may be substantially monotonic. For example, when the flow rate is continuously increased, the respiration rate correspondingly decreases and heads towards zero. There are clinical situations where it is not desirable for the respiration rate to approach zero. However, the control system <NUM> can identify a range of flow rates where increasing the flow rate does not decrease the respiration rate. In some embodiments, the control system <NUM> can identify a section where the rate of change of the respiration rate is reduced.

The process <NUM> can begin at block <NUM> with the control system <NUM> setting an initial flow rate. At block <NUM>, the control system <NUM> can receive sensor measurements corresponding to respiration rate. In an embodiment, the sensor measurement is a plethysmographic signal. Other measurements for determining respiration rate are discussed above. Respiration rate may also be inputted via a user interface and received by the control system <NUM>. In some embodiments, the control system <NUM> can determine respiration rate based on the received sensor measurements at block <NUM>. The control system <NUM> can store the measured respiration rate in the memory at block <NUM>.

The control system <NUM> can determine if additional measurements of respiration rate are needed with respect to flow rate at block <NUM>. For example, the control system <NUM> can determine if the current flow rate or the last measured respiration rate is at or exceeded a boundary condition. If the control system <NUM> determines that additional measurements are needed, then the control system <NUM> can change the flow rate at block <NUM> and repeat steps <NUM> to <NUM>. In the alternative, if the control system <NUM> determines that additional measurements are not required, the control system <NUM> can analyse the stored RR measurements at block <NUM>. In some embodiments, the control system <NUM> can stop additional measurements when the rate of the change of respiration rate with respect to flow rate approaches zero. As discussed above, the control system <NUM> can use the decrease in the rate of change to determine the set value of the flow rate at block <NUM>. The decrease in the rate of change can correspond to a minimum in work of breathing. Further, the control system <NUM> can change the current value of the flow rate to the determined set value at block <NUM>.

While the processes <NUM>, <NUM>, and <NUM> are described separately, the control system <NUM> can measure multiple physiological parameters at the same time with the change in flow rate. Accordingly, the control system <NUM> can use a combination of the steps of the processes <NUM>, <NUM>, and <NUM> to determine a set value of the flow rate. In an embodiment, the control system <NUM> can average the flow rates determined independently from the different processes.

The control system <NUM> can also generate alarms or warnings based on the measured physiological patient parameters. For instance, if the respiration rate exceeds or drops below an acceptable limit, the control system <NUM> can generate an alarm for the display. Alternatively the control system can generate alarms or warnings based on relative insensitivity of measured parameters to changes in flow. For example if the work of breathing is insensitive to flow this may indicate that the therapy is less likely to be efficacious. In an embodiment, the control system <NUM> can change the flow rate and determine that the work of breathing is not affected significantly by the flow rate change. Based on the lack of correlation, the control system <NUM> can determine that the therapy may not be optimal for the patient.

The respiratory assistance system <NUM> with high flow therapy can be used to provide support to patients in emergency rooms, intensive care units (ICU), the operating room (OR), other hospital areas or in-home. In particular, the respiratory assistance system <NUM> can be used to support a patient under anaesthesia, during preoxygenation and postoperation. Using high flow therapy can have advantages in some embodiments because the patient can still communicate and the mouth is not covered by a mask. Any time a patient requires intubation or endoscopy, the mouth may be blocked and cannot be used for providing invasive air support. Accordingly, high flow therapy along with the nasal cannula configuration of the respiration assistance system <NUM> can be used in those situations to provide breathing support. The control system <NUM> can determine work of breathing or other physiological parameters in these cases and automatically determine a set value for flow rate. When patients use the respiratory assistance system <NUM> in their homes, the control system <NUM> can be used to adjust the set value of flow rate at the initial stage. The patient can also measure their respiration rate and enter it using the controller.

The disclosed apparatus and systems may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Depending on the embodiment, certain acts, events, or functions of any of the algorithms, methods, or processes described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially.

Claim 1:
A respiratory assistance system (<NUM>) for delivering gas to a patient, said respiratory assistance system (<NUM>) comprising:
an unsealed nasal interface (<NUM>) configured to deliver a gas flow to a patient;
a gas source (<NUM>) configured to drive the gas flow to the unsealed nasal interface (<NUM>) at an operating flow rate;
characterised by the respiratory assistance system (<NUM>) further comprising a control system (<NUM>) executed by one or more hardware processors of a controller (<NUM>), the control system (<NUM>) including programming instructions and configured to:
instruct the gas source (<NUM>) to apply a plurality of test flow rate values in a range as the operating flow rate;
receive measurement of at least one patient parameter from one or more components of the respiratory assistance system (<NUM>) corresponding to each of the plurality of test flow rate values;
determine a new flow rate value based at least in part on the measured at least one patient parameter; and
instruct the gas source (<NUM>) to change the operating flow rate to the new flow rate value;
wherein the one or more hardware processors are further configured to determine a rate of change in the measured at least one patient parameter as a function of the change in the applied plurality of test flow rate values.