Respiratory support system alarms

Abstract

Disclosed is a respiratory apparatus including a flow generator, a flow path, and a controller. The flow path may be configured to provide a flow of breathable gas to a patient. The controller may be configured to control the flow generator by controlling a flow generator output to the flow generator, and the controller may be configured to identify an expected flow rate for the flow path and / or an expected maximum flow rate for the flow path and / or an expected minimum flow rate for the flow path.

Description

[Technical field]

[0001] The present invention relates to a method and system for controlling and / or operating a respiratory assistance device. [Background technology]

[0002] Respiratory support devices are used to deliver a gas flow to patients in a variety of environments (hospitals, medical facilities, institutional care, or home environments). Respiratory support devices (e.g., flow therapy devices) may include an oxygen intake that allows the respiratory device to deliver supplemental oxygen along with the gas flow. Respiratory support devices may also (or alternatively) include a humidification device that allows the respiratory device to deliver heated and humidified gas. Respiratory support devices may allow for adjustment and control of the characteristics of the gas flow. These characteristics may include, for example, flow rate, temperature, gas concentration (such as supplemental oxygen concentration), humidity, and pressure.

[0003] Patients with various health conditions and diseases can benefit from respiratory therapy. In at least one form, the respiratory therapy can be oxygen therapy. For example, patients with chronic obstructive pulmonary disease (COPD), pneumonia, asthma, bronchopulmonary dysplasia, heart failure, cystic fibrosis, sleep apnea, lung disease, trauma to the respiratory system, acute respiratory disease, and / or other conditions or diseases can benefit from respiratory therapy. Similarly, patients receiving pre- and post-operative oxygen delivery can also benefit from respiratory therapy. Summary of the Invention [Means for solving the problem]

[0004] In one aspect of the present disclosure, a respiratory apparatus is provided, the respiratory apparatus comprising: A flow generator; a flow path configured to provide a flow of breathable gas to a patient; a controller configured to control the flow generator by controlling a flow generator output to the flow generator to provide a flow of breathable gas, the flow generator output being within an acceptable flow generator output range; and The controller comprises: Identifying a variable indicative of the conductance of the flow path; A predicted maximum flow rate and / or a predicted minimum flow rate of the flow path, A variable indicating the conductance of the flow path, Allowable flow generator output range and The present invention is configured to:

[0005] In some embodiments, the flow generator output is: i. motor speed, ii. motor current; iii. Motor duty; iv. The pressure of the gas in the flow path, or Any combination of vi to iv Is or contains these(s).

[0006] In some embodiments, the variable indicative of the conductance of the flow path is: i. the conductance of a flow path or a portion of a flow path; ii. Resistance to flow in the flow path or part of the flow path; or iii. The pressure drop along the flow path or a portion of the flow path; iv. Any combination of i to iii is or is based on this(these).

[0007] In some embodiments, the flow generator comprises an impeller.

[0008] In some embodiments, the respiratory apparatus comprises a flow sensor, the flow sensor configured to measure the flow rate of the flow of breathable gas to the patient.

[0009] In some embodiments, the variable indicative of the conductance of the flow path is based on a variable indicative of the conductance of the flow path at a previous time step.

[0010] In some embodiments, the variable indicative of the conductance of the flow path is based on the variable indicative of the conductance of the flow path over a time window, optionally the time window being the previous 20 seconds.

[0011] In some embodiments, the variable indicative of the conductance of the flow path is based on the current flow generator output and the current flow rate.

[0012] In some embodiments, the variable indicative of the conductance of the flow path is based on the current flow divided by the current flow generator.

[0013] In some embodiments, the variable indicative of conductance is:

number

[0014] In some embodiments, the variable indicative of conductance is:

number

[0015] In some embodiments, the flow path comprises: Humidification chamber, One or more breathing tubes, Patient interface, Elbow, and Sensor Module Includes one or more of the following.

[0016] In some embodiments, the flow path may be downstream of the flow generator (and optionally at the output of the flow generator).

[0017] In some embodiments, the flow path may be downstream of the humidifier (and optionally at the output of the humidification chamber).

[0018] In some embodiments, the flow path may be downstream of the elbow.

[0019] In some embodiments, the flow path may be downstream of the sensor module.

[0020] In some embodiments, the flow path may include at least a humidification chamber, a patient interface, and a conduit (and optionally a sensor module).

[0021] In some embodiments, the flow path may include at least a patient interface and a conduit (and optionally a sensor module).

[0022] In some embodiments, the predicted maximum flow rate and / or the predicted minimum flow rate are determined periodically (optionally at each time step).

[0023] In some embodiments, the controller is configured to control the motor to provide or attempt to provide a flow of breathable gas to the patient at a flow set point.

[0024] In some embodiments, the allowable flow generator output range is based on a flow rate set point.

[0025] In some embodiments, the allowable flow generator output range is an allowable motor speed range, the allowable motor speed range including an upper motor speed limit and / or a lower motor speed limit.

[0026] In some embodiments, the predicted maximum flow rate is based on the current motor speed and / or the motor speed upper limit.

[0027] In some embodiments, the predicted maximum flow rate is based on the difference between the current motor speed and the motor speed upper limit.

[0028] In some embodiments, the predicted minimum flow rate is based on the current motor speed and / or a lower motor speed limit.

[0029] In some embodiments, the predicted minimum flow rate is based on the difference between the current motor speed and a lower motor speed limit.

[0030] In some embodiments, the controller is configured to compare the predicted maximum flow rate and / or the predicted minimum flow rate and the flow rate set point and generate at least one alarm condition based on the comparison.

[0031] In some embodiments, the at least one alarm condition is: Flow Set Point Unreachable Alarm and Blockage Alarm Includes one or more of the following.

[0032] In some embodiments, the flow setpoint not reachable alarm comprises: a flow rate unreachable alarm associated with the flow rate set point exceeding the maximum expected flow rate (i.e., a flow rate set point too high alarm); and / or Flow unreachable alarms associated with flow setpoints falling below predicted minimum flow (i.e., flow setpoint too low alarms) Includes.

[0033] In some embodiments, the controller is configured to determine a situation in which the flow set point cannot be reached based on the predicted maximum flow rate and the flow set point, and in response, the controller is configured to generate a flow set point not reachable alarm.

[0034] In some embodiments, the controller is configured to generate at least one alarm condition if the flow set point is greater than the predicted maximum flow rate (optionally the alarm condition is a flow set point not reachable alarm, i.e., an alarm that the flow set point is too high).

[0035] In some embodiments, the controller is configured to generate at least one alarm condition (optionally the alarm condition is a flow set point not reachable alarm, i.e., an alarm that the flow set point is too high) if the flow set point is greater than the predicted maximum flow rate by more than an alarm threshold.

[0036] In some embodiments, the alarm threshold is a percentage of the flow set point (optionally the alarm condition is a flow set point not reachable alarm, ie an alarm that the flow set point is too high).

[0037] In some embodiments, the percentage of the flow set point is from about 5% to about 20% or about 10% of the flow set point.

[0038] In some embodiments, the alarm threshold is based on the type of therapy being provided by the respiratory device.

[0039] In some embodiments, if the flow set point exceeds the occlusion threshold and is greater than the predicted maximum flow rate, the controller is configured to generate an occlusion alarm.

[0040] In some embodiments, the occlusion threshold is from about 20% to about 70% or about 50% of the flow set point.

[0041] In some embodiments, the controller is configured to determine a situation in which the flow set point cannot be reached based on the predicted minimum flow rate and the flow set point, and in response, the controller is configured to generate a flow set point not reachable alarm.

[0042] In some embodiments, the controller is configured to generate at least one alarm condition if the flow set point is less than the predicted minimum flow rate (optionally the alarm condition is a flow set point not reachable alarm, i.e., an alarm that the flow set point is too low).

[0043] In some embodiments, the controller is configured to generate at least one alarm condition (optionally the alarm condition is a flow set point not reachable alarm, i.e., an alarm that the flow set point is too low) if the flow set point is less than the predicted minimum flow rate by more than an alarm threshold.

[0044] In some embodiments, the alarm threshold is a percentage of the flow setpoint (optionally the alarm condition is a flow setpoint unreachable alarm).

[0045] In some embodiments, the percentage of the flow set point is from about 5% to about 20% or about 10% of the flow set point.

[0046] In some embodiments, the alarm threshold is based on the type of therapy being provided by the respiratory device.

[0047] In some embodiments, in response to the generation of at least one alarm condition, the controller controls the motor speed to a predetermined safe motor speed.

[0048] In some embodiments, the controller controls the motor speed to a predetermined safe motor speed until the predicted maximum flow rate is greater than a safe threshold flow rate and / or until the predicted minimum flow rate is less than a safe threshold flow rate.

[0049] In some embodiments, the controller controls the motor speed to a predetermined safe motor speed until the flow set point is less than the predicted maximum flow rate and / or until the flow set point is greater than the predicted minimum flow rate.

[0050] In some embodiments, the predetermined safe motor speed is 8000 RPM.

[0051] In some embodiments, the alarm condition is: Audible alarm and Visual alarm Includes one or more of the following.

[0052] In some embodiments, the respiratory apparatus is a nasal high flow apparatus.

[0053] In some embodiments, the respiratory apparatus provides the flow of gas to the patient through a non-sealed interface.

[0054] In another aspect of the present disclosure, a respiratory apparatus is provided, the respiratory apparatus comprising: A flow generator; a flow path configured to provide a flow of breathable gas to a patient; a controller configured to control the flow generator by controlling a flow generator output to the flow generator to provide a flow of breathable gas to the patient; The controller comprises: Identifying a variable indicative of the conductance of the flow path; The predicted flow rate of the flow path is A variable indicating the conductance of the flow path and Current flow generator output and The present invention is configured to:

[0055] In some embodiments, during a first time step, the controller is configured to identify a variable indicative of the conductance of the flow path.

[0056] In a second time step, the controller is configured to determine an expected flow rate based on a variable indicative of the conductance of the flow path.

[0057] In some embodiments, the flow generator output is: i. motor speed, ii. motor current; iii. Motor duty; iv. The pressure of the gas in the flow path, or Any combination of vi to iv Is or contains these(s).

[0058] In some embodiments, the variable indicative of the conductance of the flow path is: i. the conductance of a flow path or a portion of a flow path; ii. Resistance to flow in the flow path or part of the flow path; or iii. The pressure drop along the flow path or a portion of the flow path; iv. Any combination of i to iii is or is based on this(these).

[0059] In some embodiments, the controller is configured to compare the current flow rate and the predicted flow rate and generate at least one alarm condition based on the comparison.

[0060] In some embodiments, the controller is configured to compare the current flow rate and at least one flow rate threshold and generate at least one alarm condition based on the comparison.

[0061] In some embodiments, the controller is configured to generate a leak alarm condition if the current flow rate is greater than at least one leak flow rate threshold (optionally if the predicted flow rate is less than the current flow rate).

[0062] In some embodiments, a leak alarm condition is generated if the current flow rate is greater than all of at least one leak flow rate threshold.

[0063] In some embodiments, a leak alarm condition is generated after multiple instances of the current flow rate are greater than at least one leak flow rate threshold.

[0064] In some embodiments, the at least one leak rate threshold is: A percentage threshold based on a percentage of the predicted flow rate; a limit threshold based on the flow generator output and optionally a constant; Fluctuation threshold based on predicted flow fluctuation Includes one or more of the following.

[0065] In some embodiments, the controller is configured to generate a leak alarm condition if the current flow rate is greater than any combination of a percentage threshold, a limit threshold, and / or a variation threshold.

[0066] In some embodiments, the percentage of predicted flow is from about 105% to about 180%, or from about 110% to about 120%, or from about 150% to about 180%.

[0067] In some embodiments, the limit threshold is based on the flow generator output and a constant, where the constant is a predetermined conductance.

[0068] In some embodiments, the variation threshold is based on the standard deviation of a variable indicative of the conductance of the flow path.

[0069] In some embodiments, the variation threshold is based on a predicted flow rate.

[0070] In some embodiments, the variation threshold is based on the error of the mean of a variable indicative of the conductance of the flow path.

[0071] In some embodiments, the controller is configured to generate at least one occlusion alarm condition if the current flow rate is less than at least one occlusion flow rate threshold.

[0072] In some embodiments, an occlusion alarm condition is generated if the current flow rate is less than all of the at least one occlusion flow rate thresholds.

[0073] In some embodiments, an occlusion alarm condition is generated after multiple instances where the current flow is less than at least one occlusion flow threshold.

[0074] In some embodiments, the at least one occlusion flow threshold is: A percentage threshold based on a percentage of the predicted flow rate; a limit threshold based on the flow generator output and optionally a constant; Fluctuation threshold based on predicted flow fluctuation Includes one or more of the following.

[0075] In some embodiments, if the current flow rate is less than any combination of the percentage threshold, the limit threshold, and / or the variation threshold, the controller is configured to generate an occlusion alarm condition.

[0076] In some embodiments, the percentage of predicted flow is from about 40% to about 95%, or from about 50% to about 90%, or from about 60% to about 80% of the predicted flow.

[0077] In some embodiments, the limit threshold is based on the flow generator output and a constant, where the constant is a predetermined conductance.

[0078] In some embodiments, the variation threshold is based on the standard deviation of a variable indicative of the conductance of the flow path.

[0079] In some embodiments, the variation threshold is based on a predicted flow rate.

[0080] In some embodiments, the variation threshold is based on the error of the mean of a variable indicative of the conductance of the flow path.

[0081] In some embodiments, in response to the generation of at least one occlusion alarm condition and / or at least one leakage alarm condition, the controller controls the motor speed to a predetermined safe motor speed.

[0082] In some embodiments, the controller controls the motor speed at a predetermined safe motor speed until at least one leak alarm condition or at least one occlusion alarm condition is cleared.

[0083] In some embodiments, the leak alarm condition and / or the occlusion alarm condition are: Audible alarm and Visual alarm Includes one or more of the following.

[0084] In some embodiments, the variable indicative of the conductance of the flow path can be represented by a probability density function.

[0085] In some embodiments, the variable indicative of the conductance of the flow path is based on one or more weighting coefficients.

[0086] In some embodiments, the variable indicative of the conductance of the flow path is based on conductance data, the conductance data including at least one past determination of the conductance of the flow path.

[0087] In some embodiments, the variable indicative of flow path conductance is based on flow path conductance data over a time window, optionally the time window being the previous 20 seconds.

[0088] In some embodiments, at each time step or periodically, a determination of the conductance of the flow path is stored as at least one previous determination of the conductance of the flow path.

[0089] In some embodiments, the conductance data includes timestamp information associated with each past determination of the conductance of the flow path.

[0090] In some embodiments, the timestamp information includes the amount of time that has elapsed since a previous determination of the conductance of the flow path was determined.

[0091] In some embodiments, the conductance data is weighted in identifying a variable indicative of the conductance of the flow path based on associated time stamp information.

[0092] In some embodiments, more recent conductance data is given more weight than older conductance data.

[0093] In some embodiments, the conductance data includes a weighting factor associated with each past determination of the conductance of the flow path.

[0094] In some embodiments, the controller is configured to determine the conductance of the flow path and to constantly or periodically determine an expected flow rate for the flow path.

[0095] Numerical ranges disclosed herein (e.g., 1 to 10) are intended to incorporate reference to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10), as well as any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7).

[0096] The embodiments described herein may be broadly related to the parts, elements, and features referred to or shown in the specification of this application, individually or collectively, as well as any or all combinations of any two or more of said parts, elements, or features, and where specific wholes for which there are known equivalents in the art to which the invention pertains are set forth herein, such known equivalents are deemed to be incorporated herein as if individually set forth.

[0097] When references are made herein to external sources of information, including patents and other publications, this is generally for the purpose of providing a context for discussing features of the present invention. Unless otherwise noted, the references to such sources should not be construed as an admission that such sources are prior art in any jurisdiction or that such sources form part of the common general knowledge in the art. [Brief description of the drawings]

[0098] [Figure 1] 1 illustrates in schematic form a respiratory assistance device; [Diagram 2] 1 shows a sensing circuit board that may be used in a respiratory assistance device. [Diagram 3] FIG. 1 is a first bottom perspective view of the main housing of the respiratory assistance device showing a recess within the housing for the motor and / or sensor module subassembly. [Figure 3A] FIG. 13 is a second bottom perspective view of the main housing of the respiratory assistance device showing recesses for the motor and / or sensor module subassembly. [Figure 4] FIG. 1 is a perspective view of a respiratory assistance device. [Diagram 5]FIG. 13 is a perspective view of the motor and / or sensor subassembly under the main housing and fixed elbow of the respiratory assistance device. [Figure 6] FIG. 1 is an exploded perspective view of components of the motor and / or sensor subassembly, showing the gas flow path through the subassembly diagrammatically by →. [Figure 7] FIG. 13 is a bottom view of the cover and the sense PCB of the motor and / or sensor subassembly showing the location of the sensors. [Figure 8] FIG. 2 is a schematic gas flow diagram of the filter module and valve module with solid arrows indicating flow. [Figure 9] 1 illustrates an example process for determining whether a flow set point is reachable. [Figure 10] 1 illustrates an example of a relationship between motor speed limits and predicted flow rates. [Figure 11A] 4 shows various comparisons of predicted minimum flow rates and flow set points. [Figure 11B-1] 4 shows various comparisons of predicted minimum flow rates and flow set points. [Figure 11B-2] 4 shows various comparisons of predicted minimum flow rates and flow set points. [Figure 11C] 1 illustrates an example process for determining whether a flow set point is reachable. [Figure 12A] 4 shows various comparisons of predicted maximum flow rate and flow rate set points. [Figure 12B] 4 shows various comparisons of predicted maximum flow rate and flow rate set points. [Figure 12C] 4 shows various comparisons of predicted maximum flow rate and flow rate set points. [Figure 12D] 4 shows various comparisons of predicted maximum flow rate and flow rate set points. [Figure 12E] 1 illustrates an example process for determining whether a flow set point is reachable and whether an occlusion exists. [Figure 13] 1 illustrates an example of determining whether a flow set point is reachable and whether an occlusion exists. [Figure 14] A method for determining a leak or blockage based on a predicted flow rate is shown. [Figure 15A]1 shows a diagram of leak flow threshold plotted with predicted flow and current flow. [Figure 15B] 1 shows a diagram of leak flow threshold plotted with predicted flow and current flow. [Figure 15C] 1 shows a diagram of occlusion flow threshold plotted with predicted flow and current flow. [Figure 15D] 1 shows a diagram of occlusion flow threshold plotted with predicted flow and current flow. [Figure 16] 1 shows an example of a motor speed and associated predicted flow rate. [Figure 17] 1 shows an example of a leak event and several leak flow rate thresholds. [Figure 18] 1 shows an example of an occlusion event and several occlusion flow thresholds. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0099] Respiratory assistance device 10 is shown in Figure 1. Respiratory assistance device 10 may comprise a main housing 100 that includes one or more of a flow generator 11, in some embodiments in the form of a motor-impeller arrangement (e.g., a blower), an optional humidifier 12, a controller 13, and a user interface 14 (e.g., comprising a display and input devices such as buttons, touch screen, etc.).

[0100] In some embodiments, the humidifier 12 may include a humidification chamber. The humidification chamber may be configured to be removed from the humidifier (e.g., for replacement, cleaning, and / or refilling). Alternatively, the humidification chamber may be integral with the humidifier.

[0101] In some embodiments, the humidifier 12 may include a humidifier warming element 310 (see FIG. 4). The humidifier warming element provides heat to the liquid chamber 300. The liquid in the liquid chamber may be water or another liquid and / or may include one or more liquid mixtures (e.g., a mixture of water and a medicinal agent).

[0102] The humidifier 12 (if present) may humidify and / or warm the gas flow to an appropriate level. The controller 13 may be configured to control the humidifier 12 (e.g. by controlling at least a humidifier warming element).

[0103] The controller 13 may be configured or programmed to control the operation of the respiratory assistance apparatus 10. For example, the controller 13 may control components of the respiratory assistance apparatus 10, including, but not limited to, the operation of the flow generator 11 to generate the gas flow(s) for delivery to the patient, the operation of the humidifier 12 (if present) to humidify and / or warm the generated gas flow, control of oxygen flow to the flow generator blower, receiving user input from a user interface 14 for reconfiguring and / or user-defined operation of the respiratory assistance apparatus 10, and outputting information to a user (e.g., on a display).

[0104] The controller 13 may include one or more computer processors and associated non-transitory memory or storage media that store processor-executable instructions or code that, when executed by the one or more processors, cause the respiratory treatment device to perform the steps and processes described herein.

[0105] The term respiratory assistance device may be used interchangeably with respiratory assistance device, respiratory treatment device, or flow therapy device.

[0106] The term respiratory assistance system may be used interchangeably with respiratory assistance system, respiratory treatment system, or flow therapy system.

[0107] The term current flow rate may refer to a measurement of flow rate that has just been made (e.g., at a current time step). It will be appreciated that the term current flow rate is not limited to the most recent flow rate determination, but includes a recently made flow rate determination (e.g., a previous time step or a most recent flow rate determination) and / or a filtered flow data determination (which may optionally include signal filtering and / or processing) made based on a series of past measurements.

[0108] It will be appreciated that the methods described herein may be performed by a controller (or another processor).

[0109] The methods described herein may be implemented as software or software modules as part of control software (e.g., computer readable instructions) stored in the controller (or associated memory) and executed by the controller (and / or associated processor).

[0110] The user may be one or more of a patient, a medical professional (eg, a clinician), or anyone else interested in using the device.

[0111] As used herein, "gas flow" may refer to any gas flow that may be provided by a respiratory assistance device, such as a flow of ambient air, a flow containing substantially 100% oxygen, and / or a flow containing any combination of ambient air and oxygen.

[0112] The patient respiratory conduit 16 is coupled at one end to a gas outlet 21 of the housing 100 of the respiratory assistance apparatus 10. The patient respiratory conduit 16 is coupled at the other end to a patient interface 17, such as a non-sealing nasal cannula having a manifold 19 and prongs 18. Additionally or alternatively, the patient respiratory conduit 16 may be coupled to a face mask, a nasal mask, a nasal pillow mask, an endotracheal tube, and / or a tracheostomy interface, or the like.

[0113] The gas flow produced by the respiratory assistance device 10 may be humidified and delivered to the patient via a patient respiratory conduit 16 and a patient interface 17.

[0114] The patient breathing conduit 16 may include a heating element 16a for heating the gas flow delivered therethrough to the patient. The heating element 16a may be under the control of the controller 13. In at least one configuration, the heating element 16a is a heater wire. The patient breathing conduit 16 and / or the patient interface 17 may be considered part of a respiratory assistance treatment system. The respiratory assistance system 1 may include the respiratory assistance device 10, the patient breathing conduit 16, and the patient interface 17.

[0115] The controller 13 can control the flow generator 11 to generate a gas flow at a desired rate. The controller 13 can also control the supplemental oxygen inlet so that supplemental oxygen can be delivered.

[0116] The controller 13 may also control a humidifier warming element in the humidifier 12 and / or a warming element 16a in the patient conduit 16 to warm the gas to a desired temperature for a desired therapeutic level and / or patient comfort level.

[0117] The controller 13 may be provided with, or may determine, a suitable target temperature for the gas stream. The controller 13 may control the humidifier 12 and / or the humidifier heating element in heating element 16b based on the suitable target temperature or temperatures for the gas stream.

[0118] In some embodiments, the controller 13 may control a humidifier heating element in the humidifier 12 based on a set dew point at the patient interface and / or the end of the respiratory conduit.

[0119] In some embodiments, the controller 13 may control the warming element 16b based on a set point temperature of the gas at the patient interface and / or the end of the breathing conduit.

[0120] 4, the oxygen inlet 28 includes a valve 1003 through which pressurized gas can enter the respiratory treatment device 10. The valve can control the flow of oxygen to the respiratory treatment device 10. The valve can be any type of valve, including a proportional valve or a binary valve.

[0121] The oxygen source can be an oxygen tank or a hospital oxygen supply. Medical oxygen is typically 95%-100% pure. Lower purity oxygen sources can also be used. Examples of valve modules and filters are disclosed in International Publication WO 2018074935, filed October 18, entitled "Valve Module and Filter," which is hereby incorporated by reference in its entirety.

[0122] Respiratory assistance device 10 is capable of measuring and controlling the oxygen content of the gas being delivered to the patient and, therefore, the oxygen content of the gas inhaled by the patient.

[0123] In some embodiments, respiratory assistance device 10 may provide high-flow therapy, where a high flow rate of delivered gas meets or exceeds the patient's peak respiratory demand.

[0124] Operational sensors 3a, 3b, 3c, such as flow, temperature, humidity and / or pressure sensors, may be located at various locations in the respiratory assistance apparatus 10. Additional sensors (e.g. sensors 20, 25) may be located at various locations in the patient conduit 16 and / or patient interface 17 (e.g. there may be a temperature sensor 29 at or near the end of the respiratory tube).

[0125] The flow path of gas through device 10 may be provided by one or more components of the system. For example, in Figure 1, the flow path of gas may be defined between the output of flow generator 11 and the patient via humidifier 12, conduit 16, patient interface 19, and any intermediate components. It will be appreciated that the flow path may be provided by different combinations of system components.

[0126] Respiratory treatment device 10 may have a transmitter, receiver, and / or transceiver 15 to enable controller 13 to receive signals 8 from sensors and / or control various components of respiratory assistance device 10, including but not limited to flow generator 11, humidifier 12, heating element 16a, humidifier heating element, or accessories or peripherals associated with respiratory assistance device 10. Additionally or alternatively, transmitter, receiver, and / or transceiver 15 may send data to a remote server or enable remote control of respiratory treatment device 10 or respiratory treatment system 1.

[0127] In some embodiments, the transmitter, receiver, and / or transceiver 15 may be provided as or as part of a modem. The transmitter, receiver, and / or transceiver 15 may use one or more communication protocols known in the art, such as Bluetooth, cellular (3G, 4G, or 5G, etc.).

[0128] In some embodiments, one or more leak or occlusion events and / or alarms (described in more detail below) may be transmitted to one or more servers and / or devices (e.g., computers, phones, or tablets). Additional information associated with the events or alarms (e.g., time, duration, or severity) may further be transmitted to the servers and / or devices.

[0129] In some embodiments, one or more leak or obstruction events and / or alarms (described in more detail below) may be sent to a remote patient management system. The remote patient management system may be implemented, for example, as a distributed computer system including one or more servers and / or a cloud-based system. The one or more leak or obstruction events and / or alarms may be incorporated into a report. The report may be a patient report () or may be related to a patient population. The number of one or more leak or obstruction events and / or alarms may be included in the report along with other information (e.g., associated times of the events and / or alarms).

[0130] As described above, the respiratory assistance device 10 can measure and control the oxygen content of the gas being delivered to the patient. The oxygen may be measured by placing one or more gas composition sensors (such as an ultrasound transducer system) after mixing of the oxygen and ambient air. Measurements may occur within the respiratory treatment device 10, at the patient breathing conduit 16, at the patient interface 17, or at any other suitable location.

[0131] The oxygen concentration measured by the device may be equivalent to the fraction of oxygen delivered (FdO2) and may be approximately the same as the concentration of oxygen the patient is breathing, the fraction of oxygen inspired (FiO2), and therefore these terms may be considered equivalent.

[0132] The oxygen concentration can also be measured by using flow sensors in at least two of the ambient air inlet conduit, the oxygen inlet conduit, and the patient breathing conduit to determine the flow rates of at least two gases. By determining the flow rates of both inlet gases or one inlet gas and one total flow rate along with the assumed or measured oxygen concentration of the inlet gases (approximately 20.9% for ambient air and approximately 100% for oxygen), the oxygen concentration of the final gas composition can be calculated. Alternatively, flow sensors can be placed in all three of the ambient air inlet conduit, the oxygen inlet conduit, and the patient breathing conduit to allow testing that each sensor is functioning correctly by checking for redundancy and consistency of readings. Other methods of measuring the oxygen concentration being delivered by the respiratory assistance device 10 can also be used.

[0133] The respiratory assistance device 10 may include a patient sensor 26, such as a pulse oximeter or patient monitoring system, that measures one or more physiological parameters of the patient, such as the patient's blood oxygen level (e.g., blood oxygen saturation (SpO2)), heart rate, respiration rate, perfusion index, etc., and provides a measure of signal quality. The sensor 26 may communicate with the controller 13 through a wired connection or by communication through a wireless transmitter in the sensor 26. The sensor 26 may be a disposable adhesive sensor designed to be connected to the patient's finger. The sensor 26 may also be a non-disposable sensor (i.e., a reusable sensor). Sensors designed for different age groups and connected to different locations on the patient are available and may be used with the respiratory assistance system 1. The pulse oximeter may be attached to the patient, typically on a finger, although other locations such as the earlobe are also options. The pulse oximeter may be connected to a processor in the respiratory treatment device 10 and may provide a signal indicative of the patient's blood oxygen saturation at all times. The patient sensor 26 may be a hot-swappable device that may be attached or replaced during operation of the respiratory assistance device 10. For example, patient sensors 26 may connect to respiratory assistance apparatus 10 using a USB interface or a wireless communication protocol (such as Bluetooth®). During operation, if patient sensors 26 are disconnected, respiratory assistance apparatus 10 may continue to operate in a previous operating state for a defined period of time. After the defined period of time, respiratory assistance apparatus 10 may trigger an alarm, transition from an automatic mode to a manual mode, and / or exit a control mode (e.g., automatic or manual mode) entirely. Patient sensors 26 may be a bedside monitoring system or other patient monitoring system that communicates with respiratory assistance apparatus 10 through a physical or wireless interface.

[0134] Respiratory assistance device 10 may include or be in the form of a high-flow therapy device.

[0135] High flow therapy as discussed herein is intended to be given its typical ordinary meaning as understood by those skilled in the art and generally refers to a respiratory assistance device delivering a targeted flow of humidified respiratory gas through an intentionally unsealed patient interface, generally at a flow rate intended to meet or exceed the patient's inhalation flow. Exemplary patient interfaces include, but are not limited to, nasal or tracheal patient interfaces. Typical flow rates for adults are often, but are not limited to, in the range of about 15 liters / minute to about 60 liters / minute or more. Typical flow rates for pediatric patients (such as neonates, infants, and children) are often, but are not limited to, in the range of about 1 liter / minute per kilogram of patient body weight to about 3 liters / minute per kilogram of patient body weight or more. High flow therapy may also optionally include a gas mixture composition that includes administration of supplemental oxygen and / or therapeutic drugs. High flow therapy is often referred to as high flow nasal (NHF), humidified high flow nasal cannula (HHFNC), high flow nasal oxygen (HFNO), high flow therapy (HFT), or high flow tracheal (THF), among other common names.

[0136] For example, in some configurations, for an adult patient, "high flow therapy" can refer to delivery of gas to the patient at a flow rate of about 10 liters per minute (10 LPM) or greater, such as from about 10 LPM to about 100 LPM, from about 15 LPM to about 95 LPM, from about 20 LPM to about 90 LPM, from about 25 LPM to about 85 LPM, from about 30 LPM to about 80 LPM, from about 35 LPM to about 75 LPM, from about 40 LPM to about 70 LPM, from about 45 LPM to about 65 LPM, or from about 50 LPM to about 60 LPM. In some configurations, for neonatal, infant, or child patients, "high flow therapy" may refer to delivery of gas to the patient at a flow rate of greater than 1 LPM, such as about 1 LPM to about 25 LPM, about 2 LPM to about 25 LPM, about 2 LPM to about 5 LPM, about 5 LPM to about 25 LPM, about 5 LPM to about 10 LPM, about 10 LPM to about 25 LPM, about 10 LPM to about 20 LPM, about 10 LPM to about 15 LPM, or about 20 LPM to about 25 LPM. In adult, neonatal, infant, or child patients, high flow therapy devices may, in some configurations, deliver gas to the patient at a flow rate of about 1 LPM to about 100 LPM, or within any of the subranges outlined above. The delivered gas may include a percentage of oxygen. In some configurations, the percentage of oxygen in the delivered gas can be about 20% to about 100%, about 30% to about 100%, about 40% to about 100%, about 50% to about 100%, about 60% to about 100%, about 70% to about 100%, about 80% to about 100%, about 90% to about 100%, about 100%, or 100%.

[0137] High-flow therapy can be effective in meeting or exceeding a patient's inspiratory flow, increasing a patient's oxygenation, and / or reducing the work of breathing.

[0138] High flow therapy may be administered to the patient's nostrils and / or via an oral or tracheostomy interface.

[0139] High flow therapy can create a flushing effect on the nasopharynx such that the anatomical dead spaces in the upper airway are flushed with high inflow gas flow. This can create a reservoir of fresh gas available for every breath while reducing nitrogen and carbon dioxide rebreathing. Meeting respiratory demand and flushing the airway is even more important when attempting to control the patient's FdO2. High flow therapy can be delivered using a non-sealing patient interface, such as a nasal cannula. High flow therapy can reduce the patient's breathing rate. High flow therapy can provide expiratory resistance to the patient.

[0140] The term "non-sealed patient interface" (i.e., a patient interface that is not sealed), as used herein, may refer to an interface that provides an air link between the patient's airway and a source of gas flow (such as from the flow generator 11) that does not completely occlude the patient's airway. A non-sealed air link may include less than about 95% occlusion of the patient's airway. A non-sealed air link may include less than about 90% occlusion of the patient's airway. A non-sealed air link may include between about 40% and about 80% occlusion of the patient's airway. The airway may include one or both of the patient's nostrils and / or the patient's mouth. In the case of a nasal cannula, the airway is through the nares.

[0141] The flow generator 11 may be or may comprise a blower module. The blower module may comprise at least one blower 11 configured to generate the gas flow.

[0142] The flow generator 11 may include an ambient air inlet 27 that may allow ambient air from the room to be drawn into the blower. The respiratory assistance apparatus 10 may also include an oxygen inlet 28 that leads to a valve that allows pressurized gas to enter the flow generator 11. The valve may control the flow of oxygen to the flow generator 11. The valve may be any type of valve, including a proportional valve or a binary valve.

[0143] The blower 11 may operate at a motor speed of greater than about 1,000 RPM and less than about 8,000 RPM, greater than about 2,000 RPM and less than about 10,000 RPM, or between any of the above values. The blower 11 may mix gases entering the blower 11 through inlets (e.g., ambient air inlet 27 and / or oxygen inlet 28). Using the blower 11 as a mixer may reduce the pressure drop over a system having a separate mixer, such as a static mixer with a baffle.

[0144] The respiratory assistance device may further comprise a gas composition sensor, which may be a sensor as described below (e.g. an ultrasonic transducer arrangement).

[0145] The respiratory assistance device 10 includes a flow sensor that may be configured to measure the flow rate of breathable gas to the patient.

[0146] The controller 13 may include one or more processors, in which computer readable instructions may be configured.

[0147] The controller 13 may include at least one memory element. The memory element may be configured to store the computer readable instructions.

[0148] The memory element may be non-transitory.

[0149] The respiratory assistance device may include at least one display module configured to display the alarm output.

[0150] The respiratory assistance device may include at least one audio module configured to emit an audible alarm.

[0151] In some embodiments, the at least one audible module may include a speaker.

[0152] The display module may include at least one display (eg, a liquid crystal display (LCD) or a light emitting diode (LED) display, although it will be appreciated that any display technology may be used).

[0153] The display module may be a removable display (e.g., a display that can be disconnected from the device). The removable display may be configured to be connected to the device (e.g., a controller for the device) via a wired or wireless connection to send and receive data from the device (e.g., a controller for the device).

[0154] The display module may be a remote display external to the device.

[0155] The display module may be configured to receive input to the system (eg, as a touch screen).

[0156] The display module may be configured to be an input / output (I / O) module, for example, the display module may be configured to receive input from a user and provide output to the user.

[0157] The display module may be in communication with the controller 13. In some embodiments, the display module may provide information to the controller 13 (e.g., set points). In some embodiments, the display module may receive information from the controller 13 (e.g., alarms, sensor outputs, and / or other calculated variables).

[0158] With further reference to FIG. 2, there is shown a sensing circuit board 2200 that may be implemented in the respiratory assistance device 10. The sensing circuit board 2200 may be located in the sensor chamber such that the sensing circuit board 2200 is at least partially immersed in the gas flow. The gas flow may exit the blower 11 through a conduit and enter a flow path in the sensor chamber. At least some of the sensors of the sensing circuit board 2200 may be located in the gas flow (indicated in the direction by arrow 2203) to measure properties of the gas in the flow. After passing through the flow path in the sensor chamber, the gas may exit the sensor chamber and enter the humidifier 12 as described above.

[0159] The sensing circuit board 2200 can be a printed sensing circuit board (PCB). Alternatively, the circuit on the board 2200 can be made with electrical wires connecting electronic components instead of being printed on a circuit board. At least a portion of the sensing circuit board 2200 can be mounted outside the gas flow. The gas flow can be generated by the flow generator 11 described above. The sensing circuit board 2200 can include an ultrasonic transducer 2204. The sensing circuit board 2200 can include one or more thermistors 2205. The thermistor 2205 can be configured to measure the temperature of the gas flow. The sensing circuit board 2200 can include a thermistor flow sensor 2206. The sensing circuit board 2200 can also include other types of sensors, such as humidity sensors (including humidity only sensors used with a separate temperature sensor and combination humidity and temperature sensors), sensors for measuring atmospheric pressure, sensors for measuring differential pressure, and / or sensors for measuring gauge pressure. The thermistor flow sensor 2206 may include a hot wire anemometer, such as a platinum wire, and / or a thermistor, such as a negative temperature coefficient (NTC) thermistor or a positive temperature coefficient (PTC) thermistor. Other non-limiting examples of heated temperature sensing elements include glass or epoxy encapsulated or unencapsulated thermistors. The thermistor flow sensor 2206 may be configured to measure the flow rate of the gas by being supplied with a constant power or by being maintained at a constant temperature or by maintaining a constant temperature difference between the sensor and the gas flow.

[0160] Positioning the thermistor 2205 and / or thermistor flow sensor 2206 downstream of the blower and mixer combination means that the sensor readings are dependent on the heat provided to the gas flow by the blower. Additionally, immersing at least a portion of the sensing circuit board and sensor in the flow path can increase the accuracy of the measurement. Compared to non-immersed sensors, sensors immersed in the flow are more likely to experience the same conditions, such as temperature and pressure, as the gas flows. Thus, these immersed sensors may provide a better representation of the gas flow characteristics.

[0161] The sensing circuit board 2200 may include an ultrasonic transducer, transceiver, or other sensor that measures properties of the gas stream, such as the composition or concentration of one or more gases in the gas stream. As will be appreciated, any suitable transducer, transceiver, or sensor may be mounted on the sensing circuit board 2200. In this configuration, the gas composition sensor is an ultrasonic transducer that employs ultrasonic or sound waves to determine gas concentration.

[0162] Some examples of flow therapy devices are disclosed in International Patent Application No. PCT / NZ2016 / 050193, filed December 2, 2016, entitled "Flow Path Sensing for Flow Therapy Apparatus," and International Patent Application No. PCT / IB2016 / 053761, filed June 24, 2016, entitled "Breathing Assistance Apparatus," which are hereby incorporated by reference in their entireties.

[0163] The configuration of the respiratory assistance device 10 is shown in Figures 3 to 7. For example, as shown in Figure 4, the respiratory assistance device includes a main housing 100. The main housing 100 has an upper main housing chassis 102 and a lower main housing chassis 202.

[0164] As shown in Figures 3 and 3A, the lower chassis 202 has a motor recess 250 for receiving a removable or non-removable motor and / or sensor module 400 shown in Figures 13-15 and described in more detail below. A recess opening 251 is provided in the bottom wall 230 adjacent the rear edge for receiving a removable or non-removable motor / sensor module 400 shown in Figures 5 and 6 and described in more detail below.

[0165] 5-7 show in more detail the motor and / or sensor module or subassembly 400. As mentioned above, the lower chassis 202 includes a recess 250 for receiving the motor and / or sensor module 400.

[0166] 5-7, the motor and / or sensor module 400 includes a stacked arrangement of three main components: a base 403 of the subassembly 400 (on which the motor 402 is located), an outlet gas flow path and sensing layer 420 located on the base 403, and a cover layer 440. The base 403, the sensing layer 420, and the cover layer 440 are assembled to form a subassembly housing having a shape complementary to the shape of the recess 250 such that the subassembly 400 can be received in the recess 250. The base 403 is configured to close the recess opening 251 when the subassembly 400 is located in the recess 250. The subassembly 400 may be maintained in place or non-removably secured in the recess in any suitable manner, such as, for example, with a fastener, clip, or quick release device.

[0167] The sensing layer includes a gas flow passage having one or more sensors, the gas flow passage being positioned to deliver gas to an outlet of the housing.

[0168] The motor 402 has a body 408 that defines an impeller chamber containing an impeller. The motor 402 can be any suitable gas blower motor, such as a motor and impeller assembly of the type described in published PCT specification WO 2013 / 009193, the contents of which are incorporated herein by reference in their entirety.

[0169] The gas outlet 406 is in fluid communication with the gas inlet of the outlet gas flow path and a sensing layer 420 overlying the motor. The layer 420 comprises a body 422 with a number of mounting legs 425 that can be inserted into a number of mounting slots (not shown) in the base 403 to secure the body 422 to the base 403. In one configuration, the body 422 defines a gas flow path coupling the gas outlet 406 with the gas inlet of the gas flow path and the sensing layer 420.

[0170] The body 422 defines a lower portion 426 of the detection gas passageway. The cover layer 440 has a body 442 that defines an upper portion 446 of the detection gas passageway, the upper and lower portions 426, 446 having shapes that substantially correspond to one another.

[0171] 6 and 7, the gas flow path comprises a linear elongated gas flow section 428, 448. The inlet is in fluid communication with a tangential inlet section 430, 450 of the gas flow path located at or adjacent the inlet end of the linear elongated section 428, 448 of the gas flow path. Recesses 433, 453 and 434, 454 may be provided at both ends of the linear elongated section of the gas flow path.

[0172] A gas outlet 452 extends vertically through the body 442 of the cover layer 440 and is disposed at or adjacent the opposing outlet ends of the linear elongated portions 428, 448 of the gas flow passage. The gas outlet 452 is in fluid communication with the top of the motor recess 250, which in turn is in fluid communication with the gas flow passage. Again, due to the configuration of the walls 252 and ceiling 262 of the recess 250, if there is any gas leakage from the motor / sensor module 400, it will be vented to atmosphere rather than entering the portion of the main housing 100 that contains most of the electronics and controls. The recess 250 may include spacers, such as lugs, that project downwardly from the ceiling 262 as shown in FIG. 15 to maintain adequate space for gas flow from the gas outlet 452 and the ceiling 262 of the recess.

[0173] 7, it can be seen that at least a portion of the gas flow through and exiting the motor and / or sensing module 400 has a serpentine or undulating configuration. For example, the direction of gas flow moving through the elongated portions 428, 448 is generally opposite the direction of gas flow moving from the gas outlet 452 to the gas flow inlet through the elbow 324.

[0174] As shown in Figures 6 and 7, the cover layer 440 includes a sensing printed circuit board (PCB) 456. The cover layer 440 may also include one or more temperature sensors, such as thermistors, on the elongated portions 428, 448 of the gas flow path. One sensor will measure the gas temperature, and the other sensor may act as a redundant temperature sensor. Alternatively, one of the thermistors may be used as a reference flow sensor (e.g., via use as a constant temperature thermistor), and the measured temperature may be used to determine the gas flow rate through the portions 428, 448 of the gas flow path. The one or more temperature sensors may be located on a portion of the sensing PCB 456 that faces the gas flow. The sensing PCB 456 may further include other sensors, including, but not limited to, pressure sensors, humidity sensors, and dew point sensors.

[0175] One or both electronics boards 272 may be in electrical communication with or coupled to the sensors to process information received from the sensors and to operate the device 10 based on the information received from the sensors.

[0176] In an alternative configuration, the motor / impeller unit may be provided separate from the apparatus 10. In that configuration, the module received in the recess 250 may include only a gas flow path and various sensors for delivering gas to the fixed elbow 324 and thereby to the liquid chamber 300. In an alternative configuration, the module received in the recess 250 may include only a motor and gas flow path and may not include sensors.

[0177] In another alternative configuration, the motor and / or sensor module 400 may not be removable from the recess 250 , but instead may be permanently mounted to the recess 250 .

[0178] Some configurations may provide the benefit of isolating electronic circuits / components from gases in the gas stream.

[0179] The flow path is compact and has reduced turns / sharp turns, thereby reducing flow separation and resistance to flow.

[0180] The motor and flow path arrangement provides another layer of isolation through the wall arrangement.

[0181] Having a modular motor and / or sensor module allows different portions of the module to be disconnected when necessary for cleaning and / or servicing.

[0182] In some embodiments, there are no leakage paths in the motor and / or sensor module.

[0183] In some embodiments, the motor and / or sensor module may be potential leak points, as a leak in that area could lead to oxygen being vented to the atmosphere or liquid chamber.

[0184] For example, as shown in Figure 8, device 10 may include a valve module that controls the flow of oxygen and / or other gases into the gas flow path of device 10, allowing device 10 to regulate the percentage of oxygen introduced into the airflow. The valve module is formed as a modular unit for ease of manufacture, assembly, servicing, or replacement, e.g., in the event of malfunction, routine maintenance, or future upgrades / improvements.

[0185] The apparatus 10 may include a filter module 1001 that may include a filter.

[0186] The filter and valve modules described herein may provide various gas flow paths to the device. For example, the valve module may control the flow of oxygen into the gas flow path of the device through the valve and filter modules. Alternatively, the valve module may be bypassed by direct connection of an alternate oxygen source to the filter module via an alternate supply inlet. This may be practical in situations where a user may wish to manually adjust the oxygen supply (i.e., via a wall-fed rotameter).

[0187] It will be appreciated that the filter modules and valve modules described herein may be used separately in an apparatus to deliver a gas flow, or alternatively, the filter and valve modules may be used together as a filter and valve assembly for improved performance.

[0188] In the illustrated configuration, the device 10 receives oxygen by at least one of the following: via a valve module (for automatic oxygen regulation by the device) or Via an alternative gas inlet provided at the top of the filter (allowing for attachment of a manually adjustable oxygen source - such as a wall supply regulated by a regulator).

[0189] The various configurations described are merely exemplary configurations: any one or more features from any configuration may be used in combination with any one or more features from any other configuration.

[0190] As another example, the motor and / or sensor subassembly recesses are described as being on the underside of the main housing, but may alternatively be on the rear, side, front, or top of the housing. The air and / or oxygen inlets may also be in different locations as desired.

[0191] As another example, rather than the liquid chamber and chamber bay being configured so that the liquid chamber is inserted into and removed from the chamber bay from the front of the housing, the configuration may be such that the liquid chamber is inserted into and removed from the chamber bay from the side, rear, or top of the housing.

[0192] As another example, although the filter module is described as being inserted into the housing from above and the valve module is described as being inserted into the housing from below, either or both of those components can be inserted into any suitable portion of the housing, such as the top, bottom, side, front, or back.

[0193] The filter and valve modules are described with reference to a respiratory assistance device capable of delivering heated and humidified gas to a patient or user. The device may be suitable for treating patients with chronic obstructive pulmonary disease (COPD) and / or patients experiencing difficulty in breathing. For example, treating patients with difficulty in breathing, low oxygen saturation (i.e. SpO2), or high partial pressure of carbon dioxide (i.e. PaCO2). The device may be configured to deliver gas to the patient interface at a high flow rate (i.e. high flow therapy - in particular nasal high flow therapy). Nasal high flow therapy may also be used to treat infectious diseases causing difficulty in breathing, such as COVID19.

[0194] Alternatively, the filter module and / or valve module may be used in a device for different purposes. The device may be a high flow therapy device or a low flow therapy device. The feature may also be provided in a device providing continuous positive airway pressure (CPAP) that may deliver gas (humidified or otherwise) at positive pressure.

[0195] The filter module and / or valve module may alternatively be used with devices that do not require a humidifier and therefore do not require a liquid chamber 300. For example, it will be appreciated that the configuration that separates the motor and gas flow path from the electrical and electronic components has wide application in other types of gas delivery devices.

[0196] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of methods and apparatus for predicting the minimum and / or maximum flow provided by a breathing apparatus will now be described.

[0197] As described above, a user or clinician may input a flow rate setpoint into the device via a user interface, and the device will then attempt to control a motor or other flow generator to provide the flow rate of the flow rate setpoint.

[0198] If a particular flow path cannot be used to deliver flow to the patient at the flow set point (eg, if the conductance of the flow path is too high or too low), the patient may not receive proper therapy.

[0199] For example, if the flow set point is greater than the predicted maximum flow rate for the flow path, the patient may receive a flow rate that is less than the flow rate expected by the clinician (e.g., a flow rate equal to the predicted maximum flow rate for the flow path) because the current condition of the flow path does not allow the device to provide a flow rate high enough to meet the flow set point (which may indicate, for example, an occlusion).

[0200] In another example, if the flow set point is less than the expected minimum flow rate, the user may receive a higher flow rate than the clinician expects because the current condition of the flow path does not allow the device to provide a low enough flow rate to meet the flow set point, in which case the patient may not receive proper therapy, which may pose a risk to the patient.

[0201] Prior art systems only provide an alarm if breathing gas does not reach the flow setpoint for a period of time. However, in some cases, some of these types of systems may take a long time to detect such a situation and generate an alarm, and therefore there may be a delay before the clinician or user is notified. During this time, the patient may not receive flow at the flow setpoint and therefore may not receive proper treatment.

[0202] Identification of predicted maximum and minimum flow rates for a particular flow path (based on the allowable flow generator output range and the conductance of the flow path) can significantly reduce the time that inappropriate therapy is provided (e.g., therapy that cannot reach the flow set point). Identification of predicted maximum and minimum flow rates for a particular flow path can also reduce the time it takes to generate an alarm (and, for example, the time for a clinician to respond and take any necessary action).

[0203] Additionally, the time it takes to generate an alarm (indicating an inability to reach the flow set point) may be reduced because the device 10 does not need to attempt to reach the flow set point only to determine that it cannot be reached.

[0204] The predicted minimum flow rate and / or predicted maximum flow rate may be based on a variable indicative of the conductance of the flow path through which breathing gas is provided and on the range of acceptable flow generator outputs. For example, once a variable indicative of the conductance is calculated, the maximum and minimum flow rates may be predicted as a function of this variable indicative of the conductance and the maximum and minimum flow generator outputs, respectively. These predicted maximum and minimum flow rates represent the boundaries of the range of predicted flow rates that the flow generator can provide, given the range of acceptable flow generator outputs.

[0205] The variable indicative of the conductance of the flow path may be the conductance of the flow path or may be based on the conductance of the flow path (eg, based on conductance data, as described in more detail below).

[0206] The device may additionally or alternatively determine whether the device is approaching the ability to achieve the flow set point (given the current flow path conditions) based on minimum and maximum flow rates.

[0207] As discussed above, for example, the minimum and maximum flow rates are based on a variable that is indicative of the conductance of the flow path.

[0208] The flow path may include one or more components. The components that make up the flow path may be removable and / or replaceable, and each component may have one or more alternatives. For example, there may be several possible patient interfaces that can be connected to form part of the flow path.

[0209] The flow path may include one or more of a humidification chamber, one or more breathing conduits, a patient interface, an elbow, and a sensor module.

[0210] The flow path may be downstream of the flow generator 10 (and optionally the output of the flow generator 10).

[0211] The flow path may be downstream of the humidifier 12 (and optionally the output of the humidification chamber).

[0212] The flow path may be downstream of the elbow.

[0213] The flow path can be downstream of the sensor module.

[0214] For example, depending on the location of the sensor, the flow path (for which a variable indicative of conductance is specified) may be defined differently. For example, if a sensor is used at the output of the humidifier (i.e. 3b) or at the inlet of the conduit (i.e. 3c), the flow path may be defined as being downstream from this sensor.

[0215] In some embodiments, the flow path may include at least a humidification chamber, a patient interface, and a conduit (and optionally a sensor module).

[0216] In some embodiments, the flow path may include at least a patient interface and a conduit (and optionally a sensor module).

[0217] The value of one or more variables indicative of the conductance of a flow path will depend on the particular components within the flow path, for example, a variable indicative of the conductance of a flow path having a conduit with a larger diameter may be greater than a variable indicative of the conductance of the same flow path having a conduit with a smaller diameter.

[0218] The variable indicative of the conductance of the flow path may be based on parameters external to the flow path, such as the patient's anatomy or condition and the connection between the patient and the patient interface.

[0219] The variable indicative of the conductance of the flow path may also be based on the characteristics of the connection between the patient interface 17 and the patient. For example, the closer the fit between the prongs and the nares, the smaller the variable indicative of the conductance of the flow path (because less of the gas flow is vented to atmosphere). However, if the fit between the prongs and the nares is looser, a greater portion of the gas flow is vented to atmosphere, and therefore the variable indicative of the conductance of the flow path may be larger. This effect is more pronounced in non-sealed systems because a significant portion of the variable indicative of the conductance is based on the connection between the patient interface 17 and the patient.

[0220] As a further example, deformation of the nasal prongs may also affect variables indicative of pathway conductance.

[0221] The variable indicative of the conductance of the pathway may also be based on characteristics of the patient's respiratory system. For example, structural characteristics of the patient's respiratory system may lead to differences in the conductance of the flow paths.

[0222] A variable indicating the conductance of the flow path determines the relationship between the flow generator output and the flow rate of the breathing gas.

[0223] The variable indicative of the conductance of the flow path may be or may include the conductance of the flow path (or a portion of the flow path), the resistance to flow of the flow path (or a portion of the flow path), the pressure drop along the flow path (or a portion of the flow path), or any combination of the above.

[0224] FIG. 9 illustrates an example process for determining whether a flow setpoint is reachable.

[0225] In step 910, the controller 13 identifies a variable indicative of the conductance of the flow path.

[0226] In step 911, the controller 13 identifies the maximum and / or best flow rate for the flow path.

[0227] In step 912, the controller 13 compares the maximum and / or minimum flow rate of the flow path to the flow set point.

[0228] In step 912, the controller 13 determines whether the flow setpoint is reachable.

[0229] As mentioned above, the device may include a controller 13. The controller 13 is configured to control the flow rate of breathable gas.

[0230] The controller 13 may control the flow rate of breathable gas by controlling the flow generator output (eg, motor speed).

[0231] The controller 13 may generate the flow generator output based on one or more control algorithms.

[0232] The controller 13 may be configured to control the flow generator output within an acceptable flow generator output range. The acceptable flow generator output range may indicate operating limits within which the flow generator may operate safely. In some embodiments, the acceptable flow generator output range may indicate safety limits.

[0233] In some embodiments, for example, where the flow generator comprises a motor, the flow generator output may be a motor output. Although the flow generator output is described herein with reference to a motor output, it will be appreciated that depending on the type of flow generator, the flow generator output may be any output. In some embodiments, the flow generator output may be, for example, a target pressure for the flow path.

[0234] The allowable motor power range (eg, the flow generator power range as discussed above) may include an upper motor speed limit and / or a lower motor speed limit.

[0235] The allowable motor power range can be based on the flow set point. For example, the magnitude and / or limits of the allowable motor power range can be proportional to the flow set point or can be mathematically related to the flow set point in other ways.

[0236] The predicted maximum flow rate is based on an upper motor speed limit. The predicted minimum flow rate may be based on a lower motor speed limit.

[0237] In some embodiments, the predicted maximum flow may be further based on the current motor speed.

[0238] Figure 10 shows an example of a relationship between motor speed limits and predicted flow rates. For example, the predicted minimum flow rate (8 liters per minute (LPM)) shown in Figure 10 corresponds to a lower motor speed limit (2,000 RPM) and the predicted maximum flow rate (30 LPM) corresponds to an upper motor speed limit (10,000 RPM). In this example, the relationship between motor speed and predicted flow rate is based on a variable indicative of the conductance of the flow path.

[0239] An example of the relationship between flow rate and motor speed within an allowable motor speed range is shown at 920 in Figure 10. It will be appreciated that a variable indicative of the conductance of a flow path may represent or be based on a relationship between flow rate and motor speed in that flow path.

[0240] In some embodiments, the predicted maximum flow rate may be determined by evaluating the difference between the current motor speed and an upper motor speed limit. Similarly, the predicted minimum flow rate may be based on the difference between the current motor speed and a lower motor speed limit.

[0241] The motor output 1306 may be or may include motor speed, motor current, motor duty (duty cycle), pressure of gas in the flow path, or any combination of the above.

[0242] The controller 13 is configured to determine a variable indicative of the conductance of the flow path.

[0243] The variable indicative of the conductance of the flow path may be based on a variable indicative of the conductance of the flow path at a previous time step.

[0244] The variable indicative of the conductance of the flow path may be based on another variable indicative of the conductance of the flow path over a time window, optionally the time window being a previous time period, for example the previous 20 seconds. For example, the variable indicative of the conductance may be based on a time-weighted average conductance of the flow path.

[0245] The variable indicative of the conductance of the flow path may be a function of the current motor power and the current flow rate.

[0246] In one example of the present invention, a variable indicative of the conductance of a flow path may be proportional to the current flow rate divided by the current motor power. For example,

number

[0247] The use of motor speed to determine a variable indicative of conductance can be particularly beneficial in non-sealed systems because other variables that can be used to determine conductance (e.g., pressure) can be difficult to use due to the non-sealed patient interface.

[0248] In another example, a variable indicative of the conductance of a flow path can be proportional to the current flow divided by the square root of the current pressure. For example,

number

[0249] The predicted maximum flow rate and / or the predicted minimum flow rate may be identified periodically (optionally at each time step of the controller 13).

[0250] The controller 13 may also be configured to compare the predicted maximum flow rate and / or the predicted minimum flow rate to one or more flow rate set points.

[0251] Based on a comparison of the predicted maximum flow rate and / or the predicted minimum flow rate to the one or more flow rate set points, the controller may be further configured to generate or activate at least one alarm condition.

[0252] The at least one alarm condition may include a flow setpoint not reachable alarm and / or an occlusion alarm.

[0253] Alarm conditions related to flow set point not reachable may include a flow set point not reachable alarm associated with a flow set point being greater than a predicted maximum flow rate.

[0254] Alarm conditions related to flow set point not reachable may include a flow set point not reachable alarm associated with a flow set point being less than a predicted minimum flow rate.

[0255] In addition to or instead of the alarms described herein, the alarm may display a general alarm indication (e.g., a message that may be explained in an associated manual) and / or an indication to the user to check for specific faults in the system that may have caused the alarm. It will be appreciated that the above description of alarms is by way of example and that the specific wording may be varied.

[0256] In some situations, a flow generator output lower limit (e.g., a motor output lower limit) may prevent the device from reaching the flow setpoint. For example, if the device does not allow the flow generator output to be lowered below the flow generator output lower limit. Such a situation may occur, for example, if one or more components are disconnected from the flow path, one or more components are improperly connected, one or more components are used improperly, and / or one or more incorrect components are used.

[0257] The controller 13 may be configured to determine a situation in which the flow set point cannot be reached based on the predicted minimum flow rate and the flow set point, and in response generate a flow set point not reachable alarm.

[0258] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the flow set point is less than the predicted minimum flow rate (optionally the alarm condition is a flow set point not reachable alarm). An example of this condition is shown in Figure 11A. In Figure 11A, the flow set point 901 is 8 LPM, which is less than the predicted maximum flow rate (10 LPM).

[0259] 11A to 11B-2 and 12A to 12D show partial examples of the flow range shown in FIG.

[0260] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the flow set point is less than the predicted minimum flow rate by more than an alarm threshold. In FIG. 11B-1, the flow set point 901 is 8 LPM, which is less than the predicted minimum flow rate 906 (10 LPM) by more than an alarm threshold 905 (0.8 LPM). For example, if the flow set point were less than 9.2 LPM, an alarm condition would occur.

[0261] The minimum predicted flow rate minus the alarm threshold 905 may define the alarm limit 902 .

[0262] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the predicted minimum flow rate is greater than the flow rate set point by more than an alarm threshold. In FIG. 11B-2, the predicted minimum flow rate 906 is greater than the flow rate set point 901 (8 LPM) by more than an alarm threshold 905 (1.2 LPM). For example, if the predicted minimum flow rate were greater than 9.2 LPM, an alarm condition would occur.

[0263] The alarm threshold is a percentage of the flow set point. The alarm threshold can be about 5% to about 20% or about 10% of the flow set point. Figure 11B shows an example of this situation where the alarm threshold 905 is 0.8 LPM (i.e., 10% of the flow set point minus 8 LPM).

[0264] The alarm condition may be a "Flow setpoint not reachable" alarm, optionally a "Flow setpoint not reachable - setpoint below minimum flow" alarm.

[0265] In some embodiments, the alarm threshold may be a percentage of the expected minimum flow rate. In some embodiments, the alarm threshold may be a set amount.

[0266] 11C illustrates an example process for determining if the flow setpoint is unreachable. If the flow setpoint is unreachable, a flow setpoint unreachable alarm may be generated.

[0267] In step 950, the controller 13 identifies a variable indicative of conductance (as described in more detail elsewhere herein). The controller 13 in the respiratory device may perform step 950 at each time step during treatment.

[0268] In step 951, a predicted minimum flow rate is identified based on the variable indicative of conductance (calculated in step 950) and the minimum motor power of the allowable motor power range (which in this example represents the flow generator power).

[0269] In step 952, the predicted minimum flow is compared to the flow set point and alarm thresholds (eg, as shown in FIG. 11B).

[0270] In step 953, the controller 13 determines whether the flow set point can be reached based on the comparison in step 952. If the flow set point is less than the predicted minimum flow by more than an alarm threshold, the controller 13 may generate an alarm condition (i.e., a "set flow unreachable" alarm).

[0271] In some embodiments, the controller 13 may require several instances of the flow set point to be less than the predicted minimum flow rate by more than an alarm threshold. In these embodiments, the controller 13 may require several consecutive "set flow not reachable" events to exceed a consecutive count threshold. If the consecutive count threshold is exceeded, the controller 13 may generate an alarm condition indicating that the flow set point is less than the predicted minimum flow rate (optionally the alarm condition is a flow set point not reachable alarm).

[0272] In some embodiments, the controller 13 may require a threshold time to generate an alarm condition. For example, the controller 13 may require a threshold time that the flow set point is less than the predicted minimum flow rate by more than an alarm threshold. In these embodiments, the controller 13 may require the time that the "set flow unreachable" event is active to exceed the threshold time. If the threshold time is exceeded, the controller 13 may generate an alarm condition indicating that the flow set point is less than the predicted minimum flow rate (optionally the alarm condition is a flow set point unreachable alarm). In some embodiments, the threshold time may be from about 1 second to about 5 seconds.

[0273] In some situations, a flow generator upper limit (e.g., motor speed upper limit) may prevent the device from reaching the flow set point. For example, if the device is prevented from increasing the flow generator output beyond the flow generator output upper limit. This could be, for example, because the flow set point entered by the user is higher than the flow rate appropriate for the patient interface, because the patient interface is too large for the patient, because there is an obstruction or a kink in the tubing, or because there is some other blockage in the flow path (e.g., caused by the patient lying on the tubing).

[0274] The controller 13 may be configured to determine a situation in which the flow set point cannot be reached based on the predicted maximum flow rate and the flow set point, and in response generate a flow set point not reachable alarm.

[0275] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the flow set point is greater than the predicted maximum flow rate (optionally the alarm condition is a flow set point not reachable alarm). In Figure 12A, the flow set point 901 is 40 LPM, which is greater than the predicted maximum flow rate 906 (30 LPM).

[0276] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the flow set point is greater than the predicted maximum flow rate by more than an alarm threshold.

[0277] In some embodiments, the controller 13 may be configured to generate at least one alarm condition if the predicted maximum flow rate is less than the flow rate set point by more than an alarm threshold 908 .

[0278] The predicted maximum flow rate plus an alarm threshold 908 may define an alarm limit 903 .

[0279] The alarm threshold is a percentage of the flow set point. The alarm threshold can be about 5% to about 20% or about 10% of the flow set point. Figure 12B shows an example of this situation where the alarm threshold is 5 LPM (i.e., 10% of the flow set point minus 50 LPM).

[0280] The alarm condition may be a "Flow setpoint not reachable" alarm, optionally a "Flow setpoint not reachable - setpoint too high" alarm.

[0281] In some embodiments, the controller may be configured to generate an occlusion alarm if the flow set point is greater than the predicted maximum flow rate by more than an occlusion threshold value. For example, in FIG. 12C, the flow set point 901 is 50 LPM, which is greater than the predicted maximum flow rate 907 (30 LPM) by more than an occlusion threshold value 909 (10 LPM).

[0282] The occlusion threshold may indicate when the difference between the flow set point and the predicted maximum flow rate is large enough to indicate an occlusion in the flow path (eg, when the flow set point is much greater than the predicted maximum flow rate).

[0283] The predicted maximum flow rate plus the occlusion threshold may define the occlusion limit 904 .

[0284] In some embodiments, the controller is configured to generate an occlusion alarm if the predicted maximum flow rate is less than the flow set point by more than an occlusion threshold value. For example, in FIG. 12C, the predicted maximum flow rate 907 (30 LPM) is less than the flow set point 901 (50 LPM) by more than an occlusion threshold value 909 (10 LPM).

[0285] The occlusion threshold is about 20% to about 70% or about 50% of the flow set point. Figure 12C shows an example of this situation where the occlusion threshold is 10 LPM (i.e., 20% of the flow set point minus 50 LPM). Figure 12D shows an example of this situation where the occlusion threshold is 15 LPM (i.e., 37.5% of the flow set point minus 40 LPM).

[0286] In some embodiments, the occlusion threshold may be a percentage of the expected maximum flow rate or may be a set amount, for example.

[0287] In some embodiments, the percentage of the predicted maximum flow rate that defines the occlusion threshold may be based on the predicted maximum flow rate.

[0288] The alarm condition may be an occlusion alarm.

[0289] It will be appreciated that flow setpoint not reachable alarms and occlusion alarms may be independently identified and generated. For example, as shown in FIG. 12D, if the flow setpoint is greater than the predicted maximum flow rate, but not greater than the predicted maximum flow rate by more than an occlusion threshold, a flow setpoint not reachable alarm may be generated, but an occlusion alarm will not be generated.

[0290] In some embodiments, for example as shown in FIG. 13, both the alarm limit 903 and the occlusion limit 904 may both be utilized at the same time as described above.

[0291] FIG. 12E illustrates an example of a method implemented by controller 13 for determining flow setpoint not reachable and occlusion alarms (both of which are described in more detail above).

[0292] In step 1101, the controller 13 identifies a variable indicative of conductance (as described in more detail above). Step 1101 can be performed at each time step during treatment by the controller 13 provided within the respiratory device.

[0293] In step 1102, the controller 13 identifies an expected maximum flow rate based on a variable indicative of conductance (calculated in step 1101) and a flow generator power range, which in this particular embodiment is the upper motor power limit of the allowable motor power range.

[0294] In step 1103, the predicted maximum flow is compared to the flow set point and the alarm threshold.

[0295] In step 1104, the controller 13 determines whether the flow set point can be reached, for example, if the flow set point is greater than the predicted maximum flow rate by more than an alarm threshold, the controller 13 may generate an alarm condition (e.g., a flow set point not reachable alarm).

[0296] In step 1105, the predicted maximum flow is compared to the flow set point and the occlusion threshold.

[0297] In step 1106, the controller 13 determines whether an occlusion is present or likely to be present, and if so, the controller 13 may generate an occlusion alarm. For example, if the flow set point is greater than the predicted maximum flow rate by more than an occlusion threshold, the controller 13 may generate an occlusion alarm.

[0298] In some embodiments, the controller 13 may require multiple instances of the flow setpoint to be greater than the predicted maximum flow rate by more than an alarm threshold (or blockage threshold) to activate an associated alarm. In these embodiments, the controller 13 may require that the number of consecutive "set flow not reachable" or "blockage" events exceed a consecutive count threshold. If the consecutive count threshold is exceeded, the controller 13 may generate an alarm condition (e.g., a flow setpoint not reachable alarm or a blockage alarm).

[0299] Additionally, in response to the generation of at least one alarm condition as described above, the controller 13 may control the motor speed (or flow generator output) to a predetermined safe motor speed (or safe flow generator output).

[0300] In some embodiments, the controller 13 may control the motor speed (or flow generator output) to a predetermined safe motor speed (or safe flow generator output) if an occlusion alarm occurs.

[0301] In some embodiments, the controller 13 may switch off the humidifier warming element 310 and / or the warming element 16a if an alarm condition occurs.

[0302] In some embodiments, the controller 13 may switch off the humidifier warming element 310 and / or the warming element 16a if an occlusion alarm occurs.

[0303] In some embodiments, the controller 13 may control the valve to reduce or prevent the flow of auxiliary gas (eg, oxygen) through the valve if an alarm condition occurs.

[0304] The controller 13 may control the motor speed to a predetermined safe motor speed until the predicted maximum flow rate is greater than the safe threshold flow rate and / or the predicted minimum flow rate is less than the safe threshold flow rate.

[0305] The controller 13 may control the motor speed to a predetermined safe motor speed until the flow set point is less than the predicted maximum flow rate and / or until the flow set point is greater than the predicted minimum flow rate.

[0306] The predetermined safe motor speed may be from about 6000 RPM to about 10000 RPM or about 8000 RPM.

[0307] An alarm condition may be triggered after one or more instances in which the device is predicted to be unable to reach the flow setpoint.

[0308] An example of the above alarm conditions is shown in a single graph in Figure 13. Figure 13 shows the flow setpoint unreachable and occlusion regions. If the flow setpoint is in either of these regions, the corresponding alarm will be activated.

[0309] For example, as shown in FIG. 13, if the flow setpoint is greater than the alarm limit 903 (e.g., in the flow setpoint unreachable region), a flow setpoint unreachable alarm and / or a flow setpoint too high alarm may be generated.

[0310] If the flow set point is greater than the occlusion limit 904 (eg, in the occlusion region), an occlusion alarm may be generated.

[0311] If the flow setpoint is less than the alarm limit 902 (eg, in a flow setpoint unreachable region), a flow setpoint unreachable alarm and / or a flow setpoint too low alarm may be generated.

[0312] It will be appreciated that the flow setpoint not reachable alarm for the predicted minimum flow rate may be given a different name (i.e., flow setpoint too low) or the flow setpoint not reachable alarm for the predicted minimum flow rate may generate a separate alarm condition (from the flow setpoint not reachable alarm for the predicted maximum flow rate).

[0313] It will be appreciated that the flow setpoint unreachable alarm for predicted maximum flow may be given a different name (ie, flow setpoint too high).

[0314] The alarm condition may include one or more of an audible alarm and a visual alarm.

[0315] One or more thresholds (eg, an alarm threshold or an occlusion threshold) may vary based on the type of therapy provided by the respiratory device (which may be, for example, a nasal high flow device).

[0316] As mentioned above, the alarm thresholds used in the comparison to the predicted maximum flow rate may be the same as or different from the alarms used in the comparison to the predicted minimum flow rate.

[0317] A comparison of the predicted flow rate and the current flow rate of the flow path is also provided to determine if there has been a change in the flow path conditions (eg, a new leak or a new blockage).

[0318] This approach, described in more detail below, can be particularly useful in systems where there are many potential combinations of components, each of which may lead to a different flow path conductance and / or leak rate. For example, when using a high flow therapy device, each different non-sealed interface may have a different leak rate.

[0319] The system may be used with different interfaces (e.g., different interface types or different interface sizes) and / or different conduits (e.g., for different treatments). There may be variations in how the components are used (e.g., differences in fit of the interface to the user) and variations in the system over the course of treatment (e.g., changes in conduit position, changes in condensation in the tubing, and / or changes in fit of the interface to the user).

[0320] Patient interface variability can be an issue in systems with non-sealing interfaces (e.g., high flow systems) due to the large range of interface sizes. For example, the largest interfaces (e.g., large adult size interfaces) may have orders of magnitude less resistance to flow than the smallest interfaces (e.g., neonatal interfaces). Thus, prior art approaches are ineffective because the range of resistance to flow across all interfaces is too large to allow one pre-set threshold (or even several pre-set thresholds) to accurately detect patient interface leaks, blockages, and / or connections or disconnections across the full range of interfaces.

[0321] The system may be used with different patients having different respiratory system anatomies and / or different respiratory system conditions (eg, caused by disease).

[0322] Thus, the system may experience a wide range of conditions and therefore prior art methods for determining leaks and / or blockages may not function consistently across the full range of circumstances (without at least some knowledge of the system's state) and may, for example, risk setting off unnecessary alarms or not setting off alarms when they should.

[0323] Identifying the components of a system can be time consuming for a clinician or can introduce additional complexity to the component or system.

[0324] In the approach outlined below, the system predicts the flow rate of gas to determine if there is a leak and / or blockage in the flow path. The system then compares this predicted flow rate to the current measured flow rate or compares the current measured flow rate to one or more thresholds (some of which may be based on the predicted flow rate). Because the predicted flow rate is a function of the conductance of the flow path (and thus the combination of components), the accuracy with which the system can detect leaks and / or blockages is relatively less affected by the combination of components being used. This is in contrast to prior art systems that may need to have information about the particular components present or make assumptions.

[0325] The current flow rate may be the flow rate measured at the current time of the controller 13 or may be a recently measured flow rate (e.g., a flow rate measured at a previous time step). The current flow rate may be a filtered (or otherwise conditioned) output from a sensor. Alternatively, the current flow rate may be a raw output from a sensor (e.g., a flow sensor as described above).

[0326] A current flow rate greater than the predicted flow rate (and / or a leak flow rate threshold) may indicate, for example, a leak or a dislodged component.

[0327] A current flow rate less than the predicted flow rate (and / or the leak flow rate threshold) may indicate, for example, a blockage or obstruction of the tube (eg, due to condensation or kinking).

[0328] The flow thresholds required to indicate a leak, occlusion, or another flow path alteration event (e.g., as shown in Figures 17 and 18) may change over time. This variability may be due to the thresholds being a function of several measurements in the system (e.g., the past values ​​of variables indicative of the conductance of the circuit).

[0329] The flow thresholds may include one or more occlusion flow thresholds (to determine an occlusion) and / or one or more leak flow thresholds (to determine a leak).

[0330] If the predicted flow is greater than the current flow (eg, as shown in FIG. 18), the current flow may be compared to an occlusion flow threshold.

[0331] If the predicted flow rate is less than the current flow rate (eg, as shown in FIG. 17), the current flow rate may be compared to a leak flow rate threshold.

[0332] It will be appreciated that in addition to performing a comparison with both the leak and occlusion flow thresholds, the occlusion flow threshold comparison may be performed without the leak flow threshold comparison, and vice versa.

[0333] In some embodiments, the controller 13 is configured to identify an expected flow rate for the flow path.

[0334] The predicted flow rate of a flow path is based on a variable indicative of the conductance of the flow path and the current flow generator output (as described in more detail above).

[0335] It will be appreciated that the flow generator output may also be a motor output (as described in more detail above). The following examples relate to the flow generator output as a motor output (e.g., motor speed, as described in more detail above).

[0336] The controller 13 is configured to compare the current flow rate to the predicted flow rate and generate at least one alarm condition based on the comparison.

[0337] Additionally or alternatively, the controller 13 may be configured to compare the current flow rate with a flow rate threshold (e.g., at least one occlusion flow rate threshold and / or at least one leakage flow rate threshold) that is a function of the predicted flow rate, and may generate at least one alarm condition based on the comparison.

[0338] As discussed above, the at least one flow threshold may include at least one occlusion flow threshold and / or at least one leakage flow threshold.

[0339] The controller 13 is configured to generate at least one alarm condition (optionally a leak alarm condition) if the current flow rate is greater than a leak flow rate threshold.

[0340] The controller 13 is configured to generate at least one alarm condition when the predicted flow rate is less than the current flow rate (ie, indicating a leak rather than an occlusion) if the current flow rate is greater than at least one leak flow rate threshold.

[0341] The controller 13 is configured to generate at least one alarm condition (optionally an occlusion alarm condition) if the current flow rate is less than at least one leak occlusion flow rate threshold (eg, as shown in FIG. 18).

[0342] The controller 13 is configured to generate at least one alarm condition when the predicted flow rate is greater than the current flow rate (ie, indicating an occlusion rather than a leak) if the current flow rate is less than at least one occlusion flow rate threshold.

[0343] FIG. 14 illustrates a method for determining a leak or blockage based on a predicted flow rate.

[0344] In step 1120, the controller 13 identifies a variable indicative of the conductance of the flow path. As will be explained in more detail below, this may involve stored historical information regarding the conductance of the flow path.

[0345] In step 1121, the controller 13 determines an expected flow rate based on a variable indicative of the conductance of the flow path and the current flow generator output (eg, motor speed).

[0346] In step 1122, the controller 13 determines at least one flow threshold value (as described in more detail below).

[0347] In step 1123, the controller compares the current flow rate to flow rate thresholds. These flow rate thresholds may be occlusion flow rate thresholds if the predicted flow rate is greater than the current flow rate, or leakage flow rate thresholds if the predicted flow rate is less than the current flow rate. The controller then generates at least one alarm condition if the current flow rate is greater than at least one (or optionally all) leakage flow rate thresholds or less than at least one (or optionally all) occlusion flow rate thresholds.

[0348] In response to the generation of the at least one alarm condition, the controller may control the motor speed to a predetermined safe motor speed. The controller 13 may control the motor speed to a predetermined safe motor speed until the at least one alarm condition is cleared. The predetermined safe motor speed may be from about 6000 RPM to about 10000 RPM or about 8000 RPM (as described in more detail above).

[0349] In some embodiments, the controller 13 may switch off the humidifier warming element 310 and / or the warming element 16a if an alarm condition occurs.

[0350] In some embodiments, the controller 13 may control the valve to reduce or prevent the flow of auxiliary gas (eg, oxygen) through the valve if an alarm condition occurs.

[0351] In response to the generation of at least one alarm condition, the controller may continue to attempt to provide therapy at the target flow rate.

[0352] The alarm status is Audible alarm and Visual alarm Includes one or more of the following.

[0353] At least one alarm condition may be generated after multiple instances of the current flow rate being greater than at least one leak flow rate threshold.

[0354] At least one alarm condition may be generated if the current flow rate is greater than at least one leak flow rate threshold for a threshold time period, which may be from about 0.5 seconds to about 5 seconds.

[0355] At least one alarm condition may be generated after multiple instances where the current flow is less than at least one occlusion flow threshold.

[0356] At least one alarm condition may be generated if the current flow is less than at least one occlusion flow threshold for a threshold time period, which may be from about 0.5 seconds to about 5 seconds.

[0357] The leakage flow threshold and / or the obstruction flow threshold are A percentage threshold based on a percentage of the predicted flow rate; A limit threshold based on the flow generator output and a constant, A variability threshold based on a measure of variability in the predicted flow may include one or more of:

[0358] 15A and 15B show diagrams of the leak flow threshold plotted with predicted flow and current flow.

[0359] In FIG. 15A, the current flow rate is greater than all of the leak flow rate thresholds, therefore an alarm condition occurs (eg, a leak alarm).

[0360] In FIG. 15B, the current flow rate is less than all of the leak flow rate thresholds, so no alarm condition occurs.

[0361] 15C and 15D show diagrams of occlusion flow threshold plotted with predicted flow and current flow.

[0362] In FIG. 15C, the current flow is less than all of the occlusion flow thresholds, therefore an alarm condition (eg, an occlusion alarm) occurs.

[0363] In FIG. 15D, the current flow is greater than all of the occlusion flow thresholds, therefore no alarm condition occurs.

[0364] It will be appreciated that an alarm condition may be generated based on the magnitude between the current flow rate and the predicted flow rate, however, in some configurations, the controller 13 may take into account whether the difference between the current flow rate and the predicted flow rate is positive (i.e., the current flow rate is greater than the predicted flow rate, indicating a leak, as shown, for example, in FIG. 15A) or negative (i.e., the current flow rate is less than the predicted flow rate, indicating an occlusion, as shown, for example, in FIG. 15C).

[0365] In some embodiments, an alarm condition is generated if the current flow rate is greater than all of the leak flow rate thresholds (ie, the percentage threshold, the limit threshold, and the variation threshold).

[0366] In some embodiments, an alarm condition is generated if the current flow is less than all of the occlusion flow thresholds (ie, the percentage threshold, the limit threshold, and the variation threshold).

[0367] The percentage threshold, limit threshold, and variation threshold may be the same or different for multiple leak flow thresholds. The percentage threshold, limit threshold, and variation threshold may be the same or different for multiple occlusion flow thresholds. It will be appreciated that the values ​​of these thresholds may be different for the leak flow thresholds and the occlusion flow thresholds.

[0368] The percentage threshold for the leak flow rate threshold is from about 105% to about 180%, from about 110% to about 120%, or from about 150% to about 180% of the expected flow rate.

[0369] The percentage threshold for the occlusion flow threshold is from about 40% to about 95%, from about 50% to about 90%, or from about 60% to about 80% of the predicted flow.

[0370] In some embodiments, the percentage threshold of the occlusion flow threshold and / or the leakage flow threshold may be based on the predicted flow magnitude.

[0371] The limit threshold may be based on the flow generator output and a constant, or alternatively, it may be a limit threshold and a constant.

[0372] In some embodiments, the constant is a predetermined conductance (or another variable indicative of conductance, for example). In other embodiments, the constant is a predetermined flow rate.

[0373] The limit threshold for the leak flow threshold may use a first predetermined conductance and / or a first predetermined flow rate.

[0374] The limit threshold of the occlusion flow threshold may use a first predetermined conductance and / or a first predetermined flow rate or a second predetermined conductance and / or a second predetermined flow rate.

[0375] The variability threshold may be based on the standard deviation of the predicted flow rate.

[0376] The variance threshold for the leak flow threshold may be the predicted flow plus the standard deviation of the predicted flow.

[0377] The variance threshold for the occlusion flow threshold may be the predicted flow minus the standard deviation of the predicted flow.

[0378] In some embodiments, the variation threshold may additionally or alternatively be based on the standard deviation of a variable indicative of the conductance of the flow path.

[0379] The variation threshold may be a function of the variation in the predicted flow rate, the variation in a variable indicative of the conductance of the flow path, and / or the variation in the flow generator output.

[0380] For example, if the fluctuation in the predicted flow rate is large, the fluctuation threshold may also be a large value, and if the fluctuation in the predicted flow rate is small, the fluctuation threshold may also be a small value.

[0381] The variation threshold may be based on stored motor speed data (eg, where the variation threshold can be represented by a probability distribution function).

[0382] The variation threshold may be based on a stored variable indicative of the conductance data (eg, where the variation threshold can be represented by a probability distribution function).

[0383] The variation threshold may be based on stored conductance data.

[0384] The variation threshold may be based on noise associated with a variable indicative of the conductance signal.

[0385] FIG. 16 shows an example of motor speed 1132 (as a flow generator output) and the associated predicted flow rate 1131.

[0386] 16 shows how the variation thresholds can change in response to changes in motor speed 1132. The variation thresholds are plotted as a range around the predicted flow rate, both for the occlusion flow threshold 1130a and for the leakage flow threshold 1130b. The magnitude of the variation thresholds 1130a, 1130b increases in proportion to the corresponding change in motor speed 1132. As the motor speed 1132 increases, the predicted flow rate 1131 also increases in this example (with the conductance of the flow path remaining constant).

[0387] Each time the predicted flow rate increases (in response to an increase in motor speed 1132), the magnitude of the variation threshold is momentarily increased and then decreased again.

[0388] Although the predicted flow rate is shown as varying in time along with the motor speed 1132 , it will be appreciated that the predicted flow rate 1131 may lag behind the motor speed 1132 .

[0389] In region 1135, the variation threshold or variation uncertainty 1130 is reasonably stable.

[0390] In region 1136, the motor speed changes, and therefore the standard deviation (or other probability measure) of the predicted flow increases, and therefore the variation threshold 1130. As time progresses and the motor speed stabilizes, the variation threshold 1130 decreases and then stabilizes.

[0391] In some embodiments, the variation threshold 1130 is based on the magnitude of the predicted flow rate.

[0392] In some embodiments, the magnitude of the variation threshold 1130 is based on the standard deviation (or other probability measure) of a variable indicative of the conductance of the flow path.

[0393] The variation threshold may be proportional to the change in a variable indicative of flow rate, motor speed, and / or conductance within a time window, which may be a predetermined period of time (e.g., the last 10 seconds).

[0394] The variation threshold may be larger closer to the most recent change in motor speed, as shown in Figure 16. The variation threshold may then be reduced as the motor speed settles to a steady state.

[0395] In region 1137, the motor speed changes more than in region 1136, and therefore the standard deviation (or other probability measure) of the variable indicative of flow path conductance also increases by a larger amount than in region 1136, and therefore so does the variation threshold. In regions 1136 and 1137, as time progresses and the motor speed stabilizes, the variation threshold 1130 decreases and then stabilizes.

[0396] It will be appreciated that other variables indicating statistical variation or error (eg, variance, standard deviation, interquartile range, range, or mean absolute difference) may be used in determining the variation threshold.

[0397] The variable threshold may be based on conductance data (as described in more detail below).

[0398] In some embodiments, the fluctuation threshold may be a function of the predicted flow rate (e.g., may be proportional to the predicted flow rate). For example, the stabilized fluctuation threshold 1130 in region 1137 is greater than the fluctuation thresholds in regions 1135 and 1136 because the magnitude of the predicted flow rate is greater.

[0399] In some embodiments, the variation threshold may be a function of (eg, proportional to) the amount of variation in a variable indicative of the conductance of the flow path.

[0400] FIG. 17 illustrates an example 1140 of a cannula disconnection event.

[0401] As shown in FIG. 17, prior to a cannula disconnection event 1140 , the current flow rate 1131 is provided at a set point flow rate 1142 .

[0402] When a cannula disconnection event 1140 occurs, the current flow rate 1131 increases due to an increase in the conductance of the circuit, and the motor speed decreases to control the current flow rate to the flow rate setpoint. The predicted flow rate 1143, as determined by the controller, is shown decreasing in accordance with the decrease in motor speed.

[0403] 17 shows several leak rate thresholds, such as a limit threshold 1151, a percentage threshold 1152, and a variation threshold 1153.

[0404] Note that the thresholds 1151, 1152, 1153 are calculated before the event, but the thresholds before the leak event are not shown in FIG.

[0405] The thresholds 1151, 1152, 1153 are shown as time continuous but are recalculated at each time step and compared to the predicted flow. If the current flow rate is greater than the thresholds 1151, 1152, 1153, indicative of a leak, in this example, an alarm condition will occur.

[0406] FIG. 18 illustrates an example 1140 of an occlusion event.

[0407] As shown in FIG. 18, before an occlusion event 1140 , the current flow rate 1131 is provided at the set point flow rate 1142 .

[0408] When an occlusion event 1141 occurs, the current flow rate 1131 decreases due to a decrease in the conductance of the circuit, and the motor speed increases to control the current flow rate to the flow setpoint. The predicted flow rate 1143 determined by the controller is shown to increase as the motor speed increases.

[0409] The controller 13 may select the occlusion flow threshold.

[0410] 18 shows several occlusion flow thresholds, such as a limit threshold 1151, a percentage threshold 1152, and a variation threshold 1153.

[0411] Note that the thresholds 1151, 1152, 1153 are calculated before the event, but the thresholds before the occlusion event are not shown in FIG.

[0412] The thresholds 1151, 1152, 1153 are shown as time continuous but are recalculated at each time step and compared to the predicted flow. If the current flow is less than the thresholds 1151, 1152, 1153, indicating an obstruction in this example, an alarm condition will occur.

[0413] In some embodiments, the difference between the current flow rate and the predicted flow rate may additionally or alternatively be compared to a flow rate difference threshold. The flow rate difference threshold may be calculated based on the predicted flow rate. In these cases, instead of calculating a flow rate threshold and comparing it to the current flow rate, the difference between the current flow rate and the predicted flow rate is calculated and compared to the flow rate difference threshold.

[0414] The flow difference threshold may be determined based on the current flow and the flow threshold (as described below).

[0415] The controller 13 may perform the above-described process in a time-step process, for example as described below.

[0416] In some embodiments, the controller 13 may identify a variable indicative of the conductance of the flow path (or update a variable indicative of the conductance of the flow path based on a new measurement, for example) at a first time step.

[0417] In some embodiments, the controller 13 may be configured to determine, at the second time step, a predicted flow rate in a variable indicative of the conductance of the flow path determined at the first time step.

[0418] In some embodiments, at each time step, a variable having a conductance of a flow path may be updated based on a variable indicating the conductance at the current time step and a variable having a conductance at a previous time step.

[0419] In some embodiments, at each time step, a variable indicative of the conductance of the flow path may be updated based on the current flow generator output and the current flow rate.

[0420] In some embodiments, at each time step, the variable indicative of the conductance of the flow path may be updated based on a number of weighting factors, for example, in one embodiment, one of the weighting factors may be based on measurement noise associated with one or more of the variable indicative of the conductance at the current time step, the flow rate, and the flow generator output.

[0421] The variable indicative of the conductance of the flow path may be determined as described elsewhere herein.

[0422] The variable indicative of the conductance of the flow path can be represented by a probability density function. For example, the variable indicative of the conductance of the flow path can be (or can include) a function indicative of the relative likelihood that the variable indicative of the conductance takes on a particular value. Features of this probability density function can be used to determine the variation threshold (or any other threshold).

[0423] In some embodiments, the function (represented by a probability density function) that updates the variable indicative of the conductance of the flow path may be based on weighting coefficients as described above.

[0424] The variable indicative of the conductance of the flow path may be based on stored data, which may include past determinations of at least one of one or more measured or determined variables (e.g., a variable indicative of conductance (which may be, for example, conductance), flow rate, pressure, and motor power).

[0425] In some embodiments, the stored data may be conductance data and may include past determinations of variables indicative of conductance (e.g., the conductance of a flow path). In these embodiments, it will be appreciated that the variables indicative of conductance as part of the conductance data may be or may be of a different type than the variables indicative of conductance used by the system (as described above) in determining the predicted flow.

[0426] The controller 13 may store in memory at least one past determination of the one or more measured or determined variables and use the at least one past determination to calculate a variable indicative of the current conductance. In this manner, the variable indicative of the conductance of the flow path may be dynamically updated based on previous values ​​of one or more of the measured or determined variables.

[0427] The variable indicative of the conductance of the flow path may be based on stored data and weighting factors, as described above. The variable indicative of the conductance of the flow path may be based on stored data of the flow path over a time window. For example, the controller 13 may calculate the variable indicative of the conductance of the flow path based on stored data from within a previous time window. The time window may be, for example, the previous 20 seconds.

[0428] At each time step, or periodically, a determination of the conductance of the flow path may be stored as at least one previous determination of the conductance of the flow path.

[0429] The stored data may include time stamp information associated with each past determination of one or more measured or determined variables, which may be used by the controller 13 in determining the variable indicative of the conductance of the flow path.

[0430] The timestamp information may include the amount of time that has elapsed since a previous determination of one or more actual measurements or determined variables.

[0431] The controller 13 may weight the stored data in determining the conductance of the flow path based on the associated time stamp information.

[0432] In some embodiments, more recently stored data is given greater weight than less recent conductance data.

[0433] The conductance data may include weighting coefficients associated with each past determination of one or more measured or determined variables.

[0434] The controller may be configured to determine the conductance of the flow path and to determine an expected flow rate for the flow path continuously or periodically.

[0435] In some embodiments, the controller is configured to determine a predicted flow uncertainty.

[0436] As described above, the variable indicative of the conductance of the flow path may be defined, for example, by one value or several values ​​of the variable indicative of the conductance (i.e., defining, for example, a probability distribution or vector). When identifying the variable indicative of the conductance of the flow path, the controller may, for example, identify one value or several values.

[0437] It will be appreciated that any listing herein also discloses all combinations of the items in the list.

Claims

1. 1. A breathing apparatus comprising: A flow generator; a flow path configured to provide a flow of breathable gas to a patient; a controller configured to control the flow generator by controlling a flow generator output to the flow generator to provide the flow of breathable gas, the flow generator output being within an acceptable flow generator output range; and The controller comprises: identifying a variable indicative of conductance of the flow path; A predicted maximum flow rate and / or a predicted minimum flow rate of the flow path, the variable indicative of the conductance of the flow path; said permissible flow generator output range and 4. A breathing apparatus configured to:

2. The flow generator output is: i. motor speed; ii. Motor current; iii. Motor duty; iv. the pressure of the gas in the flow path; or v. any combination of i to iv 2. A respiratory apparatus as claimed in claim 1, which is or comprises:

3. The variable indicating the conductance of the flow path is i. the conductance of the flow path or a portion of the flow path; ii. Resistance to flow in the flow path or a portion of the flow path; or iii. A pressure drop along the flow path or a portion of the flow path; iv. Any combination of i to iii 3. Respiratory apparatus according to claim 1 or 2, which is or is based on this(s).

4. 4. A respiratory apparatus according to any preceding claim, wherein the respiratory apparatus comprises a flow sensor, the flow sensor being configured to measure the flow rate of the flow of breathable gas to a patient.

5. 5. A respiratory apparatus according to any one of claims 1 to 4, wherein the variable indicative of the conductance of the flow path is based on a variable indicative of the conductance of the flow path at a previous time step, or the variable indicative of the conductance of the flow path is based on a variable indicative of the conductance of the flow path over a time window.

6. The respiratory apparatus of claim 5, wherein the time window is the previous 20 seconds.

7. Respiratory apparatus according to any preceding claim, wherein the variable indicative of the conductance of the flow path is based on a current flow generator output and a current flow rate.

8. The variable indicating the conductance is [0010] or [0025] 8. A breathing apparatus as claimed in any preceding claim, wherein the breathing apparatus is proportional to one or more of:

9. the allowable flow generator output range is an allowable motor speed range, the allowable motor speed range including an upper motor speed limit and / or a lower motor speed limit; the predicted maximum flow rate is based on a current motor speed and / or a motor speed upper limit; 9. Respiratory apparatus according to any one of claims 1 to 8, wherein the predicted minimum flow is based on the current motor speed and / or a lower motor speed limit.

10. 10. A respiratory apparatus according to any preceding claim, wherein the controller is configured to compare the predicted maximum flow rate and / or the predicted minimum flow rate and a flow rate set point and to generate at least one alarm condition based on the comparison.

11. The at least one alarm condition includes a flow set point unreachable alarm, the flow set point unreachable alarm comprising: a flow rate unreachable alarm associated with the flow rate set point exceeding the predicted maximum flow rate; and / or a flow rate unreachable alarm associated with the flow rate set point falling below the predicted minimum flow rate; 11. The respiratory apparatus of claim 10, comprising:

12. 12. The respiratory apparatus of claim 10 or 11, wherein the controller is configured to generate at least one alarm condition if the flow set point is greater than the predicted maximum flow rate, and / or the controller is configured to generate at least one alarm condition if the flow set point is less than the predicted minimum flow rate.

13. 12. The respiratory apparatus of claim 10 or 11, wherein the controller is configured to generate at least one alarm condition if the flow set point is greater than the predicted maximum flow rate by more than an alarm threshold, and / or the controller is configured to generate at least one alarm condition if the flow set point is less than the predicted minimum flow rate by more than the alarm threshold.

14. 14. The respiratory apparatus of claim 13, wherein the alarm threshold is a percentage of the flow set point, the percentage of the flow set point being from about 5% to about 20% or about 10% of the flow set point.

15. Respiratory apparatus according to any one of claims 10 to 14, wherein in response to the generation of the at least one alarm condition the controller controls the motor speed to a predetermined safe motor speed.

16. the controller controls the motor speed at the predetermined safe motor speed until the predicted maximum flow rate is greater than a safe threshold flow rate and / or until the predicted minimum flow rate is less than the safe threshold flow rate; and / or 16. The respiratory apparatus of claim 15, wherein the controller controls the motor speed to the predetermined safe motor speed until the flow set point is less than the predicted maximum flow rate and / or until the flow set point is greater than the predicted minimum flow rate.

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