Method and apparatus for detecting respiratory effort

Abstract

Devices and systems provide methods for detecting respiratory related effort from movements associated with the head or face. In one embodiment, a strain signal is measured by one or more sensors. A processor may analyze the head strain signal to detect respiratory related effort. Detection of effort may serve as a basis for identifying sleep disordered breathing events. For example, the analysis may serve as part of a detector to identify central or obstructive apneas or central or obstructive hypopneas. Sensors may be integrated with headgear to support them at desired locations of the face or head. Strain from head movement may be detected by measuring, for example, tension of the headgear or force applied against the headgear. The headgear may serve as an independent support for the sensors or as a component of a respiratory treatment apparatus, such as a mask or cannula.

1 . A method for detecting respiratory related effort comprising:
 (a) using a sensor to generate a strain signal, the strain signal including one or both of a mouth strain signal and a jaw strain signal, the sensor being configured with a respiratory mask or headgear for a respiratory treatment apparatus to sense mask force or headgear tension, the headgear tension concerning change in tension of a strap of the headgear, wherein the sensor is configured to generate the strain signal in response to movement of one or both of a user's mouth and jaw;   (b) receiving the strain signal in a processor,   (c) detecting respiratory events in the processor based on the strain signal, the detecting comprising analyzing the strain signal in the processor to detect respiratory related effort, the analyzing of the strain signal comprising:
 (1) generating a first and a second filtered strain signals based on the strain signal, and 
 (2) making a comparison based on the first and the second filtered strain signals; and 
   (d) based on the analyzing of the strain signal or on the detected respiratory events, effecting with the processor at least one of the following:
 (1) generating an indicator of a presence or absence of significant respiratory effort; 
 (2) generating an indicator of detected respiratory events, and 
 (3) automatically controlling a change to a respiratory treatment variable in a controller of the respiratory treatment apparatus. 
   
     
     
         2 . The method of  claim 1  wherein the first and the second filtered strain signals comprise a historic threshold signal and a recent strain signal respectively. 
     
     
         3 . The method of  claim 1  wherein the first and the second filtered strain signals are generated by processing the strain signal for removing offset and/or for smoothing. 
     
     
         4 . The method of  claim 1  wherein the first and second filtered strain signals are generated by high pass filtering. 
     
     
         5 . The method of  claim 1  wherein the first and the second filtered strain signals are generated by combining a plurality of strain signals from a plurality of sensors, the plurality of sensors including the sensor. 
     
     
         6 . The method of  claim 5  wherein the combining comprises summing the plurality of strain signals. 
     
     
         7 . The method of  claim 6  wherein the plurality of sensors comprises first and second sensors arranged in a symmetric orientation. 
     
     
         8 . The method of  claim 1  wherein the first filtered strain signal is generated by low pass filtering with a long term time constant; and wherein the second filtered strain signal is generated by low pass filtering with a short term time constant. 
     
     
         9 . The method of  claim 8  wherein the long term time constant is on an order of minutes and wherein the short term time constant is on an order of seconds. 
     
     
         10 . The method of  claim 8  wherein the first and second filtered strain signals are derived at least in part from an absolute value signal of an output of high pass filtering of the strain signal. 
     
     
         11 . The method of  claim 8  further comprising deriving a threshold signal as a proportion of one of the first and second filtered strain signals. 
     
     
         12 . The method of  claim 11  wherein the second filtered strain signal is compared to the threshold signal. 
     
     
         13 . The method of  claim 1  wherein the first filtered strain signal is a long term average strain signal, and the second filtered strain signal is a short term average strain signal. 
     
     
         14 . The method of  claim 13  wherein the comparison comprises comparing the second filtered strain signal with a function of the first filtered strain signal. 
     
     
         15 . The method of  claim 1  wherein the comparison comprises comparing a function of the second filtered strain signal with a function of the first filtered strain signal. 
     
     
         16 . The method of  claim 1  wherein the comparison comprises comparing a function of the second filtered strain signal with the first filtered strain signal. 
     
     
         17 . The method of  claim 1  further comprising, in the processor, receiving a flow signal from a flow sensor and wherein the detecting of the respiratory events in the processor is based on the flow signal. 
     
     
         18 . Apparatus for detecting respiratory related effort comprising:
 a respiratory mask or headgear for a respiratory treatment apparatus;   a sensor, the sensor configured to generate a strain signal, the strain signal including one or both of a mouth strain signal and a jaw strain signal, the sensor being configured with the respiratory mask or headgear to sense mask force or headgear tension, the headgear tension concerning change in tension of a strap of the headgear, wherein the sensor is configured to generate the strain signal in response to movement of one or both of a user's mouth and jaw; and   a processor coupled with the sensor, wherein the processor is configured to:   (a) receive the strain signal;   (b) detect respiratory events based on the strain signal, the detection comprising an analysis of the strain signal in the processor to detect respiratory related effort, the analysis of the strain signal comprising:
 (1) generation of a first and a second filtered strain signals based on the strain signal, and 
 (2) a comparison based on the first and the second filtered strain signals; and 
   (c) based on the analysis of the strain signal or on the detected respiratory events, effect at least one of the following:
 (1) generate an indicator of a presence or absence of significant respiratory effort; 
 (2) generate an indicator of detected respiratory events, and 
 (3) automatically control a change to a respiratory treatment variable in a controller of the respiratory treatment apparatus. 
   
     
     
         19 . The apparatus of  claim 18  wherein the first and the second filtered strain signals comprise a historic threshold signal and a recent strain signal respectively. 
     
     
         20 . The apparatus of  claim 18  wherein the first and the second filtered strain signals are generated by processing the strain signal for removing offset and/or for smoothing. 
     
     
         21 . The apparatus of  claim 18  wherein the first and second filtered strain signals are generated by high pass filtering. 
     
     
         22 . The apparatus of  claim 18  wherein the first and the second filtered strain signals are generated by combining a plurality of strain signals from a plurality of sensors, the plurality of sensors including the sensor. 
     
     
         23 . The apparatus of  claim 22  wherein the processor is configured to combine the plurality of strain signals by summing the plurality of strain signals. 
     
     
         24 . The apparatus of  claim 23  wherein the plurality of sensors comprises first and second sensors arranged in a symmetric orientation. 
     
     
         25 . The apparatus of  claim 18  wherein the first filtered strain signal is generated by low pass filtering with a long term time constant; and wherein the second filtered strain signal is generated by low pass filtering with a short term time constant. 
     
     
         26 . The apparatus of  claim 25  wherein the long term time constant is on an order of minutes and wherein the short term time constant is on an order of seconds. 
     
     
         27 . The apparatus of  claim 25  wherein the processor is configured to generate the first and second filtered strain signals at least in part by deriving an absolute value signal from an output of high pass filtering of the strain signal. 
     
     
         28 . The apparatus of  claim 25  wherein the processor is further configured to derive a threshold signal as a proportion of one of the first and second filtered strain signals. 
     
     
         29 . The apparatus of  claim 28  wherein the second filtered strain signal is compared to the threshold signal. 
     
     
         30 . The apparatus of  claim 18  wherein the first filtered strain signal is a long term average strain signal, and the second filtered strain signal is a short term average strain signal. 
     
     
         31 . The apparatus of  claim 30  wherein the comparison comprises comparing the second filtered strain signal with a function of the first filtered strain signal. 
     
     
         32 . The apparatus of  claim 18  wherein the comparison comprises comparing a function of the second filtered strain signal with a function of the first filtered strain signal. 
     
     
         33 . The apparatus of  claim 18  wherein the comparison comprises comparing a function of the second filtered strain signal with the first filtered strain signal. 
     
     
         34 . The apparatus of  claim 18  further comprising a flow sensor, and wherein the processor is coupled with the flow sensor, and wherein the processor is further configured to:
 receive a flow signal from the flow sensor; and 
 detect the respiratory events based on the flow signal.