Automated control for detection of flow limitation

Abstract

A respiratory flow limitation detection device, which can include an airway pressure treatment generator, determines a flow limitation measure 506 based one or more shape indices for detecting partial obstruction and a measure of a patient's ventilation or respiratory duty cycle. The shape indices may be based on function(s) that ascertain the likelihood of the presence of M-shaped breathing patterns and/or chair-shaped breathing patterns. The measure of ventilation may be based on analysis of current and prior tidal volumes to detect a less than normal patient ventilation. The duty cycle measure may be a ratio of current and prior measures of inspiratory time to respiratory cycle time to detect an increase in the patient's inspiratory cycle time relative to the respiratory cycle time. A pressure setting based on the flow limitation may then be used to adjust the treatment pressure to ameliorate the patient's detected flow limitation condition.

1 . In a device for treating sleep disordered breathing, a method of automatically determining a change in treatment pressure to be delivered by the device comprising:
 determining a first measure of extent to which patient inspiratory effort correlates with patient inspiratory flow;   determining a second measure of patient ventilation; and   determining the change in treatment pressure as a first function of said first measure and second measure.   
     
     
         2 . The method of  claim 1  wherein said first measure is an index of partial obstruction. 
     
     
         3 . The method of  claim 1  wherein said second measure of patient ventilation is a measure of the extent to which patient ventilation is adequate. 
     
     
         4 . The method of  claim 1 , wherein said first measure is a measure of relative duration of inhalation and exhalation. 
     
     
         5 . The method of  claim 1  further comprising:
 determining a measure of respiratory flow; 
 determining a first partial obstruction measure from the measure of respiratory flow; 
 determining a second partial obstruction measure from the measure of respiratory flow; and 
 determining a third partial obstruction measure as a function of the first and second partial obstruction measures, wherein the treatment pressure is based on the third partial obstruction measure. 
 
     
     
         6 . The method of  claim 5  wherein the first partial obstruction measure is an index indicative of an M shape breath pattern. 
     
     
         7 . The method of  claim 5  wherein the second partial obstruction measure is an index indicative of a chair shape breath pattern. 
     
     
         8 . The method of  claim 1  further comprising automatically determining a beginning of inspiration by:
 determining a measure of respiratory flow; 
 detecting a first peak from the measure of respiratory flow; and 
 determining a start of a respiration cycle as a function of the first peak; 
 wherein the detecting of the first peak is bounded to avoid detection of a second peak in the respiration cycle, and 
 wherein the treatment pressure is based on the determined start of the respiration cycle. 
 
     
     
         9 . The method of  claim 1  further comprising:
 determining a measure of respiratory flow; 
 determining a measure of partial obstruction from the measure of respiratory flow; 
 determining a measure of jamming from the measure of respiratory flow, the measure of jamming being a measure indicative of a transient change in a leak; and 
 adjusting the measure of partial obstruction as a function of the measure of jamming, 
 wherein the treatment pressure is based on the adjusted measure of partial obstruction. 
 
     
     
         10 . The method of  claim 9  wherein the measure of partial obstruction is a function of a detection of an M shape pattern breath. 
     
     
         11 . Apparatus for treating sleep disordered breathing to automatically determine a change in treatment pressure to be delivered by the apparatus comprising:
 a flow generator configured to generate the treatment pressure to a patient interface; and   a controller for the flow generator, the controller, including a processor, the controller configured to:
 determine a first measure of extent to which patient inspiratory effort correlates with patient inspiratory flow; 
 determine a second measure of patient ventilation; and 
 determine the change in treatment pressure as a first function of said first measure and second measure. 
   
     
     
         12 . The apparatus of  claim 11  wherein said first measure is an index of partial obstruction. 
     
     
         13 . The apparatus  claim 11  wherein said second measure of patient ventilation is a measure of the extent to which patient ventilation is adequate. 
     
     
         14 . The apparatus of  claim 11 , wherein said first measure is a measure of relative duration of inhalation and a breathing cycle. 
     
     
         15 . The apparatus of  claim 11  wherein the controller is configured to:
 determine a measure of respiratory flow with a sensor; 
 determine a first partial obstruction measure from the measure of respiratory flow; 
 determine a second partial obstruction measure from the measure of respiratory flow; and 
 determine a third partial obstruction measure as a function of the first and second partial obstruction measures, wherein the treatment pressure is based on the third partial obstruction measure. 
 
     
     
         16 . The apparatus of  claim 15  wherein the first partial obstruction measure is an index indicative of an M shape breath pattern. 
     
     
         17 . The apparatus of  claim 15  wherein the second partial obstruction measure is an index indicative of a chair shape breath pattern. 
     
     
         18 . The apparatus of  claim 11  wherein the controller is further configured to automatically determine a beginning of inspiration by:
 determining a measure of respiratory flow; 
 detecting a first peak from the measure of respiratory flow; and 
 determining a start of a respiration cycle as a function of the first peak; 
 wherein the detecting of the first peak is bounded to avoid detection of a second peak in the respiration cycle, and 
 wherein the treatment pressure is based on the determined start of the respiration cycle. 
 
     
     
         19 . The apparatus of  claim 11  wherein the controller is configured to:
 determine a measure of respiratory flow with a sensor; 
 determine a measure of partial obstruction from the measure of respiratory flow; 
 determine a measure of jamming from the measure of respiratory flow, the measure of jamming being a measure indicative of a transient change in a leak; and 
 adjust the measure of partial obstruction as a function of the measure of jamming, 
 wherein the treatment pressure is based on the adjusted measure of partial obstruction. 
 
     
     
         20 . The apparatus of  claim 19  wherein the measure of partial obstruction is a function of a detection of an M shape pattern breath.