Method, apparatus, and system for measuring respiratory effort

Abstract

A method, apparatus, and system for measuring respiratory effort of a subject are provided. A thorax effort signal and an abdomen effort signal are obtained. The thorax effort signal and the abdomen effort signal are each divided into a volume-contributing component of the respiratory effort and a paradox component. The paradox component represents a non-volume-contributing component of the respiratory effort. The abdomen paradox component is negatively proportional to the thoracic paradox component. The thorax effort signal or the abdomen effort signal or both are weighted by a weight factor to obtain a volume-proportional signal. The volume-proportional signal is proportional to the actual respiratory volume of the respiratory effort. A calibration factor for calibrating the thorax effort signal and the abdomen effort signal is obtained by optimizing the weight factor by minimizing thoracic paradox component and the abdomen paradox component.

What is claimed: 
     
         1 . A method of measuring respiratory effort of a subject, the method comprising:
 obtaining a thorax effort signal (T), the thorax effort signal (T) being an indicator of a thoracic component of the respiratory effort;   obtaining an abdomen effort signal (A), the abdomen effort signal (A) being an indicator of an abdominal component of the respiratory effort;   separating the thorax effort signal (T) into a volume-contributing thoracic component (V ST ) and a thoracic paradox component (P T ), the thoracic paradox component (P T ) representing a non-volume-contributing thoracic component of the respiratory effort, and the volume-contributing thoracic component (V ST ) representing a volume-contributing component of the respiratory effort;   separating the abdomen effort signal (A) into a volume-contributing abdominal component (V SA ) and an abdomen paradox component (P A ), the abdomen paradox component (P A ) representing a non-volume-contributing abdominal component of the respiratory effort, and the volume-contributing abdominal component (V SA ) representing a volume-contributing component of the respiratory effort, wherein the non-volume-contributing abdominal component (P A ) is negatively proportional to the non-volume-contributing thoracic component (P T );   weighting the thorax effort signal (T) by a first weight factor (k T ) and weighting the abdomen effort signal (A) by a second weight factor (k A ) to obtain a volume-proportional signal (V Sw ), the volume-proportional signal (V Sw ) being proportional to the actual respiratory volume of the respiratory effort; and   optimizing the weight factors (k T  and k A ) by minimizing the non-volume-contributing thoracic component (P T ) and the non-volume-contributing abdominal component (P A ) in the resulting volume-proportional signal (V Sw ).   
     
     
         2 . The method according to  claim 1 , further comprising obtaining a calibration factor for calibrating the thorax effort signal (T) and the abdomen effort signal (A) based on the optimized first and second weight factors (k T and k A ). 
     
     
         3 . The method according to  claim 1 , further comprising determining the power loss based on the optimized first and second weight factors (k A  and k T ). 
     
     
         4 . The method according to  claim 3 , wherein determing the power loss includes maximizing the power loss of a resulting signal compared with a sum of the power of the thorax effort signal (T) weighted by the optimized first weight factor (k T ) and the abdomen effort signal (A) weighted by the optimized second weight factor (k A ) over a period of time. 
     
     
         5 . The method according to  claim 1 , wherein a volume-proportional signal (V S2 ) is obtained by weighting the thorax effort signal (T) by the first weight factor (k T ). 
     
     
         6 . The method according to  claim 1 , wherein the volume-proportional signal (V S ) is obtained by weighting the abdomen effort signal (A) by the second weight factor (k A ). 
     
     
         7 . The method according to  claim 6 , wherein the second weight factor (k A ) is a weight ratio for the abdomen effort signal (A) towards the thorax effort signal (T) such that the resulting volume-proportional signal (V S ) equals T+(k A ×A). 
     
     
         8 . The method according to  claim 1 , further comprising calculating the respiratory flow proportional signal (F S ) by calculating the first derivative of the thorax effort signal (T) with respect to time (T′) and the first derivative of the abdomen effort signal (A) with respect to time (A′) to minimize the non-volume-contributing thoracic component (P T ) and the non-volume-contributing abdominal component (P A ). 
     
     
         9 . The method according to  claim 1 , wherein the first and second weight factors (k T  and k A ) are optmized by comparing a maximized proportion power of lower frequencies of the thorax effort signal (T) and the abdomen effort signal (A) with a proportional power of higher frequencies of the thorax effort signal (T) and the abdomen effort signal (A) over a period of time. 
     
     
         10 . The method according to  claim 1 , further comprising maximizing an amplitude loss of a resulting signal compared with a sum of the amplitude of the thorax effort signal (T) and the abdomen effort signal (A) over a period of time. 
     
     
         11 . The method according to  claim 1 , further comprising obtaining a calibration factor for calibrating the thorax effort signal (T) and the abdomen effort signal (A) over a plurality of time spans including a first timespan within a second time span, the first time span being shorter than the second time span, and
 selecting a calibration ratio for the second time span based on the most determinant calibration factor of the obtained calibration factors of the plurailty of time spans.   
     
     
         12 . The method according to  claim 1 , further comprising selecting a value for the first and second weight factors (k T  and k A ) by determining intermediate values for weighing ratios for a set of a plurality of consecutive intermediate time spans and calculating the value for the first and second weight factors (k A  and k T ) by weighing values within the set of time spans so as to maximize the continuity of weighed values over the set. 
     
     
         13 . The method according to  claim 1 , further comprising deriving a paradox signal, a derivative of the paradox signal, or an integration of the paradox signal of the thorax effort signal (T) or the abdomen effort signal (A) by deriving an intermediate value of the first and second weight factors (k T  and k A ) by determing a value for the first and second weight factors (k T  and k A ) that results in the minimization of the amplitude or power of the paradox signal of the thorax effort signal (T) or the abdomen effort signal (A). 
     
     
         14 . The method according to  claim 1 , further comprising evaluating flow resistance from the obtained paradox signal of the thorax effort signal (T) or the abdomen effort signal (A) and the first derivative of the volume-proportion signal (V S ) with respect to time. 
     
     
         15 . A method of measuring respiratory effort of a subject, comprising evaluating respiration energy by integrating the multiplication product of the thorax paradox signal derived according to  claim 8 , with the first derivative of the volume-proportion signal (V S ) with respect to time. 
     
     
         16 . A method of measuring respiratory effort of a subject, comprising determining the first and second weight factors (k T  and k A ) according to the methods of  claim 1 ,
 using the first and second weight factors (k T  and k A ) to create a weighted sum of signals based on the thorax effort signal (T) and the abdomen effort signal (A),   calculating the ratio between the amplitude or power or any transformation function of the amplitude or power towards the sum of the amplitudes, power, or the other transformation function of each of the signals derived from the thorax effort signal (T) and the abdomen effort signal (A).   
     
     
         17 . The method according to  claim 16 , wherein the thorax effort signal (T) is obtained by providing a first sensor device configured to measure the thoracic component of the respiratory effort of the subject, and
 the abdomen effort signal (A) is obtained by providing a second sensor device configured to measure the abdomen component of the respiratory effort of the subject.   
     
     
         18 . The method according to  claim 1 , further comprising determing a respiratory volume calibration based on a measured heart rate of the subject. 
     
     
         19 . A hardware storage device having stored thereon computer executable instructions which, when executed by one or more processors, implement a method of measuring respiratory effort of a subject comprising:
 separating a received thorax effort signal (T) into a volume-contributing thoracic component (V ST ) and a thoracic paradox component (P T ), the thorax effort signal (T) being an indicator of a thoracic component of the respiratory effort, the thoracic paradox component (P T ) representing a non-volume-contributing thoracic component of the respiratory effort, and the volume-contributing thoracic component (V ST ) representing a volume-contributing component of the respiratory effort;   separating an abdomen effort signal (A) into a volume-contributing abdominal component (V SA ) and an abdomen paradox component (P A ), the abdomen effort signal (A) being an indicator of an abdominal component of the respiratory effort, the abdomen paradox component (P A ) representing a non-volume-contributing abdominal component of the respiratory effort, and the volume-contributing abdominal component (V SA ) representing a volume-contributing component of the respiratory effort, wherein the non-volume-contributing abdominal component (P A ) is negatively proportional to the non-volume-contributing thoracic component (P T );   weighting the thorax effort signal (T) by a first weight factor (k T ) and weighting the abdomen effort signal (A) by a second weight factor (k A ) to obtain a volume-proportional signal (V Sw ), the volume-proportional signal (V Sw ) being proportional to the actual respiratory volume of the respiratory effort; and   optimizing the first and second weight factors (k T  and k A ) by minimizing the non-volume-contributing thoracic component (P T ) and the non-volume-contributing abdominal component (P A ) in the resulting volume-proportional signal (V Sw ).   
     
     
         20 . A respiratory effort measuring system comprising:
 a first sensor device configured to obtain a thorax effort signal (T), the thorax effort signal (T) being an indicator of a thoracic component of the respiratory effort;   a second sensor device configured to obtain an abdomen effort signal (A), the abdomen effort signal (A) being an indicator of an abdominal component of the respiratory effort; and   a processor configured to receive the thorax effort signal (T) and the abdomen effort signal (A); wherein the processor   separates the thorax effort signal (T) into a volume-contributing thoracic component (V ST ) and a thoracic paradox component (P T ), the thoracic paradox component (P T ) representing a non-volume-contributing thoracic component of the respiratory effort, and the volume-contributing thoracic component (V ST ) representing a volume-contributing component of the respiratory effort,   separates the abdomen effort signal (A) into a volume-contributing abdominal component (V SA ) and an abdomen paradox component (P A ), the abdomen paradox component (P A ) representing a non-volume-contributing abdominal component of the respiratory effort, and the volume-contributing abdominal component (V SA ) representing a volume-contributing component of the respiratory effort, wherein the non-volume-contributing abdominal component (P A ) is negatively proportional to the non-volume-contributing thoracic component (P T ),   weights the thorax effort signal (T) by a first weight factor (k T ) and weights the abdomen effort signal (A) by a second weight factor (k A ) to obtain a volume-proportional signal (V Sw ), the volume-proportional signal (V Sw ) being proportional to the actual respiratory volume of the respiratory effort; and   optimizes the first and second weight factors (k T  and k A ) by minimizing the non-volume-contributing thoracic component (P T ) and the non-volume-contributing abdominal component (P A ) in the resulting volume-proportional signal (V Sw ).