Systems and methods for detecting and monitoring arrhythmias using the ppg

Abstract

Systems and methods for detecting and monitoring arrhythmias from a signal are provided. A signal processing system may transform a signal using a wavelet transformation and analyze changes in features of the transformed signal to detect pulse rhythm abnormalities. For example, the system may detect pulse rhythm abnormalities by analyzing energy parameters, morphology changes, and pattern changes in the scalogram of a PPG signal. Further, the system may detect pulse rhythm abnormalities by analyzing both the PPG signal and its corresponding scalogram. Physiological information, such as cardiac arrhythmia, may be derived based on the detected pulse rhythm abnormality.

What is claimed is: 
     
         1 . A method for determining cardiac arrhythmia in a subject, comprising:
 electronically receiving a photoplethysmograph signal of a subject from a sensing device, wherein the photoplethysmograph signal comprises a plurality of pulse regions;   calculating, using a processor, a measure of an area of a first pulse region;   calculating, using the processor, an average measure of areas of two or more pulse regions;   comparing, using the processor, the measure of an area of a first pulse region and the average measure;   detecting, using the processor, a change in an area characteristic of the signal based at least in part on the comparison; and   determining, using the processor, the cardiac arrhythmia in the subject based at least in part on the detected change in the area characteristic of the signal.   
     
     
         2 . The method of  claim 1 , further comprising:
 calculating a measure of an AC component of a first pulse region;   calculating an average measure of AC components of two or more pulse regions;   comparing the measure of an AC component of a first pulse region and the average measure; and   detecting a change in an AC characteristic of the signal based at least in part on the comparison,   wherein the determining the cardiac arrhythmia in the subject further comprises determining the cardiac arrhythmia in the subject based at least in part on the detected change in the AC characteristic of the signal.   
     
     
         3 . The method of  claim 1 , further comprising:
 calculating a measure of a period of a first pulse region;   calculating an average measure of periods of two or more pulse regions;   comparing the measure of a period of a first pulse region and the average measure; and   detecting a change in a period characteristic of the signal based at least in part on the comparison,   wherein the determining the cardiac arrhythmia in the subject further comprises determining the cardiac arrhythmia in the subject based at least in part on the detected change in the period characteristic of the signal.   
     
     
         4 . The method of  claim 1 , further comprising:
 generating a transformed signal based at least in part on a transformation of the photoplethysmograph signal;   detecting a change in a feature of the transformed signal; and   identifying information indicative of a pulse rhythm abnormality based at least in part on the detected change in the feature of the transformed signal,   wherein the determining the cardiac arrhythmia in the subject further comprises determining cardiac arrhythmia in the subject based at least in part on the information indicative of the pulse rhythm abnormality.   
     
     
         5 . The method of  claim 4 , wherein the transformation of the photoplethysmograph signal comprises a wavelet transformation. 
     
     
         6 . The method of  claim 5 , wherein the transformed signal comprises a scalogram. 
     
     
         7 . The method of  claim 6 , wherein the scalogram comprises a pulse band region, a region of scales greater than the pulse band region, and a region of scales lower than the pulse band region, the method further comprising:
 determining an energy distribution of the scalogram for a time interval; and   comparing the energy distribution of the scalogram for the time interval against a reference energy distribution,   wherein the detecting the change in the feature of the transformed signal comprises detecting a change in the energy distribution of one or more of the pulse band region, the region of scales greater than the pulse band region, and the region of scales lower than the pulse band region based at least in part on the comparison.   
     
     
         8 . The method of  claim 4 , wherein the detecting the change in the feature of the transformed signal comprises detecting the change in the feature of the transformed signal based at least in part on a comparison of the feature and a threshold value. 
     
     
         9 . The method of  claim 1 , wherein the cardiac arrhythmia comprises one of atrial flutter, sinus tachycardia, ventricular tachycardia, ventricular fibrillation, bradycardia, an ectopic beat, bigeminy, trigeminy, and a combination thereof. 
     
     
         10 . The method of  claim 1 , further comprising providing for display an indication of cardiac arrhythmia based at least in part on the determined cardiac arrhythmia. 
     
     
         11 . A system for determining cardiac arrhythmia in a subject, the system comprising:
 a signal input configured to receive a photoplethysmograph signal of a subject from a sensing device, wherein the photoplethysmograph signal comprises a plurality of pulse regions; and   a processor coupled to the signal input, the processor configured to:
 calculate a measure of an area of a first pulse region; 
 calculate an average measure of areas of two or more pulse regions; 
 compare the measure of the area of a first pulse region and the average measure; 
 detect a change in an area characteristic of the signal based at least in part on the comparison; and 
 determine the cardiac arrhythmia in the subject based at least in part on the detected change in the area characteristic of the signal. 
   
     
     
         12 . The system of  claim 11 , wherein the processor is further configured to:
 calculate a measure of an AC component of a first pulse region;   calculate an average measure of AC components of two or more pulse regions;   compare the measure of an AC component of a first pulse region and the average measure;   detect a change in an AC characteristic of the signal based at least in part on the comparison; and   determine the cardiac arrhythmia in the subject based at least in part on the detected change in the AC characteristic of the signal.   
     
     
         13 . The system of  claim 11 , wherein the processor is further configured to:
 calculate a measure of a period of a first pulse region;   calculate an average measure of periods of two or more pulse regions;   compare the measure of a period of a first pulse region and the average measure;   detect a change in a period characteristic of the signal based at least in part on the comparison; and   determine the cardiac arrhythmia in the subject based at least in part on the detected change in the period characteristic of the signal.   
     
     
         14 . The system of  claim 11 , wherein the processor is further configured to:
 generate a transformed signal based at least in part on a transformation of the photoplethysmograph signal;   detect a change in a feature of the transformed signal;   identify information indicative of a pulse rhythm abnormality based at least in part on the detected change in the feature of the transformed signal; and   determine the cardiac arrhythmia in the subject based at least in part on the information indicative of the pulse rhythm abnormality.   
     
     
         15 . The system of  claim 14 , wherein the transformation of the photoplethysmograph signal comprises a wavelet transformation. 
     
     
         16 . The system of  claim 15 , wherein the transformed signal comprises a scalogram. 
     
     
         17 . The system of  claim 16 , wherein the scalogram comprises a pulse band region, a region of scales greater than the pulse band region, and a region of scales lower than the pulse band region and wherein the processor is further configured to:
 determine an energy distribution of the scalogram for a time interval;   compare the energy distribution of the scalogram for the time interval against a reference energy distribution; and   detect the change in the feature of the transformed signal by detecting a change in the energy distribution of one or more of the pulse band region, the region of scales greater than the pulse band region, and the region of scales lower than the pulse band region based at least in part on the comparison.   
     
     
         18 . The system of  claim 14 , wherein the processor is configured to detect the change in the feature of the transformed signal by detecting the change in the feature of the transformed signal based at least in part on a comparison of the feature and a threshold value. 
     
     
         19 . The system of  claim 1 , wherein the cardiac arrhythmia comprises one of atrial flutter, sinus tachycardia, ventricular tachycardia, ventricular fibrillation, bradycardia, an ectopic beat, bigeminy, trigeminy, and a combination thereof. 
     
     
         20 . The system of  claim 1 , further comprising a display configured to display an indication of cardiac arrhythmia based at least in part on the determined cardiac arrhythmia.