Systems and methods for processing physiological signals in wavelet space

Abstract

Methods and systems are disclosed for analyzing multiple scale bands in the scalogram of a physiological signal in order to obtain information about a physiological process. An analysis may be performed to identify multiple scale bands that are likely to contain the information sought. Each scale band may be assessed to determine a band quality, and multiple bands may be combined based on the band quality. Information about a physiological process may determined based on the combined band. In an embodiment, analyzing multiple scale bands in a scalogram arising from a wavelet transformation of a photoplethysmograph signal may yield clinically relevant information about, among other things, the blood oxygen saturation of a patient.

What is claimed is: 
     
         1 . A method for processing a physiological signal of a subject, comprising:
 receiving, from a sensor, the physiological signal;   determining, using a processor, a pulse rate of the subject based at least in part on the physiological signal;   transforming, using the processor, the physiological signal into a transformed signal based at least in part on a wavelet transform;   determining, using the processor, a quality associated with each of a plurality of scales of the transformed signal, wherein each of the plurality of scales is based at least in part on the pulse rate;   combining, using the processor, the plurality of scales of the transformed signal to generate combined scale data based at least in part on the associated qualities; and   determining, using the processor, physiological information of the subject based at least in part on the combined scale data.   
     
     
         2 . The method of  claim 1 , wherein the plurality of scales corresponds to scales associated with the pulse rate and multiples of the pulse rate. 
     
     
         3 . The method of  claim 1 , wherein the plurality of scales comprises a first scale corresponding to the pulse rate, a second scale corresponding to two times the pulse, and a third scale corresponding to three times the pulse rate. 
     
     
         4 . The method of  claim 1 , wherein combining the plurality of scales comprises calculating a weighted combination based on each of the plurality of scales, wherein the weight associated with each of the plurality of scales is based at least in part on a corresponding associated quality. 
     
     
         5 . The method of  claim 1 , further comprising removing a portion of a scale over a time interval based at least in part on a quality over the time interval. 
     
     
         6 . The method of  claim 1 , further comprising:
 receiving, from the sensor, a second physiological signal; and   transforming, using the processor, the second physiological signal into a second transformed signal based at least in part on a wavelet transform, wherein determining the quality associated with each of the plurality of scales is based on the transformed signal and the second transformed signal.   
     
     
         7 . The method of  claim 1 , wherein determining the quality associated with each of a plurality of scales comprises measuring the consistency of features in the transformed signal. 
     
     
         8 . The method of  claim 1 , wherein determining the quality associated with each of a plurality of scales comprises comparing energy of a scale and energy of the plurality of scales. 
     
     
         9 . The method of  claim 1 , wherein determining the quality associated with each of a plurality of scales comprises assessing noise in the transformed signal. 
     
     
         10 . The method of  claim 1 , wherein determining the physiological information of the subject comprises determining blood oxygen saturation of the subject.