Low perfusion signal processing systems and methods

Abstract

In some embodiments, systems and methods for identifying a low perfusion condition are provided by transforming a signal using a wavelet transform to generate a scalogram. A pulse band and adjacent marker regions in the scalogram are identified. Characteristics of the marker regions are used to detect the existence of a lower perfusion condition. If such a condition is detected, an event may be triggered, such as an alert or notification.

What is claimed is: 
     
         1 . A system comprising:
 a signal generator for generating a signal;   a processor coupled to the signal generator, wherein the processor is configured to perform operations comprising:
 generating a scalogram based at least in part on a wavelet transform of the signal; 
 identifying a pulse band in the scalogram; 
 identifying a marker region in the scalogram based at least in part on the position of the pulse band in the scalogram; 
 identifying a characteristic of the marker region; and 
 determining, based at least in part on the characteristic of the marker region, an indication of perfusion. 
   
     
     
         2 . The system of  claim 1 , wherein the marker region is substantially parallel to the pulse band. 
     
     
         3 . The system of  claim 1 , wherein the pulse band is between portions of the marker region. 
     
     
         4 . The system of  claim 1 , wherein the marker region is adjacent to the pulse band. 
     
     
         5 . The system of  claim 1 , wherein the marker region is spaced apart from the pulse band. 
     
     
         6 . The system of  claim 1 , wherein the marker region is positioned above, below, or both above and below the pulse band. 
     
     
         7 . The system of  claim 1 , wherein identifying the marker region comprises identifying the marker region based at least in part on user input, a ridge of the scalogram, or a modulus maximum of the scalogram. 
     
     
         8 . The system of  claim 1 , wherein the indication of perfusion is determined based at least in part on the energy of the marker region. 
     
     
         9 . The system of  claim 1 , wherein the signal comprises a photoplethysmograph signal from a subject. 
     
     
         10 . The system of  claim 1 , wherein the characteristic of the marker region is selected from the group consisting of:
 a change in energy within the marker region over time, a change in amplitude within the marker region over time, a residual marker, a number of residual markers, a size of the residual marker, a location of the residual marker, energy of the residual marker, amplitude of the residual marker, strength of the residual marker, and any combination thereof.   
     
     
         11 . The system of  claim 1 , wherein the processor is configured to perform operations further comprising receiving a threshold for a characteristic of the marker region. 
     
     
         12 . The system of  claim 11 , wherein the threshold is based at least in part on a user classification. 
     
     
         13 . The system of  claim 11 , wherein the processor is configured to perform operations further comprising:
 comparing the characteristic of the marker to the threshold; and   triggering an event based at least in part on the comparison.   
     
     
         14 . A method comprising:
 receiving, using a processor, a signal   generating, using the processor, a scalogram based at least in part on a transform of the signal;   identifying, using the processor, a pulse band in the scalogram;   identifying, using the processor, a marker region in the scalogram based at least in part on the position of the pulse band in the scalogram;   identifying, using the processor, a characteristic of the marker region;   determining, using the processor, based at least in part on the characteristic of the marker region, an indication of perfusion.   
     
     
         15 . The method of  claim 14 , wherein identifying the marker region comprises identifying a region substantially parallel to the pulse band. 
     
     
         16 . The method of  claim 14 , wherein identifying the pulse band comprises identifying a band between portions of the marker region. 
     
     
         17 . The method of  claim 14 , wherein identifying the marker region comprises identifying a region adjacent to the pulse band. 
     
     
         18 . The method of  claim 14 , wherein identifying the marker region comprises identifying a region spaced apart from the pulse band. 
     
     
         19 . The method of  claim 14 , wherein identifying the marker region comprises identifying a region positioned above, below, or both above and below the pulse band. 
     
     
         20 . The method of  claim 14 , wherein identifying the marker region comprises identifying a region based at least in part on user input, a ridge of the scalogram, or a modulus maximum of the scalogram. 
     
     
         21 . The method of  claim 14 , wherein determining an indication of perfusion comprises determining an indication based at least in part on the energy of the marker region. 
     
     
         22 . The method of  claim 14 , wherein receiving the signal comprises receiving a photoplethysmograph signal from a subject. 
     
     
         23 . The method of  claim 14 , wherein identifying the characteristic of the marker region comprises identifying a characteristic selected from the group consisting of:
 a change in energy within the marker region over time, a change in amplitude within the marker region over time, a residual marker, a number of residual markers, a size of the residual marker, a location of the residual marker, energy of the residual marker, amplitude of the residual marker, strength of the residual marker, and any combination thereof.   
     
     
         24 . The method of  claim 14 , further comprising receiving a threshold for a characteristic of the marker region. 
     
     
         25 . The method of  claim 24 , wherein receiving the threshold comprises receiving a threshold based at least in part on a user classification. 
     
     
         26 . The method of  claim 24 , further comprising:
 comparing the characteristic of the marker to the threshold; and   triggering an event based at least in part on the comparison.