Methods And Systems For Predicting Hypovolemic Hypotensive Conditions Resulting From Bradycardia Behavior Using A Pulse Volume Waveform

Abstract

A method for identifying cardiac bradycardia behavior may include acquiring pulse volume wave data from a sensor associated with a patient, and calculating metrics associated with peaks detected therein. The metrics may include changes in peak amplitudes of pulse volume peaks and in the times of occurrence of pulse volume peaks. Alternative metrics may include changes in frequency domain parameters derived from the time domain pulse volume wave data. Peak amplitude values may be compared to an amplitude baseline, and differences in successive peak occurrence times may be compared to a time baseline. Cardiac bradycardia behavior may be identified by a combination of a decrease in the pulse volume peak amplitude and an increase in successive peak occurrence times. A system to implement the method may include a computing device in data communication with a photo-plethysmograph. Alternative sensors may include a blood pressure cuff and an ECG device.

What is claimed: 
     
         1 . A method for predicting a hemodynamic instability condition for a patient resulting from cardiac behavior, the method comprising:
 receiving, by a computing device, a biological signal of a human body emulating an arterial pulse wave;   performing an analysis on the biological signal in a plurality of data windows over time and identifying a plurality of signal peaks within the biological signal, identifying a time occurrence for signal peaks of the plurality of signal peaks and identifying an amplitude for signal peaks of the plurality of signal peaks over the plurality of data windows;   determining a plurality of time differences, wherein each time difference is determined from a first time occurrence of a first peak and a second time occurrence of a second peak;   determining, by the computing device, a plurality of pulse rate metrics from the biological signal based on the plurality of time differences from the signal peaks over the plurality of data windows;   determining, by the computing device, a plurality of pulse strength metrics from the biological signal based on the amplitudes of the plurality of signal peaks over the plurality of data windows;   determining a pulse rate baseline and a pulse strength baseline;   determining, by the computing device, a plurality of pulse rate differences, wherein each pulse rate difference is determined from pulse rate metrics of data windows subsequent to the early data windows and the pulse rate baseline;   determining, by the computing device, a plurality of pulse strength differences, wherein each pulse strength difference is determined from pulse strength metrics of data windows subsequent to the early data windows and the pulse strength baseline;   determining a threshold associated with the pulse strength differences;   determining a threshold associated with the pulse rate differences;   comparing at least one anomalous pulse rate difference with the pulse rate difference threshold to determine when the pulse rate difference decreases below the pulse rate difference threshold;   comparing at least one anomalous pulse strength difference with the pulse strength difference threshold to determine when the pulse strength difference decreases below the pulse strength difference threshold; and   identifying, by the computing device, the hemodynamic instability condition resulting from cardiac behavior in the human body based upon the simultaneous decrease of the at least one anomalous pulse rate difference and the at least one anomalous pulse strength difference below the respective thresholds; and   upon the identification of the hemodynamic instability condition alerting a caregiver with an output device coupled with the computing device to take action to prevent trauma to the patient.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining, by the computing device, an average time difference from a portion of the plurality of determined time differences; and   determining an inverse of the average time difference.   
     
     
         3 . The method of  claim 2 , wherein determining an average time difference from a portion of the plurality of time differences comprises determining an average time difference from a portion of the plurality of time differences within a data window. 
     
     
         4 . The method of  claim 3 , wherein determining an average time difference within a data window comprises determining an average time difference throughout at least one respiratory cycle of the human body. 
     
     
         5 . The method of  claim 3 , wherein the data window is about 5 seconds to about 30 seconds. 
     
     
         6 . The method  claim 3 , wherein the data window is about 10 seconds. 
     
     
         7 . The method of  claim 1 , further comprising:
 determining an inverse time difference for each time difference within a portion of the plurality of time differences; and   determining an average inverse time difference from a plurality of inverse time differences.   
     
     
         8 . The method of  claim 7 , wherein determining an average inverse time difference from the plurality of inverse time differences comprises determining an average inverse time difference from the plurality of inverse time differences within a data window. 
     
     
         9 . The method of  claim 1 , further comprising determining an average amplitude of a portion of the amplitudes of the plurality of signal peaks. 
     
     
         10 . The method of  claim 9 , wherein determining an average amplitude of a portion of the amplitudes comprises determining an average amplitude of a portion of the amplitudes of the plurality of signal peaks within a data window. 
     
     
         11 . The method of  claim 10 , wherein determining an average amplitude within a data window comprises determining an average amplitude throughout at least one respiratory cycle of the human body. 
     
     
         12 . The method of  claim 10 , wherein the data window is about 5 seconds to about 30 seconds. 
     
     
         13 . The method  claim 10 , wherein the data window is about 10 seconds. 
     
     
         14 . The method of  claim 1 , wherein determining the pulse rate baseline comprises:
 identifying a plurality of signal peaks within a data window of the biological signal, wherein the data window includes a period of a normative cardiac rhythm of the human body;   identifying a time occurrence for signal peaks of the plurality of signal peaks in the data window;   determining plurality of time differences, wherein each time difference is determined from a first time occurrence of a first peak and a second time occurrence of a second peak;   identifying a maximum time difference of the plurality of time differences; and   determining an inverse of the maximum time difference.   
     
     
         15 . The method of  claim 1 , wherein determining the pulse rate baseline comprises determining an average pulse rate baseline from a plurality of biological signals, wherein each of the plurality of biological signals is obtained from one of a plurality of human bodies. 
     
     
         16 . The method of  claim 1 , wherein determining the pulse rate baseline comprises determining an average of a normative pulse rate obtained from the human body. 
     
     
         17 . The method of  claim 1 , wherein determining the pulse rate baseline comprises determining an average of a plurality of normative pulse rates, wherein each of the plurality of normative pulse rates is obtained from one of a plurality of human bodies. 
     
     
         18 . The method of  claim 1 , wherein determining a pulse strength baseline from a plurality of signal peaks comprises determining an average peak amplitude of the plurality of signal peaks. 
     
     
         19 . The method of  claim 1 , wherein determining the pulse strength baseline from a plurality of signal peaks comprises determining a maximum peak amplitude of the plurality of signal peaks. 
     
     
         20 . The method of  claim 1 , wherein determining the pulse strength baseline comprises determining a pulse strength baseline from a plurality of biological signals, each biological signal obtained from one of a plurality of human bodies.