Systems and methods for reducing signal noise when monitoring autoregulation

Abstract

A method for monitoring autoregulation includes, using a processor, receiving a blood pressure signal, a regional oxygen saturation signal, and a blood volume signal from a patient. The method also includes determining a first linear correlation between the blood pressure signal and the regional oxygen saturation signal and determining a second linear correlation between the blood pressure signal and the blood volume signal. The method also includes determining a confidence level associated with the first linear correlation based at least in part on the second linear correlation and providing a signal indicative of the patient's autoregulation status to an output device based on the linear correlation and the confidence level.

What is claimed is: 
     
         1 . A method for monitoring autoregulation of a patient, the method comprising:
 receiving, by one or more processors, a blood pressure signal indicative of a blood pressure of the patient, a regional oxygen saturation signal indicative of a blood oxygen saturation of the patient, and a blood volume signal indicative of a blood volume of the patient;   determining, by the one or more processors, a first linear correlation between the blood pressure signal and the regional oxygen saturation signal;   determining, by the one or more processors, a second linear correlation between the blood pressure signal and the blood volume signal;   determining, by the one or more processors, a confidence level associated with the first linear correlation based at least in part on a combination parameter, wherein the combination parameter is an average or a weighted average of the first and second linear correlations, wherein the confidence level is indicative of a reliability of the first linear correlation, the reliability being based on signal noise in the blood pressure signal or the regional oxygen saturation signal;   determining, by the one or more processors, a value indicative of autoregulation status of the patient based on the first linear correlation and the confidence level; and   outputting, by the one or more processors, via at least one of a display or audio device, information indicative of the autoregulation status of the patient, wherein the information is based on the value indicative of the autoregulation status of the patient.   
     
     
         2 . The method of  claim 1 , wherein determining the confidence level comprises comparing, by the one or more processors, the combination parameter to a predetermined threshold or value. 
     
     
         3 . The method of  claim 1 , further comprising determining, by the one or more processors, the confidence level is high by at least comparing the confidence level to a predetermined threshold or value. 
     
     
         4 . The method of  claim 1 , wherein outputting the information comprises at least one of:
 presenting, via the display, the information indicative of the autoregulation status of the patient; or   outputting, via the audio device, the information indicative of the autoregulation status of the patient.   
     
     
         5 . The method of  claim 1 , further comprising determining, by the one or more processors, the first linear correlation between the blood pressure signal and the oxygen saturation signal over a correlation window having a first period. 
     
     
         6 . The method of  claim 5 , further comprising varying, by the one or more processors, the first period of the correlation window to reduce variability associated with signal noise within the first linear correlation. 
     
     
         7 . A monitor for monitoring autoregulation of a patient, the monitor comprising:
 at least one of a display or an audio device; and   one or more processors configured to:
 receive a blood pressure signal indicative of a blood pressure of the patient, a regional oxygen saturation signal indicative of a blood oxygen saturation of the patient, and a blood volume signal indicative of a blood volume of the patient; 
 determine a first linear correlation between the blood pressure signal and the regional oxygen saturation signal; 
 determine a second linear correlation between the blood pressure signal and the blood volume signal; 
 determine a confidence level associated with the first linear correlation based at least in part on a combination parameter, wherein the combination parameter is an average or a weighted average of the first and second linear correlations, wherein the confidence level is indicative of a reliability of the first linear correlation, the reliability being based on signal noise in the blood pressure signal or the regional oxygen saturation signal; 
 determine a value indicative of autoregulation status of the patient based on the first linear correlation and the confidence level; and 
 output, by at least one of the display or the audio device, information indicative of the autoregulation status of the patient, wherein the information is based on the value indicative of the autoregulation status of the patient. 
   
     
     
         8 . The method of  claim 7 , wherein the one or more processors are further configured to compare the combination parameter to a predetermined threshold or value to determine the confidence level. 
     
     
         9 . The method of  claim 7 , wherein the one or more processors are further configured to compare the confidence level to a predetermined threshold or value to determine the confidence level is high. 
     
     
         10 . The method of  claim 7 , wherein the one or more processors are further configured to at least one of:
 present, via the display, the information indicative of the autoregulation status of the patient; or   output, via an audio device, the information indicative of the autoregulation status of the patient.   
     
     
         11 . The method of  claim 7 , wherein the one or more processors are further configured to determine the first linear correlation between the blood pressure signal and the oxygen saturation signal over a correlation window having a first period. 
     
     
         12 . The method of  claim 11 , wherein the one or more processors are further configured to vary the first period of the correlation window to reduce variability associated with signal noise within the first linear correlation. 
     
     
         13 . A system for monitoring autoregulation of a patient, the system comprising:
 a regional oxygen saturation sensor configured to obtain a regional oxygen saturation signal indicative of a blood oxygen saturation of the patient; and   a monitor comprising:
 at least one of a display or an audio device; and 
 one or more processors configured to:
 receive a blood pressure signal indicative of a blood pressure of the patient, the regional oxygen saturation signal, and a blood volume signal indicative of a blood volume of the patient; 
 determine a first linear correlation between the blood pressure signal and the regional oxygen saturation signal; 
 determine a second linear correlation between the blood pressure signal and the blood volume signal; 
 determine a confidence level associated with the first linear correlation based at least in part on a combination parameter, wherein the combination parameter is an average or a weighted average of the first and second linear correlations, wherein the confidence level is indicative of a reliability of the first linear correlation, the reliability being based on signal noise in the blood pressure signal or the regional oxygen saturation signal; 
 determine a value indicative of autoregulation status of the patient based on the first linear correlation and the confidence level; and 
 output, by the at least one of the display or the audio device, information indicative of the autoregulation status of the patient, wherein the information is based on the value indicative of the autoregulation status of the patient. 
 
   
     
     
         14 . The method of  claim 13 , wherein the one or more processors are further configured to compare the combination parameter to a predetermined threshold or value to determine the confidence level. 
     
     
         15 . The method of  claim 13 , wherein the one or more processors are further configured to compare the confidence level to a predetermined threshold or value to determine the confidence level is high. 
     
     
         16 . The method of  claim 13 , wherein the one or more processors are further configured to at least one of:
 present, via the display, information indicative of the autoregulation status of the patient; or   output, via the audio device, information indicative of the autoregulation status of the patient.   
     
     
         17 . The system of  claim 13 , wherein the regional oxygen saturation sensor is configured to obtain the regional oxygen saturation signal and at least one of the blood volume signal or the blood pressure signal. 
     
     
         18 . The system of  claim 13 , wherein the one or more processors are further configured to cause display of at least one of a cerebral oximetry index value indicative of the patient's autoregulation status, a hemoglobin volume index, the confidence level associated with the cerebral oximetry index value or the hemoglobin volume index, or an indication of the patient's autoregulation status. 
     
     
         19 . The system of  claim 13 , wherein the one or more processors are further configured to:
 display, via the display, a correlation window comprising a first period; and   determine the first linear correlation between the blood pressure signal and the regional oxygen saturation signal over the correlation window.   
     
     
         20 . The method of  claim 19 , wherein the one or more processors are further configured to vary the first period of the correlation window to reduce variability associated with signal noise within the first linear correlation.