Assessing Cardiovascular Function Using an Optical Sensor

Abstract

This document describes assessing cardiovascular function using an optical sensor, such as through sensing relevant hemodynamics understood by pulse transit times, blood pressures, pulse-wave velocities, and, in more breadth, ballistocardiograms and pressure-volume loops. The techniques disclosed in this document use various optical sensors to sense hemodynamics, such as skin color and skin and other organ displacement. These optical sensors require little if any risk to the patient and are simple and easy for the patient to use.

What is claimed is: 
     
         1 . A computer-implemented method comprising:
 receiving, from an optical sensor capable of detecting blood volume at two or more regions of a patient, an image indicating a first blood volume for a first region and another image indicating a second blood volume for a second region;   comparing the first blood volume for the first region and the second blood volume for the second region to provide a blood-volume asymmetry; and   determining, based on the blood-volume asymmetry, a difference in vascular function between the first region and the second region.   
     
     
         2 . The method of  claim 1 , wherein determining the difference in vascular function is based on the comparing the first and second blood volumes indicating a lower peak blood volume at one of the first or second blood volumes than the other of the first or second blood volumes. 
     
     
         3 . The method of  claim 1 , further comprising indicating, to the patient or a medical professional associated with the patient, a potential stroke or other vascular disease based on the difference in vascular function. 
     
     
         4 . The method of  claim 1 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin colors and further comprising determining the first blood volume and the second blood volume using the skin colors of the first and second regions, respectively. 
     
     
         5 . The method of  claim 1 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin displacements and further comprising determining the first blood volume and the second blood volume using the skin displacements of the first and second regions, respectively. 
     
     
         6 . The method of  claim 1 , further comprising calibrating the optical sensor with one or more external sensors effective to calibrate the first blood volume and the second blood volume to a calibration blood-volume asymmetry, the calibrating prior to determining the blood-volume asymmetry, and wherein providing the blood-volume asymmetry is based at least in part on the calibration. 
     
     
         7 . A system comprising:
 an optical sensor capable of detecting blood volume at two or more regions of a patient;   a computer processor; and   one or more computer-readable storage media having instructions stored thereon that, responsive to execution by the computer processor, performs operations comprising:
 receiving, from the optical sensor, an image indicating a first blood volume for a first region and another image indicating a second blood volume for a second region; 
 comparing the first blood volume for the first region and the second blood volume for the second region to provide a blood-volume asymmetry; and 
 determining, based on the blood-volume asymmetry, a difference in vascular function between the first region and the second region. 
   
     
     
         8 . The system of  claim 7 , wherein determining the difference in vascular function is based on the comparing the first and second blood volumes indicating a lower peak blood volume at one of the first or second blood volumes than the other of the first or second blood volumes. 
     
     
         9 . The system of  claim 7 , the operations further comprising indicating, to the patient or a medical professional associated with the patient, a potential stroke or other vascular disease based on the difference in vascular function. 
     
     
         10 . The system of  claim 7 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin colors and the operations further comprise determining the first blood volume and the second blood volume using the skin colors of the first and second regions, respectively. 
     
     
         11 . The system of  claim 7 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin displacements and the operations further comprise determining the first blood volume and the second blood volume using the skin displacements of the first and second regions, respectively. 
     
     
         12 . The system of  claim 7 , the operations further comprising calibrating the one or more optical sensors with one or more external sensors effective to calibrate the first blood volume and the second blood volume to a calibration blood-volume asymmetry, the calibrating prior to determining the blood-volume asymmetry, and wherein providing the blood-volume asymmetry is based at least in part on the calibration. 
     
     
         13 . The system of  claim 7 , the operations further comprising:
 performing the operations again at a later time to determine a later-time difference in vascular function; and   determining a cardiac trend for the patient based on the later-time vascular difference and the vascular difference.   
     
     
         14 . One or more computer-readable storage media having instructions stored thereon that, responsive to execution by a computer processor, performs operations comprising:
 receiving, from an optical sensor capable of detecting blood volume at two or more regions of a patient, an image indicating a first blood volume for a first region and another image indicating a second blood volume for a second region;   comparing the first blood volume for the first region and the second blood volume for the second region to provide a blood-volume asymmetry; and   determining, based on the blood-volume asymmetry, a difference in vascular function between the first region and the second region.   
     
     
         15 . The media of  claim 14 , wherein determining the difference in vascular function is based on the comparing the first and second blood volumes indicating a lower peak blood volume at one of the first or second blood volumes than the other of the first or second blood volumes. 
     
     
         16 . The media of  claim 14 , wherein the instructions further perform operations comprising indicating, to the patient or a medical professional associated with the patient, a potential stroke or other vascular disease based on the difference in vascular function. 
     
     
         17 . The media of  claim 14 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin colors and the instructions further perform operations comprising determining the first blood volume and the second blood volume using the skin colors of the first and second regions, respectively. 
     
     
         18 . The media of  claim 14 , wherein the image and the other image indicate the first blood volume and the second blood volume with skin displacements and the instructions further perform operations comprising determining the first blood volume and the second blood volume using the skin displacements of the first and second regions, respectively. 
     
     
         19 . The media of  claim 14 , wherein the instructions further perform operations comprising calibrating the one or more optical sensors with one or more external sensors effective to calibrate the first blood volume and the second blood volume to a calibration blood-volume asymmetry, the calibrating prior to determining the blood-volume asymmetry, and wherein providing the blood-volume asymmetry is based at least in part on the calibration. 
     
     
         20 . The media of  claim 14 , wherein the instructions further perform operations comprising:
 performing the operations again at a later time to determine a later-time difference in vascular function; and   determining a cardiac trend for the patient based on the later-time vascular difference and the vascular difference.