System and method for probability based determination of estimated oxygen saturation

Abstract

Present embodiments include providing an initial estimate of a value representative of a blood flow characteristic at a current timestep, and determining a probability distribution of transition, wherein the probability distribution of transition includes potential values of the blood flow characteristic at the current timestep with associated probabilities of occurrence based solely on the initial estimate. Present embodiments further include obtaining an initial measurement of the blood flow characteristic, and determining a probability distribution of measured values, wherein the probability distribution of measured values includes potential values of the blood flow characteristic at the current timestep with associated probabilities of occurrence based on the initial measurement. Further, present embodiments include combining the probability of distribution of transition with the probability of distribution of measured values to determine a meaningful blood flow characteristic value, and posting the meaningful blood flow characteristic value.

1 .- 20 . (canceled) 
     
     
         21 . A method, comprising:
 using a monitor for:   providing an initial estimate of a value representative of blood oxygen saturation at a current timestep;   correlating one or more optical observations obtained during a previous timestep;   obtaining a noise estimate based on the correlation; and   performing a maximum likelihood calculation to determine a value of blood oxygen saturation that is most likely given the initial estimate, the one or more optical observations, and the noise estimate.   
     
     
         22 . The method of  claim 21 , wherein correlating the one or more optical observations obtained during the previous timestep comprises performing a linear regression of the one or more optical observations. 
     
     
         23 . The method of  claim 21 , wherein obtaining the noise estimate comprises determining a sample standard deviation of residuals. 
     
     
         24 . The method of  claim 21 , wherein performing the maximum likelihood calculation comprises combining a first probability distribution and a second probability distribution. 
     
     
         25 . The method of  claim 24 , wherein the first probability distribution comprises a probability distribution of potential values of blood oxygen saturation at the current timestep based on the initial estimate. 
     
     
         26 . The method of  claim 24 , wherein the second probability distribution comprises a probability distribution of observed blood oxygen saturation values based on an actual value. 
     
     
         27 . The method of  claim 26 , wherein the probability distribution of observed values is based at least in part upon the noise estimate. 
     
     
         28 . The method of  claim 24 , wherein the first probability distribution comprises a probability distribution of potential values of blood oxygen saturation at the current timestep based on the initial estimate, wherein the second probability distribution comprises a probability distribution of observed blood oxygen saturation values based on an actual value, and wherein performing the maximum likelihood calculation comprises multiplying the first probability distribution by the second probability distribution. 
     
     
         29 . The method of  claim 21 , wherein obtaining the initial estimate comprises assigning a previous value of blood oxygen saturation at a previous timestep as the initial estimate. 
     
     
         30 . The method of  claim 21 , wherein obtaining the initial estimate comprises obtaining a current physical measurement of blood oxygen saturation at the current timestep. 
     
     
         31 . A system for providing a meaningful blood oxygen saturation value at a current timestep, comprising:
 a pulse oximetry monitor configured to:
 determine a first probability distribution of potential blood oxygen saturation values, based on an initial estimate of a blood oxygen saturation value; 
 determine a second probability distribution of potential blood oxygen saturation values based on an initial measurement of a blood oxygen saturation value; and 
 combine the first and second probability distributions to provide a meaningful blood oxygen saturation value, 
 wherein each probability distribution of potential values includes potential values at a current timestep with associated probabilities of occurrence. 
   
     
     
         32 . The system of  claim 31 , comprising a sensor including an emitter configured to emit first and second wavelengths of light, a detector configured to detect the first and second wavelengths of light, and a transmitter configured to transmit photocurrent signals indicative of the first and second wavelengths of light to the pulse oximetry monitor, and wherein the initial measurement is based on the photocurrent signals. 
     
     
         33 . The system of  claim 31 , wherein the initial estimate comprises a previous value representative of blood oxygen saturation at a preceding timestep. 
     
     
         34 . The system of  claim 31 , wherein the initial estimate comprises a stored estimate value based on a patient type. 
     
     
         35 . The system of  claim 31 , wherein the probability distribution of transition is a Markov Model transition probability. 
     
     
         36 . The system of  claim 31 , wherein the probability distribution of measured values is a linear spline measured value distribution. 
     
     
         37 . A pulse oximeter, comprising:
 a processing device configured to:   provide an initial estimate of a value representative of blood oxygen saturation at a current timestep;   provide an initial measurement of a value representative of blood oxygen saturation at a current timestep;   determine a noise estimate based on a correlation of one or more optical observations during a previous timestep; and   perform a maximum likelihood calculation to determine a value of blood oxygen saturation that is most likely given the initial estimate, the initial measurement, and the noise estimate.   
     
     
         38 . The pulse oximeter of  claim 37 , wherein the processing device is configured to perform the maximum likelihood calculation by combining a first probability distribution of potential values based on the initial estimate and a second probability distribution of potential values based on the initial measurement and the noise estimate. 
     
     
         39 . The pulse oximeter of  claim 37 , wherein the processing device is configured to perform a linear regression of the one or more optical observations to correlate the one or more optical observations. 
     
     
         40 . The pulse oximeter of  claim 37 , wherein the processing device is configured to determine a sample standard deviation of residuals to determine the noise estimate.