Pulse oximeter sensor with piece-wise function

Abstract

A memory in a sensor is used to store multiple coefficients for a physiological parameter. In one embodiment, not only are the sensor's specific calibration coefficients stored in a memory in the sensor for the formula to determine oxygen saturation, but multiple sets of coefficients are stored. The multiple sets apply to different ranges of saturation values to provide a better fit to occur by breaking the R to SpO2 relationship up into different pieces, each described by a different function. The different functions can also be according to different formulas for determining oxygen saturation.

What is claimed is: 
     
         1 . A method of manufacturing an oximeter system, comprising:
 providing a memory of an oximeter sensor having coefficients stored therein, the coefficients for use in at least one formula for determining oxygen saturation, the coefficients including at least a first set of coefficients and a second set of coefficients for a light emitter, wherein the first and second sets of coefficients are for use in different formulas.   
     
     
         2 . The method of  claim 1 , wherein the different formulas comprise different linear formulas. 
     
     
         3 . The method of  claim 1 , wherein the different formulas comprise different non-linear formulas. 
     
     
         4 . The method of  claim 1 , wherein at least one of the different formulas comprises a spline function or a ratio-of-ratios function. 
     
     
         5 . A method of operating an oximeter sensor, comprising:
 directing light at a patient with a light emitter;   receiving the light from the patient with a light detector; and   transmitting coefficients from a memory of the oximeter sensor to a monitor, the coefficients for use in at least one formula for determining oxygen saturation, the coefficients including at least a first set of coefficients and a second set of coefficients for the light emitter, wherein the first and second sets of coefficients are for use in different formulas.   
     
     
         6 . The method of  claim 5 , wherein the different formulas comprise different linear formulas. 
     
     
         7 . The method of  claim 5 , wherein the different formulas comprise different nonlinear formulas. 
     
     
         8 . The method of  claim 5 , wherein at least one of the different formulas comprises a spline function or a ratio-of-ratios function. 
     
     
         9 . An oximeter system, comprising:
 an oximeter sensor, comprising:
 a light emitter configured to direct light at a patient; 
 a light detector configured to receive the light from the patient; and 
 a memory storing coefficients, the coefficients including at least a first set of coefficients and a second set of coefficients for the light emitter, wherein the first and second sets of coefficients are for use in different formulas for determining oxygen saturation; 
   an oximeter monitor, comprising:
 a drive circuit configured to provide signals to the oximeter sensor; and 
 a read circuit configured to read the coefficients from the memory of the oximeter sensor. 
   
     
     
         10 . The oximeter system of  claim 9 , wherein the different formulas comprise different linear formulas. 
     
     
         11 . The oximeter system of  claim 9 , wherein the different formulas comprise different nonlinear formulas. 
     
     
         12 . The oximeter system of  claim 9 , wherein at least one of the different formulas comprises a spline function or a ratio-of-ratios function. 
     
     
         13 . An oximeter monitor, comprising:
 a drive circuit configured to provide signals to an oximeter sensor that is coupleable to a patient;   a read circuit configured to receive coefficients from a memory of the oximeter sensor, the coefficients including first and second sets of coefficients for a light emitter of the oximeter sensor; and   a calculation mechanism configured to utilize the first and second sets of coefficients in different formulas to determine a blood oxygen saturation level of the patient.   
     
     
         14 . The oximeter monitor of  claim 13 , wherein the different formulas comprise different linear formulas. 
     
     
         15 . The oximeter monitor of  claim 13 , wherein the different formulas comprise different nonlinear formulas. 
     
     
         16 . The oximeter monitor of  claim 13 , wherein at least one of the different formulas comprises a spline function or a ratio-of-ratios function. 
     
     
         17 . A method of monitor operation, comprising:
 providing signals to circuitry of an oximeter sensor that is coupleable to a patient;   receiving information from a memory of the oximeter sensor, the information comprising first and second sets of coefficients for a light emitter of the oximeter sensor; and   utilizing the first and second sets of coefficients in different formulas to determine a blood oxygen saturation level of a patient.   
     
     
         18 . The method of  claim 17 , wherein the different formulas comprise different linear formulas. 
     
     
         19 . The method of  claim 17 , wherein the different formulas comprise different nonlinear formulas. 
     
     
         20 . The method of  claim 17 , wherein at least one of the different functions comprises a spline function or a ratio-of-ratios function.