Physiological parameter confidence measure
Confidence in a physiological parameter is measured from physiological data responsive to the intensity of multiple wavelengths of optical radiation after tissue attenuation. The physiological parameter is estimated based upon the physiological data. Reference data clusters are stored according to known values of the physiological parameter. At least one of the data clusters is selected according to the estimated physiological parameter. The confidence measure is determined from a comparison of the selected data clusters and the physiological data.
1. A method of determining a measure of confidence in a physiological parameter, the physiological parameter determined by transmitting multiple wavelengths of optical radiation into a tissue site and detecting the optical radiation after tissue attenuation, the method comprising:
deriving physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
estimating a physiological parameter based upon the physiological data;
providing a physiological data reference;
obtaining at least one data cluster from the physiological data reference wherein the at least one data cluster is a probability distribution of normalized pleth ratios; and
determining a measure of confidence in the estimated physiological parameter based upon the at least one data cluster and the derived physiological data.
2. The method according to claim 1 wherein the providing step comprises:
predetermining the physiological data for known values of the physiological parameter across a sample population;
clustering the data according to the physiological parameter values; and
storing the data clusters so as to be retrievable according to the physiological parameter values.
3. The method according to claim 2 wherein the obtaining step comprises selecting the at least one data cluster according to the estimated physiological parameter.
4. The method according to claim 3 wherein the selecting step comprises:
determining at least one data cluster having a corresponding physiological parameter value closest to the estimated physiological parameter; and
reading the determined at least one data cluster from the memory.
5. The method according to claim 4 wherein the physiological parameter is at least one of SpO 2 , MetHb and HbCO.
6. A physiological parameter confidence measurement method comprising:
deriving physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
estimating a physiological parameter based upon the physiological data;
providing a physiological data reference having a plurality of data clusters each corresponding to a particular value of the physiological parameter,;
comparing at least one of the data clusters to the physiological data;
indicating confidence in the estimated physiological parameter based upon the comparison; and
associating a probability function with each of the data clusters.
7. The physiological parameter confidence measurement method according to claim 6 wherein the comparing step comprises determining a probability that the derived physiological data corresponds to the estimated physiological parameter.
8. The physiological parameter confidence measurement method according to claim 7 wherein the indicating step comprises generating at least one of a visual indication and an audible indication corresponding to the determined probability.
9. The physiological parameter confidence measurement method according to claim 8 further comprising triggering an alarm that a probe-off condition exists when the determined probability is below a predetermined threshold.