Patent ID: 8190227

Claim:
In a signal processor, a method of determining a measurement value for a characteristic of arterial blood, the method comprising: receiving a first signal from a light-sensitive detector, the first signal being indicative of light of a first wavelength that has been attenuated over a period of time by body tissue carrying arterial blood; receiving a second signal from the light-sensitive detector, the second signal being indicative of light of a second wavelength that has been attenuated over the period of time by the body tissue carrying arterial blood; electronically identifying peak frequency components of the first and second signals; electronically determining a slope value corresponding to each of one or more of the peak frequency components, each slope value comprising a comparison of the respective amounts of the corresponding peak frequency component in the first and second signals; electronically selecting a peak frequency component that exhibits physiological characteristics of arterial blood using, at least in part, the corresponding slope value; and electronically determining the measurement value for the characteristic of arterial blood using the selected peak frequency.