Patent ID: 7277741

Claim:
A method of measuring a physiological parameter, comprising: obtaining a first signal derived from electromagnetic energy transmitted through a tissue portion at a first wavelength, said first signal including a signal portion corresponding with motion-related events and a signal portion corresponding with arterial pulsation events, wherein at said first wavelength water is a dominant absorber of electromagnetic energy in the tissue portion; obtaining a second signal derived from electromagnetic energy transmitted through a tissue portion at a second wavelength, said second signal including a signal portion corresponding with motion-related events and a signal portion corresponding with arterial pulsation events, wherein at said second wavelength hemoglobin is a dominant absorber of electromagnetic energy in the tissue portion; and combining said first signal and said second signal to generate a combined signal comprising a plethysmograph, said combined signal having a signal portion corresponding with motion-related events that is smaller than that present in said first signal or said second signal.