Pulse Wave

The Oximeter on the Finger

Pulse Oximetry:

Two wavelengths (colors) of light (red and infrared) are transmitted through the finger.  The relative intensities of lights are measured by the internal computer, which determines the oxygen saturation.  More red than infrared means more oxygen on the hemoglobin molecule within the red blood cell.  The reading is taken at the top of the pulse wave as it represents arterial (oxygenated) blood.