Measurement Principle

This instrument measures the oxygen saturation (SpO2) in arterial blood and pulse rate continuously in a non-invasive method by applying optical principles.

With this instrument, SpO2 is defined by the following equation.

SpO2＝

C（HbO2）

× 100 (% SpO2)

C（HbO2）＋C（Hb）

where

Concentration of reduced hemoglobin

C (Hb):

C (HbO2): Concentration of oxyhemoglobin

The light-absorption characteristics of reduced hemoglobin (Hb) are very different from those of oxyhemoglobin. This instrument measures the changes in the absorption of red and infrared lights passing through the tissue to determine the SpO2 of the blood. Thus, this method is free from the effects of skin color, muscles, bones, and veins.

¢Spectral Absorption of Hb and HbO2

Appendix

34

Red light

Infrared light

Absorption coefficient

Wavelength