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Figure 36-10
Principle of pulse oximetry. Light passing through tissue
containing blood is absorbed by tissue and by arterial, capillary, and venous blood.
Usually, only the arterial blood is pulsatile. Light absorption may therefore be
split into a pulsatile component (AC) and a constant or nonpulsatile component (DC).
Hemoglobin O2
saturation may be obtained by application of Equation 19
in the text. (Data from Tremper KK, Barker SJ: Pulse oximetry. Anesthesiology
70:98, 1989.)
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