Variation in absorption of light by which of the following tissue components is the basic physical principle of pulse oximetry?

The introduction of arterial pulse oximetry to clinical anesthesia in the late 1980s led to improved patient safety by allowing anesthesiologists to be alerted earlier to critical arterial desaturation. This enabled rapid identification of esophageal intubation and optimization of ventilation during general anesthesia. In the 1990s, continuous monitoring of arterial oxygen saturation became a standard of care during general anesthesia, and for all moderate or deep sedation cases in the 2000s.

The physical principle behind pulse oximetry is relatively simple. The sensor shines light through a tissue bed – typically a fingertip or an earlobe – and measures the absorption of two different wavelengths. Light at 660 nm is preferentially absorbed by deoxygenated hemoglobin; light at 940 nm is preferentially absorbed by oxygenated hemoglobin. Most of the tissue in the...

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