Which statement best describes the measurement of oxygen saturation by pulse oximetry?

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Multiple Choice

Which statement best describes the measurement of oxygen saturation by pulse oximetry?

Pulse oximetry measures how much of the hemoglobin in arterial blood is carrying oxygen. It estimates the percentage of binding sites occupied by oxygen on hemoglobin (SpO2) by comparing how two wavelengths of light are absorbed by oxyhemoglobin versus deoxyhemoglobin as blood pulses through the tissue. This is different from the amount of oxygen dissolved in plasma or the actual pressure of oxygen in the blood, and it’s not a direct measure of how much oxygen is being delivered to tissues. So the reading reflects hemoglobin saturation, not dissolved oxygen or PaO2, and not delivery rate. Keep in mind that factors like poor perfusion, motion, nail polish, and certain hemoglobin abnormalities can affect accuracy.

Pulse oximetry measures how much of the hemoglobin in arterial blood is carrying oxygen. It estimates the percentage of binding sites occupied by oxygen on hemoglobin (SpO2) by comparing how two wavelengths of light are absorbed by oxyhemoglobin versus deoxyhemoglobin as blood pulses through the tissue. This is different from the amount of oxygen dissolved in plasma or the actual pressure of oxygen in the blood, and it’s not a direct measure of how much oxygen is being delivered to tissues.

So the reading reflects hemoglobin saturation, not dissolved oxygen or PaO2, and not delivery rate. Keep in mind that factors like poor perfusion, motion, nail polish, and certain hemoglobin abnormalities can affect accuracy.

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