Which parameter does a pulse oximeter measure?

Which parameter does a pulse oximeter measure?

• A. O2Hb
• B. Hb
• C. COHb
• D. MetHb

Answer: (A)

Pulse oximetry is measuring how much of the hemoglobin in arterial blood is bound to oxygen. It does this by using two light wavelengths and comparing how oxygenated and deoxygenated hemoglobin absorb light. The result is the oxygen saturation, which is the fraction of hemoglobin that is oxygenated (O2Hb) out of the total hemoglobin (O2Hb plus HHb). So the parameter being read is the amount of O2Hb relative to total Hb, i.e., the oxygenated form of hemoglobin. It doesn’t directly measure total Hb concentration, nor does it quantify CO-bound or MetHb as the primary metric (though high levels of COHb or MetHb can affect the reading).

Pulse oximetry is measuring how much of the hemoglobin in arterial blood is bound to oxygen. It does this by using two light wavelengths and comparing how oxygenated and deoxygenated hemoglobin absorb light. The result is the oxygen saturation, which is the fraction of hemoglobin that is oxygenated (O2Hb) out of the total hemoglobin (O2Hb plus HHb). So the parameter being read is the amount of O2Hb relative to total Hb, i.e., the oxygenated form of hemoglobin. It doesn’t directly measure total Hb concentration, nor does it quantify CO-bound or MetHb as the primary metric (though high levels of COHb or MetHb can affect the reading).