SpO2 is the abbreviation for which measurement?

• A. Blood oxygen content
• B. Partial pressure of oxygen
• C. Oxygen saturation
• D. Oxygen delivery

Answer: (C)

SpO2 represents the percentage of hemoglobin binding sites in arterial blood that are occupied by oxygen, measured noninvasively with a pulse oximeter. It tells you how saturated the hemoglobin is with oxygen, not the total amount of oxygen content or the pressure of oxygen in the blood. The partial pressure of oxygen (PaO2) is a separate measurement obtained from an arterial blood gas and is expressed in mmHg. Oxygen content depends on both how saturated the hemoglobin is and how much hemoglobin is present, plus a small amount of dissolved oxygen. Oxygen delivery combines arterial oxygen content with cardiac output. In clinical use, SpO2 is used to assess oxygenation and guide oxygen therapy, typically aiming for values in the normal range (about 95–100%).