Which parameter provides the most objective measure of oxygenation?

• A. Lung sounds
• B. Mental status
• C. Pulse oximetry reading
• D. Skin color

Answer: (C)

A pulse oximetry reading is the most objective way to assess oxygenation because it gives a numeric value of arterial oxygen saturation (SpO2) noninvasively and continuously. This directly reflects how much oxygen hemoglobin is carrying in the blood, making it a quantifiable, real-time measure. Lung sounds describe airway or lung conditions but don’t quantify how well oxygen is being carried; mental status can change for many reasons beyond oxygen levels and isn’t a direct measure of oxygenation; skin color is a subjective sign and can be unreliable, especially under varying lighting or in different skin tones. While arterial blood gas testing would be more precise, it’s invasive, so among these options, the SpO2 reading provides the most objective assessment of oxygenation.