Oxygen saturation primarily reflects what physiologic parameter?

• A. A The amount of oxygen bound to white blood cells
• B. B The amount of oxygen delivered to body tissues
• C. C The reference range is 90% to 100%
• D. D Capillary refill time guarantees accuracy of SpO2 measurement

Answer: (B)

Oxygen saturation measured by pulse oximetry reflects how much oxygen is bound to hemoglobin in arterial blood, i.e., arterial oxygenation. This saturation helps indicate how much oxygen is available to be carried to tissues, because the amount of oxygen that can be delivered depends on how well the blood is oxygenated (the saturation), along with how much blood is flowing and how much hemoglobin is present.

So, higher SpO2 means more oxygen is carried by the blood and available for tissues, assuming adequate cardiac output. It’s not about oxygen in white blood cells, it’s not a fixed reference range by itself, and capillary refill time does not determine the accuracy of SpO2 readings.