SpO2 measures what?

SpO2 measures what?

• A. The percentage of hemoglobin saturated with oxygen in the blood.
• B. The arterial partial pressure of oxygen
• C. The amount of dissolved oxygen in plasma
• D. The percentage of oxygen in inspired air

Answer: (A)

SpO2 shows the percentage of hemoglobin molecules in arterial blood that are carrying oxygen. It’s measured noninvasively with a pulse oximeter by estimating how much of the hemoglobin is saturated with oxygen using light absorption at two wavelengths. This differs from the arterial oxygen partial pressure (PaO2), which is the actual amount of oxygen dissolved in blood plasma and is measured by an arterial blood gas. It also isn’t the amount of dissolved oxygen in plasma (that amount is very small), nor the oxygen fraction in inspired air (FiO2). SpO2 is a practical marker of how well oxygen is being carried by the blood, typically correlating with SaO2 under normal conditions, and is influenced by factors like perfusion, motion, or skin conditions.

SpO2 shows the percentage of hemoglobin molecules in arterial blood that are carrying oxygen. It’s measured noninvasively with a pulse oximeter by estimating how much of the hemoglobin is saturated with oxygen using light absorption at two wavelengths. This differs from the arterial oxygen partial pressure (PaO2), which is the actual amount of oxygen dissolved in blood plasma and is measured by an arterial blood gas. It also isn’t the amount of dissolved oxygen in plasma (that amount is very small), nor the oxygen fraction in inspired air (FiO2). SpO2 is a practical marker of how well oxygen is being carried by the blood, typically correlating with SaO2 under normal conditions, and is influenced by factors like perfusion, motion, or skin conditions.