Which ABG parameter indicates oxygenation status?

Which ABG parameter indicates oxygenation status?

• A. PaCO2 indicates oxygenation status.
• B. pH indicates oxygenation status.
• C. HCO3- indicates oxygenation status.
• D. PaO2 (and SaO2) reflect arterial oxygenation status.

Answer: (D)

Oxygenation status is about how much oxygen actually moves from the lungs into the arterial blood. The ABG values that directly show this are PaO2, the amount of oxygen dissolved in arterial blood, and SaO2, the percentage of hemoglobin bound with oxygen. These two tell you how well blood is being oxygenated as it leaves the lungs. In contrast, PaCO2 reflects ventilation—the effectiveness of removing carbon dioxide from the blood—so it speaks to ventilatory status rather than oxygen content. pH shows overall acid-base balance, and HCO3- reflects the metabolic component of that balance; neither directly measures how much oxygen is carried by the blood. Normal PaO2 is about 80–100 mmHg, and normal SaO2 is about 95–100%. If oxygenation is impaired, PaO2 drops and SaO2 falls, signaling hypoxemia.

Oxygenation status is about how much oxygen actually moves from the lungs into the arterial blood. The ABG values that directly show this are PaO2, the amount of oxygen dissolved in arterial blood, and SaO2, the percentage of hemoglobin bound with oxygen. These two tell you how well blood is being oxygenated as it leaves the lungs.

In contrast, PaCO2 reflects ventilation—the effectiveness of removing carbon dioxide from the blood—so it speaks to ventilatory status rather than oxygen content. pH shows overall acid-base balance, and HCO3- reflects the metabolic component of that balance; neither directly measures how much oxygen is carried by the blood.

Normal PaO2 is about 80–100 mmHg, and normal SaO2 is about 95–100%. If oxygenation is impaired, PaO2 drops and SaO2 falls, signaling hypoxemia.