Which arterial blood gas change would indicate improved oxygenation after therapy?

• A. Decreased PaO2
• B. Increased PaCO2
• C. Increased HCO3-
• D. Increased PaO2

Answer: (D)

Oxygenation is assessed by the arterial partial pressure of oxygen, PaO2, which shows how well oxygen moves from the lungs into the bloodstream. When therapy improves oxygenation, more O2 enters the blood, so PaO2 rises toward normal levels (roughly 80–100 mmHg).

If PaO2 increases, that directly reflects better oxygenation. A lower PaO2 would mean worse oxygenation. A higher PaCO2 points to ventilation issues (how well you’re blowing off CO2) rather than oxygenation improving. A higher HCO3- is a metabolic adjustment and doesn’t indicate a change in the current oxygenation status.