An ABG in a patient with MI often shows which abnormality?

• A. Hypercapnia
• B. Hyperoxemia
• C. Hypoxemia
• D. Normal

Answer: (C)

Hypoxemia is the pattern you’d expect in an acute MI because left‑sided heart problems from the infarct can lead to pulmonary edema and ventilation–perfusion mismatch. Fluid in the lungs and reduced oxygen transfer across the alveolar membrane lower the arterial oxygen tension (PaO2), so the ABG shows a decreased PaO2. PaCO2 can be normal or low if the patient is hyperventilating from pain or anxiety, but it may rise if ventilation becomes impaired; however, the hallmark or most likely abnormality here is reduced oxygenation. Hypercapnia or hyperoxemia are not typical findings in this scenario, and a normal ABG would miss the oxygenation problem.