What ABG pattern is typically seen with pulmonary embolism?

• A. Respiratory alkalosis w hypoxemia
• B. Respiratory acidosis with hypoxemia
• C. Metabolic acidosis with hypoxemia
• D. Normal ABG

Answer: (A)

Pulmonary embolism causes a sudden ventilation-perfusion mismatch, leading to hypoxemia from inefficient oxygen transfer. In response, the patient often hyperventilates to compensate, blowing off CO2. This reduces arterial CO2 and raises pH, producing a respiratory alkalosis. So the typical ABG pattern is respiratory alkalosis with hypoxemia (low PaO2 and low PaCO2 with elevated pH). Metabolic acidosis would suggest lactic acidosis from shock, and respiratory acidosis would indicate hypoventilation—not the common scenario in acute PE. A normal ABG is unlikely when hypoxemia is present.