A 50-year-old man suddenly develops dyspnea, chest pain, and tachypnea. ABG shows respiratory alkalosis (pH 7.52, PaCO₂ 28 mmHg). Which condition best explains this finding?

Correct option is B

Pulmonary embolism causes hyperventilation due to hypoxemia, leading to low PaCO₂ and respiratory alkalosis in the acute stage.
Explanation of options: (a) ✘ COPD → respiratory acidosis, not alkalosis. (b) ✔ Correct; acute PE → tachypnea → respiratory alkalosis. (c) ✘ Asthma → obstructive pattern, CO₂ retention. (d) ✘ Opioid overdose → hypoventilation → respiratory acidosis.