A client with a pulmonary embolus has the following arterial blood gas (ABG) values: pH. 7.49: partial pressure of arterial oxygen (PaO2), 60 mm Hg partial pressure of arterial carbon dioxide (PaCO2), 30 mm Hg: bicarbonate (HCO3-1 25 mEq/L. What should the nurse do first?

Rationale: A. Increasing fluid intake does not address the immediate problem of impaired oxygenation. B. The ABG shows respiratory alkalosis (pH 7.49, PaCO₂ 30) with hypoxemia (PaO₂ 60). The priority intervention is to administer oxygen therapy to correct hypoxemia caused by the pulmonary embolus. C. Sodium bicarbonate is used for metabolic acidosis, not respiratory alkalosis. D. Mechanical ventilation may be required if oxygen therapy fails, but it is not the first action.