A nurse is caring for a client who develops a pulmonary embolism. Which of the following interventions should the nurse implement first?

Pulmonary embolism disrupts the ventilation-perfusion ratio, leading to sudden hypoxemia and respiratory distress. Prioritizing interventions requires applying the airway, breathing, circulation framework. Knowledge of gas exchange and emergency protocols is necessary to stabilize the client and maintain systemic cellular oxygenation. Choice A rationale Oxygen administration is the priority to treat hypoxemia caused by the physiological dead space created by the embolism. Improving arterial oxygen saturation supports myocardial and cerebral function while reducing the workload of the right ventricle during obstruction. Choice B rationale Morphine acts as an analgesic and vasodilator which can reduce anxiety and preload. However, it does not address the primary physiological threat of impaired gas exchange. Breathing and oxygenation must be stabilized before managing pain or sedation. Choice C rationale Cardiac monitoring identifies arrhythmias and right-sided heart strain associated with pulmonary hypertension. While diagnostic, it is a secondary action that follows the restoration of oxygenation. Assessment tools should not delay the implementation of life-saving oxygen therapy. Choice D rationale Lactated Ringer's is used for volume expansion and electrolyte replacement. In pulmonary embolism, excessive fluid can worsen right ventricular failure and pulmonary edema. Circulatory support is important but remains secondary to correcting the immediate life-threatening respiratory deficit..