A client has a pulmonary embolism and is started on oxygen. The student nurse asks why the client's oxygen saturation has not significantly improved. What response by the nurse is best?

A. “The client needs immediate intubation and mechanical ventilation.” Intubation may be required in severe respiratory failure, but not all clients with pulmonary embolism need mechanical ventilation. Suggesting intubation without assessment of the client’s respiratory effort or ABGs is premature. B. "Maybe the client has respiratory distress syndrome." ARDS is can impair oxygenation, but it is not the most likely explanation for persistent low oxygen saturation in PE. PE more commonly causes ventilation-perfusion mismatch due to blocked blood flow. C. "The client is breathing too slowly and it interferes with oxygenation." Slow breathing could impair ventilation, but in PE, oxygenation is impaired because blood flow to parts of the lung is blocked, not necessarily due to a respiratory rate issue. D. "The blood clot interferes with perfusion in the lungs." Pulmonary embolism obstructs blood flow in the pulmonary arteries, resulting in areas of the lung being ventilated but not perfused. This causes a ventilation-perfusion mismatch and leads to reduced oxygenation despite supplemental oxygen.