In awake, cooperative patients with acute pulmonary edema, what is the role of CPAP or BiPAP?

• A. Not indicated
• B. Worsens oxygenation
• C. Improves oxygenation and reduces preload
• D. Requires immediate intubation

Answer: (C)

Noninvasive positive pressure ventilation uses CPAP or BiPAP to support a patient with acute pulmonary edema. The positive airway pressure keeps the small airways and alveoli open, which recruits collapsed alveoli, improves ventilation-perfusion matching, and enhances oxygenation. At the same time, the continuous positive pressure raises intrathoracic pressure, which reduces venous return to the heart (preload) and lowers left-sided filling pressures. This drop in preload helps decrease pulmonary capillary hydrostatic pressure, lessening fluid leakage into the lungs and thereby reducing pulmonary edema. BiPAP adds inspiratory pressure support, which can further decrease the work of breathing if the patient is fatigued, making ventilation more effective. Together, these effects improve gas exchange and can help avoid endotracheal intubation in appropriate, cooperative patients. If the patient cannot tolerate the mask, becomes hypotensive, deteriorates, or remains hypoxic despite optimal noninvasive support, escalation to invasive ventilation may be necessary.