What is the effect of noninvasive ventilation on cardiogenic pulmonary edema?

• A. NIV reduces work of breathing and improves oxygenation.
• B. NIV increases respiratory effort.
• C. NIV reduces oxygen saturation.
• D. NIV has no effect.

Answer: (A)

Noninvasive ventilation helps cardiogenic pulmonary edema by delivering positive airway pressure that unloads the work of breathing and improves gas exchange. By providing pressure support and/or continuous positive airway pressure, it keeps airways open, recruits collapsed alveoli, and increases functional residual capacity, which leads to better oxygenation and easier breathing. The positive pressure also modestly reduces venous return and left ventricular afterload, lowering the pulmonary capillary hydrostatic pressure that drives edema. So patients typically breathe more comfortably, have reduced respiratory effort, and show improved oxygen saturation. The idea that NIV increases respiratory effort, reduces oxygenation, or has no effect does not fit the physiology, since NIV directly lessens the work of breathing and improves gas exchange in this setting.