Negative-pressure pulmonary edema with a patent airway

Negative pressure is a rarely occurring cause of pulmonary edema. It has previously been reported only in the presence of a closed glottis or obstructed airway. A 64-year-old man with 74% body surface burn without any inhalation injury experienced acute pulmonary edema on hospital day 11 associated with high-minute volume and negative inspiratory pressures at the ventilator. The edema cleared after sedation and paralysis. Workup disclosed pulmonary emboli and normal cardiac-filling pressures. A mechanical model, simulating his breathing, measured intrathoracic pressure of -37 +/- 12 mm Hg, which is sufficiently negative to cause pulmonary edema despite a patent airway. Pulmonary emboli increased his respiratory drive to amounts greater than what the ventilator could deliver, thus leading to the large negative intrathoracic pressure and pulmonary edema.