NEGATIVE-PRESSURE PULMONARY-EDEMA WITH A PATENT AIRWAY

Negative pressure is a rarely occurring cause of pulmonary edema. It h as previously been reported only in the presence of a closed glottis o r obstructed airway. A 64-year-old man with 74% body surface burn with out any inhalation injury experienced acute pulmonary edema on hospita l day 11 associated with high-minute volume and negative inspiratory p ressures at the ventilator. The edema cleared after sedation and paral ysis. Workup disclosed pulmonary emboli and normal cardiac-filling pre ssures. A mechanical model, simulating his breathing, measured intrath oracic pressure of -37 +/- 12 mm Hg, which is sufficiently negative to cause pulmonary edema despite a patent airway. Pulmonary emboli incre ased his respiratory drive to amounts greater than what the ventilator could deliver, thus leading to the large negative intrathoracic press ure and pulmonary edema.