Acute postobstructive pulmonary edema may occur after airway obstruction. A decrease in intrathoracic and intraalveolar pressures causes an increased blood flow into the pulmonary vasculature and favors the development of pulmonary edema. Two mechanisms for the development of acute postobstructive pulmonary edema are proposed: type 1 follows acute airway obstruction, and type 2 follows relief of chronic airway obstruction.