Experimental pulmonary edema following re-expansion of pneumothorax.

The development of acute edema in a lung that is re-expanded after a pneumothorax was studied in Rhesus monkeys. In 12 animals, unilateral pneumothorax with 80 to 100 per cent collapse of the lung was induced and maintained for 3 days. In 6 of the animals, rapid re-expansion of the lung by applying suction at a pressure of −10 cm Hg produced marked, acute pulmonary edema ipsilaterally within 2 hours. Re-expansion of the lung by underwater seal in the other 6 animals did not result in pulmonary edema. In 6 other monkeys, pulmonary edema did not develop when the lung was re-expanded with a pressure of −10 cm Hg within 1 hour after the pneumothorax was induced. Thus a large pneumothorax of 3 or more days’ duration and the application of a large negative pressure to re-expand the lung were factors predisposing to pulmonary edema. These factors were also commonly present in reported human cases of the syndrome.