Pulmonary edema associated with upper airway obstruction in dogs

In order to evaluate the effect of acute upper airway obstruction upon pulmonary edema (PE) formation, we studied seven dogs that were subjected to inspiratory obstruction for three hours. Hypoxia was avoided by the administration of supplemental oxygen during the study period. Six dogs developed pulmonary vascular congestion, and four developed histologic findings of PE. Inspiratory intrapleural pressure decreased to -28 +/- 4 mmHg in dogs that developed PE and to -23 +/- 2 mmHg in dogs that did not. Transmural pulmonary artery pressure and pulmonary artery wedge pressure did not increase significantly. Central venous pressure during inspiration (CVPi) increased in all dogs, and CVP at end expiration (CVPe) was significantly higher in dogs with PE. Dogs that developed PE experienced a decrease in cardiac output and an increase in systemic vascular resistance. Furthermore, alveolar ventilation declined in dogs with PE, ultimately resulting in ventilatory failure. Pulmonary edema formation was not preceded by an increase in pulmonary vascular pressures but was associated with higher CVP, pulmonary vascular congestion, and hypercarbia.