Abstract
Introduction
Postobstructive pulmonary edema is generally characterized by fulminant pulmonary edema that becomes apparent within seconds or minutes after the relief of severe upper airway obstruction. The development of postobstructive pulmonary edema is believed to result from the generation of extremely high negative intrathoracic pressures against an occluded airway. However, the mechanism responsible for the development of acute pulmonary edema in this setting is uncertain. Measurement of the ratio of total protein concentration between pulmonary edema fluid and plasma is an established, accurate method for distinguishing hydrostatic from increased-permeability pulmonary edema.
Case Summaries
We report 3 cases of severe postobstructive pulmonary edema. The pulmonary edema fluid to plasma total protein concentration ratio was measured immediately following relief of the obstruction. The ratio of the pulmonary edema fluid protein concentration to plasma total protein concentration was 0.42(0.10) mean (± standard deviation). Ratios < 0.65 are characteristic of hydrostatic pulmonary edema, whereas patients with increased-permeability pulmonary edema, as seen in acute lung injury, have a ratio between 0.75 and 1.0. Pulmonary edema in all 3 cases resolved within 24 hours.
In Conclusion
These data indicate that postobstructive pulmonary edema may result from a primary hydrostatic mechanism. These cases also illustrate the value of measuring the ratio of pulmonary edema fluid to plasma total protein concentration to determine the mechanism of pulmonary edema.
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