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Pulmonary mechanics during induced pulmonary edema in anesthetized dogs
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1959
Year
Acute Lung InjuryEngineeringEdematous LungsLung ComplianceEdema FluidBiomechanicsLung HealthMechanobiologyLung DepositionPulmonary CirculationVentilationPulmonary MechanicsPulmonary MedicineRespiration (Physiology)PhysiologyPulmonary PhysiologyLung MechanicsAnesthesiaMedicineAnesthesiology
The study aimed to investigate how pulmonary edema alters lung mechanics by inducing vascular congestion in anesthetized dogs through partial aortic obstruction and intravenous fluid infusion. Brief congestion produced only minor compliance changes, whereas prolonged congestion caused a dramatic 78 % reduction; forced inflation to 30 cm H₂O yielded only a 6 % drop in compliance and revealed pronounced static hysteresis, indicating that surface phenomena—not vascular congestion or intrinsic tissue changes—drive the mechanical behavior of edematous lungs, a conclusion supported by excised‑lung experiments where minimized surface forces yielded elastic properties.
In order to study the mechanisms underlying the changes in the mechanical properties of the lungs during pulmonary edema, pulmonary vascular congestion was produced in spontaneously breathing, anesthetized dogs by partial aortic obstruction and intravenous infusion. Brief periods of congestion were associated with small changes in the lung compliance compared with the progressive and striking compliance reduction (-78%) noted with more prolonged congestion. Lung volume at end-expiration showed little change if edema fluid and trapped gas as well as the ventilated gas volume were taken into account. When edematous lungs were forcibly inflated beyond the tidal range, it was found that the overall compliance at a distending pressure of 30 cm H 2 O was not much less (-6%) than that of normal lungs. Furthermore, edematous lungs manifested marked ‘static’ hysteresis during such maneuvers. These findings suggested that surface phenomena were responsible for the mechanical behavior of edematous lungs rather than vascular congestion, per se, or intrinsic tissue changes. This was borne out by experiments on excised lungs which showed that the elastic properties of edematous lungs were not significantly different from normal lungs when surface forces were minimized. Submitted on August 25, 1958