Effect of pulmonary vascular engorgement on respiratory mechanics in the dog

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Abstract
The immediate effects of pulmonary vascular engorgement (PVE) on lung and chest wall mechanics were studied in anesthetized, paralyzed dogs with the chest wall intact. A balloon-tipped catheter advanced retrograde into the left atrium was used to produce partial mitral valve obstruction and increases in pulmonary artery and left atrial pressures equal to 15 and 20 cm H2O, respectively. This increased pulmonary blood volume (PBV) and 50% and reduced dynamic lung compliance 14%. With the airway occluded at different lung volumes, transient PVE produced a 6% decrease in compliance on the deflation limb of the pressure volume curve of the lung and a shift in the chest wall pressure-volume curve, which was consistent with an increase in chest wall volume equal to the increase in PBV. During apnea with the airway open, PVE reduced lung gas volume and increased chest wall recoil. The changes in chest wall recoil associated with PVE are the result of an increase in total lung displacement volume. This study is relevant for the pathophysiology of respiratory abnormalities in congestive heart failure.