Effect of pulmonary vascular engorgement on respiratory mechanics in the dog.

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 preassures equal to 15 and 20 cm H2O, respectively. This increased pulmonary blood volume (PBV) by 50% and reduced dynamic lung ocmplicance 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. We conclude that the changes in chest wall recoil associated with PVE are the result of an increase in total lung displacement volume.