INFLUENCE OF PULMONARY VASCULAR PRESSURE ON BRONCHIAL COLLAPSIBILITY OF EXCISED DOG LUNGS

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Abstract
The main bronchi of excised dog lobes were obstructed with beads, 5-6 cm from their origin so that they did not communicate with the peripheral air spaces. Both pulmonary artery and vein were cannulated and both pulmonary vascular pressures were controlled. With the lobe held at constant transpulmonary pressure, bronchial pressure-volume curves were studied during acute pulmonary vascular engorgement. The bronchial compliance was reduced at higher vascular pressure and the effect of vascular engorgement on the bronchial collapsibility was larger at higher transpulmonary pressure: bronchial compliance at vascular pressure 10 cm H2O were 70, 84, 98 and 100% of the bronchial compliance at vascular pressure -40 cm H2O at transpulmonary pressure 20, 10, 5 and 0 cm H2O, respectively. Vascular engorgement apparently increased parenchymal radial traction to the bronchi when the bronchi reduced its diameter, although it appeared that vascular engorgement resulted in little change in the lung elastic recoil pressure.