Physiologic Changes Associated with Increasing Pulmonary Wedge Pressures in the Dog

Abstract

The effects of systematically increasing pulmonary wedge pressure (PWP) between baseline normal values and 30 mmHg on physiologic parameters was studied in ten mongrel dogs.After obtaining baseline normal values, the PWP was raised in stepwise increments of 5–7.5 mm Hg by inflating an intra-aortic balloon and infusing iso-oncotic fluids.The following decreased significantly at most levels of PWP measured: PaO₂, mmHg, supine (r=-0.708, p < 0.001); semi-upright (r=-0.681, p < 0.01); DLCO, ml/min/mmHg/kg (r=-0.543, p < 0.01). Circulation time (r=0.612, p < 0.01) and central blood volume (r = 0.471, p < 0.01) increased significantly at most levels of PWP observed. Upright chest X-ray changed from baseline at PWP of 19 mmHg

Minimal Increases in Pulmonary Wedge Pressure Associated with Improved PaO₂s in Dogs

“…The single breath DLCO was performed according to the method of Olgilvie et al [I I], except that two I -liter syringes were employed and the gas mixture introduced under pressure. This method has been described previously [4]. Due to technical factors the alveolar samples were obtained at 15 instead of 10 sec.…”

“…e.g. 12 mm Hg or below [4], In this report we examine more critically the relationship between minimal increases in PWP. lung perfusion pattern, alterations in blood gases and single breath diffusing capacity (DLCO).…”