Effects of pulmonary vascular recruitment on gamma scintigraphy and pulmonary capillary protein leak

Pulmonary vascular recruitment (PVR) was altered and lung-heart radioactivity ratio (L:H) measured using 99mTc-tagged human serum albumin (Tc-HSA) in five dogs each by inflating a left atrial balloon (LAB) to produce a 20 mm Hg pulmonary capillary wedge pressure (PCWP) or opening a 5 mm diameter aortoinferior caval shunt (ACS) before and after oleic and injury. Cardiac output (CO), pulmonary arterial pressure (PAP), and PCWP were measured with each alteration in PVR. In an additional 10 dogs, multiple doses of Tc-HSA, administered over 5 hours, 2 hours after 0.1 ml/kg oleic acid, produced parallel "slopes of injury" over the 5-hour period. Each rise in PVR was associated with an acute increase in L:H but demonstrated no significant increase in slope after equilibration. Closure of the ACS or LAB deflation returned the L:H to projected baseline. A "slope of injury" (P less than 0.001) was seen after the administration of oleic acid, which was significantly (P less than 0.01) steeper with an increased PVR. This was confirmed by repeat doses of Tc-HSA. This study confirmed the following hypotheses: (1) the "slope of injury" curves were reproducible so that the effects of experimental interventions on the rate of protein leak could be determined; (2) the L:H rapidly became constant after an acute change in PVR prior to oleic acid injury: and (3) a raised PVR would increase the rate of albumin leak after pulmonary microvascular injury.