PULMONARY CAPILLARY-PRESSURE MEASUREMENT FROM PULMONARY-ARTERY OCCLUSION PRESSURE DECAY PROFILE ANALYSIS IN SHEEP

Pulmonary capillary pressure (Ppc), the major factor responsible for p ulmonary edema, cannot be directly measured in intact subjects but may be estimated by analysis of the pressure decay profile after pulmonar y artery catheter balloon inflation. We compared three different metho ds of pulmonary artery occlusion pressure (Ppao) decay profile analysi s to estimates of Ppc derived from lymph flow measurements in halothan e-anesthesized sheep. The relationship between Ppc and lymph flow was first determined by increasing Ppc by left atrial balloon inflation, a nd was then used to determine Ppc during pulmonary hypertension produc ed by infusion of a thromboxane analog. All three methods of Ppao deca y profile analysis demonstrated a correlation with Ppc estimated from lymph flow. However, the method using a single exponential analysis si gnificantly overestimated Ppc, and none of the methods reliably estima ted changes in the longitudinal distribution of pulmonary vascular res istance during pulmonary hypertension. These results suggest that Ppao decay profile analysis as currently performed has limited application .