Alterations in hemodynamics and Kf,c during lung mass resection.

The effects of progressive lung mass reduction on total pulmonary vascular resistance (RT), compliance (CT), arterial (Pa), venous (PV), and capillary (Pc) pressures, and the capillary filtration coefficient (Kf,c) were evaluated in whole isolated dog lungs perfused with autologous blood. RT increased (P less than 0.05) in a nonlinear fashion when mass was reduced by greater than 35% in zone 3 lungs (Pa greater than PV greater than airway pressure) perfused at constant pressure (CP, n = 9), a finding predicted by a model of rigid parallel flow channels subjected to loss of cross-sectional area. Furthermore, these findings were not altered by pretreatment with ibuprofen or diphenhydramine (n = 7). In contrast, in zone 3 lungs perfused with constant flow (CF, n = 4), RT did not increase until at least 60-75% of mass was removed. Since Pa and Pc were constant in the former group, but increased in the latter group (P less than 0.05), the attenuation of RT by CF is best explained by vascular distension. This is supported by the finding that microvascular C, as a fraction of CT, decreased significantly with CF, but not with CP. Kf,c and CT (referenced to the initial lung mass) decreased linearly with reductions in lung mass % delta Kf,c = 1.26-0.98% mass removed (r = 0.90, P less than 0.01) and % delta CT = -3.99-0.98% mass removed (r = 0.82, P less than 0.01) relationships that were not altered by blocker pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)