Vascular segmental permeabilities at high peak inflation pressure in isolated rat lungs

Abstract

The response of segmental filtration coefficients ( K f) to high peak inflation pressure (PIP) injury was determined in isolated perfused rat lungs. Total ( K f,t), arterial ( K f,a), and venous ( K f,v) filtration coefficients were measured under baseline conditions and after ventilation with 40–45 cmH2O PIP. K f,a and K f,v were measured under zone I conditions by increasing airway pressure to 25–27 cmH2O. The microvascular segment K f ( K f,mv) was then calculated by: K f,mv = K f,t − K f,a − K f,v. The baseline K f,twas 0.090 ± 0.022 ml · min−1 · cmH2O−1 · 100 g−1 and segmentally distributed 18% arterial, 41% venous, and 41% microvascular. After high PIP injury, K f,t increased by 680%, whereas K f,a, K f,v, and K f,mv increased by 398, 589, and 975%, respectively. Pretreatment with 50 μM gadolinium chloride prevented the high PIP-induced increase in K f in all vascular segments. These data imply a lower hydraulic conductance for microvascular endothelium due to its large surface area and a gadolinium-sensitive high-PIP injury, produced in both alveolar and extra-alveolar vessel segments.