Comparison of microvascular filtration characteristics in isolated and intact lungs

To determine whether the microvascular membrane of isolated perfused dog lungs is damaged by the isolation procedure, we compared the filtration coefficient (Kf,c) and minimum capillary pressure (Pcc) required to cause continuous edema formation in 10 intact and 8 isolated dog lower left lobes. We used the same gravimetric technique to measure Kf,c and Pcc in both preparations. The Kf,c averaged 0.09 +/- 0.03 (SD) ml . min-1 . Torr-1 . 100 g-1 in the intact and 0.30 +/- 0.16 in the isolated lobes; Pcc averaged 20.1 +/- 4.7 and 1.7 +/- 3.6 Torr in the intact and isolated lobes, respectively. Both Pcc and Kf,c were significantly different in the two preparations (P less than 0.01). These data indicate that the increased tendency of isolated lungs to become edematous at lower pressures may be caused by damage to the microvascular membranes.