Fluid trapping in postmortem guinea pig lungs.

To examine severe bronchoconstriction obstructing airways in the fluid-filled postmortem guinea pig lung, lungs were infused and deflated with isotonic solution following exsanguination. Guinea pigs were classified into 2 groups: young and mature, and each group was further classified into 2 subgroups: those receiving saline (Ca2+-free) and Tyrode's (Ca2+-containing) solutions. Each subgroup consisted of 7-8 animals. No significant change in total lung capacity from the baseline (prior to exsanguination) air value was observed in any subgroup within the experimental period of 60 min. However, both deflation volume (DV) and inflation volume (IV) decreased gradually with time; these decreases were larger in the saline-filled lungs than those of lungs infused with Tyrode's solution at 20-30 min. In the Tyrode's solution-filled lungs, larger decreases in DV and IV were found in the mature animals than in the young animals at 15-20 min. Trapped fluid volume (VT) increased gradually with time and reached mean values ranging from 9.1 to 11.5 times the baseline value at 60 min. No significant difference in VT between subgroups was observed. At any given time in all animals, the increase in VT was always equal to or larger than the decrease in DV or IV. Fluid cuffing around vessels and airways was demonstrated in the saline, but not in the air-filled lung. The data suggest that severe bronchoconstriction obstructing airways did not occur in postmortem fluid-filled guinea pig lungs. Dilution of mediators may be responsible for eliminating postmortem severe airway spasm and swelling of interstitium may induce the temporal increase in trapped volume in the fluid-filled lung.