Fig. 5. A twofold increase in intra-abdominal pressure (P_IA) caused a decrease in post caval vein transmural pressure (P_TRANS) and a 52% decrease in flow through the post cava vein (_PC). Despite inter-animal variation, a threefold increase in P_IA significantly decreased P_TRANS but did not alter _PC. The gray panel indicates negative P_TRANS which theoretically correspond to the partial or complete collapse of the post cava vein. The open square represents resting P_IA, the black square represents double P_IA and the gray square represents triple P_IA. The dotted line indicates resting _PC. ^*Indicates a significant decrease in P_TRANS and indicates a significant decrease in _PC (Bonferroni's corrected paired t-tests, P<0.05). Data presented are means ± S.E.M. (N=5).