Spatial interaction between tissue pressure and skeletal muscle perfusion during contraction

The vascular waterfall theory attributes decreased muscle perfusion during contraction to increased intramuscular pressure (P-IM) and concomitant incr ease in venous resistance. Although P-IM is distributed during contractions , this theory does not account for heterogeneity. This study hypothesises t hat pressure heterogeneity could affect the interaction between P-IM rise a nd perfusion. Regional tissue perfusion during submaximum (100 kPa) tetanic contraction is studied, using a finite element model of perfused contracti ng skeletal muscle. Capillary flow in muscles with one proximal artery and vein (SIM1) and with an additional distal artery and vein (SIM2) is compare d. Blood flow and pressures at rest and PIM during contraction (similar to 25 kPa maximally) are similar between simulations, but capillary flow and v enous pressure differ. In SIM2, venous pressure and capillary flow correspo nd to PIM distribution, whereas capillary flow in SIM1 is less than 10% of flow ill SIM2, in the muscle half without draining vein. This difference is caused by a high central P-IM, followed by central venous pressure rise, i n agreement with the waterfall theory. The high central pressure (SIM1), ob structs outflow from the distal veins. Distal venous pressure rises until c entral blood pressure is reached, although local P-IM is low. Adding a dist al vein (SIM2) restores the perfusion. It is concluded that regional effect s contribute to the interaction between P-IM and perfusion during contracti on. Unlike stated by the vascular waterfall theory, venous pressure may loc ally exceed P-IM, Although this can be explained by the principles of this theory, the theory does not include this phenomenon as such. (C) 2001 Elsev ier Science Ltd. All rights reserved.