Flow cessation pressures in the rabbit tenuissimus muscle.

Cessation of muscle capillary flow was studied in rabbit tenuissimus muscle, using intravital microscopy. Perfusion pressure was reduced by arterial occlusion or simultaneously elevated venous and tissue pressure. Muscle capillary flow ceased in the presence of arteriolar dilation at a median perfusion pressure of 17.5 mmHg during arterial occlusion and at 25.3 mmHg in case of simultaneously increased tissue and venous pressure. The pressure difference of 7.8 mmHg was confirmed in a series of experiments where arterial occlusion and increased tissue pressure were randomly alternated in the same animal. The mechanisms responsible for the difference in pressure level at which flow ceases in the capillaries under these circumstances are incompletely understood. Possible mechanisms are discussed.