Physiological effects of increased tissue pressure.

The physiological effects of increased tissue pressure were studied using a model system in which known pressures were applied uniformly to the hindlimbs of rabbits for a period of 5 h. Muscle blood flow was monitored using a new argon washout technique. Muscle pO2, pCO2, and pAr were measured using a Teflon membrane catheter-mass spectrometer system. The myoneural conduction velocity served as a measure of the functional status of the limb. Higher tissue pressures led to successively greater compromise of muscle blood flow and pO2. Myoneural conduction velocity decreased significantly only when a pressure of 80 mm of mercury was applied, at which time muscle blood flow and pO2 were zero. These observations suggest that abnormalities of neuromuscular function are relatively late manifestations of a pressureinduced circulatory deficiency.