Distensibility in human veins as affected by 5 weeks of repeated elevations of local transmural pressure.

The objectives were to investigate the effects of repeated increments in local intravascular pressure (pressure training; PT) on (1) distensibility in two arm veins, and (2) pain in the arm induced by markedly increased intravascular pressure. Elevation of venous distending pressure (DP) in an arm was induced by placing the subject (n = 8) in a pressure chamber with one arm protruding to the outside via a port in the chamber door, and increasing chamber pressure. During 5 weeks, venous DP in one arm was repeatedly (3 × 40 min/week) increased (65-105 mmHg). Pressure-distension relationships were determined in the brachial and cephalic veins by measuring diameter changes by ultrasonography during stepwise increments in DP to 180 mmHg. In the brachial vein, the diameter change in response to an increase in DP from 30 to 180 mmHg (distensibility) was reduced (P < 0.05) in the pressure-trained arm (11%) compared to that in the control arm before (23%) and after (21%) PT. The cephalic vein showed a similar response with a reduced (P < 0.05) distensibility in the pressure-trained arm (20%) compared to that in the control arm before (29%) and after (25%) PT. At any given DP, arm pain was less (P < 0.05) in the pressure-trained arm than in the control arm before and after PT, presumably reflecting the reduced venous distensibility in the pressure-trained arm. The results support the concept that the distensibility of venous walls adapts to meet the demands imposed by the prevailing local transmural pressures.