Vascular distensibility of the hand during reduction of the effective blood volume in man.

Expression of results. The increase in hand volume during venous obstruction was expressed graphically against the simultaneous increase in vascular distending pressure: these parameters were measured at intervals of 0.2 to 0.5 sec throughout the period of venous obstruction. A curve was obtained representing the vascular volume-pressure relationship of the hand during each period of venous obstruction. The gradient of this curve represents the change in hand volume resulting from change in vascular distending pressure and was therefore equal to the hand vascular distensibility. As the vascular volume-pressure relationship of the hand was commonly curvilinear (fig. 1) it was necessary to measure the gradient of the resulting line at a constant band volume so that