An analysis of the effects of nitroglycerin on forearm circumference, with simultaneous recordings of arterial and venous diameters and blood pressure. 
The aim of this study is to define the effect of sublingually administered nitroglycerin (NTG) on the diameters of the forearm arteries and veins as well as to define the relationship between these vascular changes and the forearm circumference in healthy volunteers.  For this purpose, we employed a noninvasive method permitting the simultaneous quantitative recording of vascular diameters, forearm circumference and blood pressure using a miniature load cell, linear differential transformers and mercury-in-rubber strain gauge.  Sublingually administered NTG (0.3 mg) increased the radial arterial diameter and the forearm circumference, whereas the cephalic vein capacitance was decreased; consequently, the cephalic vein acts to moderate the increase in forearm circumference.  The results clearly indicate that nitroglycerin dilates forearm arteries but not forearm veins in the normal state.