Investigation of the arterial and venous upper arm vascular bed.

Studies concerning vascular changes in hypertension and exercise have shown an increasing need to investigate the properties of a complete vascular bed in vivo. In this study, the repeatability of a non-invasive method for quantifying properties of the vascular bed of an upper arm segment, was investigated in two groups of volunteers (age 22-55 years). One group of subjects (n = 9) were measured twice at a 15 min interval. The other group (n = 8) were measured 4 times with each subject measured daily at the same time. The estimated quantities included the arterial and venous blood volume, the static arterial compliance, the myogenic response of the arm veins and the extravascular fluid volume of the tissue under an occluding cuff at the upper arm. They not only describe properties of the arterial vascular bed as a whole but also of different sized arteries functioning at different intra-arterial pressure. They were derived from the fluid shifts under the occluding cuff that arise when cuff pressure changes, as determined by electrical impedance and blood pressure measurements. The repeatability of the method was well within the physiologically acceptable range and of the same order of magnitude as that of established methods. Established methods however, provide less information about the properties of a vascular bed and result in controversial estimates of the dynamic arterial compliance. Furthermore, the method eliminates the need to match subjects in comparative studies for arterial blood pressure. These features and the sensitivity of the method for (patho)physiological changes, offer the possibility to investigate in vivo many still unknown aspects of the peripheral circulation.