Understanding basic vein physiology and venous blood pressure through simple physical assessments

Abstract

An understanding of the complexity of the cardiovascular system is incomplete without a knowledge of the venous system. It is important for students to understand that, in a closed system, like the circulatory system, changes to the venous side of the circulation have a knock-on effect on heart function and the arterial system and vice versa. Veins are capacitance vessels feeding blood to the right side of the heart. Changes in venous compliance have large effects on the volume of blood entering the heart and hence cardiac output by the Frank-Starling Law. In healthy steady-state conditions, venous return has to equal cardiac output, i.e., the heart cannot pump more blood than is delivered to it. A sound understanding of the venous system is essential in understanding how changes in cardiac output occur with changes in right atrial pressure or central venous pressure, and the effect these changes have on arterial blood pressure regulation. The aim of this paper is to detail simple hands-on physiological assessments that can be easily undertaken in the practical laboratory setting and that illustrate some key functions of veins. Specifically, we illustrate that venous valves prevent the backflow of blood, that venous blood pressure increases from the heart to the feet, that the skeletal muscle pump facilitates venous return, and we investigate the physiological and clinical significance of central venous pressure and how it may be assessed.

A novel model to simulate venous occlusion plethysmography data and to estimate arterial and venous parameters

“…Arteriolar resistance can range from 7.5 to 18.7 times the venous resistance, using Eq. 5 and mean arterial and venous pressure reported in the literature (Tansey et al 2019;Kundu et al 2017;Olver et al 2016;Pescatello et al 2014;Turner et al 2000;Anderson et al 1986;Seagar et al 1984). As the R v = R a /16 was arbitrarily chosen, the current research suggests that a lower proportion (similar to the results found) should be considered in future studies.…”

“…The venous pressure (Fig. 5) remained within basal levels (Tansey et al 2019;Skoog et al 2015;Anderson et al 1986) when the cuff is off. The venous pressure rises with venous occlusion (Skoog et al 2015).…”

“…Nevertheless, values below 93.33 are considered optimal (Kundu et al 2017). Considering a mean venous pressure between 5 mmHg (Anderson et al 1986) and 10 mmHg (Tansey et al 2019), arterial resistance should be between 8.1 and 18.7 times the venous resistance. The present study arbitrarily adopted a R a value of 16…”

Comparative Study of Morphology and Distribution of Valves in Human Retromandibular Vein

“…The venous valve functions as a blood reservoir 29) . Veins are highly distensible, with compliance approximately 30 times that of arteries 24) . To enable veins to function efficiently as reservoirs, the pressure imposed on the blood within should always be controlled.…”

Invasive Assessment of Hemodynamic, Metabolic and Ionic Consequences During Blood Flow Restriction Training

“…However, our findings regarding the impact of BFR on the venous system provide important information on the applicability of this training method. Considering that in a standing position at rest gravity causes a hydrostatic venous hypertension of about 35 mmHg at the hand and 90 mmHg above the ankle (Arnoldi, 1965;Tansey et al, 2019), BFR-training can enhance hypertension by ∼60 mmHg. Whereas this condition can be tolerated by a healthy venous system with functioning venous valves which prevent a pathological venous reflux (Sarin et al, 1992), patients with venous insufficiency or postoperative lymphedema could experience worsening of their cardiovascular health status through BFR-training.…”