Decrease of Venous Refluxes and Improvement of the Venous Pump

Using APG in patients with deep venous incompetence, it could be shown that compression with increasing interface pressure was associated with a decreasing amount of total reflux measured by venous filling index.

A statistically significant reduction of refluxes was achieved with pressures over 30 mm Hg for inelastic and over 40 mm Hg for elastic material.4

The reduction of venous refluxes in patients with chronic venous insufficiency by external compression explains the improvement of the venous pumping function. Plethysmo-graphic studies have shown an increasing improvement of the venous pump with increasing stocking pressures, starting with an ankle pressure of around 20 mm Hg.7,20

Higher compression pressure using stiff material leads to short phases of intermittent occlusion of the deep veins with every step during muscle contraction. Such intermittent occlusions of deep veins on the leg can be visualized by Duplex.14 By encasing the veins in a rigid envelope ambulatory venous hypertension may thereby be reduced in patients with deep venous incompetence.7 Similarly, a progressively increasing pressure on the thigh by using a blood pressure cuff blown up to 40-80 mm Hg led to a progressively decreasing vein diameter and to an abolishment of reflux when the femoral vein segment contained incompetent valves.18 Reduction of venous refluxes and improvement of ambulatory venous hypertension by external cuff compression could be demonstrated even in patients without any valves (avalvulia). This effect therefore cannot be explained by the common explanation of a coaptation of distended valve leaflets, but seems rather to be due to the intermittent occlusion of the incompetent vein during walking.19

Conflicting results have been reported concerning an improvement of ambulatory venous hypertension by compression stockings.2,7 This may be explained by the fact that the pressure exerted by stockings is too low in order to sufficiently compress the veins in the leg in the upright position. In addition, the elastic material gives way with every step, whereas inelastic, short-stretch bandages with a double as high resting pressure are able to achieve intermittently short venous occlusions during muscle systole while walking. In patients with severe stages of chronic venous insufficiency a higher compression pressure is needed to improve the disturbed venous pumping function, whereas lower pressure is sufficient in simple varicose veins.20

The key mechanism of compression therapy to reduce ambulatory venous hypertension in patients with severe chronic venous insufficiency is an intermittent occlusion of the veins during walking.

In contrast, continuous obliteration of veins by external compression may be desirable after varicose vein surgery in order to stop bleeding and after sclerotherapy to prevent refilling of blood.

To achieve complete venous occlusion the external pressure has to be higher than the intravenous pressure, depending on the body position. It could be demonstrated that an occlusion of the leg veins can be obtained with an external pressure in the range of 20 mm Hg in the supine position, but that in the sitting and standing positions the pressure has to be between 50 and 70 mm Hg.14 With compression stockings such pressure ranges can be achieved only when rolls or pads are applied over the vein. According to the law of Laplace this will increase the local pressure due to the reduction of the local radius.

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