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| The Return of Blood to the Heart: Venous pumps in health and disease |
| Source: Gardner AMN, Fox RH. Second Edition. London, John Libbey and Company Ltd., 1993 |
| Summary: In this text, the authors discuss the role of EDRF (endothelial-derived relaxing factor or nitric oxide) and impulse inflation in the prevention of venous thrombosis. EDRF is produced "in response to rapid velocity changes (shear-stress) in the vascular system and is a most powerful relaxant of vascular smooth muscle… The ability of EDRF both to increase blood flow and disaggregate platelets, helps to explain how both muscular activity and impulse pumping are effective in preventing venous thrombosis." The slow inflation rate of intermittent compression devices does not mimic the calf pump action in normal ambulation. Rapid inflation produces turbulence in valve pockets where thrombosis commonly originates. They conclude that rapid impulse compression may be a more effective form of mechanical DVT prophylaxis since it "can mimic the effect of exercise on the circulation by producing pulsatile venous flow and thus causing endothelial shear-stress, generating locally the natural antithrombotic agents prostacyclin and EDRF that also increase arterial flow." |