The effects of water immersion on venous return

Abstract

Introduction: The common belief about the beneficial effects of water immersion on leg veins function is mostly based on empirical experiences. We have performed a series of tests to evaluate the real effects of the increase of interstitial pressure generated by water immersion on the leg veins morphology, venous return and veno-lymphatic drainage. Methods: The immediate effects of water hydrostatic pressure (wHP) on vein morphology and venous flow were evaluated by underwater duplex sonography (DS) during immersion. The immediate effects of HP on calf volume and ejection fraction (EF) were evaluated by underwater strain gauge pletysmography (SGP). The effects of prolonged immersion on leg volume and on subcutaneous tissues were evaluated by both water displacement volumetry (WDV) and DS. Results: The caliper of normal and varicose veins were immediately and significantly reduced by immersion (p.004 and p 0.012 for the femoral and great saphenous veins, respectively). Simultaneously, the spontaneous centripetal flow increased. In varicose legs, the reflux was reduced or even disappeared. SGP demonstrated an immediate reduction of the calf circumference and the simultaneous increase of the EF (+68.9%). Finally, a marked reduction in ankle circumference (-2.89%), subcutaneous tissue thickness (-24.35%) and leg volume (-4,2%) was demonstrated after 30’ of standing into the water. Walking into the pool for the same time resulted in an even more significant reduction of all these three parameters (-5.98%; -32.66% and -6.50%, respectively). Discussion: our results suggest that the wHP-related reduction of vein caliber is responsible for the immediate increase of the centripetal flow, the immediate reduction of the calf volume and of the reduced reflux, when present. The great reduction of the leg volume after prolonged static immersion seems to be due to the positive effects of wHP on the balance between interstitial fluid filtration and lymphatic reabsorption. A mutual enhancement between the effects of HP on interstitial fluids dynamics and those of muscle activity on EF, may explain the greater reduction of the leg volume, ankle circumference and epifascial thickness after underwater walking compared to those after static immersion. Conclusions: The possible clinical and rehabilitative implications of these findings in the treatment and rehabilitation of leg venous disorders are finally outlined.