Hydraulics of tissue fluid during pneumatic compression in lymphedema of lower limbs

Abstract

Background: Physiotherapy of edema in cases with obstructed main lymphatics of lower limbs requires knowledge of how high external pressures should be applied manually or set in compression devices in order to generate tissue pressures high enough to move tissue fluid to the non-swollen regions and how to measure its flow rate. Methods: We measured tissue fluid pressure and flow in subcutaneous tissue of lymphedematous limbs stage II to IV at rest and during pneumatic compression under various pressures and inflation timing. An 8-chamber sequential compression device inflated to pressures 50 to 120 mmHg, for 50 sec each chamber, with no distal deflation was used. Pressures were measured using wick-in-needle and electronic manometer. Fluid flow was calculated from continuously recorded changes in limb circumference using strain gauge plethysmography. Results: Before massage, in all stages of lymphedema, stagnant tissue fluid pressures in subcutaneous tissue ranged between -1 to +10 mmHg and did not differ from those measured in normal subjects. Pressures generated in tissue fluid by pneumatic compression reached 40 to 100 mmHg and were lower than those in inflated chambers. High pressure gradient through the skin was caused by its rigidity (fibrosis) and dissipation of applied compression force to proximal non-compressed limb regions. The calculated volumes of displaced tissue fluid ranged from 10 to 30 ml per compression cycle to reach in some cases 100 ml in the groin region. Conclusions: tissue fluid pressures generated by a pneumatic device were found lower than in the compression chambers. The obtained results point to the necessity of applying high pressures and longer compression times to generate effective tissue fluid pressures and provide enough time for moving the stagnant fluid.