[Hemodynamics of the lower extremity with pneumatic foot compression. Effect on leg position]

External pneumatic compression of the foot is being used more and more to increase the venous blood flow in the lower limbs and thus reduce the risk of postoperative deep venous thrombosis. We have investigated the efficacy of the foot pump pneumatic compression device (A-V Impulse, Novamedix, Andover, England) in 10 healthy subjects and in 10 patients undergoing total hip arthroplasty. The velocity of venous blood flow in the common femoral artery was measured in the horizontal, Trendelenburg (head-down, foot-up) and reverse Trendelenburg (head-up and foot-down) positions using a duplex ultrasound unit (Sonoline Elegra, Siemens, Erlangen, Germany) with a 5 MHz linear array probe. Application of the foot pump produced an increase in venous blood flow velocity in all healthy subjects and in all patients. In healthy subjects the mean increase in the horizontal position was 31.18% (SD = 15.86%), and in the Trendelenburg position 20.72 (SD = 15.69%) (right limb). In the reverse Trendelenburg position, the foot pump produced a mean increase of 94.08% (SD = 55.00%). The difference is statistically significant (p < 0.005). In patients with a total hip arthroplasty, the mean increase in the horizontal position was 28.67% (SD = 9.95%), and in the Trendelenburg position 20.34% (SD = 17.85%) (operated limb). In the reverse Trendelenburg, the foot pump produced a mean increase of 91.55% (SD = 42.38%). The difference is statistically significant (p < 0.005). There was no noteworthy difference in results between the controls and patients. Pneumatic compression devices designed to reduce venous stasis are effective in decreasing the rate of deep venous thrombosis after surgery on the lower limb. The results of the present study show that the efficiency of the foot pump in increasing venous return is improved by adopting the reverse Trendelenburg position. This may increase its thromboprophylactic effect.