Effect of External Sequential Compression Devices on Femoral Venous Blood Flow

David C. Markel, MD, Gary D. Morris, MD


J South Orthop Assoc. 2002;11(1) 

In This Article

Materials and Methods

After appropriate institutional review board approval and patient consent, 7 patients (2 men and 5 women) were selected for study, fulfilled inclusion criteria, and had evaluation of the lower extremity venous system using advanced computed ultrasonography (Acuson 128XP/10, Acuson, Mountain View, Calif) with proprietary software (Acuson). Subjects were excluded from the study if the medical history revealed the presence of venous disease, diabetes, previous ipsilateral extremity surgery, or obesity. No subjects were excluded because of inadequate studies. Three right knees and four left knees were operated on. The average age of the patients was 66.4 years (range, 61 to 81 years). Duplex ultrasonography was done on the operative extremity at an average of 3.9 days postoperatively (range, 3 to 5 days). Timing was based on availability of the technologist and the unique proprietary software that allowed direct measurement of venous blood flow volume and velocity. Each patient was evaluated with each of the devices -- thigh-length, calf-length, and foot compression -- as well as active motion at the ankle. The femoral venous blood flow velocity and femoral venous blood flow volume were recorded at a site 1 cm above and 1 cm below the saphenous vein bifurcation on the operative leg. The bifurcation effectively divided the lower extremity venous circulation into superficial and deep components. By dividing the systems in this way, it was possible to independently determine the effect of the three pumps on blood flow in the two systems and determine what, if any, effect the compression cycles had on venous circulation.

A baseline value was obtained before initiation of the pumping cycle of each device on the supine patients. The value is computed by the proprietary software of the ultrasonography machine as a mean during the peaks and troughs of the blood flow velocity and volume flow pattern within the vascular system. The devices were allowed to cycle for several minutes to obtain recording equilibrium before recording measurements. A period of rest was provided, and a new baseline value was obtained before undertaking the next series of measurements with a different device. The order in which the devices were tested was randomized. The same ultrasonography technician performed all of the examinations, and one of us was present for each examination. The devices were placed on both extremities to simulate the postoperative situation, even though recordings were taken only on the operative extremity. In addition to the three external pneumatic sequential compression devices, measurements were taken after the patient flexed and extended the foot 20 times in rapid succession. This activity served to simulate the effect of active motion on the venous system.

In addition to the patients having total knee replacement, 6 young, healthy volunteers aged 18 to 35 (average age, 26.7 years) were evaluated with the same technique as described. This group served as a control group and allowed comparison of the effects of the devices on nonoperative, healthy, younger subjects vs older postoperative patients. Values for each device were compared statistically by univariate analysis and analysis of variance.


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