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


Deep venous thrombosis of the lower extremity is a potentially serious complication of total knee replacement. Either mechanical or pharmacologic prophylaxis against thromboembolic disease is routine and effective in the postoperative setting.[2,5,8,9,10,12,13,14,15,16,17,18,19,20,21,23,24,25,26,28,35,36] Past studies have established that sequential pneumatic compression devices increase peak blood flow velocity.[30,31,32,33,34,37] Yet until now, few studies have compared the devices directly,[9,23] had the ultrasonographic software to calculate blood flow volume quantitatively,[23] or differentiated between the superficial venous system and the more clinically important deep venous system.

The venous system of the lower extremity can be divided anatomically into three parts: the greater and lesser saphenous subsystem, the communicating venous system, and the deep venous system.[38] The greater and lesser saphenous veins are the two major vessels that drain the subcutaneous tissues of the lower extremity.[39] This subsystem of cutaneous vessels comprises the superficial venous system. At the medial aspect of the thigh in the deep fascia, the lesser saphenous subsystem enters the femoral vein at the saphenous opening, approximately 2.5 cm below and lateral to the pubic tubercle.[39] It is at the saphenous opening that the two systems join, forming the saphenous bifurcation.

Measurements taken below the bifurcation represent flow in the deep venous system, whereas measurements taken above the bifurcation represent the added contribution from the superficial venous system. The anatomic distinction at the bifurcation effectively allowed data subtraction and an indication of the flow in each system in this study, though thrombus in the deep system is the most clinically relevant finding. To date, blood flow studies have not attempted to distinguish the contribution of the two individual systems.

Several methods can be used to assess function and disease of the venous system. Contrast phlebography (venography) has been the standard for diagnosis of venous thrombosis,[38] since it is highly sensitive and specific despite its intraobserver variability of up to 10%.[40,41] Venography does not assess dynamics of the venous system, it poorly visualizes areas above the inguinal ligament, and injection of contrast material may be painful and may cause phlebitis or anaphylaxis. Thus, duplex ultrasonography has become the most commonly used modality for clinical screening of venous thrombosis.[6,33,42,43] The accuracy, sensitivity, and specificity of duplex ultrasonography has proved to be up to 100% for detection of proximal deep venous thrombosis and 98% accurate (88% sensitivity, 98% specificity) for the detection of distal deep venous thrombosis.[15,44,45,46,47,48,49] The positive and negative predictive values for deep venous thrombosis have been reported to be 66.6% and 98.1%, respectively.[43] Limitations of this modality may be intraobserver error and imperfect reliability of thrombus detection in the calf.[3,48,50] In the current study, an Acuson 128XP/10 computed ultrasonography system was applied. Proprietary software provided by the company allowed reliable assessment blood flow velocity and quantitative blood flow volume. The measurements were made at identifiable and reproducible anatomic landmarks and therefore allowed data subtraction to indicate the flow in the deep and superficial systems.

Thigh-length, calf-length, and foot sequential pneumatic external compression devices have been shown to increase peak venous blood flow velocity.[9,23,30,31,32,33,34,37] In the current study, these modalities also increased blood flow volume.[23] The mechanism for prevention of deep venous thrombus involves external compression of the lower extremity via periodic inflation. The externally applied compression theoretically directs venous blood proximally, preventing stasis. Pooling, or stasis, of venous blood is believed to be partially responsible for the development of deep venous thrombus and is a cornerstone of Virchow's triad. Ilgenfritz and Meier[31] found a significant increase in peak femoral venous blood flow velocity using pneumatic foot compression garments. Using normal volunteers, they were able to show a highly significant difference between resting values and those recorded while the subjects were wearing the device. Killewich et al[33] used ultrasonic scanning to evaluate the effects of intermittent pneumatic compression of the plantar venous plexus on the popliteal vein and common femoral vein velocities. A significant increase over baseline in both the popliteal vein and common femoral vein was found in 15 healthy volunteers. A significantly higher percentage increase was found in the popliteal vein than in the common femoral vein. Others have reported similar findings.[37,51,52] A decrease in venous capacitance and venous outflow was noted to occur in postoperative patients when the devices were worn during surgery.[30] With calf-length compression devices, Muhe[27] noted venous blood flow velocities that were almost four times higher than baseline. He used direct measurement of xenon Xe 133 introduced into the bloodstream of patients confined to bed. Keith et al[32] directly compared thigh-length pneumatic intermittent compression boots and knee-length intermittent pneumatic compression boots. Both devices produced significant increases in the peak venous velocity at rest, but no statistical difference was observed between the two devices. Janssen et al[37] directly compared a below-the-knee single-chambered sleeve and a thigh-length sequential pneumatic device and concluded that both devices produced a significant rise in venous blood flow velocity. The thigh-length device, however, proved superior to the below-the-knee device and sustained a higher average blood flow velocity. In contrast, Flam et al,[53] using duplex ultrasonography, showed higher venous blood flow augmentation in knee-high intermittent pneumatic compression systems than in thigh-high sequential-pulse system. Westrich et al[23] used techniques and software similar to ours to evaluate the hemodynamic effects of several pneumatic compression devices. While there were differences in the performances of the various devices, all of them did improve blood flow volume.

The paucity of direct comparison data for the different style of compression devices, as well as the limited number of volumetric measurements, prompted the current investigation. Thigh-length, knee-length, and foot intermittent pneumatic compression devices from the same manufacturer using the same pump were compared directly and in a random order. The results confirmed that all three devices effectively increased deep and superficial blood flow volume and velocity above baseline. There were no significant differences between the devices or between muscle activity and the devices with regard to either blood flow volume or velocity. Interestingly, the postoperative population differed in this respect when compared with a control group of normal healthy volunteers. In the control group, muscle activity proved superior to all devices. These findings support the use of external sequential compression devices for prevention of deep venous thrombosis in the postoperative period.


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