Hemodynamic evaluation of foot venous compression devices

Effect of foot stato-dynamic disorders on hemodynamics of the lower limb using strain-gauge plethysmography

BACKGROUND

The plantar venous pump (PVP), composed of deep plantar veins, is the most distal contributor to venous return from the lower limbs. A pressing need still exists to assess how plantar muscle contraction and gait affect PVP function, how foot stato-dynamic disorders (FSDs) can contribute to venous insufficiency, and how venous return can be optimally stimulated. Our first objective is to compare the venous blood hemodynamics in lower limbs between healthy subjects with a FSD and healthy subjects without a FSD to understand the influence of foot morphology in the performance of the PVP. Our second objective is to evaluate whether PVP function varies with different plantar pressures.

METHODS

A total of 52 healthy volunteers (26 feet with a normal arch as the control group and 26 feet with dysmorphism [13 flat feet and 13 hollow feet]) were included. Strain-gauge plethysmography was performed 8 cm above the medial malleolus at different conditions of PVP stimulation: (1) toe flexion, (2) intermittent pneumatic compression (IPC) with and without an insole, and (3) 3-km/h speed walking on a treadmill barefoot, with shoes, and with shoes and insoles. From the strain-gauge plethysmography, we measured the venous blood ejection fraction (EF). From the pressure sensor placed at the midfoot on the plantar arch during IPC, we obtained the maximal pressure (N/cm2).

RESULTS

Toe flexion allowed for ejection of an average of 20% of the total venous volume in both groups. IPC and gait generated a mean EF superior to 100% of the available venous volume. The maximal pressure applied at the midfoot during IPC was lower than the pressure set. No significant differences in the EF or maximal pressure were observed between the two groups. The mean EF was not significantly affected for the pronator and supinator walkers compared with those with normal walking dynamics. Wearing shoes did not significantly affect the mean EF. However, wearing insoles during gait significantly increased the venous return in feet with plantar dysmorphism.

CONCLUSIONS

To the best of our knowledge, this clinical study is the first to assess the PVP function in 52 healthy volunteers with and without FSDs. We found that wearing shoes did not significantly affect PVP efficiency but that wearing morphologically adapted insoles significantly improved the venous return in the dysmorphic feet. In our sample of healthy volunteers, the differences observed between the control group and feet with FSDs were not statistically significant.

Use of a Mobile Intermittent Pneumatic Compression Device (Vekroosan) in Mobile Patients With Chronic Venous Disease

Background

Compression therapy is an essential part of chronic venous disorder (CVD) treatment in reducing associated complications. This observational study aimed to note the use, effects and tolerance of a mobile intermittent pneumatic calf compression (IPC) device, Vekroosan^® (DVT Solution P/L).

Methods

In 56 patients, Doppler ultrasonography was used to measure venous blood peak flow velocity (PFV) at external iliac, common femoral, distal superficial femoral and popliteal vein levels both before and after application of Vekroosan calf compressor for comparison.

Results

Vekroosan was able to show significant clinical benefit in 45 patients (80%). There was a significant increase in femoral PFV pressure in post-compression measurement when compared to the pre-compression measurement (43.1 vs. 32.4 cm/s, P < 0.001), even when patients mobilize. On average, the PFV pressure increased by 10.7 cm/s when compared to baseline. A significant decrease was seen in calf swelling after calf compression (31.3 vs. 21.9 cm, P < 0.01), also with mobilization. Eighty-seven percent of patients tolerated the device well.

Conclusions

Our study shows that use of mobile IPC devices, such as Vekroosan, is safe and effective in the treatment of CVD, can be used while mobilizing and can achieve results comparable to non-mobile devices.

Increasing Circulation in the Lower Limb Under General Anesthesia Using the A-V Impulse System

The action of foot impulse technology (FIT) in reducing the risk of deep vein thrombosis (DVT) is well established. We hypothesized that intraoperative use of FIT devices will be effective in the prophylaxis of DVT. The aim of this study was to investigate the effect of a FIT device (A-V impulse system) on the venous flow of the lower extremity using duplex ultrasound scanning while the patient was under general anesthesia. Thirteen surgical patients who had no lower limb vessel lesions were selected for the study. Duplex scanning was used to measure blood velocity in the right common femoral vein, with and without the foot pump, before and during general anesthesia. The mean resting velocity was 33.2 ±5.5 cm/sec in the pre-anesthetic state, 32.1 ±4.2 cm/sec under anesthetic, and 30.4 ±5.0 cm/sec postoperatively. The peak velocities with the pump active were 38.6 ±5.0 cm/sec before anesthetic, 54.6 ±5.9 cm/sec while anesthetized, and 52.7 ±7.8 cm/sec postoperatively. The measured increases while under anesthesia and postoperatively both reached statistical significance (p < 0.05). Our study demonstrated that use of the A-V impulse system causes a statistically significant increase in venous velocity of the lower extremity while the patient is under general anesthesia.

Comparative lower limb hemodynamics using neuromuscular electrical stimulation (NMES) versus intermittent pneumatic compression (IPC)

Deep Vein Thrombosis (DVT) is a life threatening condition and a serious concern among hospitalised patients, with death occurring in approximately 6% of cases. Intermittent pneumatic compression (IPC) is commonly used for DVT prevention, however suffers from low compliance and issues of usability and portability. Neuromuscular electrical stimulation (NMES) has been shown to improve lower limb hemodynamics but direct comparison with IPC in terms of hemodynamics is rare but very important to determine the potential effectiveness of NMES in DVT prevention.Lower limb IPC was compared to calf NMES, in 30 healthy volunteers (18-23 years). Each intervention was carried out on each leg, on the popliteal vein measured using Doppler ultrasound. All interventions produced significantly greater haemodynamic responses compared to baseline. Calf-IPC and NMES produced significant increases in venous blood velocity (cm/s) and volume of blood ejected per cycle (1 cycle of NMES expels 23.22 ml compared to the baseline ejected volume of 2.52 ml, measured over 1 s (p < 0.001 versues baseline).Improving lower limb hemodynamics is vital in preventing DVT. NMES resulted in larger ejected volumes compared to IPC (x3 greater than foot-IPC and x1.7 greater than calf-IPC) more effectively emptying the veins and soleal sinuses. This is an important finding as DVT occurs predominantly in the soleal sinuses. NMES is silent and portable and thus does not suffer many of the issues associated with IPC. This work supports the potential widespread application of NMES in hospital and home settings where the risk of DVT formation is high.

Analysis of flow and wall shear stress in the peroneal veins under external compression based on real-time MR images

As a widely accepted prophylaxis for deep vein thrombosis, the underlying mechanism of compression stocking still remains unclear. In this study, computational fluid dynamics was applied to in vivo data to provide quantitative insight into the hemodynamic response of the deep venous system to static external compression. The geometry and flow information of deep veins before and after compression was acquired from ten healthy volunteers using magnetic resonance imaging. Our results indicated that application of the compression stocking led to a small reduction in blood flow rate but a significant reduction in cross-sectional area of the peroneal veins in the calf, resulting in an increase in wall shear stress (WSS), but the individual effects were highly variable. The mean volume reduction of the deep veins was 58%, while the time-averaged WSS showed an average increase of 398% after compression (median 98%). The analysis also showed a strong linear correlation between the time-averaged WSS and mean blood velocity, suggesting that flow in the deep veins under the level of compression examined here can be approximated by Poiseuille's law despite local geometric variations. It is hoped that quantitative analysis of WSS in the deep venous system will aid in the future design and optimisation of the compression stocking.

The impact of intermittent pneumatic compression devices on deep venous flow velocity in patients with congestive heart failure

BACKGROUND

Intermittent pneumatic compression (IPC) has been used to prevent deep venous thrombosis (DVT), but the effects of IPC on the hemodynamics of popliteal and soleal veins, especially in patients with congestive heart failure (CHF) have not been evaluated. The aim of this study was to evaluate the effects of IPC on the flow velocity of deep veins in the lower extremities and to compare the efficacy of two different types of IPC in deep venous flow enhancement in patients with CHF.

METHODS

Flow velocities of popliteal and soleal veins were recorded in 19 patients with CHF and in 19 control subjects using a high-resolution linear probe. Peak and mean flow velocities were measured (1) at rest, (2) with sequential foot and calf IPC (SFC-IPC) which consists of an electrically driven air compressor and four air chambers, and (3) with impulse foot IPC (IF-IPC) which consists of a pneumatic impulse generator operated at an applied pressure of 130 mmHg.

RESULTS

In the resting condition, popliteal venous flow velocity in the CHF group was attenuated (12.8+/-4.7 cm/s vs. 21.1+/-13.5 cm/s; p<0.05). Both SFC-IPC and IF-IPC increased venous velocity, but the increase with IF-IPC in CHF patients was lower than that in control subjects. In the soleal veins, after applying SFC-IPC, the peak and mean velocity in CHF increased to the same extent as in the control group. IF-IPC increased soleal venous velocity in control subjects, but there was no increase in CHF patients.

CONCLUSION

Two-dimensional Doppler scanning revealed a significant increase in the mean and peak velocities in the soleal and popliteal veins with SFC-IPC but not with IF-IPC in patients with CHF. These results indicate that SFC-IPC could have favorable effects in preventing DVT in patients with CHF.

Venous tonus enhancement after a short cycle of intermittent pneumatic compression

Objectives

To test if intermittent pneumatic compression (IPC) used with a short cycle could reproduce and confirm the 30 min vasoconstriction effect observed after a long cycle of pressure.

Methods

Eighteen subjects took part in the study, 12 with venous insufficiency (VI) and six without VI (NonVI). Duplex scanner was used to evaluate the diameter of six sites of veins on each of both lower limbs before and after the treatment. The IPC was applied to only one limb.

Results

The control limb showed no change in venous diameter. The treated limb, showed in the NonVI group one vasoconstriction: the greater saphena at the knee level (GS) ( P < 0.05). In the VI group, four sites out of six showed a vasoconstriction: the common femoral ( P < 0.005), the GS at its cross ( P < 0.001), the GS ( P < 0.001) and the lesser saphena ( P < 0.05).

Conclusions

Both long and short cycle of IPC are suitable to enhance the venous tone in VI patients for at least 30 min after the end of the treatment.

Mechanical compression in the prophylaxis of venous thromboembolism

Venous thromboembolism (VTE) is an important cause of morbidity and mortality in a substantial number of the Australian community. There exists a considerable range of potential prophylactic measures aimed at reducing the risk of VTE. These antithrombotic regimens include pharmacological interventions and mechanical techniques to counteract venous stasis including graduated compression stockings and intermittent pneumatic compression (IPC) devices. This review particularly concentrates on evidence for the use of mechanical prophylaxis and the interrelationship with pharmacological methods of VTE prophylaxis. Mechanical and pharmacological methods of VTE prophylaxis are both effective and when used in combination have synergistic effects. Although there are a number of different IPC systems, little evidence is available at present that differentiates these on the basis of VTE prevention. Compliance and patient acceptance of IPC as a preventative measure has improved with miniaturization and device weight reduction. IPC should be used according to recommended guidelines. In moderate-risk patients when pharmacological prophylaxis is contraindicated, IPC can be used as an alternative. High-risk patients should receive both mechanical and pharmacological prophylaxis to reduce their relative risk. Until further evidence becomes available, the specific type of IPC unit chosen will generally be determined by ease of use, availability and cost.

A novel intermittent mechanical compression device for stasis prevention in the lower limbs during limited mobility situations

INTRODUCTION

Intermittent pneumatic mechanical compression is commonly applied to obviate venous stasis in patients with increased risk of thromboembolism. Aviafit is a small battery-operated intermittent compression device using a patented mechanical, non-pneumatic technology. Our objective was to examine its ability to prevent venous stasis.

MATERIALS AND METHODS

Doppler ultrasonography was used to determine venous hemodynamics of 22 healthy volunteers in both legs, before applying the Aviafit to one randomly selected leg, upon device activation and after 30 min. Each measurement provided values for peak flow velocity (PFV) and total volume flow (TVF).

RESULTS

The PFV values were significantly higher in the treated leg upon activation of the Aviafit and at 30 min, compared to the baseline value and to the PFV of the untreated leg at the corresponding time points (p<0.001 for each). The TVF increased in the treated leg from baseline of 48 ml/min to 56 ml/min at T0, and then gradually decreased, similar to the untreated leg. At T30, 64% of the treated legs had a higher TVF than their untreated counterparts.

CONCLUSIONS

The lightweight, battery-operated and user-friendly Aviafit can provide the same hemodynamic benefits as larger conventional intermittent pneumatic compression devices. Its potential advantages for prophylaxis of thromboembolism and increased compliance in rehabilitation and homecare, and for use during long periods of immobility such as during flights, are evident.

Evidence-based compression: prevention of stasis and deep vein thrombosis

OBJECTIVE

To summarize the currently published scientific evidence for the venous flow effects of mechanical devices, particularly intermittent pneumatic compression, and the relation to prevention of deep vein thrombosis (DVT).

SUMMARY BACKGROUND DATA

While intermittent pneumatic compression is an established method of DVT prophylaxis, the variety of systems that are available can use very different compression techniques and sequences. In order for appropriate choices to be made to provide the optimum protection for patients, the general performance of systems, and physiological effects of particular properties, must be analyzed objectively.

METHODS

Medline was searched from 1970 to 2002, and all relevant papers were searched for further appropriate references. Papers were selected for inclusion when they addressed specifically the questions posed in this review.

RESULTS

All the major types of intermittent compression systems are successful in emptying deep veins of the lower limb and preventing stasis in a variety of subject groups. Compression stockings appear to function more by preventing distension of veins. Rapid inflation, high pressures, and graded sequential intermittent compression systems will have particular augmentation profiles, but there is no evidence that such features improve the prophylactic ability of the system.

CONCLUSIONS

The most important factors in selecting a mechanical prophylactic system, particularly during and after surgery, are patient compliance and the appropriateness of the site of compression. There is no evidence that the peak venous velocity produced by a system is a valid measure of medical performance.

Evaluation of Pulmonary Arterial Catheter Parameters Utilizing Intermittent Pneumatic Compression Boots in Congestive Heart Failure

The use of intermittent pneumatic compression boots to reduce the risk of deep venous thrombosis is contraindicated in patients with congestive heart failure (CHF) due to a theoretical increase in venous return to the heart and exacerbation of heart failure. This study evaluates intermittent pneumatic compression effects on pulmonary artery catheter parameters in CHF patients. We conducted a prospective within-patient study of CHF patients monitored by pulmonary artery catheterization. Hemodynamic variables were assessed with and without the use of intermittent pneumatic compression boots. A sample size of 18 patients was calculated a priori to obtain an 80 per cent power to detect a mean difference of 10 per cent. Twenty patients were studied; no patient suffered hemodynamic instability during the application of pneumatic compression; no statistically significant change in any hemodynamic parameters was noted. A trend toward decreasing mean arterial blood pressure ( P = 0.057), pulmonary artery wedge pressure ( P = 0.065), and systemic vascular resistance ( P = 0.08) was observed. None were clinically significant. The application of intermittent pneumatic compression to the feet of patients in CHF does not significantly alter central hemodynamic parameters in CHF patients. This study suggests that intermittent pneumatic compression may be used in CHF patients for venous thromboembolic risk reduction.

Spinal cord injury medicine. 1. Etiology, classification, and acute medical management

This self-directed learning module highlights basic management and approaches to intervention-both established and experimental. The revised American Spinal Injury Association classification (2000) of spinal cord injury (SCI) further defines the examination and classification guidelines. The incidence of traumatic SCI remains at approximately 10,000 cases per year, with 32 years the average age at injury. Initial management includes establishment of oxygenation, circulation (mean blood pressure >85 mm Hg), radiographic evaluations for spine instability, intravenous methylprednisolone, and establishment of spinal alignment. Prevention measures for medical complications include pressure relief for skin, thromboembolism prophylaxis, prevention of gastric ulcers, Foley catheter drainage to prevent urine retention, and bowel care to prevent colonic impaction. Nontraumatic SCI from spinal stenosis, neoplastic compression, abscess, or multiple sclerosis becomes more common with aging. Experimental treatments for SCI include antibodies to block axonal growth inhibitors, gangliosides to augment neurite growth, 4-aminopyridine to enhance axonal conduction through demyelinated nerve fibers, and fetal tissue to fill voids in cystic spinal cord cavities. Early comprehensive rehabilitation at a SCI center prevents complications and enhances functional gains.

OVERALL ARTICLE OBJECTIVE

To summarize the comprehensive evaluation and management of a newly injured individual.

Minimizing venous thromboembolic complications in the orthopaedic patient

Venous thromboembolic events (VTE), which include deep venous thrombosis (DVT) and pulmonary embolus (PE), are the most common life-threatening complications associated with orthopaedic surgical procedures. DVT is particularly prevalent in patients undergoing total knee and hip arthroplasty, occurring at a rate of 50 to 60%. In addition, up to 2% of orthopaedic patients receiving pharmacologic prophylaxis still develop PE. Because the majority of candidates for these procedures are older adults with a multitude of comorbid conditions, standard prophylactic practices may not always result in optimal clinical outcomes. Thus, it is important for nurses to have a general understanding of appropriate thromboprophylaxis. This article will provide an overview of the current recommended guidelines and explore the risks and benefits of both pharmacologic agents and adjunctive treatment modalities.

Home use of impulse compression of the foot and compression stockings in the treatment of chronic venous insufficiency

PURPOSE

The use of intermittent pneumatic compression, in addition to elastic bandages or stockings, accelerates the healing of leg ulcers in patients with severe chronic venous insufficiency (CVI). There is recent evidence that impulse compression of the plantar venous plexus reduces post-traumatic ankle swelling and prevents postoperative venous thromboembolism. The purpose of this study was to evaluate the clinical and hemodynamic responses after home use of impulse foot compression for 3 months in patients already using therapeutic compression stockings for the management of CVI.

METHODS

Twelve extremities from 9 patients with documented CVI, class 4 to 5 according to the Clinical, Etiology, Anatomy, Pathophysiology classification system, were included in this prospective cohort study. All patients were instructed to use a foot pump device at home for 2 hours a day for 3 months in addition to therapeutic compression stockings (30-40 mm Hg) worn during the day. The device was set to three cycles (3 seconds) of compression (120 mm Hg) per minute. A clinical scoring system was completed before foot compression and 1, 2, and 3 months thereafter. In addition, all patients underwent air plethysmography studies at the same time intervals, including venous volume, venous filling index, ejection fraction, and residual volume fraction.

RESULTS

Patients reported significant improvement in their scores for swelling (P <.05) and pain (P <.04). Air plethysmography showed a reduction in venous volume and venous filling index, although these differences were not significant. Ejection fraction remained unchanged and residual volume fraction was significantly reduced (P <.05) compared with baseline. The foot compression devices were well tolerated by all the patients in the study.

CONCLUSIONS

The use of home foot impulse compression plus elastic stockings significantly reduced the residual volume fraction as measured by air-plethysmography in a group of patients with severe CVI. This favorable hemodynamic response could, in part, explain the clinical improvement achieved by this combined treatment. However, this represents a preliminary pilot study that needs to be confirmed in future randomized controlled studies with more patients included.

The use of intermittent pneumatic compression in venous ulceration

Even with the application of four-layer bandaging, the recommended treatment for venous leg ulceration, patients with reduced mobility have delayed ulcer healing. Intermittent pneumatic compression (IPC) has an established role in deep vein thrombosis prophylaxis and has been shown to influence fibrinolysis, tissue oxygenation, oedema and venous return. It has also been suggested, but not yet proven, that IPC may improve the healing of venous leg ulcers. An extensive review of the literature has demonstrated that the use of this treatment on patients with reduced mobility has not been previously studied; yet, analysis of difficult-to-heal ulcer patients would indicate that this method of treatment may be appropriate and requires further study.

Optimising the performance of intermittent pneumatic compression devices

OBJECTIVES

this study was designed to determine whether an intermittent pneumatic compression device (IPC) with an increased maximal inflation pressure, a decreased time to maximal pressure and a longer duration of compression would improve venous return compared to a standard IPC device.

METHODS

thirty limbs in 15 volunteers without evidence of venous disease were studied using duplex scanning at rest and during the application of two different IPC devices with different compression parameters. The first device IPC-1 (SCD 5325, Kendall) has a six-chambered cuff applying 45 mmHg after 12 s, sequentially from ankle to thigh followed by 60 s of non-compression. The second device IPC-2 (Vena-Assist(R), ACI Medical) has a foot, ankle and calf cuff, applies a pressure of 80 mmHg, has a pressure rise time of 0.3 s, maintains inflation for 5.5 s, and has a cycling time of 1 min. Peak venous velocity and acceleration time were measured at rest and during the IPC application. Measurements were obtained in supine position from the common femoral vein 1 cm above the saphenofemoral junction to include the entire venous outflow from the limb.

RESULTS

peak venous velocity at rest was significantly higher in the right limb than in the left limb (26+/-7.2 vs. 22+/-5.7 cm/s, p<0.01). Peak venous velocity was significantly increased by both IPC devices (p <0.0001). IPC-2 achieved significantly higher peak venous velocity than IPC-1 (55.1+/-17.8 vs. 37.4+/-6.9 cm/s, p<0.0001). Acceleration time was also found to be significantly shorter (370+/-93.4 vs. 560+/-83.5 ms, p<0.0001) in IPC-2 than in IPC-1, respectively.

CONCLUSIONS

we have demonstrated that progressive inflation at the foot, ankle and calf, increasing maximal inflation pressure and decreasing time to maximal pressure result in increased venous return. These changes may improve the efficacy of IPC devices in the prevention of deep-venous thrombosis (DVT) formation.

High-pressure, rapid-inflation pneumatic compression improves venous hemodynamics in healthy volunteers and patients who are post-thrombotic

PURPOSE

Deep vein thrombosis (DVT) is a preventable cause of morbidity and mortality in patients who are hospitalized. An important part of the mechanism of DVT prophylaxis with intermittent pneumatic compression (IPC) is reduced venous stasis with increased velocity of venous return. The conventional methods of IPC use low pressure and slow inflation of the air bladder on the leg to augment venous return. Recently, compression devices have been designed that produce high pressure and rapid inflation of air cuffs on the plantar plexus of the foot and the calf. The purpose of this study is to evaluate the venous velocity response to high-pressure, rapid-inflation compression devices versus standard, low-pressure, slow-inflation compression devices in healthy volunteers and patients with severe post-thrombotic venous disease.

METHOD

Twenty-two lower extremities from healthy volunteers and 11 lower extremities from patients with class 4 to class 6 post-thrombotic chronic venous insufficiency were studied. With duplex ultrasound scanning (ATL-Ultramark 9, Advanced Tech Laboratory, Bothell, Wash), acute DVT was excluded before subject evaluation. Venous velocities were monitored after the application of each of five IPC devices, with all the patients in the supine position. Three high-pressure, rapid-compression devices and two standard, low-pressure, slow-inflation compression devices were applied in a random sequence. Maximal venous velocities were obtained at the common femoral vein and the popliteal vein for all the devices and were recorded as the mean peak velocity of three compression cycles and compared with baseline velocities.

RESULTS

The baseline venous velocities were higher in the femoral veins than in the popliteal veins in both the volunteers and the post-thrombotic subjects. Standard and high-pressure, rapid-inflation compression significantly increased the popliteal and femoral vein velocities in healthy and post-thrombotic subjects. High-pressure, rapid-inflation compression produced significantly higher maximal venous velocities in the popliteal and femoral veins in both healthy volunteers and patients who were post-thrombotic as compared with standard compression. Compared with the healthy volunteers, the patients who were post-thrombotic had a significantly attenuated velocity response at both the popliteal and the femoral vein levels.

CONCLUSION

High-pressure, rapid-inflation pneumatic compression increases popliteal and femoral vein velocity as compared with standard, low-pressure, slow-inflation pneumatic compression. Patients with post-thrombotic venous disease have a compromised hemodynamic response to all IPC devices. However, an increased velocity response to the high-pressure, rapid-inflation compression device is preserved. High-pressure, rapid-inflation pneumatic compression may offer additional protection from thrombotic complications on the basis of an improved hemodynamic response, both in healthy volunteers and in patients who were post-thrombotic.