The effect of the position of the limb on venous impulse foot pumps

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.

Impact of intermittent pneumatic foot pumps on delay to surgery following ankle fracture

BACKGROUND

Ankle fractures requiring open reduction and internal fixation (ORIF) are common and place considerable burden on inpatient beds. ORIF cannot be performed once the associated swelling is too excessive to permit tension-free wound closure. Where ORIF cannot be performed before the onset of swelling in the first 24-48h, patients typically require up to 7 days of inpatient bed-rest and elevation to reduce swelling to an acceptable level for ORIF. The primary aim of this study was to determine whether delay to ORIF could be reduced with the pre-operative application of an intermittent pneumatic foot pump (IPF). These devices were designed as anti-embolic adjuncts, but have also been shown to be effective in the reduction of swelling. We compared 12 patients managed with an IPF to 12 matched historical controls who were not. No previous studies have addressed this question in unselected patients requiring ankle ORIF.

METHODS

We performed a retrospective, controlled, before and after study of 24 patients who underwent ankle ORIF at our orthopaedic unit. Foot pumps were applied in the Accident and Emergency Department to ankle fracture patients requiring admission, and kept in place until ORIF. Data was collected from patient case notes for all patients. Patients were matched for age, gender, American Society of Anaesthesiologists (ASA) Grade, and pre-injury mobility. The primary outcome measure was time to surgery. We also recorded total hospital stay, and calculated cost savings.

RESULTS

Patients managed with IPFs had a statistically significant 50% reduction in time from presentation to surgery compared to those managed without (p=0.024), and had a reduced hospital stay (p=0.116). This resulted in a net saving of £10,480 (£953 per patient).

CONCLUSIONS

We conclude that foot pumps reduce the time to surgery and total hospital stay of patients requiring ankle ORIF, and are cost effective.

Micro-mobile foot compression device compared with pneumatic compression device

BACKGROUND

A combination mechanical-pharmacologic regimen is an accepted prophylactic treatment against symptomatic venous thromboembolism for patients undergoing total hip and knee arthroplasties. Foot pumps have been recognized as effective mechanical devices. Research suggests pharmacologic prophylaxis for venous thromboembolism is associated with complications and foot pumps offer an adjunct or alternative approach. Presumably the effectiveness of foot pumps relate to enhancement of venous flow.

QUESTIONS/PURPOSES

We compared an established foot pump system with a new mobile foot pump for their ability to influence mean peak venous velocity in the common femoral, popliteal, and posterior tibial veins.

METHODS

We evaluated 60 healthy subjects with the established and the novel foot-pump systems. Ultrasonography was used to measure baseline and peak venous velocity with mechanical compression. We constructed 95% confidence intervals (CI) on the mean differences between the two devices to establish equivalence limits. We compared ratios of peak velocity to resting velocity. Subjects subjectively rated the two foot pumps with respect to size, fit, and comfort.

RESULTS

The 95% CI test for equivalence of the mean differences between the two devices was inconclusive. The novel device augmented the venous velocity 11 times greater than the resting velocity in the posterior tibial vein and three times greater than the resting velocity in the popliteal vein. The established foot pump augmented the venous velocity 15 times greater than the resting velocity in the posterior tibial vein and four times greater than the resting velocity in the popliteal vein. The novel device rated better for size, fit, and comfort when compared with the established device.

CONCLUSIONS

The established foot pump tended to be associated with greater peak velocities; the novel device produced more consistent mean peak venous velocities and may be more acceptable to patients and caregivers.

The Tromped: A Solution for Flight-Related Deep Vein Thrombosis?

Flight-related deep vein thrombosis (DVT) is well recognized. Reduced venous return occurs during immobility. This alteration in venous hemodynamics may contribute to DVT development. A prototype design of an in-flight exercise device to stimulate ambulatory bloodflow while seated has been developed, consisting of a foot pedal attached to a base by a hinge mechanism. Four devices of differing resistance were evaluated. Calf muscle pump function was assessed by air plethysmography in 10 healthy volunteers. Ejection volume fraction and RVF were determined in the standing position (control values) and were compared with those achieved by depression of the 4 devices while seated. Similar EVF and RVF values were achieved by the control and 2 of the devices. Plantar flexion against a predetermined resistance can effectively activate the calf muscle pump while seated and may reduce the incidence of flight-related DVT.

Compliance and satisfaction with foot compression devices: an orthopaedic perspective

INTRODUCTION

Although mechanical methods of thromboembolic prophylaxis have proven efficacy, relatively little is known about levels of patient compliance in the usage of these devices. Based on anecdotal evidence, we hypothesised that levels of compliance are sometimes insufficient to provide adequate thromboprophylaxis in the clinical setting. We prospectively analysed the use of foot pumps in 30 orthopaedic patients undergoing lower limb arthroplasty in order to assess levels of both patient compliance and satisfaction.

MATERIALS AND METHODS

The study was carried out over a 5-month period. Levels of compliance were measured by using a system of random "spot checks". Each patient completed a questionnaire before discharge. Parameters investigated included comfort levels while using the device and identification of factors about the device which the patients disliked.

RESULTS

Three hundred and ninety-one measurements were made. The utilisation of the device was found to be effective in 40.2% of measurements. We detected an overall progressive decline in the level of compliance as post-operative time increased [P < 0.001, Chi-square (chi(2)) test]. The average level of patient "comfort" was 7.1 on a visual analogue scale of 0-10. Sleep disturbance was reported by 57% of patients, while 43% complained of "heat intolerance". We have also shown that compliance is significantly reduced in those who complained of "sleep disturbance" while using the foot pumps (t-test, P < 0.05).

CONCLUSIONS

These findings suggest that satisfactory levels of compliance can be difficult to achieve in the clinical setting despite the proven efficacy in clinical trials of this device. Greater emphasis on patient education may help improve compliance. Unless compliance can be strictly enforced, it appears advisable to only use foot pumps in combination with other forms of pharmacological prophylaxis.

The venous pump of the first metatarsophalangeal joint: clinical implications

BACKGROUND

Although the anatomy and physiology of the venous circulation of the ankle and midfoot are well documented, the physiologic importance of forefoot mobility has not been reported in the literature. The question of this study was whether the first metatarsophalangeal (MTP) joint may operate, like the ankle, as a "pump" to encourage venous return.

METHODS

Forty-nine cadaver foot specimens were examined using dissection, plastination, vessel infiltration, and maceration, and radiographic (including venography, MRI, and magnetic resonance angiography) techniques. The anatomy and physiology were described and compared to the ankle joint. Forty patients had biphasic Doppler flow studies.

RESULTS

The major finding was the medial drainage of the plantar venous sinus, which is fibrotically bound to the joint capsule. Functional venous valves were evident distally and within fibrous vascular lumens. Mobilization of the first MTP joint led to compression and emptying of the veins. Passive mobilization of the first MTP joint led to an average flow increase of 55% +/- 7 (p < 0.0001), while active movement led to an average increase of 78% +/- 7 (p < 0.0001).

CONCLUSIONS

Our described connection between the joint capsule and veins indicates a "toe-ankle pump" with a significant increase of venous blood flow during motion of the MTP joint. Possible clinical applications for an external MTP pump include anti-edema or thromboprophylactic therapy, especially in patients with foot or ankle injuries. A new toe-pump has been designed based on these results.

Foot pumps without graduated compression stockings for prevention of deep-vein thrombosis in total joint replacement: efficacy, safety and patient compliance

Mechanical prophylaxis with foot pumps provides an interesting alternative to chemical agents in the prevention of thromboembolic disease following major orthopaedic surgical procedures. Recent studies have suggested that the simultaneous use of graduated compression stockings (GCS) may hinder the pneumatic compression effect of foot pumps. The hypothesis of this prospective study was that the use of foot pumps without GCS does not affect the efficacy of deep-vein thrombosis (DVT) prophylaxis and improves patient compliance. A total of 846 consecutive patients admitted at a single institution undergoing total hip (THR) or knee replacement (TKR) were included in the study. The A-V Impulse System foot-pump unit (Orthofix Vascular Novamedix, Andover, UK) was used in all patients. Of these 846 patients, 46 discontinued the use of foot pumps, leaving 400 patients who received foot pumps in combination with GCS and 400 patients with foot pumps alone. Eleven patients of the stocking group (2.7%) and nine patients of the no-stocking group (2.3%) developed postoperative symptomatic DVT (p=0.07). DVT was more frequent in TKR (10/364; 2.7%) than in THR (10/436; 2.3%). Non-fatal pulmonary embolism occurred in four of the 20 patients with symptomatic DVT, two patients each of the stocking and no-stocking groups. The foot-pump discontinuation rate of patients treated with stockings was 7% versus 4% of the patients treated without stockings (p<0.05). In conclusion, management of patients with foot pumps without GCS does not reduce the efficacy of DVT prophylaxis after THR and TKR and improves patient compliance.

Blood flow velocity of the femoral vein with foot exercise compared to pneumatic foot compression

STUDY OBJECTIVE

To compare the effects of foot exercise with an intermittent pneumatic foot compression (IPC) device on blood flow velocity of the femoral veins.

DESIGN

Prospective, controlled study.

SETTING

General intensive care unit of a university hospital.

PATIENTS

20 patients on bed rest in the intensive care unit.

INTERVENTIONS

Patients were divided into 2 groups: group A, foot exercise (n = 10); and group B, IPC device (n = 10). The foot exercise was done once by a nurse for 5 minutes with the dorsiflexion of the ankle (15 times per minute) in group A patients. The IPC device (A-V Impulse System, compression setting: 130 mm Hg for 3 seconds followed by a resting period of 60 seconds) was used for 2 hours in group B.

MEASUREMENTS

Peak blood flow velocity of the femoral vein was measured using the ultrasound unit with a 7.5-MHz linear array probe (ALOKA SSD-5500) at 0, 5, 15, 30, 60, and 120 minutes.

MAIN RESULTS

Peak blood flow velocities in both groups increased significantly vs the control values during the study. At 5 minutes, group A showed a significant increase in the peak blood flow velocity compared with group B.

CONCLUSIONS

Foot exercise by a nurse for 5 minutes was equally or more effective compared with the IPC device in increasing peak blood flow velocity of the femoral vein. The effect of the 5-minute foot exercise lasted for 2 hours.

Simple screening method for deep vein thrombosis by duplex ultrasonography using patients' active maximum ankle dorsiflexion

We hypothesized that venous obstruction by deep vein thrombosis (DVT) only slightly augments venous outflow from lower limbs by active ankle movements. If our hypothesis is true, we thought that we could develop a new screening method for DVT using duplex ultrasonography. Subjects were 22 lower limbs of 11 patients who gave informed consent for venography after total hip or knee arthroplasty. Around postoperative 19.0 days (range 15-32 days), we measured the ratios, called flow ratios, of the peak flow signal with active maximum ankle dorsiflexion and that at rest using duplex ultrasonography in the bilateral femoral veins. On the same day, we then performed bilateral venography. Thrombosis was detected in 5 of the 22 lower limbs. The mean flow ratios with and without DVT were 1.18 (range 1.0-1.3) and 3.31 (range 1.8-4.8), respectively. The flow ratios with DVT were significantly lower than those without DVT. Pain or difficulty performing active maximum ankle dorsiflexion was not observed in any of the operated or unoperated lower limbs during the ultrasound examination. In conclusion, ultrasonographic measurement of flow ratios may become a simple screening method for DVT in lower limbs without the pain or difficulty of performing active maximum ankle dorsiflexion.

The efficacy of the A-V Impulse system in the treatment of posttraumatic swelling following ankle fracture: a prospective randomized controlled study

OBJECTIVES

To determine whether the use of the A-V Impulse "in-cast" system conveyed any clinical benefit in the treatment of post-traumatic swelling following ankle fracture.

DESIGN

A prospective randomised study comparing the effectiveness of the A-V Impulse "in-cast" system to that of elevation and plaster in the treatment of preoperative swelling.

SETTING

Clinical management in a large level 2 trauma center.

PATIENTS

Sixty-four adult patients were recruited to the study who had sustained closed unilateral ankle fractures requiring internal fixation, but for whom immediate surgery was not possible.

INTERVENTION

All fractured ankles were treated with initial application of a plaster back-slab splint. Patients were randomized to either a control group of limb elevation or to a study group in whom an A-V Impulse bladder was fitted under the arch of the foot within the plaster back-slab and intermittent pneumatic pedal compression provided until surgery.

MAIN OUTCOME MEASUREMENTS

Daily circumferential ankle girth measurements were performed. The time taken for swelling to resolve sufficiently to permit surgery, the development of skin complications, and the duration of hospitalisation were recorded.

RESULTS

Ten patients were withdrawn from the study. Twenty-seven patients in each group were followed up until discharge from outpatient care. Statistical analysis revealed a significant reduction in time taken for ankle swelling to settle prior to surgery (P = 0.01) in the study group, together with a reduction in wound and skin complications (P < 0.01) and final preoperative ankle swelling (P = 0.03).

CONCLUSION

The A-V Impulse "in-cast" system demonstrated significant benefit in the management of adults with isolated ankle fractures who could not undergo immediate open reduction and internal fixation.

Muscle blood flow in response to concentric muscular activity vs passive venous compression

AIM

To measure muscle blood flow (MBF) using photoplethysmography (PPG) following concentric muscular activity of the leg (active treatment) or passive venous compression (passive treatment) with or without venous obstruction.

METHODS

In study A, blood flow in the anterior tibial muscle was measured in 15 healthy subjects with a mean age of 30 years. In study B, blood flow in the gastrocnemius muscle was measured in nine healthy subjects with a mean age of 34 years. Subjects performed concentric muscular activity in one leg. Passive venous compression by a venous foot pump was applied in the contralateral leg.

RESULTS

MBF increased significantly following concentric muscular activity, but not following passive venous compression. MBF decreased in both legs when venous obstruction, induced by a thigh tourniquet, was applied. However, MBF was significantly higher following concentric muscular activity than passive venous compression.

CONCLUSION

We conclude that concentric muscular activity produces higher MBF values than passive venous compression.

Effects of ankle exercise combined with deep breathing on blood flow velocity in the femoral vein

Ankle exercises are commonly used to facilitate venous return in the lower extremity and to prevent deep vein thrombosis. Moreover, the respiratory cycle affects venous return. This study examined the effects of ankle exercise combined with deep breathing on the blood flow velocity in the femoral vein. Twenty healthy males (mean age 21.3 years), who had no medical history of lower extremity disease, were recruited for this study. The blood flow velocity in the femoral vein was measured while performing four exercise protocols: quiet breathing while resting (QR), deep breathing (DB), ankle exercise with quiet breathing (AQB), and ankle exercising combined with deep breathing (ADB). Using a Doppler ultrasound with an 8 MHz probe, peak blood flow velocities were collected for a 20 second period at the start of the inspiration phase in each protocol, three times. There were statistically significant differences in the peak blood flow velocity in the femoral vein with the four protocols (p lt 0.001). The mean (SD) peak blood flow velocity in the femoral vein was as follows: QR 10.1 (4.2) cm/sec, DB 15.5 (3.9) cm/sec, AQB 20.7 (6.6) cm/sec, and ADB 26.5 (9.4) cm/sec. Post hoc analyses revealed significant differences between each of the four protocols (p(adj) lt 0.01). The mean peak blood flow velocity in the femoral vein was greatest with the ADB protocol, which implies that the ADB protocol may be useful to prevent the blood stasis in patients at risk of deep vein thrombosis.

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.

Hemodynamic effect of intermittent pneumatic compression and the position of the body

PURPOSE

The purpose of this study was to investigate the three likely mechanisms of intermittent pneumatic compression (IPC) in deep vein thrombosis prophylaxis (increased volume flow, increased flow velocity, and acceleration of flow) and to do this in a variety of positions, in different venous segments, and with the stimulus of three different compression garments.

METHODS

In 12 healthy volunteers, three types of compression cuffs were used: foot, calf, and calf + thigh. The foot was compressed with 80 mm Hg, and the calf and thigh with 40 mm Hg. Duplex ultrasound scan was performed before and during the compression in the horizontal, 15-degree head-down, and 15-degree head-up positions. The common femoral, greater saphenous, profunda femoral, superficial femoral, and popliteal veins were examined.

RESULTS

In comparison with the horizontal position, the 15-degree head-down position was associated with an increase of volume flow and velocities and the head-up position was associated with decreased flow and velocities in the deep veins. The application of IPC caused significant increases in velocities and volume flow in all venous segments. The lowest increase in velocities and volume flow in the deep veins was observed with the subjects in the head-down position, and in the two other positions, the increases were greater and similar to each other. IPC caused a much more prominent increase in flow velocities and volume flow in deep veins compared with simple elevation of the legs.

CONCLUSION

IPC produces significant increases of venous flow volume and flow velocity and acceleration of flow. This is true whether the limbs are elevated, horizontal, or dependent. Segmental flow changes vary with the position of the patient and the compression garment used. Foot compression increases volume flow and velocity primarily in the popliteal vein. Calf compression provides maximal increases of volume flow and flow velocity through the deep veins.

Venous impulse foot pumps: should graduated compression stockings be used?

It is not known whether the effect of Foot Pumps (Novamedix, Andover, UK) is enhanced by simultaneous use of graduated compression stockings (by controlling calf compliance) or hindered (by restricting preload). To address this question, we studied 20 healthy volunteers with duplex ultrasound. The peak velocity in the popliteal vein was measured at rest with the legs flat, foot-up, and foot-down, then it was measured when the AV Impulse Foot Pump was activated. These measurements each were performed with and without graduated compression stockings. In each leg position, the use of simultaneous graduated compression stockings reduced the peak velocity. On physiologic grounds, graduated stockings should not be used simultaneously with Foot Pumps.

The effects of intermittent pneumatic compression on the arterial and venous system of the lower limb: a review

A better understanding of lower limb haemodynamics and the effects of intermittent pneumatic compression on the lower limb has led to an increasing awareness of the potential value of intermittent pneumatic compression in both venous and arterial disease. Intermittent pneumatic compression can be used in both the primary and secondary care settings, with its advantages being further enhanced by excellent patient compliance and very low rate of complications. Intermittent pneumatic compression has a proven role in the prophylaxis of deep vein thrombosis and there is some evidence that it is a useful adjunct in the management of venous ulcer disease. With laboratory and more recent clinical studies demonstrating augmentation of arterial inflow with intermittent pneumatic compression, its use in arterial diseases is being increasingly explored. Further studies are needed to define the precise role of intermittent pneumatic compression in arterial disease but any treatment regimen which reduces the need for referral or intervention in the claudicant or critically ischaemic limb will be a valuable addition to those managing arterial disease.