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1 2016 EDIZIONI The online version of this article is located at ORIGINAL ARTICLE International Angiology 2016 August;35(4): Measurement of blood flow in the deep veins of the lower limb using the geko neuromuscular electro-stimulation device Maura Griffin 1 *, Dawn Bond 1, Andrew N. Nicolaides 1The Vascular Noninvasive Diagnostic Centre, London, UK; 2 Department of Vascular Surgery, Imperial College, London, UK; 3 Department of Biomedical Sciences, University of Cyprus, Nicosia, Cyprus *Corresponding author: Maura Griffin, The Vascular Noninvasive Diagnostic Centre, 4 Upper Wimpole Street, London, W1G 3FB, UK. maurabgriffin@googl .com ABSTRACT BACKGROUND: A previous study using electrical stimulation of the common peroneal nerve (geko ) to activate the venous muscle pump measured blood flow in both the femoral and popliteal veins. Increased blood flow by as much as 60% was demonstrated in the femoral vein. Such an increase is assumed to be as a result of an increase in venous flow from the deep calf veins; however this has yet to be confirmed. The aim of this study was to conduct direct measurements in these deep calf veins to confirm this assumption in healthy individuals. METHODS: This was a single centre open-label intra-subject healthy volunteer comparison of blood flow in the peroneal, posterior tibial and gastrocnemial veins with and without the geko device. The device was applied to 18 volunteers. Peak venous velocity (PV) and ejected volume per individual stimulus (VS) and volume flow (VF) was determined using ultrasound. RESULTS: Peak velocity (PV) increased 216% in the peroneal vein, by 112% in the posterior tibial vein and by 137% in the gastrocnemial vein (P<0.001). Ejected volume per stimulus increased by 113% in the peroneal vein, by 38% in the posterior tibial vein and by 50% in the gastrocnemial vein (P<0.003). Associated volume flows during the muscle contraction were increased by 36%, 25% and 17%, respectively (P=0.05) CONCLUSIONS: This is the first time that neuromuscular electro-stimulation has been shown to be an effective method of increasing flow in the axial deep veins of the calf. Significant increases in velocity and volume flow in response to the electrical stimulus were seen in all three veins studied. Enhancements of both blood velocity and volume flow are key factors in the prevention of venous stasis and ultimately deep vein thrombosis (DVT). Further studies are justified to determine the efficacy of the device in the prevention of DVT. (Cite this article as: Griffin M, Bond D, Nicolaides AN. Measurement of blood flow in the deep veins of the lower limb using the geko neuromuscular electro-stimulation device. Int Angiol 2016;35:406-10) Key words: Venous thrombosis - Venous insufficiency - Ultrasonography - Prevention and control - Transcutaneous electric nerve stimulation. Electrical calf stimulation has been used in the past (ECS) as a method for preventing DVT. However, stimuli used in these studies were painful and could only be used when the patient was anesthetized. Modern methods of neuromuscular electro-stimulation (NMES) produce stimuli which are painless. NMES of the lower limb muscles has been shown on duplex to be effective in improving blood flow in both the femoral and popliteal veins. 1, 2 Stimulating muscle contraction through NMES has also been linked to a sustained enhancement 1, 2, 3 of systemic fibrinolysis. 3 However we are not aware of studies looking at the changes in the deep calf veins where early thrombi are often thought to start. One such study that clearly highlighted this was performed by Labropoulos et al. They demonstrated that isolated calf DVT was detected in 282 limbs of 251 patients examined. The peroneal veins were most frequently involved with 115 limbs (41%) affected. Posterior tibial and gastrocnemial involvement accounted for 37% and 29% respectively International Angiology august 2016

2 ELECTRO-STIMULATION to INCREASE LOWEr LIMB VENOUS FLOW GRIFFIN The aim of this study was to determine the effect of the geko device on the velocities and volume flows in the peroneal, posterior tibial and gastrocnemial veins in healthy volunteers, and to assess its safety. Material and methods The geko a CE-marked device (Firstkind Ltd., High Wycombe, UK) is a small disposable, internallypowered, neuromuscular electro-stimulation device that is self-adhesive and applied to the outer/posterior aspect of the knee. This positioning enables integral electrodes to apply a stimulus to the common peroneal nerve, a branch of the sciatic nerve. This nerve controls a complex of muscles in the lower leg which activate the calf and foot venous pumps. Stimulation of these nerves by the geko, causes the muscles to contract isometrically and will not affect normal movement of the limb nor mobility of the subject. Contraction of the lower leg muscles will boost blood flow from the lower limbs back to the heart thus increasing venous return, local blood circulation and help prevent venous thrombosis. The geko device has seven stimulation levels to balance maximal effect of stimulation with subject comfort. Made from soft molding thermoplastic elastomer (TPE) overlaid onto a polypropylene case which houses the electronics the geko device is mounted on a hydrogel layer to stick it to the skin. Participants and procedure Eighteen normal volunteers (9 females, 9 males) were selected from a range of age groups between (19-78) for the study via information documents approved by the ethics committee for public display on 2 general hospital notice boards and a General Practitioner s waiting room. The potential volunteers were then screened during a telephone interview to confirm their suitability. Those individuals who did not fulfil the specific study criteria were excluded this included those who reported superficial or deep venous disease, previous varicose vein surgery, congestive heart failure, patients with pacemaker, lower limb arterial disease (ABPI <0.9) or active clinically suspected infection. Clinical examination and a bilateral lower limb venous duplex scan were initially performed to ensure a normal venous system. Figure 1. Position of geko TM device on lateral aspect of knee. Study protocols and informed consent documentation were approved by the National Research Ethics Service, London. All participants gave written informed consent. The leg under investigation was then prepared as per the manufacturer s instructions. This entailed using a small abrasive pad and alcohol wipe included in the geko pack to prep the skin on the lateral aspect of the knee to accommodate the device. After applying the device essentially over the head of the fibula and wrapping the tail end around the posterior aspect of the knee (Figure 1) each participant was placed in a sitting position with the legs suspended over the couch and resting on a stool. The volunteer was then left for 5 minutes to establish venous and arterial equilibrium, thereby reflecting more accurately the individual s true unaffected baseline venous flow. The intensity of the stimulus was dictated by each participant s ability to comfortably tolerate the effect. Once this particular intensity was established this was then used for the rest of the examination. Blood velocity and volume flows were measured in all three calf veins at rest before any stimulus was applied and during stimulation as described below. One leg per volunteer was examined and this was determined randomly. Vol No. 4 International Angiology 407

3 GRIFFIN electro-stimulation to INCREASE LOWEr LIMB VENOUS FLOW A Figure 2. Doppler waveforms of the peroneal vein pre- (A, baseline) and post-application (B) of geko device. Clearly seen are the significant increases detected in both peak velocity and volume flow after activation of the device. Ultrasound measurements The peroneal, posterior tibial and gastrocnemius veins were all imaged in a longitudinal section using the IU22 ultrasonic scanner (Philips Medical, Seattle, WA, USA) and a broad bandwidth L9-5 linear array transducer. Measurements were taken mid-calf for the posterior tibial and peroneal veins, whilst the gastrocnemius veins were measured just distal to the confluence with the popliteal vein. The Doppler sample gate was positioned across the entire vein diameter. Subsequently, peak velocity (PV) (cm/s), diameter of the vein at the point of sampling and the duration of the Doppler spectral waveform produced by the calf muscle contraction were measured. The equipment s software was then able to calculate the cross sectional area of the vein, the time averaged mean velocity (TAMV) and volume flow in ml/min (Figure 2). Knowing that resting venous blood flow in a subject can change over time 5 and patterns of flow will change according to breathing and the cardiac cycle 6 strict protocols were observed with the ultrasound measurements being repeated 3 times on each calf vein examined and the mean value taken. The volume expelled during a single stimulus was calculated from the following equation: volume expelled during single stimulus (ml) = (volume flow (ml/ min)/60) ejection time (s). Percentage increases in PV, TAMV and Volume flow during stimulation were calculated. All the physiological measurements were recorded DVD s and backed-up on hard drive. Statistical analysis The Kolmogorov-Smirnov test was used to test for normal distribution of the data. Having established that the data were normally distributed the mean values of the peak velocity, ejected volume per stimulus and volume flow in the peroneal, posterior tibial and gastrocnemial veins during stimulation were compared to the same measurements obtained at baseline using the paired t-test. The percentage increase of the measurements during stimulation was calculated. The statistical package SPSS Statistics v. 20 for Windows (IBM Corporation, Chicago, IL, USA) was used throughout. A P value <0.05 was considered to be statistically significant. B Reproducibility study In our laboratory measurements repeated twice on 3 volunteers, after an interval of one hour resulted in an intra-class correlation co-efficient (ICC) and 95% CI for peak velocity of (0.951 to 0.999) for the peroneal vein; (0.906 to 0.998) for the posterior tibial vein and (0.952 to 1) for the gastrocnemius vein. The ICC and 95% CI for ejected volume per stimulus of the peroneal, posterior tibial and gastrocnemius veins 408 International Angiology august 2016

4 ELECTRO-STIMULATION to INCREASE LOWEr LIMB VENOUS FLOW GRIFFIN Table I. Mean values (±SD) of velocity, ejected volume per stimulus and volume flow at baseline and during neuromuscular electrostimulation in the peroneal, posterior tibial and gastrocnemial veins in 18 healthy volunteers with normal veins in lower limb. Baseline (mean ± SD) During stimulation (mean ± SD) P (2-tailed) Increase as % of baseline Peak velocity (cm/s) Peroneal vein 6.51± ±7.91 < % Posterior tibial vein 7.31± ±4.49 < % Gastrocnemial vein 7.86± ±6.18 < % Ejected volume per stimulus (ml) Peroneal vein 35.33± ±60.33 < % Posterior tibial vein 36.37± ±20.32 < % Gastrocnemial vein 24.64± ±14.81 < % Volume flow (ml/min) Peroneal vein 19.82± ±21.43 < % Posterior tibial vein 18.74± ±12.21 < % Gastrocnemial vein 14.86± ±7.71 < % were (0.944 to ; (0.981 to 0.999) and (0.944 to 1), respectively. Results The effect of the neuromuscular electro-stimulation on PV, ejected volume per stimulus and volume flow within the 3 calf veins studied is shown in Table I. Discussion Direct electrical muscle stimulation of the common peroneal nerve which activates the calf and foot muscles pump has clearly demonstrated improvements in venous blood flow as have other studies in the field Although evidence exists to support the clinical effectiveness of electrical stimulation in reducing DVT 11,12 and increase in popliteal and femoral vein velocity 1, 2 there is no data on the effect on flow in the calf veins. Whilst the efficacy of mechanical compression is well documented their ability to prevent stasis in the deep veins has not been studied. This study is unique in terms of investigating the anti-stasis/flow/velocity impact of a new NMES device in the clinically important veins with respect to the formation of DVT. In this study on normal volunteers, we evaluated a neuromuscular stimulator which when placed on the skin over the common peroneal nerve delivered short single pulse stimulation at 1 Hz. This resulted in the rhythmic dorsiflexion of the foot and ultimately increased venous flow within the peroneal, posterior tibial and gastrocnemial veins within the calf. Most important is the fact that the effect is not confined to the peroneal compartment but to all the axial veins of the calf. Peak velocity increased by 216% in the peroneal vein, by 112% in the posterior tibial vein and by 137% in the gastrocnemial vein. Ejected volume per stimulus increased by 113%, 38% and 50% in the peroneal, posterior tibial and gastrocnemial veins respectively. Associated volume flows during the muscle contraction were increased by 36%, 25% and 17%, respectively. In reference to one of the elements involved in Virchow s triad, 13 namely venous stasis, geko stimulation is an effective way of activating the calf and foot muscle pump. Such enhancements of peroneal, posterior tibial and gastrocnemius venous blood velocity and volume flow, as shown by this study, are key factors in preventing venous stasis. Therefore such technology could justifiably become an additional method for prevention of VTE, since it is the assumption that increased flows correlate with benefit against thrombosis. 14, 15 The issue of thromboprophylaxis post-discharge from hospital is becoming increasingly relevant due to shortened hospital stays and longer recommended durations of prophylaxis. Its size, portability and easy application may make this device an important prophylactic tool, not only within but also outside the hospital environment and in certain groups of patients where pharmacological and the more traditional mechanical methods of prophylaxis devices would be cumbersome. In addition, issues around patient compliance rates are often contributing factors to the reduced effectiveness of mechanical methods of prophylaxis. The properties of the geko TM device could prove very useful in trying Vol No. 4 International Angiology 409

5 GRIFFIN electro-stimulation to INCREASE LOWEr LIMB VENOUS FLOW to improve the application and compliance rates amongst a patient population thereby optimising thrombo-prophylaxis. Conclusions It should be remembered that this study has been conducted in a normal population, only in one position (sitting) and for a short period of time, so the results cannot be extrapolated to patients with chronic venous disease or individuals in different life situations. However, based on the results of this study, such technology would seem to have a number of applications for the prevention of VTE. The unique dorsiflexion achieved by the geko device is central to delivering the enhancement of volume flow and velocity in these clinically important deep veins. Whilst ultrasound analysis of the soleal vein was not done due to naturally slow blood movement, the dorsiflexion which delivered the volume flow and velocity enhancement in the other deep veins examined is, by association, also likely to positively affect the flow and velocity in the soleal veins themselves. Therefore, the efficacy of a device that is proven to clear these clinically important veins could potentially enhance the future clinical management of DVT in acute hospital patients and further patient studies should be encouraged. References 1. Kaplan RE, Czyrny JJ, Fung TS, Unsworth JD, Hirsh J. Electrical foot stimulation and implications for the prevention of venous thromboembolic disease. Thromb Haemost 2002;88: Faghri PD, Van Meerdervort HF, Glaser RM, Figoni SF. Electrical stimulation-induced contraction to reduce blood stasis during arthroplasty. IEEE Trans Rehabil Eng 1997:5: Lin VW, Perkash A, Liu H, Todd D, Hsiao I, Perkash I. Functional magnetic stimulation: a new modality for enhancing systemic fibrinolysis. Arch Phys Med Rehabil 1999;80: Labroupoulos N, Webb M, Kang SS, Mansour A, Filliung DR, Size GP, et al. Patterns and distribution of isolated calf deep vein thrombosis. J Vasc Surg 1999;30: Nicolaides AN, Kakkar VV, Field ES, Fish P. Optimal electrical stimulus for prevention of deep vein thrombosis. Br Med J 1972;3: Abu-Yousef MM, Mufid M, Woods KT, Brown BP, Barloon TJ. Normal lower limb venous Doppler flow phasicity: is it cardiac or respiratory? AJR Am J Roentgenol 1997;169: Doran FSA, Drury M, Sivyer A. A simple way to combat the venous stasis which occurs in the lower limbs during surgical operations. Br J Surg 1964;51: Doran FSA, White HM. A demonstration that the risk of postoperative deep venous thrombosis is reduced by stimulating the calf muscles electrically during the operation. Brit J Surg 1967;54: Currier DP, Petrilli CR, Threlkeld AJ. Effect of graded electrical stimulation on blood flow to healthy muscle. Phys Ther 1986;66: Tucker A, Maass A, Bain D, Chen LH, Azzam M, Dawson H, et al. Augmentation of venous, arterial and microvascular blood supply in the leg by isometric neuromuscular stimulation via the peroneal nerve. Int J Angiol 2010;19:e Browse NL, Negus D. Prevention of postoperative leg vein thrombosis by electrical muscle stimulation: an evaluation with 125I-labelled fibrinogen. Br Med J 1970;3: Lindstrom B, Korsan BK, Jonsson O, Petruson B, Petterson S, Wikstrand J. Electrically induced short-lasting tetanus of the calf muscles for prevention of deep vein thrombosis. Br J Surg 1982;69: Virchow R. Phlogose und thrombose im gefässsystem. In: Virchow R, editor. Gesammelte Adhandlungen zur Wissenschaftlichen Medicin. Frankfurt: von Meidinger Sohn; p Warwick DJ, Martin A, Glew D, Bannister GC. Measurement of femoral vein blood flow during total hip replacement: Duplex ultrasound with and without the use of a foot-pump. J Bone Joint Surg (Br) 1994;76-B: Westrich GH, Specht LM, Sharrock NE, Windsor RE, Sculco TP, Haas SB, et al. Venous haemodynamics after total knee arthroplasty: evaluation of active dorsal to plantar flexion and several mechanical devices. J Bone Joint Surg (Br) 1998;80-B: Westrich GH, Sculco TP. Prophylaxis against deep venous thrombosis after total knee arthroplasty. Pneumatic plantar compression and aspirin compared with Aspirin alone. J Bone Joint Surg [Am] 1996;78-A: Robertson KA, Bertot AJ, Wolfe MW, Barrack RL. Patient compliance and satisfaction with mechanical devices for preventing deep venous thrombosis after joint replacement. J South Orthop Assoc 2000;9: Caprini JA. Mechanical methods for thrombosis prophylaxis. Clin Appl Thromb Hemost 2010;16: Funding. This study was sponsored by a grant from geko TM device manufacturer Firstkind Ltd. to the Cardiovascular Disease Educational and Research (CDER) Trust, London. However, the sponsors had no role in the data collection, storage, analysis, drafting of this manuscript or its submission to this Journal. Conflicts of interest. The authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript. Article first published online: March 3, Manuscript accepted: March 9, Manuscript revised: March 2, Manuscript received: February 6, International Angiology august 2016