Venous emptying from the foot: influences of weight bearing, toe curls, electrical stimulation, passive compression, and posture

Venous disorders as an occupational disease - a systematic review on epidemiology, pathophysiology, and modification strategies

Forced postures are common in the workplace. Work in the primary economic sector is characterised by a high degree of physical activity and movement; however, activities in the secondary and tertiary sectors commonly require workers to stand or sit. An expansion of the tertiary sector in recent decades has meant that people in industrialised and emerging economies primarily sit or stand at work. The aim of the systematic review was to identify occupational factors relating to the presence of chronic venous disease (CVD), to place these in the context of developments in the workplace, and to determine whether measures are in place to prevent CVD. We performed a systematic literature review to analyse studies assessing work-related risk factors for CVD. We searched for publications in the PubMed database, the clinic library of BG Hospital Bergmannstrost Halle, and the registry of the German Statutory Accident Insurance. Using occupation-specific keyword combinations, we identified 27,522 publications. The publications underwent an automatic and manual filtering process according to the PRISMA guidelines and 81 publications qualified for the review. Ultimately 25 studies were included in the systematic review. All of the subjects of the studies worked in the secondary and tertiary sectors. No studies looked at the relationship between venous disorders and primary sector occupations. Standing at work for more than four hours a day, repeated heavy lifting, and cumulative time working in a sitting or standing position are risk factors for the development of CVD. Sitting is less of a risk factor than standing or walking. Occupational history and the patient's activity profile are important diagnostic tools which can help confirm a diagnosis and justify treatment when findings are inconsistent. Compression therapy is the primary form of secondary and tertiary prevention. There continues to be a lack of primary preventive measures related to workplace design.

Pedal Musculovenous Pump Activation Effectively Counteracts Negative Impact of Knee Flexion on Human Popliteal Venous Flow

Knee scooters are commonly used for mobility instead of other devices. However, passive popliteal venous flow impedance has been observed with knee scooter usage ostensibly as a result of deep knee flexion. This study aimed to characterize the magnitude of impact knee flexion has on popliteal venous flow in relation to the degree of knee flexion when walking boot immobilized. Furthermore, the countervailing effect of standardized pedal musculovenous pump (PMP) activation was observed. Popliteal venous diameter and flow metrics were assessed with venous ultrasonography in 24 healthy individuals. Straight leg, crutch, and knee scooter positioning while wearing a walking boot and non-weight-bearing were compared. Flow was assessed with muscles at rest and with PMP activation. Of 24 participants, 16 (67%) were female. Twelve limbs (50%) were right sided. The mean age was 21.9 (SD = 3.0) years, and the mean body mass index was 21.9 (SD 1.9) kg/m². Observer consistencies were excellent (intraclass correlation range = 0.93 to 0.99). No significant differences in mean vessel diameter, time-averaged mean velocity, and total volume flow occurred (all P > .01). Corresponding knee flexion effect sizes were small (range = -0.04 to -0.26). A significant decrease (-24%) in active median time-averaged peak velocity occurred between upright and crutch positions (20.89 vs 15.92 cm/s; P < .001) with a medium effect size (-0.51). PMP activation increased all flow parameters (all P < .001), and effect sizes were comparatively larger (>0.6) across all knee flexion positions.Clinical Significance: Knee flexion has a small to medium impact on popliteal venous return in healthy patients. Active toe motion effectively counters the negative effects of gravity and knee flexion when the ankle is immobilized.Levels of Evidence: Therapeutic, Level IV.

The effects of shoe type on lower limb venous status during gait or exercise: A systematic review

This systematic review evaluated the literature pertaining to the effect of shoes on lower limb venous status in asymptomatic populations during gait or exercise. The review was conducted in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed-NCBI, EBSCO Host, Cochrane Library and Science Direct databases were searched (March 2019) for words around two concepts: shoes and venous parameters. The inclusion criteria were as follows: (1) the manuscript had to be published in an English-language peer-reviewed journal and the study had to be observational or experimental and (2) the study had to suggest the analysis of many types of shoes or orthotics on venous parameters before, during and/or after exercise. Out of 366 articles, 60 duplications were identified, 306 articles were analyzed, and 13 articles met the eligibility criteria after screening and were included. This review including approximately 211 participants. The methodological rigor of these studies was evaluated with the modified Downs and Black quality index. Nine studies investigated the effect of shoes on blood flow parameters, two on venous pressure and two on lower limb circumferences with exercise. Evidence was found that unstable shoes or shoes with similar technology, sandals, athletic or soft shoes, and customized foot orthotics elicited more improvement in venous variables than high-heeled shoes, firm shoes, ankle joint immobilization and barefoot condition. These venous changes are probably related to the efficiency of muscle pumps in the lower limbs, which in turn seem to be dependent on shoe features associated with changes in the kinetics, kinematics and muscle activity variables in lower limbs during gait and exercise.

Comparison of the Hemodynamic Performance of Two Neuromuscular Electrical Stimulation Devices Applied to the Lower Limb

Currently, 1% of the population of the Western world suffers from venous leg ulcers as a result of chronic venous insufficiency. Current treatment involves the use of moist wound healing, compression bandages, and intermittent pneumatic compression. Neuromuscular electrical stimulation is a novel potential new therapeutic method for the promotion of increased lower limb hemodynamics. The aim of this study was to measure the hemodynamic changes in the lower limb with the use of two neuromuscular electrical stimulation devices. Twelve healthy volunteers received two neuromuscular stimulation device interventions. The Geko^TM and National University of Ireland (NUI) Galway neuromuscular electrical stimulation devices were randomized between dominant and non-dominant legs. Hemodynamic measurements of peak venous velocity (cm/s), the time average mean velocity (TAMEAN) (cm/s), and ejected volume (mL) of blood were recorded. Peak venous velocity was significantly increased by the Geko^TM and the NUI Galway device compared to baseline blood flow (p < 0.0001), while only the voluntary contraction produced significant increases in TAMEAN and ejected volume (both p < 0.05). Neuromuscular muscular electrical stimulation can produce adequate increases in lower limb hemodynamics sufficient to prevent venous stasis. Greater use of neuromuscular stimulation devices could be considered in the treatment of conditions related to chronic venous insufficiency but requires further research.

S.T.R.I.D.E. Professional Guide to Compression Garment Selection for the Lower Extremity

The following supplement is a rare example of a paper that combines clinical experience and theoretical knowledge on textiles used in compression therapy. The authors' intention is to propose a decision support system for choosing specific compression devices, which can be adjusted to counteract the individual signs and symptoms in an optimally adopted way. The document concentrates on compression devices which can be self-applied by the patients—compression stockings and adjustable wraps. The acronym ‘S.T.R.I.D.E.’, incorporating both textile characteristics and clinical presentation, stands for: Shape, Texture, Refill, Issues, Dosage and Etiology. The intent of the mnemotechnical value is to highlight that successful compression includes more than dosage alone. In addition to dosage, etiology and patient presentation need to be incorporated, including a patient's physical ability to use compression effectively as part of the daily routine, thereby promoting adherence.

The suggested algorithms provide a valuable guide to stride across the important, but still underestimated field of medical compression therapy and will help to put the prescription of a specific product on a more rational basis. Enjoy reading!

Hugo Partsch Emeritus Professor Medical University of Vienna, Austria

Wheels-in-wheels: Use of gravity in human locomotion

Although a wheel is an ideal method for transportation and the invention of the spoke wheel made a wheel lighter and swifter, a wheel cannot function well on slanted or rough surfaces; these are common in the natural environment. Further, the load support of the wheel is limited to a point of the whole wheel in contact with the ground. Then, we humans may be using the legs as a part of spoke wheel and place our legs and feet on the ground alternatively to support the body weight while the gravitational torque makes the center of mass (COM) rotate around the hip joint when proper stiffness and balance is made. Through a pulley-like action involving the hamstrings and a lever-like action of back muscles via the psoas muscle, the energy expenditure for locomotion can be reduced to the energy for lifting the swing leg to maintain the proper position of the COM. Further, the stabilizing action of the psoas muscle to the spinal column can be achieved between the stance leg and the swing leg by the weight of the lifted swing leg during the forward movement. This lifting action during swing phase can assist an energy-efficient eccentric contraction of the stance leg. The passive tension generated by gravity (own weight and the carried load) can be the reason for the energy efficiency of both head-carrying and the Nepalese porter method. Using this passive gravitational force via actively synchronized neuromuscular action may be universal for animal locomotion.

Lower limbs venous kinetics and consequent impact on drainage direction

Background

Literature concerning the lower limbs physiological venous haemodynamics is still lacking of reference velocity values and consequent impact on drainage direction. Aim of the present study is to assess the flow velocities in the different venous compartments, evaluating the possible Venturi effect role, thus finding clues for the identification of the physical model governing the flow direction.

Methods

Thirty-six lower limbs underwent a velocity and diameters echo-color-Doppler assessment in several anatomical point of analysis along both the deep and superficial venous systems. The investigation protocol included and compared two different manoeuvres to elicit the flow: manual calf compression/relaxation (CR) and active foot dorsiflexion (AFD). Both peak systolic (PSV) and time average velocities (TAV) were measured.

Results

The different venous segments demonstrated an overlap among the velocity values and the anatomical subdivision of the deep and superficial compartments. At the CR, TAV was 34 ± 12 cm/s in the deep venous system (N1), 15 ± 7 cm/s in the saphenous system (N2), 5 ± 2 cm/s in the saphenous tributaries (N3); PSV was 89 ± 35 cm/s in N1, 34 ± 16 cm/s in N2, 11 ± 4 cm/s in N3, p < 0.05. At the AFD, TAV was 33 ± 13 cm/s in N1, 15 ± 7 in N2, 9 ± 5 in N3; PSV was 83 ± 35 in N1, 32 ± 17 in N2, 15 ± 4 in N3, p < 0.05. A diameter decrease was reported from N1 to N3 ( p < 0.05).

Conclusion

This investigation provides evidences of the velocity decrease from the deepest to the most superficial compartments. These data introduce the Venturi effect as potential factor in the flow aspiration from the tributary to the deeper veins. The reported data represent a first step towards an objective evaluation of the physic laws governing the drainage. These values can constitute the basis for further investigations in pathological and post-procedural scenarios.

The geko™ electro-stimulation device for venous thromboembolism prophylaxis: a NICE medical technology guidance

The geko™ device is a single-use, battery-powered, neuromuscular electrostimulation device that aims to reduce the risk of venous thromboembolism (VTE). The National Institute for Health and Care Excellence (NICE) selected the geko™ device for evaluation, and invited the manufacturer, Firstkind Ltd, to submit clinical and economic evidence. King's Technology Evaluation Centre, an External Assessment Centre (EAC) commissioned by the NICE, independently assessed the evidence submitted. The sponsor submitted evidence related to the geko™ device and, in addition, included studies of other related devices as further clinical evidence to support a link between increased blood flow and VTE prophylaxis. The EAC assessed this evidence, conducted its own systematic review and concluded that there is currently limited direct evidence that geko™ prevents VTE. The sponsor's cost model is based on the assumption that patients with an underlying VTE risk and subsequently treated with geko™ will experience a reduction in their baseline risk. The EAC assessed this cost model but questioned the validity of some model assumptions. Using the EACs revised cost model, the cost savings for geko™ prophylaxis against a 'no prophylaxis' strategy were estimated as £197 per patient. Following a second public consultation, taking into account a change in the original draft recommendations, the NICE medical technologies guidance MTG19 was issued in June 2014. This recommended the adoption of the geko™ for use in people with a high risk of VTE and when other mechanical/pharmacological methods of prophylaxis are impractical or contraindicated in selected patients within the National Health Service in England.

Fine-wire electromyography response to neuromuscular electrical stimulation in the triceps surae

Neuromuscular electrical stimulation (NMES) has previously been used to enhance venous return from the lower leg. By artificially activating lower leg muscles, venous blood may be effectively ejected from the muscle and adjacent veins. It could easily be assumed that combined NMES of the gastrocnemius and soleus would be the most effective single-channel application in this regard, as these muscles represent the largest muscular bulk in the lower leg. However, we have previously reported that soleus stimulation in isolation is substantially more effective. To understand why this is the case, we recorded fine-wire electromyography during NMES of the gastrocnemius and soleus muscles. We found that gastrocnemius and soleus stimulation are effective in eliciting selective stimulation of these muscles. However, combined stimulation of these muscles using a single set of electrodes was only capable in generating ∼ 50% of the response in each muscle, insufficient to generate their theoretical maximum venous return.

Hands and feet: physiological insulators, radiators and evaporators

The purpose of this review is to describe the unique anatomical and physiological features of the hands and feet that support heat conservation and dissipation, and in so doing, highlight the importance of these appendages in human thermoregulation. For instance, the surface area to mass ratio of each hand is 4-5 times greater than that of the body, whilst for each foot, it is ~3 times larger. This characteristic is supported by vascular responses that permit a theoretical maximal mass flow of thermal energy of 6.0 W (136 W m(2)) to each hand for a 1 °C thermal gradient. For each foot, this is 8.5 W (119 W m(2)). In an air temperature of 27 °C, the hands and feet of resting individuals can each dissipate 150-220 W m(2) (male-female) of heat through radiation and convection. During hypothermia, the extremities are physiologically isolated, restricting heat flow to <0.1 W. When the core temperature increases ~0.5 °C above thermoneutral (rest), each hand and foot can sweat at 22-33 mL h(-1), with complete evaporation dissipating 15-22 W (respectively). During heated exercise, sweat flows increase (one hand: 99 mL h(-1); one foot: 68 mL h(-1)), with evaporative heat losses of 67-46 W (respectively). It is concluded that these attributes allow the hands and feet to behave as excellent radiators, insulators and evaporators.

Comparison of single- and two-channel neuromuscular electrical stimulation sites for enhancing venous return

Neuromuscular electrical stimulation (NMES) has previously been used to activate the musculature of the lower leg and increase venous return to the heart. However, there is little evidence to suggest the superiority of one particular stimulation site over another. In this paper, we aim to reveal the optimal stimulation site on the lower leg in a group of healthy adults. Doppler ultrasound measurements of venous blood volume expelled and peak venous velocity in response to various single and two-channel applications of NMES were taken for each subject. We found that soleus NMES is the most effective single-channel stimulation method, capable of expelling 58.3% of the blood achieved during a voluntary contraction, alternatively soleus plus tibialis posterior stimulation is capable of expelling 76.5%. Based on these and other factors we suggest that the soleus and soleus plus tibialis posterior are the most effective NMES sites for improving venous return.

Hemodynamic effects of habituation to a week-long program of neuromuscular electrical stimulation

OBJECTIVES

Neuromuscular electrical stimulation (NMES) of the calf muscles has been shown to cause instantaneous increases in venous outflow from the lower leg and could be used as an adjunct to current gold-standard compression therapies for the prevention of venous stasis and its related pathologies. However, little is known about the effects of NMES in combination with compression therapies on subject comfort, compliance and popliteal venous blood flow over the course of a week-long NMES protocol. This study aimed to assess the effects of a NMES and compression protocol for the prevention of venous stasis on the compliance, comfort and venous blood flow of healthy volunteers over the course of seven days.

DESIGN

Twenty-four healthy subjects were assigned to either a stimulation or control group. The stimulation group received 1.5 h of NMES daily while the control group received none. Daily measures of popliteal venous blood flow, subject compliance and comfort were recorded over 7 days.

RESULTS

Ejected blood flow volumes and peak velocities in the popliteal vein during NMES were sustained over a 30-min stimulation session and increased by approximately 100% over the course of seven days. Mean stimulation intensities increased progressively throughout the week, while perceived pain during NMES decreased significantly. Mean compliance to the 7-day protocol was 100%.

CONCLUSION

User habituation to a combined NMES and compression protocol resulted in significant increases in ejected venous volume and peak velocity over the course of 7 days. This resulted in the highest ejected venous volume reported from a single NMES induced contraction of the calf muscles to date which was twice the magnitude of values previously reported in the literature. These findings suggest that NMES based protocols applied over an extended period of days, weeks or months may provide greater hemodynamic effect for the prevention of venous stasis than previously observed during NMES sessions lasting less than a few hours.