The Use of Intermittent Pneumatic Compression in Orthopedic and Neurosurgical Postoperative Patients: A Systematic Review and Meta-analysis.

OBJECTIVE: The objective of this systematic review and meta-analysis was to carry out an up-to-date evaluation on the use of compression devices as deep vein thrombosis (DVT) prophylaxis methods in orthopedic and neurological patients. SUMMARY OF BACKGROUND DATA: There is an increased risk of DVT with surgery, particularly in patients who are not expected to mobilize soon after their procedures, such as orthopedic and neurosurgical patients. Compression devices are often employed for DVT prophylaxis in these patients. However, the true efficacy of these devices and the standardization of use with these devices are yet to be established. METHODS: Medline, CINAHL, Embase, Google Scholar, and the Cochrane library electronic databases were searched to identify randomized controlled trials and observational studies reporting on the use of compression devices for DVT prevention. RESULTS: Nine studies were included for review and meta-analysis. Use of an intermittent pneumatic compression device alone is neither superior nor inferior to chemoprophylaxis. CONCLUSIONS: In the absence of large randomized multicenter trials comparing the use of intermittent pneumatic compression or chemoprophylaxis alone to a combination of both treatments, the current evidence supports the use of a combined approach in high-risk surgical patients.

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.

Human centred design considerations for connected health devices for the older adult.

Connected health devices are generally designed for unsupervised use, by non-healthcare professionals, facilitating independent control of the individuals own healthcare. Older adults are major users of such devices and are a population significantly increasing in size. This group presents challenges due to the wide spectrum of capabilities and attitudes towards technology. The fit between capabilities of the user and demands of the device can be optimised in a process called Human Centred Design. Here we review examples of some connected health devices chosen by random selection, assess older adult known capabilities and attitudes and finally make analytical recommendations for design approaches and design specifications.

Haemodynamic performance of neuromuscular electrical stimulation (NMES) during recovery from total hip arthroplasty.

BACKGROUND: Patients post total hip arthroplasty (THA) remain at high risk of developing Deep Vein Thrombosis (DVT) during the recovery period following surgery despite the availability of effective pharmacological and mechanical prophylactic methods. The use of calf muscle neuromuscular electrical stimulation (NMES) during the hospitalised recovery period on this patient group may be effective at preventing DVT. However, the haemodynamic effectiveness and comfort characteristics of NMES in post-THA patients immediately following surgery have yet to be established. METHODS: The popliteal veins of 11 patients, who had undergone unilateral total hip replacement surgery on the day previous to the study, were measured using Doppler ultrasound during a 4 hour neuromuscular electrical stimulation (NMES) session of the calf muscles. The effect of calf muscle NMES on peak venous velocity, mean venous velocity and volume flow were compared to resting values. Comfort was assessed using a 100mm non-hatched visual analogue scale taken before application of NMES, once NMES was initiated and before NMES was withdrawn. RESULTS: In the operated limb NMES produced increases in peak venous velocity of 99% compared to resting. Mean velocity increased by 178% compared to resting and volume flow increased by 159% compared to resting. In the un-operated limb, peak venous velocity increased by 288%, mean velocity increased by 354% and volume flow increased by 614% compared to basal flow (p<0.05 in all cases). There were no significant differences observed between the VAS scores taken before the application of NMES, once NMES was initiated and before NMES was withdrawn (p=.211). CONCLUSIONS: NMES produces a beneficial hemodynamic response in patients in the early post-operative period following orthopaedic surgery. This patient group found extended periods of calf-muscle NMES tolerable. TRIAL REGISTRATION: ClinicalTrials.gov NCT01785251.

Patient tolerance of neuromuscular electrical stimulation (NMES) in the presence of orthopaedic implants.

Neuromuscular electrical stimulation (NMES) may help reduce the incidence of deep vein thrombosis (DVT) in the postoperative total hip and knee arthroplasty patient. However, discomfort associated with stimulus may reduce patient acceptance of NMES as therapy. The aim of this study was to determine if patient comfort and tolerance of NMES was affected by applying stimulation in proximity to an orthopaedic implant. There was a concern that this may cause a concentration of current around the metal which could result in hypersensitivity of NMES and reduce its effectiveness. Twenty patients took part in this study, 10 total hip and 10 total knee arthroplasty patients. Each patient was at least 3 weeks post surgery. NMES was applied to the calf muscles of each leg using skin surface electrodes. Four excitatory levels were recorded, which were: sensory threshold, motor threshold, pain threshold and pain tolerance. Following this, patients underwent a 5 min stimulation session and indicated their overall comfort level on a visual analogue scale. Measurements of peak venous velocity, mean velocity and volume flow were recorded by duplex scanning from the popliteal vein at rest and in response to NMES elicited contractions during this session. Finally, patients completed a short verbal interview detailing their experience with the NMES treatment. The blood flow results showed increases in peak venous velocities, mean velocities and volume flow produced by NMES of 200%, 60% and 60% respectively when compared to resting blood flow. Comfort assessment indicated that the presence of a metallic implant did not give rise to hypersensitivity due to NMES. Patients found the application of calf muscle NMES comfortable and acceptable as a treatment. We conclude that the use of NMES on postoperative orthopaedic patients can be safely administered as a DVT prevention method.

Hemodynamic performance of NMES in the early post operative period following orthopaedic surgery.

Patients post total hip arthroplasty (THA) remain at high risk of developing Deep Vein Thrombosis (DVT) during the recovery period following surgery. The use of calf muscle neuromuscular electrical stimulation (NMES) during the hospitalized recovery period on this patient group may be effective at preventing DVT. However, the haemodynamic effectiveness and comfort characteristics of NMES in post-THA patients immediately following surgery has yet to be demonstrated. The popliteal veins of 5 patients, who had undergone unilateral total hip replacement surgery on the day previous to the study, were measured using Doppler ultrasound during a 4 hour calf-muscle NMES session. The effect of calf muscle NMES on peak venous velocity and volume flow were compared to resting values. Comfort was assessed using a 100 mm non-hatched visual analogue scale taken before application of NMES, once NMES was initiated and before NMES was withdrawn. Results of the study showed that NMES produces a beneficial hemodynamic response in patients in the early postoperative period following orthopaedic surgery. This patient group found extended periods of calf-muscle NMES tolerable.

The influence of orthopaedic implants on patient tolerance of neuromuscular electrical stimulation (NMES).

Neuromuscular electrical stimulation (NMES) is a potential deep vein thrombosis (DVT) preventative measure that is often over-looked. NMES could be used postoperatively in conjunction with pharmacological prophylaxis to further reduce the incidence rate of DVT following orthopaedic surgery. However, the use of NMES in the recovery period following orthopaedic surgery on patients with metallic hip/knee implants has not been tested to date. The presence of a metallic implant may interfere with the NMES generated electric field causing hypersensitivity at the implant site. This may essentially limit the use of NMES postoperatively. Consequently, patient tolerance of NMES must be assessed before any treatment can be administered. Five hip replacement patients and 5 knee replacement patients participated in this study that were at least 3 weeks post-op. NMES was applied to the calf muscles of each patient using skin surface electrodes and the stimulation intensity was slowly increased. Comfort was assessed by asking the patient to indicate the stimulation intensity corresponding to 4 thresholds: when they first felt the stimulus sensation (sensory threshold), when a muscle contraction was observed (motor threshold), when stimulation became uncomfortable (pain threshold) and when the stimulation became unbearable (pain tolerance). Patients also indicated their overall comfort level on a visual analogue scale and completed a short verbal interview detailing their experience of the NMES treatment. Results indicated that the presence of a metallic implant did not give rise to hypersensitivity to NMES. Patients found the application of calf muscle NMES comfortable and acceptable as a treatment. We conclude that use of NMES on postoperative orthopaedic patients can be safely considered as a DVT prevention method.

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

This study investigated the hemodynamic properties of the plantar venous plexus (PVP), a peripheral venous pump in the human foot, with Doppler ultrasound. We investigated how different ways of introducing mechanical changes vary in effectiveness of displacing blood volume from the PVP. The contribution of the PVP was analyzed during both natural and device-elicited compressions. Natural compressions consisted of weight bearing on the foot and toe curl exercises. Device-elicited compressions consisted of intermittent pneumatic compression (IPC) of the foot and electrically elicited foot muscle contractions. Ten healthy participants had their posterior tibial, peroneal, anterior tibial, and popliteal vein blood flow monitored while performing these natural and device-elicited compressions of the PVP supine and in an upright position. Results indicated that 1) natural compression of the PVP, weight bearing and toe curls, expelled a significantly larger volume of blood than device-elicited PVP compression, IPC and electrical stimulation; 2) there was no difference between the venous volume elicited by weight bearing and by toe curls; 3) expelled venous volume recorded at the popliteal vein under all test conditions was significantly greater than that recorded from the posterior tibial and peroneal veins; 4) there was no significant difference between the volume in the posterior tibial and peroneal veins; 5) ejected venous volume recorded in the upright position was significantly higher than that recorded in the supine position. Our study shows that weight bearing and toe curls make similar contributions to venous emptying of the foot.

Technique for the computation of lower leg muscle bulk from magnetic resonance images.

An unsupervised technique to estimate the relative size of a patient's lower leg musculature in vivo using magnetic resonance imaging (MRI) in the context of venous insufficiency is presented. This post-acquisition technique was designed to segment calf muscle bulk, which could be used to make inter- or intra-patient comparisons of calf muscle size in the context of unilateral leg ulcers and venous return. Pre-processing stages included partial volume reduction, intensity inhomogeneity correction and contrast equalization. The algorithm created a binary mask of voxels that fell within a computed threshold designated as representing muscle based on a 3-class fuzzy clustering approach. The segmentation was improved using a set of morphological operations to remove adipose tissue, spongy bone and cortical bone. The technique was evaluated for accuracy against a manual segmented ground truth. Results showed that the automatic technique performed sufficiently well in terms of accuracy and efficacy. The automatic method did not suffer from intra-observer variability.

A pilot evaluation of a neuromuscular electrical stimulation (NMES) based methodology for the prevention of venous stasis during bed rest.

Bed rest poses an increased risk factor for a potentially fatal venous thromboembolism (VTE). Lack of activation of the calf muscle pump during this resting period gives rise to venous stasis which may lead to deep vein thrombosis (DVT) development. Our aim was to investigate the effects that 4h of bed rest have on the lower limb hemodynamics of healthy subjects and to what extent electrically elicited contractions of the calf muscles can alleviate these effects. Outcome variables included popliteal vein blood flow and heart rate. Primary results indicated that the resting group experienced a significant decline in popliteal venous blood flow of approximately 47% with approximately 13% decrease in heart rate. The stimulated groups maintained a significantly higher venous blood flow and heart rate. Volume flow in the contralateral limb remained constant throughout the study and was comparable to that of the stimulated limb's recovery flow. The results suggest that even short periods of bed rest can significantly reduce lower limb blood flow which could have implications for DVT development. Electrically elicited calf muscle contractions significantly improve lower limb blood flow and can alleviate some debilitating effects of bed rest.

The anatomy and physiology of the venous foot pump.

The presence of a venous pumping mechanism in the foot may be significant for venous return in the lower extremities. However, there has been a lack of conclusive research in the area to date and controversy still exists over the detailed anatomy and physiologic mechanism of the venous foot pump. A full understanding of the anatomy and physiology of the venous foot pump is essential for designing effective interventions for the prevention, treatment, and management of venous disease in the lower limbs. This article highlights and discusses the relevant literature relating to the anatomy and physiology of the venous foot pump. In addition, the plantar aspects of 10 cadaveric feet were dissected. These dissections revealed the presence of a previously unreported secondary deep plantar arch and/or deep system of venous connections in the foot and facilitated a more detailed description of the patterns of doubling and branching of the primary veins of the foot. The results of these dissections are discussed within the context of previous work in the field with the aid of detailed diagrams of the dissected feet and may provide a backdrop for the physiology of the venous foot pump and its potential role in lower limb circulation. This is discussed in the last section of the article, which also highlights existing controversy regarding the role of weight bearing and muscular contraction as the dominant mechanisms for venous pumping in the foot.

A hemodynamic study of popliteal vein blood flow: the effect of bed rest and electrically elicited calf muscle contractions.

Venous stasis, due to lack of activation of the calf muscle pump of postoperative patients, can result in the development of a thrombus which, in turn, can lead to a potentially fatal pulmonary embolism. The presented study investigates the effects that four hours of bed rest has on the lower limb hemodynamics of healthy subjects and, to what extent electrically elicited contractions of the calf muscles can alleviate these effects. Results indicated that the non-stimulated group experienced a decline in popliteal venous blood flow of approximately 45 % and a 10 % decrease in heart rate. The stimulated group maintained a higher venous blood flow and heart rate. The results suggest that even short periods of bed rest can significantly reduce lower limb blood flow which could have implications for DVT development in post-operative patients. Electrically elicited calf muscle contractions significantly improves lower limb blood flow and can alleviate the debilitating effects of bed rest.

A haemodynamic study of the physiological mechanisms of the venous pump in the healthy human foot.

Presented is a physiological study of the plantar venous plexus in the context of venous return. It is accepted that the plantar venous plexus acts as a peripheral venous pump, capable of emptying blood from the foot into the posterior tibial veins. Controversy still exists, however, over the precise physiological mechanism which is responsible for completely emptying the deep plantar veins of the foot. This study was designed to investigate whether weight bearing or muscular contraction was the dominant mechanism involved. This was achieved by comparing blood flow measurements taken from the posterior tibial and popliteal veins while performing specific foot exercises. Measurements were taken using Doppler ultrasound. Neuromuscular electrical stimulation was also used to study the blood flow obtained by artificially inducing contraction of the plantar venous plexus.

A technique for the computation of lower leg muscle volume from MRI images in the context of venous return.

A technique to automatically calculate the volume of a patient's calf muscle using MRI scans in the context of venous insufficiency is presented. Rather than giving a quantifiable measurement of volume, the technique provides a pixel count which can be used to compare the calf muscle volume of one leg of a patient against the other in the context of unilateral leg ulcers or to compare one patient's calf muscle volume against another patient. A custom MATLAB program reads the MRI scans (in the form of JPEG images) and determines the number of pixels (right and left limbs separately) that fall within a user defined gray-scale band, designated as being muscle. The output from the MATLAB program was compared with a manual counting method. The pixel counting algorithm was found to have an acceptable accuracy with results indicating a percentage difference from the manual method of between 2 and 9.5%.