Transcutaneous electric nerve stimulation: the effect of intensity on local and distal cutaneous blood flow and skin temperature in healthy subjects

Differential changes in blood flow and oxygen utilization in active muscles between voluntary exercise and electrical muscle stimulation in young adults

The physiological effects on blood flow and oxygen utilization in active muscles during and after involuntary contraction triggered by electrical muscle stimulation (EMS) remain unclear, particularly compared with those elicited by voluntary (VOL) contractions. Therefore, we used diffuse correlation and near-infrared spectroscopy (DCS-NIRS) to compare changes in local muscle blood flow and oxygen consumption during and after these two types of muscle contractions in humans. Overall, 24 healthy young adults participated in the study, and data were successfully obtained from 17 of them. Intermittent (2-s contraction, 2-s relaxation) isometric ankle dorsiflexion with a target tension of 20% of maximal VOL contraction was performed by EMS or VOL for 2 min, followed by a 6-min recovery period. DCS-NIRS probes were placed on the tibialis anterior muscle, and relative changes in local tissue blood flow index (rBFI), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rMRO2) were continuously derived. EMS induced more significant increases in rOEF and rMRO2 than VOL exercise but a comparable increase in rBFI. After EMS, rBFI and rMRO2 decreased more slowly than after VOL and remained significantly higher until the end of the recovery period. We concluded that EMS augments oxygen consumption in contracting muscles by enhancing oxygen extraction while increasing oxygen delivery at a rate similar to the VOL exercise. Under the conditions examined in this study, EMS demonstrated a more pronounced and/or prolonged enhancement in local muscle perfusion and aerobic metabolism compared with VOL exercise in healthy participants.NEW & NOTEWORTHY This is the first study to visualize continuous changes in blood flow and oxygen utilization within contracted muscles during and after electrical muscle stimulation (EMS) using combined diffuse correlation and near-infrared spectroscopy. We found that initiating EMS increases blood flow at a rate comparable to that during voluntary (VOL) exercise but enhances oxygen extraction, resulting in higher oxygen consumption. Furthermore, EMS increased postexercise muscle perfusion and oxygen consumption compared with that after VOL exercise.

Efficacy and safety of a home-use handheld multi-energy-based device for skin rejuvenation: clinical, ex vivo, and histological studies

Alongside increases in the average lifespan and a growing interest in anti-aging remedies, the demand for at-home skincare devices is rapidly expanding in the cosmetic market. This study aimed to assess the safety and efficacy of a novel home-use handheld multi-energy-based device for skin rejuvenation that simultaneously emits low level light, low-dose radiofrequency, low-energy microcurrent, and low-intensity ultrasonic wave. This prospective, randomized, split-face clinical trial enrolled 36 healthy Korean women. After 8 weeks of device use, parameters associated with skin aging were assessed. Additionally, a preliminary ex vivo study and skin biopsy following device use were performed to confirm safety and efficiency of the device. Parameters associated with skin aging including skin hydration, elasticity, roughness, skin pore size, and eye wrinkle volume showed significant improvements after 8 weeks of the device use, relative to baseline measurements and the control side. No adverse effects were observed during the follow-up period. Results of ex vivo and in vivo skin tissue studies correlated with clinical findings, which showed an increase in the expression of type 1 collagen and a decrease in the expression of matrix metalloproteinase-1, which is related to the skin aging phenotype. The expression of loricrin and involucrin, major components of the epidermal skin barrier, also increased after the use of the device. Multi-energy-based device is effective for skin rejuvenation and tolerable, without any considerable adverse effects.

Blood flow effects of percutaneous peripheral nerve stimulation. A blinded, randomized clinical trial

BACKGROUND

The vasculature function is mainly regulated by the autonomic nervous system. Importantly, the sensory-motor nervous system also innervates peripheral vessels and has the capacity to modulate vascular tone. Here we investigated the effects of electrical stimulation of a mixed nerve trunk on blood flow in deep arteries and muscle perfusion. Our hypothesis is that stimulation of a mixed nerve can modify blood flow.

METHODS

Twenty-nine healthy participants were included into a randomized-crossover and blinded clinical trial. Each subject received a placebo and two percutaneous peripheral nerve stimulation (pPNS) protocols on the median nerve: Pain Threshold continuous Low Frequency (PT-cLF) and Sensory Threshold burst High Frequency (ST-bHF). Blood flow was then assessed bilaterally using Power Doppler Ultrasonography at the main arteries of the arm, and blood perfusion at the forearm muscles. Afterwards, blood flow was quantified using a semi-automatized software, freely shared here.

RESULTS

Placebo, consisting in needle insertion, produced an immediate and generalized reduction on peak systolic velocity in all arteries. Although nerve stimulation produced mainly no effects, some significant differences were found: both protocols increased the relative perfusion area of the forearm muscles, the ST-bHF protocol prevented the reduction in peak systolic velocity and TAMEAN of the radial artery produced by the control protocol and PT-cLF produced a TAMEAN reduction of the ulnar artery.

CONCLUSIONS

Therefore, the arterial blood flow in the arm is mainly impervious to the electrical stimulation of the median nerve, composed by autonomic and sensory-motor axons, although it produces mild modifications in the forearm muscles perfusion.

Is Electrical Stimulation Effective in Preventing or Treating Delayed-onset Muscle Soreness (DOMS) in Athletes and Untrained Adults? A Systematic Review With Meta-Analysis

The effectiveness of electrical stimulation (ES) in preventing or treating delayed-onset muscle soreness (DOMS) and its effects on muscle recovery is unclear. The systematic review investigated the benefits or harms of ES on DOMS and muscle recovery. Databases (PubMed, Medline, CENTRAL, EMBASE, CINAHL, PsycINFO, PEDro, LILACS, SPORTDiscus) were searched up to March, 31st 2021 for randomized controlled trials (RCTs) of athletes or untrained adults with DOMS treated with ES and compared to placebo/sham (simulation or without ES), or control (no intervention). Data were pooled in a meta-analysis. Risk of bias (Cochrane Collaboration tool) and quality of evidence (GRADE) were analyzed. Fourteen trials (n=435) were included in this review and 12 trials (n=389) were pooled in a meta-analysis. Evidence of very low to low quality indicates that ES does not prevent or treat DOMS as well as ES does not help to promote muscle recovery immediately, 24, 48, 72, 96 hours after the intervention. Only one study monitored adverse events. There are no recommendations that support the use of ES in DOMS and muscle recovery. PERSPECTIVES: No recommendations support the use of electrical stimulation in delayed-onset muscle soreness and muscle recovery in athletes and untrained adults. This means that electrical stimulation is not fruitful for this population according those protocols used. Therefore, unlikely that further randomized controlled trials with the same approach will yield promising results.

Eliciting blinks by transcutaneous electric nerve stimulation improves tear fluid in healthy video display terminal users: A self-controlled study

We aimed to elicit strong blinks among healthy video display terminal (VDT) users by periorbital transcutaneous electric nerve stimulation (TENS) and evaluate its impact on the tear fluid and visual task. Appropriate TENS conditions were evaluated to evoke strong blinks under minimum discomfort. Seventeen healthy VDT users with noninvasive Keratograph first breakup time (NIKf-BUT) 5-15 s and Ocular Surface Disease Index (OSDI) scores < 15 were recruited in this study. Before the trial, noninvasive Keratograph average breakup time (NIKa-BUT), tear meniscus height (TMH) and OSDI scores were evaluated. Before each TENS session, the volunteers played Tetris while the corresponding blink rate and Tetris scores were recorded. Then, the participants underwent 30 minutes of TENS, which evoked blinking of their right eye 20 times per minute. Tetris scores were evaluated again during TENS. The Tetris scores and corresponding blink rate were assessed after each TENS session while NIKa-BUT, TMH and OSDI scores were recorded after the third and sixth TENS sessions. We found that OSDI scores declined significantly after the sixth TENS (P = .003). The NIKa-BUT of the right eye was promoted after the sixth TENS (P = .02), and the TMH was higher after the third and sixth TENS in both eyes (P = .03, P = .03 for right eyes respectively, P = .01, P = .01 for left eyes respectively). There was no significant difference between the adjusted Tetris scores before and during TENS (P = .12). The blink rate before and after TENS were unaffected after 6 sessions (P = .61). The results indicated that periorbital TENS effectively ameliorated ocular irritation and improved tear secretion and tear film stability by eliciting strong blinks in healthy VDT users without disturbing the visual task.

Using TENS for Pain Control: Update on the State of the Evidence

Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological intervention used in the treatment of acute and chronic pain conditions. The first clinical studies on TENS were published over 50 years ago, when effective parameters of stimulation were unclear and clinical trial design was in its infancy. Over the last two decades, a better understanding of the mechanisms underlying TENS efficacy has led to the development of an adequate dose and has improved outcome measure utilization. The continued uncertainty about the clinical efficacy of TENS to alleviate pain, despite years of research, is related to the quality of the clinical trials included in systematic reviews. This summary of the evidence includes only trials with pain as the primary outcome. The outcomes will be rated as positive (+), negative (−), undecided (U), or equivalent to other effective interventions (=). In comparison with our 2014 review, there appears to be improvement in adverse events and parameter reporting. Importantly, stimulation intensity has been documented as critical to therapeutic success. Examinations of the outcomes beyond resting pain, analgesic tolerance, and identification of TENS responders remain less studied areas of research. This literature review supports the conclusion that TENS may have efficacy for a variety of acute and chronic pain conditions, although the magnitude of the effect remains uncertain due to the low quality of existing literature. In order to provide information to individuals with pain and to clinicians treating those with pain, we suggest that resources for research should target larger, high-quality clinical trials including an adequate TENS dose and adequate timing of the outcome and should monitor risks of bias. Systematic reviews and meta-analyses should focus only on areas with sufficiently strong clinical trials that will result in adequate sample size.

Effects of electrical stimulation on skin surface

ABSTRACT

Skin is the largest organ in the body, and directly contact with the external environment. Articles on the role of micro-current and skin have emerged in recent years. The function of micro-current is various, including introducing various drugs into the skin locally or throughout the body, stimulating skin wounds healing through various currents, suppressing pain caused by various diseases, and promoting blood circulation for postoperative muscle rehabilitation, etc. This article reviews these efforts. Compared with various physical and chemical medical therapies, micro-current stimulation provides a relatively safe, non-invasive therapy with few side effects, giving modern medicine a more suitable treatment option. At the same time, the cost of the electrical stimulation generating device is relatively low, which makes it have wider space to and more clinical application value. The current micro-current stimulation technology has become more and more mature, but there are still many problems in its research. The design of the experiment and the selection of the current parameters not standardized and rigorous. Now, clear regulations are needed to regulate this field. Micro-current skin therapy has become a robust, reliable, and well-structured system.

Blood flow velocity but not tendon mechanics relates to nerve function in carpal tunnel syndrome patients

Carpal tunnel syndrome (CTS) develops from chronic compression of the median nerve. Chronic compression results in a number of vascular, structural and functional changes to the carpal tunnel tissues which ultimately manifest in the characteristic symptoms of CTS. The purpose of this study was to investigate the interplay of median nerve function, median nerve hemodynamics, and finger flexor tendon and subsynovial connective tissue (SSCT) mechanics in CTS patients. Thirty-five patients were recruited following nerve conduction study for this double-blinded imaging study. Ultrasound B-mode, pulse-wave Doppler, and colour Doppler images and videos were collected at the proximal carpal tunnel to quantify: (1) median nerve cross-sectional area, (2) intraneural blood flow velocity in 3 wrist postures (neutral (0°), flexion (15°), extension (30°)), and (3) flexor digitorum superficialis and SSCT displacement. Results demonstrate that intraneural blood flow velocity is dependent on median nerve function and wrist posture such that patients with mild CTS are more susceptible to the effects of non-neutral wrist postures. Tendon-SSCT mechanics do not appear to differ based on severity. This study stresses the importance of limiting exposure to non-neutral wrist postures in patients with early signs of the condition.

Development of a method to maximize the transcutaneous electrical nerve stimulation intensity in women with fibromyalgia

Introduction

Transcutaneous electrical nerve stimulation (TENS) is a non-pharmacological intervention clinically used for pain relief. The importance of utilizing the adequate stimulation intensity is well documented; however, clinical methods to achieve the highest possible intensity are not established.

Objectives

Our primary aim was to determine if exposure to the full range of clinical levels of stimulation, from sensory threshold to noxious, would result in higher final stimulation intensities. A secondary aim explored the association of pain, disease severity, and psychological variables with the ability to achieve higher final stimulation intensity.

Methods

Women with fibromyalgia (N=143) were recruited for a dual-site randomized controlled trial - Fibromyalgia Activity Study with TENS (FAST). TENS electrodes and stimulation were applied to the lumbar area, and intensity was increased to sensory threshold (ST), then to "strong but comfortable" (SC1), then to "noxious" (N). This was followed by a reduction to the final stimulation intensity of "strong but comfortable" (SC2). We called this the Setting of Intensity of TENS (SIT) test.

Results

There was a significant increase from SC1 (37.5 mA IQR: 35.6-39.0) to SC2 (39.2 mA IQR: 37.1-45.3) (p<0.0001) with a mean increase of 1.7 mA (95% CI: 1.5, 2.2). Linear regression analysis showed that those with the largest increase between SC1 and N had the largest increase in SC2-SC1. Further, those with older age and higher anxiety were able to achieve greater increases in intensity (SC2-SC1) using the SIT test.

Conclusion

The SC2-SC1 increase was significantly associated with age and anxiety, with greater mean increases associated with older age and higher anxiety. Thus, although all patients may benefit from this protocol, older women and women with elevated anxiety receive the greatest benefit.

Effectiveness of Transcutaneous Electrical Nerve Stimulation Energy in Older Adults: A Pilot Clinical Trial

OBJECTIVE

To evaluate the effectiveness of a transcutaneous electric nerve stimulation (TENS) device typically used for pain suppression (analgesia) during pressure injury (PI) healing, peripheral vascularization, and secondary pain in older adults with chronic PIs and cognitive impairment.

DESIGN AND SETTING

This pilot clinical trial followed patients from 6 nursing homes.

PATIENTS AND INTERVENTION

Twenty-two patients with PIs in the distal third of their lower limbs (7 men, 15 women) were included in this study. The control group completed standard wound care (SWC), whereas the experimental group received SWC and TENS. A total of 20 sessions were conducted for each group over 2 months, 3 times a week.

MAIN OUTCOME MEASURE

PI area, PI healing rate, blood flow, skin temperature, oxygen saturation, and level of pain at baseline and posttreatment.

MAIN RESULTS

Significant improvements were achieved in PI area (mean difference, 0.92; 95% confidence interval [CI], 0.15-1.67; P =.024), healing rate (3; 95% CI, 1-4.99; P =.009), skin temperature (1.82; 95% CI, 0.35-3.28; P =.021), and pain (1.44; 95% CI, 0.49-2.39; P =.008) in the experimental group, whereas none of the variables revealed a significant change in the control group.

CONCLUSIONS

The effect of local and spinal TENS combined with the SWC for PI produced a significant improvement in size, healing, skin temperature, and pain levels.

Unilateral repetitive tibial nerve stimulation improves neurogenic claudication and bilateral F-wave conduction in central lumbar spinal stenosis

BACKGROUND

Repetitive electrical nerve stimulation of the lower limb may improve neurogenic claudication in patients with lumbar spinal stenosis (LSS) as originally described by Tamaki et al. We tested if this neuromodulation technique affects the F-wave conduction on both sides to explore the underlying physiologic mechanisms.

METHODS

We studied a total of 26 LSS patients, assigning 16 to a study group receiving repetitive tibial nerve stimulation at the ankle (RTNS) on one leg, and 10 to a group without RTNS. RTNS conditioning consisted of a 0.3-ms duration square-wave pulse with an intensity 20% above the motor threshold, delivered at a rate of 5 Hz for 5 min. All patients underwent the walking test and the F-wave and M-wave studies for the tibial nerve on both sides twice; once as the baseline, and once after either the 5-min RTNS or 5-min rest.

RESULTS

Compared to the baselines, a 5-min RTNS increased claudication distance (176 ± 96 m vs 329 ± 133 m; p = 0.0004) and slightly but significantly shortened F-wave minimal onset latency (i.e., increased F-wave conduction velocity) not only on the side receiving RTNS (50.7 ± 4.0 ms vs 49.2 ± 4.2 ms; p = 0.00081) but also on the contralateral side (50.1 ± 4.6 ms vs 47.9 ± 4.2 ms; p = 0.011). A 5-min rest in the group not receiving RTNS neither had a significant change on claudication distance nor on any F-wave measurements. The M response remained unchanged in both groups.

CONCLUSIONS

The present study verified a beneficial effect of unilaterally applied RTNS of a mild intensity on neurogenic claudication and bilateral F-wave conduction. Our F-wave data suggest that this type of neuromodulation could be best explained by an RTNS-induced widespread sympathetic tone reduction with vasodilation, which partially counters a walking-induced further decline in nerve blood flow in LSS patients who already have ischemic cauda equina.

Central Sensitization-Based Classification for Temporomandibular Disorders: A Pathogenetic Hypothesis

Dysregulation of Autonomic Nervous System (ANS) and central pain pathways in temporomandibular disorders (TMD) is a growing evidence. Authors include some forms of TMD among central sensitization syndromes (CSS), a group of pathologies characterized by central morphofunctional alterations. Central Sensitization Inventory (CSI) is useful for clinical diagnosis. Clinical examination and CSI cannot identify the central site(s) affected in these diseases. Ultralow frequency transcutaneous electrical nerve stimulation (ULFTENS) is extensively used in TMD and in dental clinical practice, because of its effects on descending pain modulation pathways. The Diagnostic Criteria for TMD (DC/TMD) are the most accurate tool for diagnosis and classification of TMD. However, it includes CSI to investigate central aspects of TMD. Preliminary data on sensory ULFTENS show it is a reliable tool for the study of central and autonomic pathways in TMD. An alternative classification based on the presence of Central Sensitization and on individual response to sensory ULFTENS is proposed. TMD may be classified into 4 groups: (a) TMD with Central Sensitization ULFTENS Responders; (b) TMD with Central Sensitization ULFTENS Nonresponders; (c) TMD without Central Sensitization ULFTENS Responders; (d) TMD without Central Sensitization ULFTENS Nonresponders. This pathogenic classification of TMD may help to differentiate therapy and aetiology.

Effect of Electrical Stimulation on Blood Flow Velocity and Vessel Size

Interferential current electrical stimulation alters blood flow velocity and vessel size. We aimed to investigate the changes in the autonomic nervous system depending on electrical stimulation parameters. Forty-five healthy adult male and female subjects were studied. Bipolar adhesive pad electrodes were used to stimulate the autonomic nervous system at the thoracic vertebrae 1-4 levels for 20 min. Using Doppler ultrasonography, blood flow was measured to determine velocity and vessel size before, immediately after, and 30 min after electrical stimulation. Changes in blood flow velocity were significantly different immediately and 30 min after stimulation. The interaction between intervention periods and groups was significantly different between the exercise and pain stimulation groups immediately after stimulation (p<0.05). The vessel size was significantly different before and 30 min after stimulation (p<0.05). Imbalances in the sympathetic nervous system, which regulates balance throughout the body, may present with various symptoms. Therefore, in the clinical practice, the parameters of electrical stimulation should be selectively applied in accordance with various conditions and changes in form.

Sensory trigeminal ULF-TENS stimulation reduces HRV response to experimentally induced arithmetic stress: A randomized clinical trial

Ultra Low Frequency Transcutaneous Electric Nervous Stimulation (ULF-TENS) is extensively used for pain relief and for the diagnosis and treatment of temporomandibular disorders (TMD). In addition to its local effects, ULF-TENS acts on the autonomic nervous system (ANS), with particular reference to the periaqueductal gray (PAG), promoting the release of endogenous opioids and modulating descending pain systems. It has been suggested that the PAG participates in the coupling between the emotional stimulus and the appropriate behavioral autonomic response. This function is successfully investigated by HRV. Therefore, our goal is to investigate the effects of trigeminal ULF-TENS stimulation on autonomic behavior in terms of HRV and respiratory parameters during an experimentally-induced arithmetic stress test in healthy subjects. Thirty healthy women between 25 and 35years of age were enrolled and randomly assigned to either the control (TENS stimulation off) or test group (TENS stimulation on). Heart (HR, LF, HF, LF/HF ratio, DET, RMSSD, PNN50, RR) and respiratory (BR) rate were evaluated under basal, T1 (TENS off/on), and stress (mathematical task) conditions. Results showed that HRV parameters and BR significantly changed during the arithmetic stress paradigm (p<0.01). Independently of stress conditions, TENS and control group could be discriminated only by non-linear HRV data, namely RR and DET (p=0.038 and p=0.027, respectively). During the arithmetic task, LF/HF ratio was the most sensitive parameter to discriminate between groups (p=0.019). Our data suggest that trigeminal sensory ULF-TENS reduces the autonomic response in terms of HRV and BR during acute mental stress in healthy subjects. Future directions of our work aim at applying the HRV and BR analysis, with and without TENS stimulation, to individuals with dysfunctional ANS among those with TMD.

Fibrinolytic effects of peroneal nerve stimulation in patients with lower limb vascular disease

Patients with lower limb vascular disease are at an increased risk of thrombotic events. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) are important components of the fibrinolytic system, responsible for clot lysis. This study aimed to establish whether peroneal nerve stimulation (PNS) could promote fibrinolysis within a cohort of vascular patients. Ethical approval was obtained for this prospective case-controlled study. Patients were randomly assigned to active stimulation or control groups. Arterial flow measurements and venous blood samples were taken bilaterally at baseline and following 45 min of PNS. ELISA analysis for plasma t-PA and PAI-1 was performed utilizing commercially available kits. Statistical analysis evaluated the changes in t-PA and PAI-1 levels from baseline for the active (device active), passive (contralateral limb) and control limbs (inactive device applied).Seventy-seven participants were recruited: 30 claudicants (25 active and five controls), 25 patients postoperative infra-inguinal bypass grafts (19 active and six controls) and 22 patients with varicose veins (17 active and five controls). t-PA levels reduced significantly in all groups; however, intergroup analysis demonstrated no statistically significant difference when comparing the active, passive and control limbs (P = 0.079). PAI-1 levels decreased by 16.2% (34.0 ng/ml, SD 52.2) in the active limbs but only 3.6% (11.4 ng/ml, SD 47.4) and 2.6% (2.7 ng/ml, SD 21.3) in the passive and control limbs, respectively (intergroup analysis P < 0.001). No relationship between changes in flow and plasma of t-PA and PAI-1 were demonstrated. Peroneal nerve stimulation may augment fibrinolysis by decreasing plasma levels of PAI-1 levels in patients with lower limb arterial and venous disease.

Hemodynamic Effects Induced by Transcutaneous Electrical Nerve Stimulation in Apparently Healthy Individuals: A Systematic Review With Meta-Analysis

OBJECTIVE

To determine the immediate effects of transcutaneous electrical nerve stimulation (TENS) on heart rate, systolic blood pressure (SBP), and diastolic blood pressure (DBP) in apparently healthy adults (age ≥18y).

DATA SOURCES

The Cochrane Library (online version 2014), PubMed (1962-2014), EMBASE (1980-2014), and LILACS (1980-2014) electronic databases were searched.

STUDY SELECTION

Randomized controlled trials were included when TENS was administered noninvasively with surface electrodes during rest, and the effect of TENS was compared with that of control or placebo TENS. A sensitive search strategy for identifying randomized controlled trials was used by 2 independent reviewers. The initial search led to the identification of 432 studies, of which 5 articles met the eligibility criteria.

DATA EXTRACTION

Two independent reviewers extracted data from the selected studies. Quality was evaluated using the PEDro scale. Mean differences or standardized mean differences in outcomes were calculated.

DATA SYNTHESIS

Five eligible articles involved a total of 142 apparently healthy individuals. Four studies used high-frequency TENS and 3 used low-frequency TENS and evaluated the effect on SBP. Three studies using high-frequency TENS and 2 using low-frequency TENS evaluated the effect on DBP. Three studies using high-frequency TENS and 1 study using low-frequency TENS evaluated the effect on heart rate. A statistically significant reduction in SBP (-3.00mmHg; 95% confidence interval [CI], -5.02 to -0.98; P=.004) was found using low-frequency TENS. A statistically significant reduction in DBP (-1.04mmHg; 95% CI, -2.77 to -0.03; I(2)=61%; P=.04) and in heart rate (-2.55beats/min; 95% CI, -4.31 to -0.78; I(2)=86%; P=.005]) was found using both frequencies. The median value on the PEDro scale was 7 (range, 4-8).

CONCLUSIONS

TENS seems to promote a discrete reduction in SBP, DBP, and heart rate in apparently healthy individuals.

Using TENS for pain control: the state of the evidence

Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacological intervention that activates a complex neuronal network to reduce pain by activating descending inhibitory systems in the central nervous system to reduce hyperalgesia. The evidence for TENS efficacy is conflicting and requires not only description but also critique. Population-specific systemic reviews and meta-analyses are emerging, indicating both HF and LF TENS being shown to provide analgesia, specifically when applied at a strong, nonpainful intensity. The purpose of this article is to provide a critical review of the latest basic science and clinical evidence for TENS. Additional research is necessary to determine if TENS has effects specific to mechanical stimuli and/or beyond reduction of pain and will improve activity levels, function and quality of life.

Electrical Stimulation and Cutaneous Wound Healing: A Review of Clinical Evidence

Electrical stimulation (ES) has been shown to have beneficial effects in wound healing. It is important to assess the effects of ES on cutaneous wound healing in order to ensure optimization for clinical practice. Several different applications as well as modalities of ES have been described, including direct current (DC), alternating current (AC), high-voltage pulsed current (HVPC), low-intensity direct current (LIDC) and electrobiofeedback ES. However, no one method has been advocated as the most optimal for the treatment of cutaneous wound healing. Therefore, this review aims to examine the level of evidence (LOE) for the application of different types of ES to enhance cutaneous wound healing in the skin. An extensive search was conducted to identify relevant clinical studies utilising ES for cutaneous wound healing since 1980 using PubMed, Medline and EMBASE. A total of 48 studies were evaluated and assigned LOE. All types of ES demonstrated positive effects on cutaneous wound healing in the majority of studies. However, the reported studies demonstrate contrasting differences in the parameters and types of ES application, leading to an inability to generate sufficient evidence to support any one standard therapeutic approach. Despite variations in the type of current, duration, and dosing of ES, the majority of studies showed a significant improvement in wound area reduction or accelerated wound healing compared to the standard of care or sham therapy as well as improved local perfusion. The limited number of LOE-1 trials for investigating the effects of ES in wound healing make critical evaluation and assessment somewhat difficult. Further, better-designed clinical trials are needed to improve our understanding of the optimal dosing, timing and type of ES to be used.

Different recovery methods and muscle performance after exhausting exercise: comparison of the effects of electrical muscle stimulation and massage

In this study we assessed the influence of the three different recovery interventions massage (MSG), electrical muscle stimulation (EMS), and passive rest (PR) on lactate disappearance and muscle recovery after exhausting exercise bouts. Twelve healthy male sport students participated in the study. They attended the laboratory on five test days. After measurement of V.O₂max and a baseline Wingate test (WG_b), the three recovery interventions were tested in random counterbalanced order. High intensity exercise, which consisted of six exhausting exercise bouts (interspersed with active recovery), was followed by MSG, EMS or PR application (24 minutes); then the final Wingate test (WG_f) was performed. Lactate, heart rate, peak and mean power, rating of perceived exertion (RPE), and total quality of recovery (TQR) were recorded. In WG_f mean power was significantly higher than in WG_b for all three recovery modalities (MSG 6.29%, EMS 5.33%, PR 4.84% increase, p < 0.05), but no significant differences in mean and peak power were observed between the three recovery modes (p > 0.05). The heart rate response and the changes in blood lactate concentration were identical in all three interventions during the entire protocol (p = 0.817, p = 0.493, respectively). RPE and TQR scores were also not different among the three interventions (p > 0.05). These results provide further evidence that MSG and EMS are not more effective than PR in the process of recovery from high intensity exercise.

The effects of transcutaneous electrical nerve stimulation on tissue repair: A literature review

Background

Transcutaneous electrical nerve stimulation (TENS) consists of a generic application of low-frequency, pulsed electrical currents transmitted by electrodes through the skin surface. It is a therapeutic modality that is nonpharmacological, noninvasive, inexpensive, easy to use and widely applied in clinical practice.

Objective

To narratively review the scientific evidence of the effects of TENS on tissue repair with respect to wound healing, skin flap viability and tendinous repair.

Methods

The study was conducted using the MEDLINE, Lilacs and Scielo databases, without limit to the period of publication, and was completed in November 2011. Inclusion criteria were randomized or nonrandomized, controlled or noncontrolled clinical trials, and experimental trials involving rats subjected to TENS for tissue repair.

Results

Thirty articles on tissue repair were found and, among these, 14 reported on wound healing, 14 reported on skin flaps and two analyzed tedinous repair.

Discussion

It was suggested that TENS stimulates skin wound healing and tendon repair, as well as the viability of random skin flaps. Such effects may be due to the release of substance P and calcitonin gene-related peptide, which would increase blood flow and, consequently, hasten the events leading to tissue repair.

Conclusions

Based on the scientific evidence regarding the effects of TENS on tissue repair, the findings of the present literature review were inconclusive because data from the randomized controlled clinical trials were insufficient to confirm such effects.

Provocation tests in doppler ultrasonography for carpal tunnel syndrome

INTRODUCTION

Doppler ultrasonography (DU) has recently been shown to be useful in imaging carpal tunnel syndrome (CTS). In this study, we aim to characterize the changes seen after exercise and electrical stimulation.

METHODS

Five patients with CTS were recruited with 5 age-matched subjects. DU was used to visualize the median nerve, flexor tendon, and bone at base line and after 1 minute of: (a) median nerve motor stimulation, (b) median nerve sensory stimulation, (c) abductor pollicis brevis contraction, and (d) adductor digiti minimi contraction.

RESULTS

Blood flow in the median nerve was greater after APB exercise. Furthermore, blood flow in the median nerve was greater in cases than controls after APB exercise. At baseline, blood flow in the flexor tendon was greater in cases than controls.

CONCLUSIONS

While limited by sample size, this study demonstrates that exercise of median innervated muscles may be useful in enhancing diagnostic utility of DU for CTS.

Short-term and long-term effects of electrical stimulation on skin properties

BACKGROUND

Electrical stimulation (ES) has been used in treating different medical conditions; however, not much is known about the effect of this application on skin properties. The purpose of this study was to investigate the short-term and long-term effects of ES on biophysical properties of the skin.

METHODS

A pretest-posttest control design was used in the study. Thirteen men (N = 13, age (M ± SD), 19 ± 5.6 years) were free of skin abnormality on the volar aspect of both forearms. Four areas were allocated and marked with a layout template of two circles 2 cm in diameter and 2 cm apart. Areas 1 and 2 were allocated on the experimental forearm and area 3 and 4 on the control forearm. ES was applied for 15 minutes with two rubber electrodes 8 cm apart surrounding areas 1 and 2 on the experimental forearm three times a week for 2 weeks. Skin properties including transepidermal water loss (TEWL), melanin content, erythema, elasticity and pH were measured pre-ES, during ES and post-ES, and after 2 weeks of applying ES to find out the short-term and long-term effects on skin.

RESULTS

The TEWL was increased during ES at 7, 15 and 15-minutes post-ES compared with the baseline (p < 0.01) and to the control forearm (p = 0.04) measurements, and no increase have been noticed of TEWL on the control forearm (p = 0.11). Also, we found no difference in the other skin properties (p > 0.05) on both forearms, and there were no long-term effects (p > 0.05) in any tested variable.

CONCLUSION

Electrical stimulation caused temporary increase in TEWL with no effects on other skin properties.

Age-related changes in the somatosensory processing of tactile stimulation--an fMRI study

Age-related changes in brain function are complex. Although ageing is associated with a reduction in cerebral blood flow and neuronal activity, task-related processing is often correlated with an enlargement of the corresponding and additionally recruited brain areas. This supplemental employment is considered an attempt to compensate for deficits in the ageing brain. Although there are contradictory reports regarding the role of the primary somatosensory cortex (SI), currently, there is little knowledge about age-related functional changes in other brain areas in the somatosensory network (secondary somatosensory cortex (SII), and insular, anterior (ACC) and posterior cingulate cortices (PCC)). We investigated 16 elderly (age range, 62-71 years) and 18 young subjects (age range, 21-28 years) by determining the current perception threshold (CPT) and applying functional magnetic resonance imaging (fMRI) using a 3.0 Tesla scanner under tactile stimulation of the right hand. CPT was positively correlated with age. fMRI analysis revealed significantly increased activation in the contralateral SI and ipsilateral motor cortex in elderly subjects. Furthermore, we demonstrated age-related reductions in the activity in the SII, ACC, PCC, and dorsal parts of the corpus callosum. Our study revealed dramatic age-related differences in the processing of a simple tactile stimulus in the somatosensory network. Specifically, we detected enhanced activation in the contralateral SI and ipsilateral motor cortex assumingly caused by deficient inhibition and decreased activation in later stages of somatosensory processing (SII, cingulate cortex) in elderly subjects. These results indicate that, in addition to over-activation to compensate for impaired brain functions, there are complex mechanisms of modified inhibition and excitability involved in somatosensory processing in the ageing brain.

Effects of physiotherapeutic TENS in a woman with unexplained infertility

Unexplained infertility (UI) is a difficult diagnosis in the field of obstetrics and gynaecology. This report describes TENS treatment as an adjunct therapy for a 30-year-old woman with long-standing UI who was scheduled to undergo ovarian stimulation for in vitro fertilization (IVF) and embryo transfer. She had three unsuccessful intrauterine insemination treatments. Her last IVF treatment also failed. The treatment consisted of burst-TENS for seven sessions, which was applied daily from the second day of induction of ovulation (IO) to hCG administration. The transvaginal ultrasonography with pulsed Doppler curves was performed to measure the uterine artery impedance indices of Pulsatility Index (PI) and Resistance Index (RI). Before TENS application, on the first day of IO, the PI and RI for right side uterine artery were 3.96 and 0.96, respectively. For left uterine artery, the PI and RI were 6.92 and 1, respectively. After treatment with TENS, on the day of hCG administration, the PI and RI for right side uterine artery were 3.39 and 0.90, respectively. On the left side, they were PI=2.62 and RI=0.86. IVF was performed and on the day of oocytes collection, 22 oocytes were collected and inseminated. Fertilization was confirmed 16 hours after insemination by visualization of 2 pronuclei. A singleton pregnancy was achieved by the presence of a fetal sac during an ultrasound examination. It is concluded that the addition of TENS resulted in remarkable reduction of uterine artery PI and RI and a successful pregnancy after IVF for this woman with UI.

Transcutaneous electrical nerve stimulation induces vasodilation in healthy controls but not in refractory angina patients

CONTEXT

Transcutaneous electrical nerve stimulation (TENS) is an effective treatment option to relieve ischemic pain in refractory angina pectoris (RAP). In healthy persons, TENS enhances local blood flow, but the mechanism responsible for the anti-ischemic effect in RAP seems to be different.

OBJECTIVE

The aim of the present investigation was to compare the difference in blood flow and vasodilatory response to TENS between angina patients and healthy controls and evaluate how vascular response in these groups is affected by amperage dosage above and below motor threshold levels.

METHODS

Our study evaluated upper limb vascular responses to low- and high-dose TENS (below and above motor threshold) in RAP patients compared with healthy controls. TENS was applied on the nondominating forearm. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Forearm vascular resistance (FVR) was determined (mean arterial pressure [MAP]/FBF). Measurements were done during baseline, low-dose TENS, high-dose TENS, and during recovery.

RESULTS

A significant dose-dependent increase in FBF in response to TENS stimulation was seen in controls (n=18) but not in RAP (n=23) (P=0.008). There was no significant difference in FVR ratio (FVR(stim)/FVR(ctrl)) between control (n=7) and RAP (n=23) groups at low dose (controls, 5.7+/-21%; RAP, 9.7+/-20%) or recovery (controls, -4.6+19%; RAP, 5.9+25%). High-dose TENS resulted in a significantly reduced FVR ratio (-16.8+/-11%) in controls (n=7) compared with RAP (1.6+/-32%, n=23) (P=0.02).

CONCLUSION

High-dose TENS induces forearm vasodilation in healthy subjects but not in patients with RAP. These findings suggest that TENS has different vascular effects in patients with severe coronary artery disease compared with healthy controls.

Blood flow changes in the trapezius muscle and overlying skin following transcutaneous electrical nerve stimulation

BACKGROUND AND PURPOSE

Various researchers have studied the effects of transcutaneous electrical nerve stimulation (TENS) on hemodynamics. The purpose of this study was to examine the effects of TENS on local blood flow in the trapezius muscle and overlying skin.

SUBJECTS

Thirty-three women who were healthy, aged 25 to 55 years, were randomly assigned to receive 1 of 3 different modes of TENS.

METHODS

Skin and muscle blood flow were monitored noninvasively using a new application of photoplethysmography for 15 minutes of TENS applied at high frequency (80 Hz) and sensory-level intensity and at low frequency (2 Hz) and motor-level intensity and for 15 minutes after stimulation. Subliminal 80-Hz TENS was used as a control. Blood flow was monitored simultaneously on stimulated and nonstimulated shoulders.

RESULTS

Blood flow in the trapezius muscle, but not skin blood flow, increased significantly with motor-level 2-Hz TENS, whereas no increase occurred with sensory-level 80-Hz TENS or subliminal 80-Hz TENS.

DISCUSSION AND CONCLUSION

Muscle contractions induced by motor-level 2-Hz TENS appear to be a prerequisite for increasing blood flow in the trapezius muscle. However, high stimulation intensity may prevent increased blood flow in the overlying skin.

The effect of transcutaneous electrical nerve stimulation on local and distal cutaneous blood flow following a prolonged heat stimulus in healthy subjects

The aim of this study was to investigate the effects of transcutaneous electrical nerve stimulation (TENS) on blood flow and skin temperature following an elevation of baseline blood flow using infrared preheating. A randomized controlled approach was used whereby 66 healthy human subjects (33 male, 33 female) were allocated to one of three intervention groups (n=22 per group, equal male and female): Control, Low frequency TENS (4 Hz/200 micros), or High frequency TENS (110 Hz/200 micros). TENS was applied just below motor threshold over the median nerve of the right forearm for 15 min immediately following an infrared preheating. Cutaneous blood flow and skin temperature were recorded at 3-min intervals from the forearm and fingertips during TENS and for 15 min following TENS. Analysis of data revealed no significant differences between High and Low frequency TENS for cutaneous blood flow or skin temperature at the forearm. A small and short lived increase in cutaneous blood flow at the index finger was observed on TENS groups compared with control when TENS was switched off. TENS reduced skin temperature when compared to control during the first 9 min of the 15-min stimulation period at the middle finger but not at the index finger. It was concluded that the effects of high and low frequency TENS when applied below motor threshold produced changes in blood flow and skin temperature that were transient and small.

Effect of defocused CO2 laser on equine tissue perfusion

Treatment with defocused CO₂ laser can have a therapeutic effect on equine injuries, but the mechanisms involved are unclear. A recent study has shown that laser causes an increase in equine superficial tissue temperature, which may result in an increase in blood perfusion and a stimulating effect on tissue regeneration. However, no studies have described the effects on equine tissue perfusion. The aim of the present study was to investigate the effect of defocused CO₂ laser on blood perfusion and to correlate it with temperature in skin and underlying muscle in anaesthetized horses. Differences between clipped and unclipped haircoat were also assessed. Eight horses and two controls received CO₂ laser treatment (91 J/cm²) in a randomised order, on a clipped and unclipped area of the hamstring muscles, respectively. The significant increase in clipped skin perfusion and temperature was on average 146.3 ± 33.4 perfusion units (334%) and 5.5 ± 1.5°C, respectively. The significant increase in perfusion and temperature in unclipped skin were 80.6 ± 20.4 perfusion units (264%) and 4.8 ± 1.4°C. No significant changes were seen in muscle perfusion or temperature. In conclusion, treatment with defocused CO₂ laser causes a significant increase in skin perfusion, which is correlated to an increase in skin temperature.

Effect of high frequency transcutaneous electrical nerve stimulation on viability of random skin flap in rats

PURPOSE

To determine the effect of high frequency Transcutaneous Electrical Nerve Stimulation (TENS) on viability of random skin flap in rats.

METHODS

The sample of this study was 75 Wistar rats. The skin flap measured 10 x 4 cm and a plastic barrier was interposed between the flap and donor site. After the operative procedure, animals of all groups were maintained anesthetized one more hour with electrodes positioned in the base of the flap and submitted to treatment according of their respective group. This procedure was repeated on the two subsequent days. G1: sham stimulation (control), G2: TENS (f = 80 Hz and I = 5 mA), G3: TENS (f = 80 Hz and I = 10 mA), G4: TENS (f = 80 Hz and I = 15 mA), G5: TENS (f = 80 Hz and I = 20 mA).

RESULTS

The average percentage of necrotic area was 43,11, 34,65, 49,44, 23,52, 45,10 in groups 1, 2, 3, 4 and 5 respectively.

CONCLUSION

The amplitude of 15 mA presented a lower necrotic area than control group and Transcutaneous Electrical Nerve Stimulation was efficient in increasing the random skin flap viability.

Agents physiques antalgiques

Analgesic electrotherapy is now based on more consistent scientific data; the biological action of the electric current, of the electromagnetic radiations and of the mechanical vibrations is better approached. But the randomized control trials still provide contradictory results concerning the analgesic efficiency of the cryotherapy, the TENS, the pulsed electro-magnetic fields, the ultrasound and laser therapy, the shock waves; iontophoresis, short waves, microwaves, infrasound vibrations are very few investigated. The analgesic electrotherapy cannot be recommended nor prohibited; physical agents represent only therapeutic options. On the basis of the scientific data and of their personal experience, the therapists can use them. More controlled clinical investigations of higher methodological levels are still required.