Effect of Electrical Stimulation on Blood Flow Velocity and Vessel Size

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.

The Impact on the Stress-Associated Autonomic Response of Physiotherapy Students Receiving Interferential Current in an Electrotherapy Training Session

Electrical currents are didactic contents widely applied in the training of physiotherapy students, but the treatment is considered a stressful situation for both the patient who receives it and the student who applies it. The aim of this study was to evaluate the stress-associated autonomic response of physiotherapy students receiving interferential current by measuring and analysing heart rate variability. An observational case-control study was conducted. Ninety healthy male volunteers, all physiotherapy degree students, were enrolled while attending laboratory practice during the 2020-2021 academic year. Participants were randomly allocated to a sham electrotherapy group (44 subjects), in which heart rate variability was recorded for 10 min, both at rest and during the application of sham technique on the lower back (10 min), and an electrotherapy group (46 subjects), applying the same procedure with the electrical current flowing. Outcome measures included baseline (seated position) and postintervention (prone position) time domain parameter, diameters of the Poincaré plot 1 and 2, stress score, and sympathetic/parasympathetic ratio. The sham electrotherapy group exhibited significant increases in time domain parameter (p = 0.027) and diameters of the Poincaré plot 1 (p = 0.032), with a small effect size (d ≤ 0.5). The electrotherapy group exhibited significant increases in time domain parameter and diameters of the Poincaré plot 1 and 2 (p < 0.001) and decreases in the stress score and sympathetic/parasympathetic ratio (p < 0.001), with a large effect size (d > 0.8) other than for the time domain parameter (d = 0.42), indicating increased parasympathetic and decreased sympathetic activity. After interventions, there were significant differences between groups in diameters of the Poincaré plot 2 (p < 0.001), stress score (p = 0.01) and sympathetic/parasympathetic ratio (p = 0.003), with moderate effect size (d > 0.5). The application of the interferential current technique produces stress-associated autonomic response characterized by greater parasympathetic activity and decreased sympathetic activity. Further studies are needed to determine possible adverse effects.

Temporal effects of two interferential current applications on peripheral circulation in children with hemiplegic cerebral palsy

Objectives

To determine the short-term effects of sympathetic and peripheral stimulation of interferential current (IFC) on blood flow (BF) in children with hemiplegic cerebral palsy (CP).

Methods

Thirty children with hemiplegic CP, ranging from 8 to 12 years old, were randomly divided into three groups (10 children/group). The first group received sympathetic stimulation of IFC, the second group received peripheral stimulation of IFC, and the third group (control) received placebo peripheral stimulation of IFC. A frequency of 80–100 Hz at an intensity of 10–20 mA was applied for 20 min. Blood volume pulse (BVP) amplitude was measured before IFC application using a plethysmography sensor at the big toe immediately after and 15 min poststimulation. The data were statistically analyzed and compared.

Results

There were statistically significant differences in BVP amplitude among the three time intervals in both the sympathetic and peripheral groups (P < 0.05) with no difference in the control group (P = 0.995). There was a significant increase in BVP amplitude immediately after stimulation compared with before stimulation in both the sympathetic and peripheral groups (P = 0.0001). However, differences between the sympathetic and peripheral groups at the three measured periods were statistically nonsignificant (P > 0.05).

Conclusion

Both IFC applications had a proper effect on improving BF in children with hemiplegic CP with no difference in efficacy between sympathetic and peripheral stimulation.

Mechanisms of electrical stimulation in eye diseases: A narrative review

Background

In the last two decades, electrical stimulation (ES) has been tested in patients with various eye diseases and shows great treatment potential in retinitis pigmentosa and optic neuropathy. However, the clinical application of ES in ophthalmology is currently limited. On the one hand, optimization and standardization of ES protocols is still an unmet need. On the other hand, poor understanding of the underlying mechanisms has hindered clinical exploitation.

Main Text

Numerous experimental studies have been conducted to identify the treatment potential of ES in eye diseases and to explore the related cellular and molecular mechanisms. In this review, we summarized the in vitro and in vivo evidence related to cellular and tissue response to ES in eye diseases. We highlighted several pathways that may be utilized by ES to impose its effects on the diseased retina.

Conclusions

Therapeutic effect of ES in retinal degenerative diseases might through preventing neuronal apoptosis, promoting neuronal regeneration, increasing neurotrophic factors production in Müller cells, inhibiting microglial activation, enhancing retinal blood flow, and modulating brain plasticity. Future studies are suggested to analyse changes in specific retinal cells for optimizing the treatment parameters and choosing the best fit ES delivery method in target diseases.

Piezoelectric Hydrogel for Prophylaxis and Early Treatment of Pressure Injuries/Pressure Ulcers

Pressure injuries/pressure ulcers (PIs/PUs) are a critical global healthcare issue and represent a considerable burden on healthcare resources. Prevention of PIs/PUs is the least costly approach and minimizes the patient suffering compared with treatment. Besides, sustained tissue load alleviation and microenvironment management are the most crucial properties for dressings in PI/PU prevention. Hydrogel dressings have attracted a lot of attention to prevent PIs/PUs because of their unique mechanical properties and ability to manage the microenvironment of skin. However, auxiliary prophylaxis and early treatment of PIs/PUs remain a challenge and an acute clinical demand. Here, we report on an electroactive hydrogel with large stretchability (∼380%) and skinlike ductility, and Young's modulus (0.48 ± 0.03 MPa) matches that of human skin (0.5-1.95 MPa). The hydrogel displayed piezoelectric properties and mechanical-electric response stability and sensitivity. Our results indicated that the hydrogel was able to promote in vitro angiogenesis under piezoelectric stimulation and exhibited biocompatibility, which has the potential for forming fine vessels at the damaged sites of PIs/PUs. Furthermore, finite element analysis and pressure dispersion experiments demonstrated that the hydrogel was suitable for preventing PIs/PUs by redistributing force, reducing tissue distortion, and maintaining the microenvironment for skin. This work offers a new strategy for designing and evaluating the dressing for prophylaxis and the early treatment of PIs/PUs.

Analgesic Effects of Interferential Current Therapy: A Narrative Review

Background and Objectives: Transcutaneous electrical stimulation of low- and medium-frequency currents is commonly used in pain management. Interferential current (IFC) therapy, a medium frequency alternating current therapy that reportedly reduces skin impedance, can reach deeper tissues. IFC therapy can provide several different treatment possibilities by adjusting its parameters (carrier frequency, amplitudemodulated frequency, sweep frequency, sweep mode or swing pattern, type of application (bipolar or quadripolar), time of application and intensity). The objective of this review article is to discuss the literature findings on the analgesic efficacy of IFC therapy. Conclusions: According to the literature, IFC therapy shows significant analgesic effects in patients with neck pain, low back pain, knee osteoarthritis and post-operative knee pain. Most of the IFC parameters seem not to influence its analgesic effects. We encourage further studies to investigate the mechanism of action of IFC therapy.

Effect of Physiotherapy Treatment in the Autonomic Activation and Pain Perception in Male Patients with Non-Specific Subacute Low Back Pain

Introduction: Physiotherapy treatment is a common intervention for low back pain (LBP) patients. These interventions have been related to physiological effects in the central nervous system. Thus, the aim of this study was to analyze the effect of physiotherapy treatment in patients with LBP in the autonomic nervous system activation and subjective pain perception of patients. Methods: A total of 30 male subjects diagnosed with non-specific subacute LBP received a 50 min session consisting of (a) a manual therapy based on joint mobilization and soft tissues techniques in the lumbo-pelvic area, (b) a stretching program, and (c) motor control exercises of the core muscles. The autonomic modification of participants was assessed prior to and after the physiotherapy treatment. Results: Heart rate variability (HRV) analysis reported a significant increase in average RR (p = 0.001), RMSSD (p = 0.008), LRMSSD (p = 0.001), SDNN (p = 0.005), and PNN50 (p = 0.024) after the session. Frequency-domain measures showed a significant increase in LF (p = 0.030) and HF (p = 0.014), and a decrease in LF/HF ratio (p = 0.046). A significant decrease was found in minimum HR values (p = 0.001) and average HR (p = 0.001). Moreover, maximal HR decreased its value from 116.7 ± 26.1 to 113.7 ± 40.8 after intervention. In addition, subjective pain perception (VAS scores) was significantly lower (p = 0.001) in the post-session assessment. Conclusions: Physiotherapy treatment produced an increase in parasympathetic nervous system activation and a decrease in subjective pain perception in non-specific subacute LBP patients.

Heart Rate Variability Monitoring during Interferential Current Application in the Lower Back Area: A Cross-Sectional Study

Vasovagal reactions may occur occasionally during electrical stimulation using interferential current (IFC). The purpose of this study was to examine variations in autonomic activity during the application of IFC in asymptomatic participants by analysis of their heart rate variability (HRV). Seventy-three male volunteers were randomly assigned to a placebo group (n = 36; HRV was documented for 10 min, both at rest and during a placebo intervention) and an intervention group (n = 37; HRV was documented for 10 min in two conditions labelled as (1) rest and (2) application of IFC technique on the lumbar segment). The diameters of the Poincaré plot (SD1, SD2), stress score (SS), and the ratio between sympathetic and parasympathetic activity (S/PS) were measured. After interventions, differences amongst the placebo group and the IFC group were found in SD2 (p < 0.001), SS (p = 0.01) and S/PS ratio (p = 0.003). The IFC technique was associated with increased parasympathetic modulation, which could induce a vasovagal reaction. Monitorization of adverse reactions should be implemented during the application of IFC technique. HRV indicators might have a part in prevention of vasovagal reactions. Further studies in patients with lumbar pain are needed to explore possible differences in HRV responses due to the presence of chronic pain.

A eletroterapia pode aprimorar o efeito de exercícios cinesiofuncionais no tratamento da dor lombar inespecífica crônica?

RESUMO O presente estudo teve como objetivo comparar o efeito de um protocolo de exercícios cinesiofuncionais (ECF) isolados ou associados a corrente interferencial (CI) ou corrente aussie (CA), sobre a intensidade da dor, a mobilidade/flexibilidade, a funcionalidade e a qualidade de vida (QV) de indivíduos com dor lombar inespecífica crônica. Trata-se de um ensaio clínico não randomizado, em que foram selecionados 42 sujeitos aleatorizados em três grupos: GI (treinamentos cinesiofuncional; n=14), GII (treinamentos cinesiofuncional + CI; n=14) e GIII (treinamento cinesiofuncional + CA; n=14). Os indivíduos foram submetidos a dez sessões de tratamento ao longo de 5 semanas e foram avaliados pré e pós-intervenção, usando escala visual analógica de dor (EVA); avaliação da QV pelo questionário SF-36; avaliação da mobilidade/flexibilidade lombar pelo teste de Schober modificado e o teste de sentar e alcançar com o banco de Wells; avaliação da incapacidade funcional através do índice Oswestry; e, para os aspectos depressivos, inventário de depressão de Beck (IDB). Na reavaliação, percebeu-se que houve melhora significativa em todos os grupos experimentais na intensidade da dor (p<0,0001) e na mobilidade/flexibilidade. No SF-36, verificamos que apenas os indivíduos tratados com exercícios associados à corrente elétrica apresentaram melhora dos domínios capacidade física, aspectos físicos e dor. A avaliação do IDB não apresentou modificações pré e pós-intervenção. Conclui-se que a associação das técnicas terapêuticas apresentou maior benefício aos indivíduos da amostra, uma vez que produziu melhora sobre as variáveis avaliadas, como dor, mobilidade/flexibilidade e qualidade de vida.

Rol de los agentes físicos en la rehabilitación vocal: una revisión de la literatura

Los agentes físicos son elementos naturales o artificiales que se aplican para el tratamiento de determinados síntomas o patologías. En la rehabilitación vocal su estudio es un área emergente, donde las revisiones sistemáticas y los meta-análisis son escasos. Esto, muchas veces, dificulta la toma de decisiones y la correcta elección por parte del clínico.  El objetivo de este trabajo fue analizar el rol de los agentes físicos en la rehabilitación vocal. Se realizó una revisión de la literatura a través de la búsqueda de artículos en las bases de datos PubMed, EBSCOHost y Scielo. Se establecieron criterios de elegibilidad según tipo, año y características de los estudios. Se evaluaron 603 artículos, de los cuales, luego del análisis de su título, abstract y del cumplimiento de los criterios de elegibilidad, se seleccionaron 16. Se entregan resultados en base a la cantidad de participantes, nivel de evidencia, tipo y configuración del agente físico, procedimientos e instrumentos de evaluación y beneficios obtenidos. Los agentes físicos de mayor utilización en la clínica vocal son la electroterapia (TENS y NMES) y la laserterapia. En general, estos actúan como coadyuvantes en la terapia vocal. La TENS reduce el dolor, la tensión laríngea y la percepción de voz apretada durante la fonación. La NMES beneficia la activación neuromuscular de las cuerdas vocales y el uso de láser permite la recuperación de los tejidos laríngeos posterior a tareas de sobrecarga.

Extracellular and Intracellular Fluid Shifts on the Onset of Transcutaneous Auricular Vagus Nerve Stimulation

In this paper, we propose multifrequency body impedance measurement technique for monitoring the onset of vagus nerve stimulation. In response to transcutaneous electrical vagus stimulation, changes occur in body fluids i.e. fluid shifts in extracellular and intracellular media that can be assessed by Cole parameters R_e and R_i before and after stimulus, by measuring single side impedance spectroscopy (from 3 kHz to 1 MHz) between wrist and ankle. Following a resting period of 5 minutes in supine position, auricular vagus nerve was stimulated for 3 minutes and BIS performed every 10 seconds, on 23-27 years old, 5 healthy subjects. During the stimulation phase, either an increase or a decrease was observed in extracellular and intracellular fluids. In 3 of the subjects, an ECF decrease of 0.02% per kg was compensated by 0.02 to 0.06% per kg increase in ICF; with a correlation coefficient of -0,70 to -0,79; suggesting fluid shifts between ECF and ICF. With the other 2 subjects, both ECF and ICF decreased by about 0.02% per kg. The study was performed with a limited number of participants; to reach statistically meaningful results measurements will be performed over a larger sample size.

Hemodynamic correlation imaging of the mouse brain for application in unilateral neurodegenerative diseases

We developed a single-camera two-channel hemodynamic imaging system that uses near-infrared light to monitor the mouse brain in vivo with an exposed, un-thinned, and intact skull to explore the effect of Parkinson's disease on the resting state functional connectivity of the brain. To demonstrate our system's ability to monitor cerebral hemodynamics, we first performed direct electrical stimulation of an anesthetized healthy mouse brain and detected hemodynamic changes localized to the stimulated area. Subsequently, we developed a unilaterally lesioned 6-hydroxydopamine (hemi-parkinsonian) mouse model and detected the differences in functional connectivity between the normal and hemi-parkinsonian mouse brains by comparing the hemispheric hemodynamic correlations during the resting state. Seed-based correlation for the oxy-hemoglobin channel from the left and right hemispheres of healthy mice was much higher and more symmetric than in hemi-parkinsonian mice. Through a k-means clustering of the hemodynamic signals, the healthy mouse brains were segmented according to brain region, but the hemi-parkinsonian mice did not show a similar segmentation. Overall, this study highlights the development of a spatial multiplexing hemodynamic imaging system that reveals the resting state hemodynamic connectivity in healthy and hemi-parkinsonian mice.

Changes of skin electrical potential in acupoints from Ren Mai and Du Mai conduits during Qigong practice: Documentation of a clinical phenomenon

Qigong is a therapeutic method of traditional Chinese medicine (TCM) that combines slow, soft movements and postures with breath control and a special mental state of 'awareness'. TCM holds that the practice of Qigong promotes the 'circulation of qi' in the human body, the 'flow' of upward yang qi and downward yin qi to establish 'balance'. In Western terms, this may be generally equivalent to vegetative homeostasis and the emotionally balanced state induced thereby. Researchers have often attempted to evaluate the functional movements of qi using measurements of the skin's electrical resistance. However, these methodologies have proven difficult to gauge, validate, repeat, and interpret. We aimed to overcome these limitations by measuring the skin's electrical potential between two points of the same system. The main goal of this study was to assess the skin's electrical potential changes in acupoints from the Ren Mai and Du Mai conduits, or meridians, as well as in other points of interest, during Qigong practice. While participants performed a specific Qigong exercise called 'White Ball', we observed significant changes in the skin electrical potential on Mìngmén (GV 4), Shèndáo (GV 11) and Baihuì (GV 20), from the Du Mai conduit, as well as on Huiyin (CV 1), Qìhai (CV 6), Zhongwan (CV 12) and Dànzhong (CV 17), from Ren Mai. These observations are in accordance with TCM theory and may contribute to the explanation of the vegetative physiological changes that are associated with 'qi flow' in TCM.