Eddy Krueger

Iontophoresis: principles and applications

Introduction Iontophoresis is a noninvasive technique used to increase transdermal penetration of substances through the skin layer (epidermis, dermis and hypodermis) in a controlled manner. Technological advance in recent decades have provided reduced cost of equipment needed for implementation, which allowed for the expansion of this technique. Objective The aim of this paper is to present the state of the art on iontophoresis, ranging from the atomic characteristics of the ion formation to the current applications of the technique. Methods Were researched papers from databases: IOP publishing, ScienceDirect, Pubmed, Springer, IEEE Xplore, Google Scholar and books with keywords iontophoresis, ions, topical applications between 1967 and 2010. Results Were selected (number of papers and database) 1 IOP Publishing, 1 from ScienceDirect, Central, 1 from Springer, 2 from PubMed, 11 from IEEE Xplore, 35 from Google Scholar, and 15 books, totaling 66 references and websites with nationally marketed electrotherapy products. Conclusion Iontophoresis is suitable for applications such as acetic acid (calcific tendinitis and myositis ossificans), calcium chloride and magnesium sulfate (control of musculoskeletal spasms), dexamethasone (inflammation), lidocaine (inflammation of soft tissues), zinc oxide (rheumatoid arthritis). It is also used in cosmetic applications with devices attached to the skin and for eye treatment aimed at specific tissues of the eye, providing a treatment option for various eye diseases, reducing the complications secondary to traditional methods of treatment. The advantages are the significant increase in the release and control of therapeutic agents, including drugs with high molecular weight. The disadvantages of iontophoresis are the complexity of the drug release system and prolonged exposure of the skin to an electrical current.

A new approach to assess the spasticity in hamstrings muscles using mechanomyography antagonist muscular group

Several pathologies can cause muscle spasticity. Modified Ashworth scale (MAS) can rank spasticity, however its results depend on the physician subjective evaluation. This study aims to show a new approach to spasticity assessment by means of MMG analysis of hamstrings antagonist muscle group (quadriceps muscle). Four subjects participated in the study, divided into two groups regarding MAS (MAS0 and MAS1). MMG sensors were positioned over the muscle belly of rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) muscles. The range of movement was acquired with an electrogoniometer placed laterally to the knee. The system was based on a LabVIEW acquisition program and the MMG sensors were built with triaxial accelerometers. The subjects were submitted to stretching reflexes and the integral of the MMG (MMGINT) signal was calculated to analysis. The results showed that the MMGINT was greater to MAS1 than to MAS0 [muscle RF (p= 0.004), VL (p= 0.001) and VM (p= 0.007)]. The results showed that MMG was viable to detect a muscular tonus increase in antagonist muscular group (quadriceps femoris) of spinal cord injured volunteers.

Advances and perspectives of mechanomyography

INTRODUCTION: The evaluation of muscular tissue condition can be accomplished with mechanomyography (MMG), a technique that registers intramuscular mechanical waves produced during a fibers contraction and stretching that are sensed or interfaced on the skin surface. OBJECTIVE: Considering the scope of MMG measurements and recent advances involving the technique, the goal of this paper is to discuss mechanomyography updates and discuss its applications and potential future applications. METHODS: Forty-three MMG studies were published between the years of 1987 and 2013. RESULTS: MMG sensors are developed with different technologies such as condenser microphones, accelerometers, laser-based instruments, etc. Experimental protocols that are described in scientific publications typically investigated the condition of the vastus lateralis muscle and used sensors built with accelerometers, third and fourth order Butterworth filters, 5-100Hz frequency bandpass, signal analysis using Root Mean Square (RMS) (temporal), Median Frequency (MDF) and Mean Power Frequency (MPF) (spectral) features, with epochs of 1 s. CONCLUSION: Mechanomyographic responses obtained in isometric contractions differ from those observed during dynamic contractions in both passive and functional electrical stimulation evoked movements. In the near future, MMG features applied to biofeedback closed-loop systems will help people with disabilities, such as spinal cord injury or limb amputation because they may improve both neural and myoelectric prosthetic control. Muscular tissue assessment is a new application area enabled by MMG; it can be useful in evaluating the muscular tonus in anesthetic blockade or in pathologies such as myotonic dystrophy, chronic obstructive pulmonary disease, and disorders including dysphagia, myalgia and spastic hypertonia. New research becomes necessary to improve the efficiency of MMG systems and increase their application in rehabilitation, clinical and other health areas.

Correlation between mechanomyography features and passive movements in healthy and paraplegic subjects

Mechanomyography (MMG) measures both muscular contraction and stretching activities and can be used as feedback in the control of neuroprostheses with Functional Electrical Stimulation (FES). In this study we evaluated the correlation between MMG features and passive knee angular movement of rectus femoris and vastus lateralis muscles acquired from healthy volunteers (HV) and spinal cord injured volunteers (SCIV). Twelve HV and thirteen SCIV were submitted to passive and FES elicited knee extensions and in each extension, eleven windows of analysis with 0.5s length were inspected. Temporal (RMS and INT) and frequency (MF and μ3) features were extracted. Spearman correlation coefficients (p) were computed in order to check correlations between the features obtained from both MMG sensors. The correlation between MMGMF and MMG temporal analysis (RMS and INT) to HV was classified as positive, moderate (p from 0.635 to 0.681) and high (p from 0.859 to 0.870), and weak (positive e negative) to SCIV. These results differ from those obtained in voluntary contraction or artificially evoked by functional electrical stimulation and may be relevant in applications with closed loop control systems.

Influence of Skinfold Thickness in Mechanomyography Features

The assessment and physiological register of muscular tissue can be done through mechanomyography (MMG). The oscillation of muscular displacement is acquired on the skin surface, insomuch that the skinfold thickness can influence in MMG response. The aim of this study is verify the influence of different skinfold thickness on MMG features responses. Triaxial MMG was used over the rectus femoris muscle belly of ten volunteers during maximal voluntary contraction. MMG spectral and temporal analyses were made and specific features (root mean square (RMS), Integral (Int), mean frequency (MF), zero-crossing (ZC), and μ3) were correlated with skinfold thickness. Moderate and high negative correlation occurred to MMG mean frequency in axes X (ρ = - 0.57) and Y (ρ = -0.75), respectively. As the fat tissue behaves like a low-pass filter, i.e. the thicker his skinfold the shorter its bandwidth; therefore, the skinfold thicknesses result in lower frequency responses. So, hereafter these results may be applied to calibrate MMG responses as biofeedback systems in, for instance, neuroprostheses.

Correlation between spectral and temporal mechanomyography features during functional electrical stimulation

Introduction: Signal analysis involves time and/or frequency domains, and correlations are described in the literature for voluntary contractions. However, there are few studies about those correlations using mechanomyography (MMG) response during functional electrical stimulation (FES) elicited contractions in spinal cord injured subjects. This study aimed to determine the correlation between spectral and temporal MMG features during FES application to healthy (HV) and spinal cord injured volunteers (SCIV). Methods: Twenty volunteers participated in the research divided in two groups: HV (N=10) and SCIV (N=10). The protocol consisted of four FES profiles transcutaneously applied to quadriceps femoris muscle via femoral nerve. Each application produced a sustained knee extension greater than 65o up to 2 min without adjusting FES intensity. The investigation involved the correlation between MMG signal root mean square (RMS) and mean frequency (MF). Results: HV and SCIV indicated that MMGRMS and MMGMF variations were inversely related with -0.12 ≥ r ≥ -0.82. The dispersion between MMGMF and MMGRMS reached 0.50 ≤ r2 ≤ 0.64. Conclusion The increase in MMGRMS and the decrease in MMGMF may be explained by the motor units coherence during fatigue state or by motor neuron adaptation (habituation) along FES application (without modification on parameters).

Fat Percentage Equation for Children with Cerebral Palsy: A Novel Approach

Nutritional changes are commonly related to children with cerebral palsy (CP), since these are problems as: dysphagia, vomiting and gastrointestinal reflux. For nutritional monitoring, body composition has become an important tool and has been present in this population assessments routine. In this sense, the aim of this study was to develop an equation for body composition estimate for children with cerebral palsy, aged between 5 and 6 years, using skinfolds, from the results of body composition obtained by Dual Energy X-rays Absormetry (DEXA). The study included 10 male children with cerebral palsy, aged between five and six-years-old, who participated in the physical therapy intensive program in Vitoria research center, Curitiba, Brazil. Participants were assessed by: the Gross Motor Function Classification System; DEXA; and skinfold thickness. The skinfolds that showed better correlation with the total fat percentage and segmental fat percentage were: biceps and abdominal. The results of the regression analysis obtained equations to estimate the fat percentage by skinfold thickness with R2: 1.000 and 0.971, to seven and two skinfold thickness, respectively. In this sense, it is recommended to use the equation that utilizes the biceps and abdominal skinfolds thickness to estimate fat percentage of children with cerebral palsy, as this presents good estimation indicators.

FES Application with Different Off Times in Paraplegic Subject during Open Chain Movement: Case Report

Functional electrical stimulation (FES) improves paraplegic subjects rehabilitation and may be used in neuroprosthesis systems. Superficial mechanomyography (MMG) monitors the contracting muscles oscillations. The goal of this paper is to compare the relationships between MMG features and knee angles during open chain movements artificially evoked by different FES off times (5s; 10s and 15s) in a spinal cord injured volunteer. FES waveform consisted of a monophasic square wave, 1kHz pulse frequency, 300μs active pulse period and 3ms active burst period with burst frequency of 70Hz. Sixteen artificial contractions were generated by FES applied to the quadriceps femoral muscle pre- and pos-interval of 15min, totalizing thirty two contractions. Temporal (RMS value) and spectral (median frequency) MMG features were analyzed for rectus femoris and vastus lateralis muscles. MMGRMS and MMGMF variations were inversely related, with correlation coefficients values from -0.30 until -0.79. These results may help create new FES closed-loop control strategies by MMG features.

Influence of subcutaneous fat on mechanomyographic signals at three levels of voluntary effort

Introduction This study aims to assess the influence of different skinfold thicknesses (ST) and their relation to the attenuation of the mechanomyographic (MMG) signal at different force levels (maximal voluntary contraction – MVC, 40% of MVC and 70% of MVC) of the rectus femoris muscle. Methods Fifteen volunteers were divided in two groups: ST lower than 10mm (G 35) (7 participants). Student t tests were employed to investigate differences between G 35 regarding MMG analysis parameters (acceleration root mean square – aRMS, zero crossing – ZC, and median frequency – MDF), for the X, Y and Z axes, as well as for the modulus of these three axes. Results We found that thicker layers of body fat act as attenuator filters for the MMG signal [MDFMVC: X (p = 0.005), Z (p = 0.003); MDF70%MVC: X (p = 0.034); ZCMVC: Z (p = 0.037), modulus (p = 0.005); ZC70%MVC: Z (p = 0.047)]. We found significant correlation between ST values and aRMS in three levels, in the Yaxis (p = 0.591), for the group G 35 in 40%MVC (R2 = 0.610), and 70%MVC (R2 = 0.592). The MDF parameter showed correlation with ST values only in the Yaxis in 70%MVC (R2 = 0.700) for G>35. Conclusions We observed MMG signal attenuation in at least one of the parameters analyzed for each level of the rectus femoris muscle force, indicating that MMG signals are significantly attenuated with increasing thickness of the subcutaneous fat layer.

Cauchy Wavelet-based Mechanomyographic Analysis for Muscle Contraction Evoked by FES in a Spinal Cord Injured Person

The goal of this paper is to evaluate the mechanomyography (MMG) response of rectus femoris muscle based on Cauchy wavelet (CaW) during contraction evoked by functional eletrical stimulation (FES) in a spinal cord injured person. The participant was ranked in American Spinal Injury Association (ASIA) impairment scale as A, i.e. without contraction or sensibility below the lesion level (T3). A triaxial (Z, X and Y axes) MMG sensor was placed over the rectus femoris muscle belly. The CaW was processed in initial and final moments of FES application. The results showed that frequency in (a) initial moment tends to be near the adjusted FES burst frequency (50 Hz), however, in (b) final moment presents compression to frequencies below 18.63 Hz in Z and X axes and in Y axis below 51.12 Hz, therefore, indicating the fibers do not follow the physiological muscular activation mode, as suggested by De Luca and Erim during FES. CaW appears to be suitable to carry out the MMG response during FES application to a spinal cord injured subject making it an important analysis tool because it can show the specific frequency band during neuromuscular physiological changes.