Handheld Electrical Impedance Myography Probe for Assessing Carpal Tunnel Syndrome

Affordable, portable and self-administrable electrical impedance tomography enables global and regional lung function assessment

Accessibility of diagnostic screening and treatment monitoring devices for respiratory diseases is critical in promoting healthcare and reducing sudden complications and mortality. Spirometry is the standard for diagnosing and monitoring several lung diseases. However, it lacks regional assessment capabilities necessary for detecting subtle regional changes in certain diseases. It also requires challenging breathing maneuvers difficult for elderlies, children, and diseased patients. Here, we actualized an affordable, portable, and self-administrable electrical impedance tomography (EIT) system for home-based lung function assessment and telemedicine. Through simultaneous EIT-spirometry trials on healthy subjects, we demonstrated that our device can predict spirometry indicators over a wide range and can provide regional mapping of these indicators. We further developed a close-to-effortless breathing paradigm and tested it by longitudinally monitoring a COVID-19 discharged subject and two healthy controls with results suggesting the paradigm can detect initial deterioration followed by recovery. Overall, the EIT system can be widely applicable for lung function screening and monitoring both at homes and clinics.

Standalone electrical impedance tomography predicts spirometry indicators and enables regional lung assessment

Electrical impedance tomography (EIT) is a bio-medical imaging modality that has several clinical applications namely for human lungs. Yet, its relationship with gold standard lung diagnostic tools including spirometry is not available. In this study, simultaneous EIT and spirometry measurements were collected for 14 healthy subjects who performed forced breathing paradigms of different efforts simulating a wide range of spirometry indicators. It is demonstrated that EIT can predict standard spirometry indicators over a wide dynamic range, with a potential sensitivity and specificity of 98% and 100%, respectively, in detecting obstructive patterns. It is also shown that EIT can provide a regional mapping of the spirometry indicator which are shown to be consistent with their corresponding global indicators. Overall, EIT can predict spirometry indicators and can assess regional lung health through parametric mapping. Clinical Relevance- This study shows that EIT can infer standard spirometry indicators and potentially assess regional lung health. Therefore, EIT can be used for screening, diagnosis, and monitoring of obstructive and resistive lung diseases.

Evaluation of Skeletal Muscle Dysfunction Associated With Acute Inflammation by Electrical Impedance Myography: A Case Report on Skeletal Muscle Dysfunction After Cardiac Surgery and Literature Review

Electrical impedance myography (EIM) is an evaluation technique for skeletal muscles that uses electrical impedance technology. Recent reviews have shown that EIM is useful as a method to assess changes in skeletal muscle quality and quantity with aging. These may be utilized for functional changes in inflammatory skeletal muscles, such as disease and operation. In this report, the impedance parameters using EIM present perioperative skeletal muscle changes in patients after cardiac surgery. In addition, we will describe the efficacy of EIM in skeletal muscle dysfunction due to inflammation or disease. This study aimed to elucidate the efficacy of EIM in acute inflammation-associated skeletal muscle dysfunction.

Modeling and Reproducibility of Twin Concentric Electrical Impedance Myography

OBJECTIVE

Electrical impedance myography (EIM) is a recent technology to assess muscle health. As of today, the clinical application of EIM has been applied only to evaluate muscle condition using non-invasive surface electrodes in contact with the skin; however, intermediate tissues at the recording site introduce confounding artifacts which reduce the technique's performance as a biomarker of neuromuscular disorders (NMD). Here, we develop and test in humans a new approach using two concentric needles for intramuscular EIM recordings.

METHODS

First, we study the recording characteristics of dual concentric needle EIM via analytical models and finite element models (FEMs). Next, the validity of the models is verified by performing experiments on saline and agar phantoms. Finally, 8 subjects with various neuromuscular diseases were studied measuring tibialis anterior, biceps, deltoid, adductor pollicis brevis, first dorsal interosseous and flexor carpi radialis muscles.

RESULTS

Analytical and FEM simulations are in good agreement with a maximum experimental discrepancy 8% and 9% using gauge needles 26 and 30, respectively. The inter-session reproducibility, as measured by the intraclass correlation coefficients for all muscles studied, was 0.926, which is comparable or exceeds the reproducibility of other well-established electrophysiological tests to assess muscle health.

CONCLUSION

The reproducibility of the technique support future clinical validation of needle EIM for assessment of disease status, either as part of standard patient care or as biomarker measure in clinical trials.

SIGNIFICANCE

Needle EIM has the potential of becoming a valuable diagnostic tool to evaluate NMD in adult population.

Electrical Impedance Methods in Neuromuscular Assessment: An Overview

Electrical impedance methods have been used as evaluation tools in biological and medical science for well over 100 years. However, only recently have these techniques been applied specifically to the evaluation of conditions affecting nerve and muscle. This specific application, termed electrical impedance myography (EIM), is finding wide application as it can provide a quantitative index of muscle condition that can assist with diagnosis, track disease progression, and assess the beneficial impact of therapy. Using noninvasive surface methods, EIM has been studied in a number of conditions ranging from amyotrophic lateral sclerosis to muscular dystrophy to disuse atrophy. Data support that the technique is sensitive to disease status and can offer the possibility of performing clinical trials with fewer subjects than would otherwise be possible. Recent advances in the field include improved approaches for using EIM as a "virtual biopsy" and the development of combined needle impedance-electromyography technology.

Electrical Impedance Myography for Assessing Paraspinal Muscles of Patients with Low Back Pain

The objective of this study was to determine the potential value of electrical impedance myography (EIM) for assessing lumbosacral paraspinal muscle (LPM) condition in lower back pain (LBP) patients. Standard methods for assessing the condition of LPMs, such as magnetic resonance imaging, are inconvenient and expensive. One tool that could be useful for this purpose is electrical impedance myography (EIM) a technique that can be performed rapidly at the bedside. After undergoing a screening history and examination, subjects were studied with the mView EIM device (Myolex, Inc, Boston). Bilateral LPMs were measured three times each and the two closest sets of measurements averaged on each side. Data analysis included non-parametric two-group comparisons between healthy subjects and back pain patients, receiver-operating curve analyses, and correlation analyses to age and body mass index. A total of 86 healthy individuals (median age (interquartile range) (IQR), 45.5 years (30.3-56.0 years), 42 men, 44 women) and 47 LBP (median age 51.0 year (39.5-57.5) years, 21 men, 26 women) were enrolled. Median EIM 100kHz phase was lower in the LBP patients (9.3°(IQR 8.4°-10.6°) versus 11.4°(IQR 9.4°-13.0°), p = 0.0007). Significantly increased normalized side-to-side differences were present for all three EIM variables (e.g., median 100 kHz phase 0.15 (IQR 0.07-0.31 in LBP patients versus 0.09 (IQR 0.04-0.17) in healthy individuals). A significant correlation between 100 kHz EIM phase and reactance was found with age (Rspearman=-0.46, P=0.0002 and Rspearman=-0.440, P=0.0003) but not for resistance. This study provides early evidence supporting that EIM has the potential to serve as a useful tool for evaluating the condition of LPMs.

Assessing Hand Muscle Structural Modifications in Chronic Stroke

The purpose of the study is to assess poststroke muscle structural alterations by examining muscular electrical conductivity and inherent electrophysiological properties. In particular, muscle impedance and compound muscle action potentials (CMAP) were measured from the hypothenar muscle bilaterally using the electrical impedance myography and the electrophysiological techniques, respectively. Significant changes of muscle impedance were observed in the paretic muscle compared with the contralateral side (resistance: paretic: 27.54 ± 0.97 Ω, contralateral: 25.46 ± 0.91 Ω, p < 0.05; phase angle: paretic: 8.81 ± 0.61°, contralateral: 10.79 ± 0.69°, p < 0.05). In addition, impedance changes correlated moderately with the CMAP amplitude in the paretic hand (phase angle: r = 0.66, p < 0.05; reactance: r = 0.58, p < 0.05). The study discloses significant muscle rearrangements as a result of fiber loss or atrophy, fat infiltration or impaired membrane integrity in chronic stroke.

The Development of a Four-Electrode Bio-Impedance Sensor for Identification and Localization of Deep Pulmonary Nodules

Identifying and localizing of deep pulmonary nodules are among the main challenges that thoracic surgeons face during operations, particularly in thoracoscopic procedures. To facilitate this, we have tried to introduce a non-invasive and safe method by measuring the lung electrical bio-impedance spectrum with a four-electrode array sensor. To study the feasibility of this method, since any change in the depth or diameter of the nodule in the lung tissue is not practical, we used the finite element modeling of the lung tissue and pulmonary nodule to allow changes in the depth and diameter of the nodule, as well as the distance in between the injection electrodes. Accordingly, a bio-impedance sensor was designed and fabricated. By measuring the electrical impedance spectrum of pulmonary tissues in four different specimens with a frequency band of 50 kHz to 5 MHz, 4 pulmonary nodules at four different depths were identified. The obtained bio-impedance spectrum from the lung surface showed that the magnitude and phase of electrical bio-impedance of the tumoral tissue at each frequency is smaller than that of the healthy tissue. In addition, the frequency characteristic varies in the Nyquist curves for tumoral and healthy lung tissues.