Bioelectrical impedance assessment of wound healing

Localized hamstring bioimpedance in marathon runners is related to muscle high-energy enzyme serum levels and predicts race time

Introduction: The aim was to analyze the response of serum levels of inflammatory, high-energy muscle biomarkers and hamstring localized bioimpedance (L-BIA) measurements to marathon running and to ascertain whether they correlate with each other or with race time. Methods: Blood samples and hamstrings tetra-polar L-BIA measurements from 14 Caucasian male recreational athletes at the Barcelona Marathon 2019 were collected at base line, immediately after and 48 h post-race. Serum C reactive protein (sCRP), creatinine kinase (sCK) and lactate dehydrogenase (sLDH) were determined using an AU-5800 chemistry analyzer. L-BIA was obtained at 50 kHz with a Quantum V Segmental phase-sensitive bioimpedance analyzer. Results: Median sCRP increased (4-fold) after 48 h post-race. Median sCK and sLDH levels increased immediately post-race (3-fold, 2-fold) and 48h post-race (5-fold, 1-fold). Left, right and combined hamstring reactance (Xc) and phase angle (PhA) increased immediately post-race. Xc combined hamstring pre- and immediately post-race correlated with race-time and with sCK and sLDH median levels pre-race. Xc combined hamstring pre- and immediately post-race > 15.6 Ω and 15.8 Ω, respectively, predicted the race time of 3:00:00 h. Conclusion: L-BIA reactance (Xc) is an objective direct, real time, easy, noninvasive bioelectrical parameter that may predict muscle and marathon athlete performance.

Differences of bioelectrical impedance in the development and healing phase of pressure ulcers and erythema in mouse model

Pressure ulcers (PUs) are economically burdensome medical conditions. Early changes in pressure ulcers are associated with erythema. In this study, bioelectrical impedance was used to measure the differences between PUs and blanchable erythema. We divided 21 ICR mice into three groups: control, 1000 mmHg-1h, and 1000 mmHg-6h. Healthy skin, blanchable erythema, and PUs were induced on the dorsal skin. The results indicated an immediate increase in impedance, resistance, and reactance values in the pressure group after release, followed by a subsequent decrease until two days after release. Compared with the control group, impedance and reactance significantly increased by 30.9% (p < 0.05) and 30.1% (p < 0.01), respectively, in the 6 h-loading group immediately after release. One and two days after release, the 1 h-loading and 6 h-loading groups exhibited significantly different degrees of decline. One day after release, impedance and resistance decreased by 30.2% (p < 0.05) and 19.8% (p < 0.05), respectively, in the 1 h-loading group; while impedance, resistance, and reactance decreased by 39.2% (p < 0.01), 26.8% (p < 0.01), and 45.7% (p < 0.05), respectively, in the 6 h-loading group. Two days after release, in the 1 h-loading group, impedance and resistance decreased by 28.3% (p < 0.05) and 21.7% (p < 0.05), respectively; while in the 6 h-loading group, impedance, resistance, and reactance decreased by 49.8% (p < 0.001), 34.2% (p < 0.001), and 59.8% (p < 0.01), respectively. One and two days after release the pressure group reductions were significantly greater than those in the control group. Additionally, we monitored changes during wound healing. Distinguishing early PUs from blanchable erythema by noninvasive bioelectrical impedance technology may have applications value in early assessment of PUs.

Panthenol Citrate Biomaterials Accelerate Wound Healing and Restore Tissue Integrity

Impaired wound healing is a common complication for diabetic patients and effective diabetic wound management remains a clinical challenge. Furthermore, a significant problem that contributes to patient morbidity is the suboptimal quality of healed skin, which often leads to reoccurring chronic skin wounds. Herein, a novel compound and biomaterial building block, panthenol citrate (PC), is developed. It has interesting fluorescence and absorbance properties, and it is shown that PC can be used in soluble form as a wash solution and as a hydrogel dressing to address impaired wound healing in diabetes. PC exhibits antioxidant, antibacterial, anti-inflammatory, and pro-angiogenic properties, and promotes keratinocyte and dermal fibroblast migration and proliferation. When applied in a splinted excisional wound diabetic rodent model, PC improves re-epithelialization, granulation tissue formation, and neovascularization. It also reduces inflammation and oxidative stress in the wound environment. Most importantly, it improves the regenerated tissue quality with enhanced mechanical strength and electrical properties. Therefore, PC could potentially improve wound care management for diabetic patients and play a beneficial role in other tissue regeneration applications.

Wireless, closed-loop, smart bandage with integrated sensors and stimulators for advanced wound care and accelerated healing

'Smart' bandages based on multimodal wearable devices could enable real-time physiological monitoring and active intervention to promote healing of chronic wounds. However, there has been limited development in incorporation of both sensors and stimulators for the current smart bandage technologies. Additionally, while adhesive electrodes are essential for robust signal transduction, detachment of existing adhesive dressings can lead to secondary damage to delicate wound tissues without switchable adhesion. Here we overcome these issues by developing a flexible bioelectronic system consisting of wirelessly powered, closed-loop sensing and stimulation circuits with skin-interfacing hydrogel electrodes capable of on-demand adhesion and detachment. In mice, we demonstrate that our wound care system can continuously monitor skin impedance and temperature and deliver electrical stimulation in response to the wound environment. Across preclinical wound models, the treatment group healed ~25% more rapidly and with ~50% enhancement in dermal remodeling compared with control. Further, we observed activation of proregenerative genes in monocyte and macrophage cell populations, which may enhance tissue regeneration, neovascularization and dermal recovery.

Phase angle in localized bioimpedance measurements to assess and monitor muscle injury

Localized bioimpedance (L-BIA) measurements are an innovative method to non-invasively identify structural derangement of soft tissues, principally muscles, and fluid accumulation in response to traumatic injury. This review provides unique L-BIA data demonstrating significant relative differences between injured and contralateral non-injured regions of interest (ROI) associated with soft tissue injury. One key finding is the specific and sensitive role of reactance (Xc), measured at 50 kHz with a phase-sensitive BI instrument, to identify objective degrees of muscle injury, localized structural damage and fluid accretion, determined using magnetic resonance imaging. The predominant effect of Xc as an indicator of severity of muscle injury is highlighted in phase angle (PhA) measurements. Novel experimental models utilizing cooking-induced cell disruption, saline injection into meat specimens, and measurements of changing amounts of cells in a constant volume provide empirical evidence of the physiological correlates of series Xc as cells in water. Findings of strong associations of capacitance, computed from parallel Xc (X_CP), with whole body counting of 40-potassium and resting metabolic rate support the hypothesis that parallel Xc is a biomarker of body cell mass. These observations provide a theoretical and practical basis for a significant role of Xc, and hence PhA, to identify objectively graded muscle injury and to reliably monitor progress of treatment and return of muscle function.

Phase angle and cellular health: inflammation and oxidative damage

Phase angle is a composite measure that combines two raw bioelectrical impedance analysis measures: resistance and reactance. Phase angle has been considered an indicator of cellular health, integrity, and hydration. As inflammation and oxidative stress can damage cellular structures, phase angle has potential utility in early detecting inflammatory and oxidative status. Herein, we aimed to critically review the current understanding on the determinants of phase angle and its relationship with markers of inflammation and oxidative stress. We also discussed the potential role of phase angle in detecting chronic inflammation and related adverse outcomes. Several factors have been identified as predictors of phase angle, including age, sex, extracellular to intracellular water ratio, and fat-free mass. In addition to these factors, body mass index (BMI) also seems to influence phase angle. Available data also show that lower phase angle values are correlated (negligible to high correlation coefficients) with higher c-reactive protein, tumour necrosis factor-α, interleukin-6, and interleukin-10 in studies involving the general and aging populations, as well as patients with chronic conditions. Although fewer studies have evaluated the relationship between phase angle and markers of oxidative stress, available data also suggest that phase angle has potential to be used as an indicator (for screening) of oxidative damage. Future studies including diverse populations and bioelectrical impedance devices are required to confirm the validity and accuracy of phase angle as a marker of inflammation and oxidative stress for clinical use.

Effect of melatonin on electrical impedance and biomarkers of damage in a gastric ischemia/reperfusion model

The damage to the gastrointestinal mucosa induced by ischemia/reperfusion (I/R) is closely related to high mortality in critically ill patients, which is attributable, in part, to the lack of an early method of diagnosis to show the degree of ischemia-induced injury in this type of patients. Electrical Impedance Spectroscopy (EIS) has been shown to be a tool to early diagnose gastric mucosal damage induced by ischemia. A therapeutic alternative to reduce this type of injury is melatonin (MT), which has gastroprotective effects in I/R models. In this work, the effect of treatment with MT on the electrical properties of gastric tissue, biomarkers of inflammatory (iNOS and COX-2), proliferation, and apoptotic process under I/R conditions in male Wistar rats was evaluated through EIS, histological and immunohistochemical analysis. Treatment with MT prevents gastric mucosa damage, causing a decrease in gastric impedance parameters related to the inflammatory process and cellular damage. This suggests that EIS could be used as a tool to diagnose and monitor the evolution of gastric mucosal injury, as well as in the recovery process in critically ill patients.

A Review of Recent Advances in Flexible Wearable Sensors for Wound Detection Based on Optical and Electrical Sensing

Chronic wounds that are difficult to heal can cause persistent physical pain and significant medical costs for millions of patients each year. However, traditional wound care methods based on passive bandages cannot accurately assess the wound and may cause secondary damage during frequent replacement. With advances in materials science and smart sensing technology, flexible wearable sensors for wound condition assessment have been developed that can accurately detect physiological markers in wounds and provide the necessary information for treatment decisions. The sensors can implement the sensing of biochemical markers and physical parameters that can reflect the infection and healing process of the wound, as well as transmit vital physiological information to the mobile device through optical or electrical signals. Most reviews focused on the applicability of flexible composites in the wound environment or drug delivery devices. This paper summarizes typical biochemical markers and physical parameters in wounds and their physiological significance, reviews recent advances in flexible wearable sensors for wound detection based on optical and electrical sensing principles in the last 5 years, and discusses the challenges faced and future development. This paper provides a comprehensive overview for researchers in the development of flexible wearable sensors for wound detection.

Multifunctional Dressing for Wound Diagnosis and Rehabilitation

A wound dressing is a sterile pad or compress that is used in direct contact with a wound to help it heal and prevent further issues or complications. Though wound healing is an intricate dynamic process that involves multiple biomolecular species, conventional wound dressings have a limited ability to provide timely information of abnormal conditions, missing the best time for early treatment. The current perspective presents and discusses the design and development of smart wound dressings that are integrated with multifunctional materials, wearable sensors and drug delivery systems as well as their application ranging from wound monitoring to timely application of therapeutics. The perspective also discusses the ongoing challenges and exciting opportunities associated with the development of wearable sensor-based smart wound dressing and provide critical insights into wound healing monitoring and management.

Electrical Impedance Myography in Health and Physical Exercise: A Systematic Review and Future Perspectives

Background: Electrical impedance myography (EIM) is a non-invasive method that provides information about muscle health and changes that occur within it. EIM is based on the analysis of three impedance variables: resistance, reactance, and the phase angle. This systematic review of the literature provides a deeper insight into the scope and range of applications of EIM in health and physical exercise. The main goal of this work was to systematically review the studies on the applications of EIM in health and physical exercise in order to summarize the current knowledge on this method and outline future perspectives in this growing area, including a proposal for a research agenda. Furthermore, some basic assessment principles are provided. Methods: Systematic literature searches on PubMed, Scopus, SPORTDiscus and Web of Science up to September 2020 were conducted on any empirical investigations using localized bioimpedance devices to perform EIM within health and physical exercise contexts. The search included healthy individuals, elite soccer players with skeletal muscle injury, and subjects with primary sarcopenia. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist was used to develop the systematic review protocol. The quality and risk of bias of the studies included were assessed with the AQUA tool. Results: Nineteen eligible original articles were included in this review, which were separated into three tables according to the nature of the study. The first table includes six studies on the bioelectrical characterization of muscle. The second table includes five studies analyzing muscle changes in injured elite soccer players. The third table includes studies on the short-, medium-, and long-term bioelectrical adaptations to physical exercise. Conclusions: EIM has been used for the evaluation of the muscle condition in the clinical field over the last few years, especially in different neuromuscular diseases. It can also play an important role in other contexts as an alternative to complex and expensive methods such as magnetic resonance imaging. However, further research is needed. The main step in establishing EIM as a valid tool in the scientific field is to standardize the protocol for performing impedance assessments.

Bioelectrical Impedance Vector Analysis: A Valuable Tool to Monitor Daily Body Hydration Dynamics at Altitude

Bioelectrical impedance vector analysis (BIVA) is a method used to estimate variation in body hydration. We assessed the potential of BIVA for monitoring daily body hydration fluctuations in nine healthy, normally active males under matching normoxic (NX) and hypobaric hypoxic (HH) experimental conditions. Furthermore, we aimed to investigate whether changes in BIVA may correspond with the development of acute mountain sickness (AMS). Subjects were exposed in a hypobaric chamber to both NX (corresponding to an altitude of 262 m) and HH conditions corresponding to an altitude of 3500 m during two four-day sojourns within which food, water intake and physical activity were controlled. Bioimpedance and body weight measurements were performed three times a day and medical symptoms were assessed every morning using the Lake Louise score (LLS). Total body water (TBW) was also assessed on the last day of both sojourns using the deuterium dilution technique. We detected circadian changes in vector length, indicating circadian body water variations that did not differ between NX and HH conditions (ANOVA effects: time: p = 0.018, eta² = 0.149; interaction: p = 0.214, eta² = 0.083; condition: p = 0.920, eta² = 0.001). Even though none of the subjects developed AMS, four subjects showed clinical symptoms according to the LLS during the first 24 hours of HH conditions. These subjects showed a pronounced (Cohen’s d: 1.09), yet not statistically significant (p = 0.206) decrease in phase angle 6 hours after exposure, which may indicate fluid shift from the intracellular to the extracellular compartment. At the end of each sojourn, vector length correlated with deuterium dilution TBW “gold standard” measurements (linear regression: NX: p = 0.002 and r² = 0.756, HH: p < 0.001 and r² = 0.84). BIVA can be considered a valuable method for monitoring body hydration changes at altitude. Whether such changes are related to the development of clinical symptoms associated with AMS, as indicated in the present investigation, must be confirmed in future studies.

Comparison of silver-plated nylon (Ag/PA66) e-textile and Ag/AgCl electrodes for bioelectrical impedance analysis (BIA)

Recently, researchers have adapted Bioelectrical Impedance Analysis (BIA) as a new approach to objectively monitor wounds. They have indicated various BIA parameters associated to specific wound types can be linked to wound healing through trend analysis relative to time. However, these studies are conducted using wet electrodes which have been identified as possessing several shortcomings, such as unstable measurements. Thus, the adaption of e-textile electrodes has become an area of interest in measuring biosignals. E-textile electrodes are known to possess a significantly large polarization impedance (Z_p) that potentially influences these biosignal measurements. In this study we aim to identify the suitability of e-textile electrodes to monitor wounds using BIA methodologies. By adapting suggested methodologies conducted in-vivo from previous studies, we used an ex-vivo model to observe the behaviour of e-textile electrodes relative to time. This was compared to common clinical wet electrodes, specifically Ag/AgCl. The objective of this study was to identify the BIA parameters that can be used to monitor wounds with e-textile electrodes. By analysing the BIA parameters relative to time, we observed the influence ofZ_pon these parameters.

Conductive Materials for Healing Wounds: Their Incorporation in Electroactive Wound Dressings, Characterization, and Perspectives

The use of conductive materials to promote the activity of electrically responsive cells is an effective means of accelerating wound healing. This article focuses on recent advancements in conductive materials, with emphasis on overviewing their incorporation with non-conducting polymers to fabricate electroactive wound dressings. The characteristics of these electroactive dressings are deliberated, and the mechanisms on how they accelerate the wound healing process are discussed. Potential directions for the future development of electroactive wound dressings and their potential in monitoring the course of wound healing in vivo concomitantly are also proposed.

New Frontiers of Body Composition in Sport

The body composition phenotype of an athlete displays the complex interaction among genotype, physiological and metabolic demands of a sport, diet, and physical training. Observational studies dominate the literature and describe the sport-specific physique characteristics (size, shape, and composition) of adult athletes by gender and levels of competition. Limited data reveal how body composition measurements can benefit an athlete. Thus, the objective is to identify purposeful measurements of body composition, notably fat and lean muscle masses, and determine their impact on the health and performance of athletes. Areas of interest include relationships among total and regional body composition measurements, muscle function, sport-specific performance, risk of injury, return to sport after injury, and identification of activity-induced fluid shifts. Discussion includes the application of specific uses of dual X-ray absorptiometry and bioelectrical impedance including an emphasis on the need to minimize measurement errors and standardize protocols, and highlights opportunities for future research. This focus on functional body composition can benefit the health and optimize the performance of an athlete.

Cell integrity indicators in university athletes: comparison among playing positions in indoor football

BACKGROUND

The aim of this study was to compare cell integrity indicators according to the playing position in university indoor football athletes.

METHODS

The sample consisted of 34 university athletes (20 female and 14 male). Dependent variables were cell integrity indicators: total body water (TBW), intracellular water (ICW), extracellular water (ECW), ECW/ICW ratio, body cell mass (BCM), ECW/BCM ratio, phase angle (PhA), resistance (R), Xc (reactance) and impedance (Z), evaluated by the electrical bioimpedance method. Independent variable was the playing position: goalkeeper (a), defender (a), winger (left and right) and pivot collected through questionnaire. Control variables were age, time of sport practice, participation in competitions per year and training load obtained by applying the anamnesis form, and body fat and fat and bone-free mass were obtained through dual emission X-ray absorptiometry (DXA). Covariance analysis (ANCOVA) was used, with post-roc Tukey's test, to identify difference between groups, with p <0.05.

RESULTS

In the adjusted analysis, female athletes in the defense position had BCM values (31.1 ±2.1) higher than those in the wing position (25.8 ±1.1) (p <0.01). In males, pivots showed higher ICW values (31.47 ±0.77) when compared to defenders (25.7 ±0.8) (p = 0.02). In addition, goalkeepers had higher TBW values (52.7 ±2.5) compared to wingers (42.3 ±1.2) (p = 0.03).

CONCLUSIONS

Cell integrity indicators may vary according to the playing position in indoor football.

Differentiation Between Tendinous, Myotendinous and Myofascial Injuries by L-BIA in Professional Football Players

Purpose

To differentiate by localized bioimpedance (L-BIA) measurements 24 h after injury, between tendinous, myotendinous junction (MTJ), and myofascial junction (MFJ) injuries, previously diagnosed by MRI exam. To evaluate by L-BIA, the severity of MTJ injuries graded from 1 to 3, and to determine the relationship between days to return to play (RTP) and L-BIA measurements.

Methods

3T MRI and tetra polar L-BIA was used to analyzed 37 muscle injuries 24 h after injury in 32 male professional football players, (23.5 ± 1.5 kg m^–2; 1.8 ± 0.1 m; 20–30 year.) between the 2016–2017 and 2017–2018 seasons. Muscle injuries were classified by The British Athletics Muscle Injury Classification (BAMIC). Percentage difference of L-BIA parameters [resistance (R), reactance (Xc), and phase angle (PA)] of the injured side were calculated considering contralateral non-injured side as the reference value.

Results

According to BAMIC classification and by MRI exam, we found tendinous (n = 4), MTJ (n = 26), and MFJ (n = 7) muscle injuries. In addition, MTJ injuries were grouped according to the severity of injury in grade 1 (n = 11), grade 2 (n = 8), and grade 3 (n = 7). Significant decrease (P < 0.01) was found in the L-BIA parameters R, Xc, and PA, in both MTJ and MFJ as well as in the different grades of MTJ injuries. In particular, in Xc (P < 0.001), which is related to muscle cell disruption. Regarding days to RTP, there was statistical significance among the three different grades of MTJ injuries (P < 0.001), especially when grade 1 was compared to grade 3 and grade 2 compared to 3.

Conclusion

L-BIA is a complementary method to imaging diagnostic techniques, such as MRI and US, to quantify MTJ and MFJ injuries. In addition, the increase in the severity of the MTJ injury resulted in higher changes of the Xc parameter and longer time to RTP.

Development of an Electrical Impedance Tomography Spectroscopy for Pressure Ulcer Monitoring Tool: Preliminary study

This study developed a sensor system that measures electrical impedance with a surrounding electrode array that is located around the wound and estimates the depth and classifies the difference in tissues of small regions in the area using tomography combined with spectroscopy method. The system is designed to integrate into the dressing to reduce unnecessary removal of dressings. In the human trial, moisturizer applied area was detected using Random Forest classifier (94.4% accuracy) and differences between every 10 minutes were significant in moisturizer applied area (p<; 0.05). The study confirmed the proof of concept that the system can monitor the change in human skin without attaching the sensor to the target area and indicate the skin area that had changed.

Imaging of a dielectric inclusion using a contactless radio-frequency inductive probe for tissue diagnosis

In this paper, a contactless radio-frequency (RF) inductive probe is used to spatially localize and characterize a complex dielectric organic inclusion in a fluid. The effect of dielectric properties (DP) of this organic material is investigated experimentally and by numerical computations.The used RF probe is a 135 MHz 3 cm diameter and 10 cm long, cylindrical bracelet resonator, placed close to a water tank filled with deionized water which includes a 1.5 cm diameter inclusion filled of air or NaCl solutions and placed in arbitrary positions. The water tank and the inclusion are used to model an organic material including a tumor. The RF probe is used as a transmit and receive sensor. It induces a magnetic field inside the water tank, which, by reciprocity, conveys information about the DP of the investigated material. The impedance changes at the end of the RF probe are directly related to the modifications of the magnetic field, and are measured by means of a network analyzer. A complex fit of the impedance frequency response around the resonance frequency gives access to two quantities proportional to the electrical conductivity and dielectric constant of the inclusion. The inclusion is moved into the water tank along the three axes by means of a robotic arm, so that two three dimensional maps of the equivalent dielectric quantities in function of the inclusion position are sensed by the probe. Then, the inclusion is filled with different conductive NaCl solutions from 0.1 to 1.1 S/m in order to test the ability of the probe to sense the modifications of the dielectric properties of the inclusion. Experimental as well as computation results obtained using the Distributed Point Source Method (DPSM) validate the ability of the proposed probe to localize the inclusion as deep as 1 cm into the water, and the ability of the probe to sense the dielectric property changes of the inclusion.

Impedance-Based Biosensing of Pseudomonas putida via Solution Blow Spun PLA: MWCNT Composite Nanofibers

Quantifiable sensing of common microbes in chronic wounds has the potential to enable an objective assessment of wound healing for diagnostic applications. Sensing platforms should be robust, simple, and flexible to provide clinicians with a point-of-care tool. In this work, solution blow spun poly (lactic acid)/multiwalled carbon nanotube nanofiber composites are used to detect the presence and concentration of Pseudomonas putida in vitro using changes in impedance. Impedance microbiology (IM) is a well-documented diagnostic technique used in many applications, including cancer detection, tuberculosis screening and pregnancy tests. Twenty-four hour real-time measurements of the equivalent circuit of three culture media were taken with an inductance, capacitance, and resistance (LCR) meter. Variations in impedance were calculated to correspond to the growth of P. putida. Additionally, instantaneous measurements of bacterial cultures were taken over a one-minute time point to display the fast sensing of bacterial load via IM. This proof-of-concept shows that conductive solution blow spun fiber mats is a valid fabrication technique to develop in situ wound dressing impedance sensors. Study results indicate successful measurement and quantification of bacterial growth in this proof-of-concept study.

Correlation of bioimpedance changes after compressive loading of murine tissues in vivo

OBJECTIVE

Rises in the incidence of pressure ulcers are increasingly prevalent in an aging population. Pressure ulcers are painful, are associated with increased morbidity and mortality, increase the risk for secondary infections and inpatient stay, and adds $26.8 billion annually to the healthcare costs of the USA. Evidence suggests that a change in the bioimpedance of living tissue in response to continuous local contact pressure can be a useful indicator for the onset of pressure injuries.

APPROACH

Thirty-five Sprague Dawley rats were subjected to various skin pressures for differing periods of time via a surgically inserted steel disk and an externally applied magnet. Contact pressure and bioimpedance were measured and correlated with tissue loading intensity and compared to clinical ulcer grading.

MAIN RESULTS

Moderate relationships between bioimpedance changes and tissue loading intensity were found. Stronger correlations were found by utilizing a combination of bioimpedance and phase angle. Thresholds were applied to the bioimpedance parameters and the usefulness of bioimpedance in classifying different ulcer stages is demonstrated.

SIGNIFICANCE

These results indicate that bioimpedance may be useful as an early indicator of pressure ulcer formation and has practical significance in the development of early pressure injury detection devices.

Bioimpedance Sensor Array for Long-Term Monitoring of Wound Healing from Beneath the Primary Dressings and Controlled Formation of H2O2 Using Low-Intensity Direct Current

Chronic wounds impose a significant financial burden for the healthcare system. Currently, assessment and monitoring of hard-to-heal wounds are often based on visual means and measuring the size of the wound. The primary wound dressings must be removed before assessment can be done. We have developed a quasi-monopolar bioimpedance-measurement-based method and a measurement system to determine the status of wound healing. The objective of this study was to demonstrate that with an appropriate setup, long-term monitoring of wound healing from beneath the primary dressings is feasible. The developed multielectrode sensor array was applied on the wound area and left under the primary dressings for 142 h. The impedance of the wounds and the surrounding intact skin area was measured regularly during the study at 150 Hz, 300 Hz, 1 kHz, and 5 kHz frequencies. At the end of the follow-up period, the wound impedance had reached the impedance of the intact skin at the higher frequencies and increased significantly at the lowest frequencies. The measurement frequency affected the measurement sensitivity in wound monitoring. The skin impedance remained stable over the measurement period. The sensor array also enabled the administration of periodical low-intensity direct current (LIDC) stimulation in order to create an antimicrobial environment across the wound area via the controlled formation of hydrogen peroxide (H₂O₂).

Non-Contact Radiofrequency Inductive Sensor for the Dielectric Characterization of Burn Depth in Organic Tissues

A flat circular transmission line-based 300 MHz resonator was implemented for the non-contact assessment of burn depths in biological tissues. Used as a transmit-and-receive sensor, it was placed at a 2 mm distance from organic material test samples (pork fillet samples) which were previously burned on their surface in various heating conditions involving different temperatures, durations, and procedures. Data extracted from the sensor by means of a distant monitoring coil were found to clearly correlate with the depth of burn observed in the tissue samples (up to 40% sensor output changes for a 7 mm burn depth) and with the heating conditions (around 5% sensor output changes observed in samples burned with identical heating procedures but at two different temperatures—75 °C and 150 °C—and around 40% sensor output changes observed between samples heated at the same temperature but with different heating procedures). These results open the way for the development of easy-to-implement assessment and monitoring techniques for burns, e.g., integrated in wearable medical dressing-like monitoring devices.

Fluid distribution and cell integrity indicators evaluated by bioelectrical impedance in university athletes: comparison between team sports and individual sports

OBJECTIVE

To compare indicators of fluid distribution and cellular integrity in university athletes through a cross-sectional study of 167 university athletes (18-35 years) who competed in team sports and individual sports.

APPROACH

Bioimpedance was used to estimate total body water (TBW), intracellular water (ICW), extracellular water (ECW), ECW/ICW ratio, impedance (Z), reactance (Xc), resistance (R), phase angle, body cell mass (BCM) and ECW/BCM ratio at a frequency of 50 kHz. X-ray absorptiometry was used to determine lean soft tissue mass and body fat. As covariables, sex, age, time of practice and type of modality were obtained by questionnaire.

MAIN RESULTS

Individual male athletes presented higher values of ECW/ICW ratio (means difference MD  =  0.006, p   =  0.020) and ECW/BCM ratio (MD  =  0.006, p   =  0.017) than team sports male athletes. Values of Z (MD  =  24.988, p   =  0.009), Xc (MD  =  3.327, p   =  0.008) and R (MD  =  24.755, p   =  0.09) were higher in male athletes practicing team sports than individual sports. Female team sports athletes presented higher values of Z (MD  =  32.029, p   =  0.015) and R (MD  =  31.987, p   =  0.015) than individual female athletes. It was concluded that ECW/ICW and ECW/BCM ratios were higher in male athletes who practiced individual sports. For the Z, R, and Xc values, the athletes in team sports presented higher values. The female athletes who practiced team sports presented higher values of Z and R than did individual female athletes.

SIGNIFICANCE

ECW/ICW and ECW/BCM ratios were higher in male athletes who practiced individual sports. For the Z, R, and Xc values, the athletes in team sports presented higher values. The female athletes who practiced team sports presented higher values of Z and R than did individual female athletes.

Smart Wound Dressings for Diabetic Chronic Wounds

Given their severity and non-healing nature, diabetic chronic wounds are a significant concern to the 30.3 million Americans diagnosed with diabetes mellitus (2015). Peripheral arterial diseases, neuropathy, and infection contribute to the development of these wounds, which lead to an increased incidence of lower extremity amputations. Early recognition, debridement, offloading, and controlling infection are imperative for timely treatment. However, wound characterization and treatment are highly subjective and based largely on the experience of the treating clinician. Many wound dressings have been designed to address particular clinical presentations, but a prescriptive method is lacking for identifying the particular state of chronic, non-healing wounds. The authors suggest that recent developments in wound dressings and biosensing may allow for the quantitative, real-time representation of the wound environment, including exudate levels, pathogen concentrations, and tissue regeneration. Development of such sensing capability could enable more strategic, personalized care at the onset of ulceration and limit the infection leading to amputation. This review presents an overview of the pathophysiology of diabetic chronic wounds, a brief summary of biomaterial wound dressing treatment options, and biosensor development for biomarker sensing in the wound environment.

Bioelectrical impedance vector analysis (BIVA) in sport and exercise: Systematic review and future perspectives

Background

Bioelectrical impedance vector analysis (BIVA) is a general concept that includes all methodologies used in the analysis of the bioelectrical vector, whereas the "classic" BIVA is a patented methodology included among these methods of analysis. Once this was clarified, the systematic review of the literature provides a deeper insight into the scope and range of application of BIVA in sport and exercise.

Objective

The main goal of this work was to systematically review the sources on the applications of BIVA in sport and exercise and to examine its usefulness and suitability as a technique for the evaluation of body composition, hydration status, and other physiological and clinical relevant characteristics, ultimately to trace future perspectives in this growing area, including a proposal for a research agenda.

Methods

Systematic literature searches in PubMed, SPORTDiscus and Scopus databases up to July, 2017 were conducted on any empirical investigations using phase-sensitive bioimpedance instruments to perform BIVA within exercise and sport contexts. The search included healthy sedentary individuals, physically active subjects and athletes.

Result

Nineteen eligible papers were included and classified as sixteen original articles and three scientific conference communications. Three studies analysed short-term variations in the hydration status evoked by exercise/training through whole-body measurements, eleven assessed whole-body body composition changes induced by long-term exercise, four compared athletic groups or populations using the whole-body assessment, and two analysed bioelectrical patterns of athletic injuries or muscle damage through localised bioimpedance measurements.

Conclusions

BIVA is a relatively new technique that has potential in sport and exercise, especially for the assessment of soft-tissue injury. On the other hand, the current tolerance ellipses of “classic” BIVA are not a valid method to identify dehydration in individual athletes and a new approach is needed. “Specific” BIVA, a method which proposes a correction of bioelectrical values for body geometry, emerges as the key to overcome “classic” BIVA limitations regarding the body composition assessment. Further research establishing standardised testing procedures and investigating the relationship between physiology and the bioelectrical signal in sport and exercise is needed.

An objective measure for the assessment and management of fluid shifts in acute major burns

BACKGROUND

Major burns are life threatening. Fluid resuscitation is required for survival to maintain intravascular volumes and prevent hypovolemic shock. Bioimpedance spectroscopy (BIS) has been recognised as a potential method of monitoring fluid shifts after burn and in other disease states. The aims of this study were to examine the reliability of BIS across different dressing conditions and electrode positions, establish the influence of Acticoat™ on BIS variable measures and determine the validity of whole-body BIS to assess net fluid shift in the presence of moderate to major burns.

METHODS

An observational longitudinal cohort study was conducted from December 2014 to February 2016. Patients with over 15% total body surface area (TBSA) burns and injury less than 48 h were enrolled in the study. BIS triplicate measures were collected in an open wound and with an ActicoatTM dressing (at 5 half hour intervals). Standard and alternate electrode placements were utilised for the reliability analysis and standard placement only for determining the validity of BIS in moderate to major burns. The ImpediMde SFB7 was used to collect whole-body and segmental BIS measures. Stata statistical software, release 14 was utilised to analyse all results. Descriptive analyses were performed and were reported using the means and standard deviations (SD).

RESULTS

BIS-repeated measures established BIS raw resistance (R), and predicted volume variables were reliable in any condition (intra-class correlation coefficient (ICC) 0.996-0.999, 95% confidence intervals (CI) 0.996-0.999) without a systematic difference. Acticoat™ dressings significantly influenced all BIS-predicted volumes (p ≤ 0.01) as determined by multilevel mixed effects (MLME) linear regression analysis. Validity of BIS was demonstrated by resistance variables significantly decreasing with increasing net ionic fluid shift and increased TBSA (severity of injury) and calculated fluid volumes increasing with increasing net fluid shift and TBSA. BIS resistance also decreased with time as oedema reduced. For clinical use, a calculator was developed to adjust BIS variables when an Acticoat™ dressing is in situ, thus facilitating BIS variable change estimates in real time, with dressings intact.

CONCLUSION

BIS may be used clinically to monitor fluid volume change in major acute burns.

Scaling and the frequency dependence of Nyquist plot maxima of the electrical impedance of the human thigh

OBJECTIVE

To define and elucidate the properties of reduced-variable Nyquist plots.

APPROACH

Non-invasive measurements of the electrical impedance of the human thigh. A retrospective analysis of the electrical impedances of 154 normal subjects measured over the past decade shows that 'scaling' of the Nyquist plots for human thigh muscles is a property shared by healthy thigh musculature, irrespective of subject and the length of muscle segment. Here the term scaling signifies the near and sometimes 'perfect' coalescence of the separate X versus R plots into one 'reduced' Nyquist plot by the simple expedient of dividing R and X by X _m , the value of X at the reactance maximum. To the extent allowed by noise levels one can say that there is one 'universal' reduced Nyquist plot for the thigh musculature of healthy subjects.

MAIN RESULTS

There is one feature of the Nyquist curves which is not 'universal', however, namely the frequency f _m at which the maximum in X is observed. That is found to vary from 10 to 100 kHz. depending on subject and segment length. Analysis shows, however, that the mean value of 1/f _m is an accurately linear function of segment length, though there is a small subject-to-subject random element as well. Also, following the recovery of an otherwise healthy victim of ankle fracture demonstrates the clear superiority of measurements above about 800 kHz, where scaling is not observed, in contrast to measurements below about 400 kHz, where scaling is accurately obeyed.

SIGNIFICANCE

The ubiquity of 'scaling' casts new light on the interpretation of impedance results as they are used in electrical impedance myography and bioelectric impedance analysis.

Monitoring wound healing in minor burns-A novel approach

Assessment of minor burn wound closure is predominately determined by visual inspection and clinical specialist assessment, which remains largely a subjective analysis and results may vary depending on the clinician's experience. Bioimpedance spectroscopy (BIS) is an instrument that has a demonstrated ability to objectively monitor the wound healing process in various patient populations but has not yet been used in acute burn wounds. The aim of the pilot study was to examine whether the BIS technique is a valid measure of wound healing. Localised BIS resistance and phase angle triplicate measures, of minor limb burns, were collected on two serial occasions. Circumference limb measures were taken at the localised burn site to determine a truncated limb volume. Proportional-odds ordered logistic regression analyses determined resistance at zero frequency (R₀, indicative of edema) and resistance of total body fluid (R_inf) were significantly associated with healing after adjustment for the influence of surgery. A one unit increase in R₀ and R_inf increased the odds of wound healing by 6% and 5% respectively (p<0.01). Phase angle at 50kHz and R_i were not significantly associated with the markers of the wound healing process. Spearman's correlation determined there was a significant association between a healing wound and limb segment volume (ml) (rho -0.30, p<0.01). BIS is a technique, which has the potential to monitor the progress of wound healing.

Bioimpedance measurement based evaluation of wound healing

OBJECTIVE

Our group has developed a bipolar bioimpedance measurement-based method for determining the state of wound healing. The objective of this study was to assess the capability of the method.

METHODS

To assess the performance of the method, we arranged a follow-up study of four acute wounds. The wounds were measured using the method and photographed throughout the healing process.

RESULTS

Initially the bioimpedance of the wounds was significantly lower than the impedance of the undamaged skin, used as a baseline. Gradually, as healing progressed, the wound impedance increased and finally reached the impedance of the undamaged skin.

CONCLUSION

The clinical appearance of the wounds examined in this study corresponded well with the parameters derived from the bioimpedance data.

SIGNIFICANCE

Hard-to-heal wounds are a significant and growing socioeconomic burden, especially in the developed countries, due to aging populations and to the increasing prevalence of various lifestyle related diseases. The assessment and the monitoring of chronic wounds are mainly based on visual inspection by medical professionals. The dressings covering the wound must be removed before assessment; this may disturb the wound healing process and significantly increases the work effort of the medical staff. There is a need for an objective and quantitative method for determining the status of a wound without removing the wound dressings. This study provided evidence of the capability of the bioimpedance based method for assessing the wound status. In the future measurements with the method should be extended to concern hard-to-heal wounds.

Detection of muscle gap by L-BIA in muscle injuries: clinical prognosis

Sport-related muscle injury classifications are based basically on imaging criteria such as ultrasound (US) and magnetic resonance imaging (MRI) without consensus because of a lack of clinical prognostics for return-to-play (RTP), which is conditioned upon the severity of the injury, and this in turn with the muscle gap (muscular fibers retraction). Recently, Futbol Club Barcelona's medical department proposed a new muscle injury classification in which muscle gap plays an important role, with the drawback that it is not always possible to identify by MRI. Localized bioimpedance measurement (L-BIA) has emerged as a non-invasive technique for supporting US and MRI to quantify the disrupted soft tissue structure in injured muscles.

OBJECTIVE

To correlate the severity of the injury according to the gap with the RTP, through the percent of change in resistance (R), reactance (Xc) and phase-angle (PA) by L-BIA measurements in 22 muscle injuries.

MAIN RESULTS

After grouping the data according to the muscle gap (by MRI exam), there were significant differences in R between grade 1 and grade 2f (myotendinous or myofascial muscle injury with feather-like appearance), as well as between grade 2f and grade 2g (myotendinous or myofascial muscle injury with feather and gap). The Xc and PA values decrease significantly between each grade (i.e. 1 versus 2f, 1 versus 2g and 2f versus 2g). In addition, the severity of the muscle gap adversely affected the RTP with significant differences observed between 1 and 2g as well as between 2f and 2g.

SIGNIFICANCE

These results show that L-BIA could aid MRI and US in identifying the severity of an injured muscle according to muscle gap and therefore to accurately predict the RTP.

Assessing the immediate impact of botulinum toxin injection on impedance of spastic muscle

This study aimed to investigate the immediate impacts of Botulinum Toxin A (BoNT-A) injections on the inherent electrical properties of spastic muscles using a newly developed electrical impedance myography (EIM) technique. Impedance measures were performed before and after a BoNT-A injection in biceps brachii muscles of 14 subjects with spasticity. Three major impedance variables, resistance (R), reactance (X) and phase angle (θ) were obtained from three different configurations, and were evaluated using the conventional EIM frequency at 50kHz as well as multiple frequency analysis. Statistical analysis demonstrated a significant decrease of resistance in the injected muscles (Multiple-frequency: R_pre=25.17±1.94Ohm, R_post=23.65±1.63Ohm, p<0.05; 50kHz: R_pre=29.06±2.16Ohm, R_post=27.7±1.89Ohm, p<0.05). Despite this decrease, there were no substantial changes in the reactance, phase angle, or anisotropy features after a BoNT-A injection. The significant changes of muscle resistance were most likely associated with the liquid injection of the BoNT-A-saline solution rather than the immediate toxin effects on the muscle. This study demonstrated high sensitivity of the EIM technique in the detection of alterations to muscle composition.

Wearable Vector Electrical Bioimpedance System to Assess Knee Joint Health

OBJECTIVE

We designed and validated a portable electrical bioimpedance (EBI) system to quantify knee joint health.

METHODS

Five separate experiments were performed to demonstrate the: 1) ability of the EBI system to assess knee injury and recovery; 2) interday variability of knee EBI measurements; 3) sensitivity of the system to small changes in interstitial fluid volume; 4) reducing the error of EBI measurements using acceleration signals; and 5) use of the system with dry electrodes integrated to a wearable knee wrap.

RESULTS

1) The absolute difference in resistance ( R) and reactance (X) from the left to the right knee was able to distinguish injured and healthy knees (p < 0.05); the absolute difference in R decreased significantly (p < 0.05) in injured subjects following rehabilitation. 2) The average interday variability (standard deviation) of the absolute difference in knee R was 2.5 Ω and for X was 1.2 Ω. 3) Local heating/cooling resulted in a significant decrease/increase in knee R (p < 0.01). 4) The proposed subject position detection algorithm achieved 97.4% leave-one subject out cross-validated accuracy and 98.2% precision in detecting when the subject is in the correct position to take measurements. 5) Linear regression between the knee R and X measured using the wet electrodes and the designed wearable knee wrap were highly correlated ( R² = 0.8 and 0.9, respectively).

CONCLUSION

This study demonstrates the use of wearable EBI measurements in monitoring knee joint health.

SIGNIFICANCE

The proposed wearable system has the potential for assessing knee joint health outside the clinic/lab and help guide rehabilitation.

A Robust System for Longitudinal Knee Joint Edema and Blood Flow Assessment Based on Vector Bioimpedance Measurements

We present a robust vector bioimpedance measurement system for longitudinal knee joint health assessment, capable of acquiring high resolution static (slowly varying over the course of hours to days) and dynamic (rapidly varying on the order of milli-seconds) bioresistance and bioreactance signals. Occupying an area of 78×90 mm(2) and consuming 0.25 W when supplied with ±5 V, the front-end achieves a dynamic range of 345 Ω and noise floor of 0.018 mΩrms (resistive) and 0.055 mΩrms (reactive) within a bandwidth of 0.1-20 Hz. A microcontroller allows real-time calibration to minimize errors due to environmental variability (e.g., temperature) that can be experienced outside of lab environments, and enables data storage on a micro secure digital card. The acquired signals are then processed using customized physiology-driven algorithms to extract musculoskeletal (edema) and cardiovascular (local blood volume pulse) features from the knee joint. In a feasibility study, we found statistically significant differences between the injured and contralateral static knee impedance measures for two subjects with recent unilateral knee injury compared to seven controls. Specifically, the impedance was lower for the injured knees, supporting the physiological expectations for increased edema and damaged cell membranes. In a second feasibility study, we demonstrate the sensitivity of the dynamic impedance measures with a cold-pressor test, with a 20 mΩ decrease in the pulsatile resistance associated with increased downstream peripheral vascular resistance. The proposed system will serve as a foundation for future efforts aimed at quantifying joint health status continuously during normal daily life.

Body composition and functional assessment of nutritional status in adults: a narrative review of imaging, impedance, strength and functional techniques

The accurate and valid assessment of body composition is essential for the diagnostic evaluation of nutritional status, identifying relevant outcome measures, and determining the effectiveness of current and future nutritional interventions. Developments in technology and our understanding of the influences of body composition on risk and outcome will provide practitioners with new opportunities to enhance current practice and to lead future improvements in practice. This is the second of a two-part narrative review that aims to critically evaluate body composition methodology in diverse adult populations, with a primary focus on its use in the assessment and monitoring of under-nutrition. Part one focused on anthropometric variables [Madden and Smith (2016) J Hum Nutr Diet 29: 7-25] and part two focuses on the use of imaging techniques, bioelectrical impedance analysis, markers of muscle strength and functional status, with particular reference to developments relevant to practice.

Impedance sensing device enables early detection of pressure ulcers in vivo

When pressure is applied to a localized area of the body for an extended time, the resulting loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure and time that results in tissue damage varies widely between patients, and the underlying damage is often severe by the time a surface wound becomes visible. Currently, no method exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible, electronic device that non-invasively maps pressure-induced tissue damage, even when such damage cannot be visually observed. Using impedance spectroscopy across flexible electrode arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health across multiple animals and wound types. Our results demonstrate the feasibility of an automated, non-invasive 'smart bandage' for early detection of pressure ulcers.

Effects of muscle injury severity on localized bioimpedance measurements

Muscle injuries in the lower limb are common among professional football players. Classification is made according to severity and is diagnosed with radiological assessment as: grade I (minor strain or minor injury), grade II (partial rupture, moderate injury) and grade III (complete rupture, severe injury). Tetrapolar localized bioimpedance analysis (BIA) at 50 kHz made with a phase-sensitive analyzer was used to assess damage to the integrity of muscle structures and the fluid accumulation 24 h after injury in 21 injuries in the quadriceps, hamstring and calf, and was diagnosed with magnetic resonance imaging (MRI). The aim of this study was to identify the pattern of change in BIA variables as indicators of fluid [resistance (R)] and cell structure integrity [reactance (Xc) and phase angle (PA)] according to the severity of the MRI-defined injury. The % difference compared to the non-injured contralateral muscle also measured 24-h after injury of R, Xc and PA were respectively: grade I (n = 11; -10.4, -17.5 and -9.0%), grade II (n = 8; -18.4, -32.9 and -16.6%) and grade III (n = 2; -14.1, -52.9 and -43.1%), showing a greater significant decrease in Xc (p < 0.001). The greatest relative changes were in grade III injuries. However, decreases in R, that indicate fluid distribution, were not proportional to the severity of the injury. Disruption of the muscle structure, demonstrated by the localized determination of Xc, increased with the severity of muscle injury. The most significant changes 24 h after injury was the sizeable decrease in Xc that indicates a pattern of disrupted soft tissue structure, proportional to the severity of the injury.

Multimodal noninvasive monitoring of soft tissue wound healing

Here we report results of non-invasive measurements of indirect markers of soft tissue healing of traumatic wounds in an observational swine study and describe the quantification of analog physiological signals. The primary purpose of the study was to measure bone healing of fractures with four different wound treatments. A second purpose was to quantify soft tissue wound healing by measuring the following indirect markers: (1) tissue oxygenation, (2) fluid content, and (3) blood flow, which were all measured by non-invasive modalities, measured with available devices. Tissue oxygenation was measured by near infrared spectroscopy; fluid content was measured by bipolar bio-impedance; and blood flow was measured by Doppler ultrasound. Immediately after comminuted femur fractures were produced in the right hind legs of thirty anesthetized female Yorkshire swine, one of four wound treatments was instilled into each wound. The four wound treatments were as follows: salmon fibrinogen/thrombin-n = 8; commercial bone filler matrix-n = 7; bovine collagen-n = 8; porcine fibrinogen/thrombin-n = 7. Fractures were stabilized with an external fixation device. Immediately following wound treatments, measurements were made of tissue oxygenation, fluid content and blood flow; these measurements were repeated weekly for 3 weeks after surgery. Analog signals of each modality were recorded on both the wounded (right) hind leg and the healthy (left) hind leg, for comparison purposes. Data were processed off-line. The mean values of 10-s periods were calculated for right-left leg comparison. ANOVA was applied for statistical analysis. Results of the bone healing studies are published separately (Rothwell et al. in J Spec Oper Med 13:7-18, 2013). For soft tissue wounds, healing did not differ significantly among the four wound treatments; however, regional oxygenation of wounds treated with salmon fibrinogen/thrombin showed slightly different time trends. Further studies are needed to establish standards for healthy wound healing and for detection of pathological alterations such as infection. Non-invasive measurement and quantification of indirect markers of soft tissue wound healing support the goals and principles of evidence-based medicine and show potential as easy to administer tools for clinicians and battlefield medical personnel to apply when procedures such as the PET scan are not available or affordable. The method we developed for storing analog physiological signals could be used for maintaining electronic health records, by incorporating vital signs such as ECG and EEG, etc.

Evolution of bioimpedance: a circuitous journey from estimation of physiological function to assessment of body composition and a return to clinical research

BACKGROUND/OBJECTIVES

Bioimpedance is the collective term that describes safe, non-invasive methods to measure the electrical responses to the introduction of a low-level, alternating current into a living organism, and the biophysical models to estimate body composition from bioelectrical measurements. Although bioimpedance techniques have been used for more than 100 years to monitor assorted biological components, the desire to translate bioelectrical measurements into physiological variables advanced the creation of empirical prediction models that produced inconsistent results.

SUBJECTS/METHODS

This paper succinctly reviews the origin, and critically evaluates the conceptual models and the implementation of bioimpedance in clinical research, including indirect assessment of assorted physiological functions and body composition (fluid volumes and fat-free mass), classification of hydration, regional fluid accumulation, prognosis in disease and wound healing.

RESULTS

Despite widespread and mounting interest in the use of bioimpedance to characterise body structure and function, most experimental findings reveal the limitations of existing physical models and reliance on multiple regression models for use in assessments of an individual.

CONCLUSIONS

Contemporary applications of bioimpedance emphasise the value of bioimpedance variables per se in some novel biomedical applications with the objective of identifying opportunities for future outcome-based research.