Arm, Leg, and Foot Skin Water in Persons With Diabetes Mellitus (DM) in Relation to HbA1c Assessed by Tissue Dielectric Constant (TDC) Technology Measured at 300 MHz

Sensors and Devices Based on Electrochemical Skin Conductance and Bioimpedance Measurements for the Screening of Diabetic Foot Syndrome: Review and Meta-Analysis

Diabetic foot syndrome is a multifactorial disease involving different etiological factors. This syndrome is also insidious, due to frequent lack of early symptoms, and its prevalence has increased in recent years. This justifies the remarkable attention being paid to the syndrome, although the problem of effective early screening for this syndrome, possibly at a patient's home, is still unsolved. However, some options appear available in this context. First, it was demonstrated that the temperature measurement of the foot skin is an interesting approach, but it also has some limitations, and hence a more effective approach should combine data from temperature and from other sensors. For this purpose, foot skin conductance or bioimpedance measurement may be a good option. Therefore, the aim of this study was to review those studies where skin conductance/bioimpedance measurement was used for the detection of diabetic foot syndrome. In addition, we performed a meta-analysis of some of those studies, where a widely used device was exploited (SUDOSCAN®) for foot skin conductance measurement, and we found that skin conductance levels can clearly distinguish between groups of patients with and without diabetic neuropathy, the latter being one of the most relevant factors in diabetic foot syndrome.

Skin tissue dielectric constant: Time of day and skin depth dependence

BACKGROUND

Skin water measurements are used to investigate skin physiology, clinically study dermatological issues, and for conditions like diabetes, oedema, and lymphedema with measurements done at various times of day (TOD). One method used is skin's tissue dielectric constant (TDC), often clinically measured to a single depth of 2.5 mm. This report characterizes intraday variations measured to multiple depths to guide expected TOD and depth dependence.

MATERIALS AND METHODS

Twelve medical students self-measured TDC on their forearm to depths of 0.5, 1.5, 2.5, and 5.0 mm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All were trained in the procedure.

RESULTS

TDC declined slightly from morning through evening, mostly at 0.5 mm for which TDC was reduced by 4%. TDC values were not related to participants' whole-body fat or water percentages. The TDC decrease was less at 1.5 mm where the reduction was 2.7%. At depths of 2.5 or 5.0 mm, there was no significant decrease in TOD.

CONCLUSION

Skin TDC shows a minor decreasing trend with an effect greater for shallower depths. In part, the clinical relevance of the findings relates to the confidence level associated with skin water estimates, based on TDC measurements, when measured at different TOD and depths during normal clinic hours. Based on the present data the TOD change is at most 4% and insignificant for measurement depths of 2.5 mm.

Intraday Variations in Skin Water Parameters

INTRODUCTION

Three interrelated skin water assessments include stratum corneum hydration (SCH) via electrical measurements, skin water using tissue dielectric constant (TDC) measurements, and transepidermal water loss (TEWL). These are differentially used for skin physiology research, clinical assessments of dermatological conditions and to assess skin water in diabetes and lymphedema. Often volar forearm skin is used for assessments done at various times of day (TOD). The present goal was to assess the extent of intraday variability in SCH, TDC, and TEWL.

METHODS

Twelve medical students self-measured SCH, TDC, and TEWL on their forearm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All participants were well trained and pre-certified in all procedures. Tests for parameter differences among TOD were via the nonparametric Friedman test.

RESULTS

No significant differences in SCH or TEWL were found among TOD over the 16-h interval for either day or combined. Contrastingly, TDC decreased slightly but significantly from morning through evening. There was no evidence of a diurnal pattern. Interestingly, a significant nonlinear relationship between TEWL and SCH was detected.

CONCLUSION

Findings indicate only minor intraday variations with TOD trend except for TDC which decreases slightly from morning through evening. The clinical relevance relates to the confidence now gained associated with the parameter estimates when measured at different TOD during normal clinic hours or beyond. This should help in estimating the potential importance of small differences if measured at a different TOD. From a physiological viewpoint, the findings uncover and describe an interesting nonlinear relationship between TEWL and SCH which may serve to propel further investigations that might better characterize this process.

The History and Current Status of Platelet-Rich Plasma Therapy in Dermatology

Since the 1800s, platelet-rich plasma (PRP) has been used as a treatment for a wide range of medical conditions with a concomitant effect of tending to reduce the need for some invasive procedures. The aim of this narrative review was to concisely document the history and current usage of PRP specifically in the field of dermatology. Four databases (PubMed, Google Scholar, CINAHL, and Web of Science) were searched for primary articles written in English that evaluated human subjects and focused on PRP use in dermatology. Initial search terms included "platelet rich plasma," "alopecia," "androgenic alopecia," "dermatology," "PDGF," "aging," "skin rejuvenation," "diabetic ulcers," "venous leg ulcers," "acne," "acne scars," "scars," "hyperpigmentation," "melasma," "hypopigmentation," "vitiligo," and "PRP." After review, articles were excluded if they were commentaries, editorials, animal studies, review articles, or were unrelated to dermatology. The bibliography of retrieved articles was also searched for relevant articles. The present review results describe the function of PRP from its first usage for thrombocytopenia to its usage for melasma. In this time frame, its use in dermatology has gone through many evolutions from using its healing factors for treating wounds to using it as the treatment for wrinkles, hair loss, scars, ulcers, and skin pigmentation disorders. Its anti-inflammatory and growth factors have been shown to initiate a healing cascade that promotes the growth and regeneration of tissues. It is hoped that this review will help educate patients and physicians about the efficacy of PRP therapy and thereby help avoid unnecessary invasive procedures for certain conditions.

Intra-day variations in volar forearm skin hydration

BACKGROUND

Skin hydration (SKH) measurements are used for multiple purposes: to study skin physiology, to clinically investigate dermatological issues, and to assess localized skin water in pathologies like diabetes and lymphedema. Often the volar forearm is measured at various times of day (TOD). This report aims to characterize intra-day variations in volar forearm SKH to provide guidance on expected TOD dependence.

MATERIALS AND METHODS

Forty medical students (20 male) self-measured tissue dielectric constant (TDC) on their non-dominant forearm in triplicate as an index of local skin tissue water every 2 h starting at 0800 and ending at 2400 h. All were trained and pre-certified in the procedure and had whole-body fat (FAT%) and water (H2O%) measured. Day average TDC (TDCAVG) was determined as the average of all time points expressed as mean ± SD.

RESULTS

Males versus females had similar ages (25.1 ± 2.2 years vs. 25.1 ± 1.5 years), higher H2O% (56.6 ± 5.0 vs. 51.8 ± 5.7, p = 0.002), and higher TDCAVG (32.7 ± 4.1 vs. 28.5 ± 5.1, p = 0.008). TDC values were not significantly impacted by H2O% or FAT%. Female TDC exhibited a significant decreasing trend from morning to night (p = 0.004); male TDC showed no trend.

CONCLUSION

Skin water assessed by TDC shows some intra-day variations for females and males but with quite different temporal patterns. Clinical relevance relates to the confidence level associated with skin hydration estimates when measured at different times of day during normal clinic hours which, based on the present data, is expected to be around 5% for both males and females.

Assessment Modalities for Lower Extremity Edema, Lymphedema, and Lipedema: A Scoping Review

Lower extremity swelling may be broadly characterized as due to edema, lymphedema, or lipedema. Differentiation between these three conditions is important for providing appropriate treatment. This review analyzes and compares different clinical diagnostic modalities for these conditions, with the aim of assisting in the process of choosing the most appropriate diagnostic modality by highlighting the advantages and limitations of each. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for a systematic search of peer-reviewed literature, the following diagnostic methods for lower extremity swelling were investigated: (1) ultrasound (US), (2) lymphoscintigraphy (LSG), (3) computed tomography (CT), (4) bioimpedance spectroscopy (BIS), (5) tissue dielectric constant (TDC), and (6) magnetic resonance imaging (MRI), including magnetic resonance lymphangiography (MRL). The databases used in the search were PubMed, ProQuest, CINAHL Complete, Web of Science, Embase, and Biomedical Reference Collection. After retrieving 115 studies based on predetermined inclusion criteria, a total of 31 studies were critically evaluated. The main results indicate the following: duplex US is the modality of choice to initially identify lower extremity edema such as deep venous thrombosis (DVT) and venous reflux due to its high sensitivity and specificity. CT venography of the lower extremity appears to bethe preferred option for gynecologic cancer patients with lower extremity swelling post-treatment, as it measures subcutaneous tissue volumes to look for DVTs, lymphoceles, and cancer recurrence. TDC is a recommended modality for a variety of conditions, including edema and lymphedema, in part, due to its noninvasive localized assessment capabilities and ease of use. LSG emerges as an effective imaging modality for lymphedema characterization with minimal invasiveness and high sensitivity and specificity. BIS is widely used to identify and monitor lower extremity lymphedema but has been reported to have low sensitivity and lacks the ability to account for changes in tissue composition such as fibrosis. US and MRL are favored for lipedema diagnosis, with MRL providing comprehensive anatomical and functional insights, albeit with cost and accessibility limitations compared to US. While CT, MRI, US, and TDC are all useful for differentiating lymphedema from lipedema, MRI is the preferred modality due to its anatomical and functional diagnostic capabilities. However, US is a pragmatic alternative for use with obese patients or when MRI is not an option.

Medical Applications of Skin Tissue Dielectric Constant Measurements

Tissue dielectric constant (TDC) values assess certain skin properties that are dependent on multiple factors but mainly on the relative amount of water content within a locally measured tissue volume. Because of the non-invasive nature of these measurements and their ease of use, the method has been widely used in various medically related applications. The goal of this paper was to review and describe the uses and findings of such TDC measurements, considering and including the wide array of medical applications. The review is in part based on information derived from an analysis of published material obtained via literature searches of four major electronic databases and, in part, based on the author's experience with the TDC measurement methods and their various applications and his professional experiences. The databases searched were PubMed, Web of Science, EMBASE, and CINAHL Complete. Based on the initial search criteria, a total of 1257 titles were identified. After removing duplicates and filtering according to relevancy, 160 remained for detailed further review. In some cases, the bibliography of these retrieved articles provided additional sources. The findings demonstrate multiple research and medical uses and applications of TDC measurements, focusing on detecting and quantifying localized edema and lymphedema in multiple target sites. These include the upper and lower extremities, breasts, and trunk as regions involved in medical conditions causing lymphedema. In addition, the findings suggest that TDC evaluations are a convenient, non-invasive method to study and evaluate other conditions impacting skin, including diabetes mellitus and skin wounds or ulcers. Its ability to detect aspects of tissue changes simply and rapidly at almost any anatomical location makes it a useful tool for investigating multiple dermatological conditions and their treatment as future applications of this method.

The effect of adjuvant radiotherapy on skin biophysical properties in patients with breast cancer at risk for breast lymphedema: A prospective study

Breast cancer (BC) is the most common type of cancer among women. Radiotherapy (RT) is one of the main and primary treatment options for BC, especially in breast-conserving surgery (BCS). BC patients who underwent RT experience a wide range of symptoms, in which breast oedema and irritation of the skin take the lion's share. Breast oedema/lymphedema, which is also a prominent side effect after RT should be well determined in earlier settings due to the chronicity of lymphedema. Therefore, this study aimed to analyze the biophysical parameters of skin on the ipsilateral (IL) and contralateral (CL) sites via Tissue dielectric constant (TDC) and Transepidermal water loss (TEWL) methods in terms of oedema and skin barrier function (SBF). The following reference points before and after the RT were measured: (R1: Pectoralis muscle, R2: Upper breast, R3: Lower breast, R4: Lateral site of the thorax). A total of 24 BC patients (mean age and BMI: 52.78 ± 9.85 years and 28.42 ± 5.64 kg/m² ) were evaluated. In the IL site, the SBF was not found significant in R1-R3, whereas significantly lower SBF was observed in R4 after RT (t = -3.361, p = 0.003). A significant increase in TDC was observed in R2 at the 5.0 mm depth (t = -2.500, p = 0.02). We suggest that a longer period of follow-up should be carefully carried out to track changes in terms of SBF and oedema in the irradiated breast. The increased need for early detection of changes associated with breast lymphedema can be achievable via noninvasive, safe, cheap, and easily repeatable devices.

Skin hydration level cutoff value to predict wound healing potential in diabetic foot ulcers

AIMS

Transcutaneous oxygen pressure (TcPO₂) is a reliable predictor of wound healing in diabetes patients; however, measurements are cumbersome. Previously, we demonstrated that skin hydration in the feet of patients with diabetic foot ulcers (DFU) is influenced by microcirculation rather than peripheral nerve function. Furthermore, skin hydration level before recanalization can predict wound healing better than TcPO₂. This study investigated the skin hydration level cutoff value to predict DFU healing.

METHODS

We retrospectively enrolled 834 patients with DFU. Wound healing outcomes were graded as healed without amputation or with minor/major amputation. Receiver operating characteristic analysis was used to evaluate the ability of skin hydration to predict wound healing outcomes and determine the optimal cutoff value for subsequent analyses.

RESULTS

Average skin hydration values in the healed without and with amputation groups were 25.0 ± 7.4 arbitrary units (a.u.) and 17.5 ± 5.7 a.u., respectively (P < 0.001). The healing rate without amputation increased with skin hydration. A skin hydration value ≥ 21 a.u. significantly lowered the incidence of amputation. The cutoff value was 21 a.u. [(Youden's index, sensitivity, specificity, P-value) = (1.6, 92, 69.6, P < 0.001)].

CONCLUSIONS

A minimal skin hydration value of 21 a.u. is required for diabetic wound healing.

Breast Tissue Dielectric Constant as a Potential Breast Edema Assessment Parameter

Background: Many methods can quantitatively assess limb lymphedema, but methods to assess breast edema/lymphedema are quite limited. Thus, there is a need for a convenient and accurate way to quantify and track changes in this condition. Herein, breast tissue dielectric constant (TDC) values that depend on tissue water were used to obtain reference TDC values and interbreast TDC ratios. Methods and Results: TDC was measured in both breasts of 61 women who were about to undergo an ultrasound-guided diagnostic biopsy of a single mass (tumor) in 1 breast. Patient age and body mass index were (mean ± SD) 65.1 ± 11.6 (41-87 years) and 28.9 ± 5.1 (19.1-43.7 kg/m2). TDC was measured at a standardized site (12 o'clock position) with the TDC probe placed with its outer edge at the periphery of the subareolar region. TDC values of healthy breasts versus tumor breasts showed tumor breasts 3% greater (30.4 ± 4.6 vs. 29.5 ± 4.6, p = 0.02). Patients with benign tumors (N = 33) showed no difference between breasts (30.5 ± 4.4 vs. 30.8 ± 4.6 p = 0.434) and had an interbreast TDC ratio (tumor breast/healthy breast) of 1.013 ± 0.077. Patients with malignant tumors (N = 28) had tumor breast values 5% greater (29.8 ± 4.8 vs. 28.4 ± 4.6, p = 0.018) and an interbreast ratio of 1.056 ± 0.117. The overall interbreast ratio (N = 61) was 1.033 ± 0.099. Conclusion: Breast TDC values from nonedematous breasts provide the basis for calculating potential edematous/lymphedematous threshold values based on the measured means +2.5 standard deviation (SD). Accordingly, a TDC threshold value of 41 and an interbreast ratio of 1.28 were determined. These parameters have potential applicability for early detection in at-risk patients and those suspected of having breast edema/lymphedema.

Assessing Potential Circadian, Diurnal, and Ultradian Variations in Skin Biophysical Properties

A variety of skin measurements are routinely made in various clinical and research settings to evaluate the skin’s biophysical properties for diagnostic and research purposes. Such measurements include transepidermal water loss (TEWL), skin pH, sebum, skin blood flow (SBF), and tissue dielectric constant (TDC) as a measure of skin water. Given the various reported circadian, diurnal, and possible ultradian and other temporal variations in skin physiological processes, it is of value to have clarity as to possible temporal variations in skin’s biophysical properties associated with such processes. It was thus the purpose of this investigation to review and detail key elements of what is currently known regarding such variations and to provide a characterization that will permit informed judgments as to the sensitivity of the timing of measurements to optimize measurement reproducibility.

Understanding these variations and their possible oscillatory effects on skin biophysical properties may aid physicians in providing optimal treatment timing for dermatological conditions and offer researchers insight into optimal measurement timing. The major findings of the present investigation that systematically searched multiple databases and critically examined pertinent findings, revealed that of the several skin parameters reviewed, which included TEWL, pH, sebum, SBF, TDC, and thickness, each had at least one study describing a statistically significant within-a-day temporal change. The magnitude of these changes varied and may be large enough to be seriously considered when assessing these parameters in clinical and research settings. However, inconsistencies in reported temporal variations suggest that further systematic research is well warranted especially with respect to temporal within-a-day and day-to-day variabilities of TEWL, TDC, and mechanical properties. At present, the impact of this type of confounding variability on reported values for skin biophysical parameters is unclear and worthy of further clarification.

Tissue Dielectric Constant Measures in Women With and Without Clinical Trunk Lymphedema Following Breast Cancer Surgery: A 78-Week Longitudinal Study

OBJECTIVE

Following breast cancer surgery with lymph node removal, women are at risk of developing lymphedema in the upper extremity or trunk. Currently, trunk lymphedema diagnosis relies on a clinical assessment because no quantifiable standard method exists. Tissue dielectric constant (TDC) values are quantifiable measures of localized skin tissue water and may be able to detect trunk lymphedema. The goal of this study was to (1) compare parameters derived from TDC measurements with those derived from clinically accepted criteria for trunk lymphedema in women following breast cancer surgery and (2) explore the potential utility of TDC to detect trunk lymphedema early in its progression.

METHODS

This prospective longitudinal study, a secondary analysis from a larger study, observed women with and without clinically determined truncal lymphedema following breast cancer surgery. TDC was measured on the lateral trunk wall at post-surgery weeks 2, 4, 12, and 78 in women who had surgical breast cancer treatment with lymph node removal. Clinical assessment for trunk lymphedema was determined at 78 weeks by a lymphedema expert. Comparison of TDC measurements in women with and without clinical trunk lymphedema was analyzed.

RESULTS

Clinical assessment identified trunk lymphedema in 15 out of 32 women at 78 weeks. These women had TDC ratios statistically higher than women without truncal lymphedema.

CONCLUSION

The overall findings indicate that TDC has the ability to quantify trunk lymphedema and might be valuable in early detection.

IMPACT

TDC may be a beneficial tool in the early detection of breast cancer-related trunk lymphedema, which could trigger intervention.

LAY SUMMARY

A new device may help recognize trunk lymphedema in patients with breast cancer so they could receive appropriate treatment.

Heat-related changes in skin tissue dielectric constant (TDC)

The impact of 20 min of whole-body heating (WBH) on the tissue dielectric constant (TDC) of forearm and hand skin was evaluated in 24 young adults. TDC was measured in triplicate at 300 MHz using an open-ended transmission line method in which the effective measurement depth was about 2 mm. TDC measurements are an effective way to assess and track localized oedema and lymphoedema. The underlying hypothesis was that heat-induced eccrine gland activation would increase TDC values via an increase in fluid within the TDC measurement volume. The goal was to test this concept and to determine the magnitude of the change when environmental temperatures were elevated to near 42°C and to estimate TDC recovery time. The practical aspect of this research is motivated by the fact that patients in whom such measurements are made may arrive at the clinic in various states of sweat gland activation. Thus, knowledge of the effect of such activation on measured TDC values permits better understanding of possible relationships between such activation and TDC values. Results showed that increasing environmental temperature from 23·3 ± 1·6 to 41·5 ± 1·3°C increased forearm and thenar eminence skin temperatures to 37·8 ± 0·5 and 37·9 ± 0·4°C, respectively. These changes were associated with increases in TDC at arm from 30·7 ± 4·6 to 36·3 ± 5·7 (18·2%) and at hand from 34·7 ± 4·9 to 45·1 ± 5·5 (30%). Based on calculated TDC recovery rates, it is concluded that temperature-related TDC variability can be minimized using a wait time of at least 15 min after bandage removal prior to TDC measurements in affected limbs.

Skin Hydration Level as a Predictor for Diabetic Wound Healing: A Retrospective Study

BACKGROUND

In the diabetic foot, the skin may crack and develop fissures, potentially increasing vulnerability to ulceration and infection. Therefore, maintaining adequate skin hydration may be crucial for diabetic wound healing. However, no clinical study has addressed this issue. This study aimed to determine and compare the effect of the skin hydration level on diabetic wound healing with that of the tissue oxygenation level, which is recognized as the most reliable parameter in predicting diabetic wound healing.

METHODS

This retrospective study included 263 diabetic patients with forefoot ulcers. Skin hydration and transcutaneous oxygen pressure data collected before and after percutaneous transluminal angioplasty were analyzed. Skin hydration and tissue oxygenation were graded as poor, moderate, or acceptable. Wound healing outcomes were graded as healed without amputation, minor amputation, or major amputation. Wound healing outcomes were compared using four parameters: skin hydration at baseline, transcutaneous oxygen pressure at baseline, post-percutaneous transluminal angioplasty skin hydration, and post-percutaneous transluminal angioplasty transcutaneous oxygen pressure.

RESULTS

Each of the four parameters exhibited statistically significant correlations with wound healing outcomes. In the concurrent analysis of both skin hydration and transcutaneous oxygen pressure, skin hydration was a dominant parameter (p = 0.0018) at baseline, whereas transcutaneous oxygen pressure was a dominant parameter (p < 0.0001) following percutaneous transluminal angioplasty.

CONCLUSIONS

Skin hydration level might be a useful predictor for diabetic wound healing. In particular, the skin hydration level before recanalization was found to be superior to transcutaneous oxygen pressure in predicting wound healing.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Minimum Detectable Changes Associated with Tissue Dielectric Constant Measurements as Applicable to Assessing Lymphedema Status

Background: Tissue dielectric constant (TDC) measurements are increasingly being used as a tool to help characterize lymphedema features, detect its presence, and assess treatment related changes. Although the underlying physics of this technology has been well described in the literature, there has been little systematic study of in vivo reliability aspects. A central unanswered question is the minimal detectable change (MDC) that, with a given level of confidence, may be ascribed to this technology. Our goal was to address this issue using test-retest measurements from which intraclass correlations coefficients (ICC) and MDC could be estimated. Methods and Results: Forty volunteers (20 females) aged 19-61 years with body mass indices of 14.7-47 kg/m² and body fat percentages of 12.0%-48.9% were evaluated. Two measurers (M1 and M2) used two different TDC measuring devices (multiprobe and compact) to measure TDC in triplicate sequentially and bilaterally at three locations; anterior forearm, hand palmar mid-thenar eminence, and dorsum mid-web. These measurements were made by each measurer twice constituting test-retest values (T1 and T2). From these measurements ICC_2,1 and MDC at 95% confidence were determined for each site and probe for absolute TDC values and for inter-side ratios. MDC values for absolute TDC ranged from 2 to 9 TDC units, and for inter-side ratios ranged from 5.3% to 8.0% depending on site and probe. ICC_2,1 values ranged from 0.765 to 0.982. Conclusions: The MDC values herein documented may be used to provide guidance to aid interpretation of measured TDC changes or differences in a clinical environment.