Bioimpedance Spectroscopy Measurements Research Articles

Determination of resistance at zero and infinite frequencies in bioimpedance spectroscopy for assessment of body composition in babies

Objective. Bioimpedance spectroscopy (BIS) is a popular technique for the assessment of body composition in children and adults but has not found extensive use in babies and infants. This due primarily to technical difficulties of measurement in these groups. Although improvements in data modelling have, in part, mitigated this issue, the problem continues to yield unacceptably high rates of poor quality data. This study investigated an alternative data modelling procedure obviating issues associated with BIS measurements in babies and infants. Approach. BIS data are conventionally analysed according to the Cole model describing the impedance response of body tissues to an applied AC current. This approach is susceptible to errors due to capacitive leakage errors of measurement at high frequency. The alternative is to model BIS data based on the resistance–frequency spectrum rather than the reactance-resistance Cole model thereby avoiding capacitive error impacts upon reactance measurements. Main results. The resistance–frequency approach allowed analysis of 100% of data files obtained from BIS measurements in 72 babies compared to 87% successful analyses with the Cole model. Resistance–frequency modelling error (percentage standard error of the estimate) was half that of the Cole method. Estimated resistances at zero and infinite frequency were used to predict body composition. Resistance-based prediction of fat-free mass (FFM) exhibited a 30% improvement in the two-standard deviation limits of agreement with reference FFM measured by air displacement plethysmography when compared to Cole model-based predictions. Significance. This study has demonstrated improvement in the analysis of BIS data based on the resistance frequency response rather than conventional Cole modelling. This approach is recommended for use where BIS data are compromised by high frequency capacitive leakage errors such as those obtained in babies and infants.

Comparison of Volume Measurements and Bioimpedance Spectroscopy Using A Stand-on Device for Assessment of Unilateral Breast Cancer-Related Lymphedema.

Breast cancer related lymphedema (BCRL) may be assessed through objective measurement of limb swelling with common techniques including volumetric measurement using a tape measure or perometry, and measurement of extracellular water using bioimpedance spectroscopy (BIS). This study aimed to evaluate the performance of a stand-on BIS device for detection of BCRL, introduce a novel graphical method to compare volumetric and BIS methods alongside traditional specificity and sensitivity analysis, and determine and compare BIS thresholds with those published previously. Female participants with indocyanine green lymphography confirmed unilateral arm lymphedema (n = 197) and healthy controls (n = 267) were assessed using a cross-sectional study design. BIS and volumetric measures were obtained in a single session. The BIS lymphedema index (L-Dex) method had a significantly higher sensitivity than the excess volume approach (area under the curve = 0.832 vs. 0.649, p = 0.0001). A threshold of L-Dex 6.5 had a higher true positive rate (70.6%) than L-Dex 10 (68.5%) although false positive rate increased from 0.4% to 2.6%. A threshold of 5% excess volume improved the true positive rate (68.5%) compared with 10% excess volume (49.7%) however the false positive rate increased to an unacceptable 47%. The L-Dex ranges in this study were not significantly different from previously published ranges. BIS was superior for identifying BCRL compared with volume measurements, reaffirming the value of this technique. However, it is recommended that BIS be used in conjunction with comprehensive evaluation of symptoms and clinical presentation. The proposed graphical method provides a simple and easily interpretable approach to compare and define concordance between the two commonly used methods for BCRL assessment namely limb volume and BIS L-Dex indices. The existing BIS (L-Dex) thresholds for presence of BCRL were also validated.

Improving multidisciplinary management of patients living with obesity: The evaluation of seated bioimpedance measures and relationship to functional performance following targeted intervention.

Management of obesity requires a multidisciplinary approach including physical activity interventions, which have significant impacts on overall health outcomes. Greater levels of lean muscle mass are significantly associated with improved health and reduced risk of comorbidities and should be preserved where possible when undertaking rapid weight loss. This article reports on the physical and functional outcomes achieved during a 12-week intensive multidisciplinary intervention targeting obesity and evaluates correlations between body composition and functional outcomes. We additionally aimed to investigate the test-retest reliability and levels of agreement in body composition measurements using bioimpedance spectroscopy between seated and standing positions. Of the 35 participants included in analysis, significant differences were observed between baseline and post-intervention measures. These included weight loss of 12.6 kg, waist circumference reduction of 10.5 cm, fat mass reduction by 2.9%, muscle mass increase by 1.6%, 54.5 m improvement in the 6-minute walk test and 3.8 rep improvement in the 30-second sit-to-stand test. No significant correlations were observed between physical and functional outcome measures. Excellent test re-test reliability was observed in bioimpedance spectroscopy seated measurements (ICC >.9). Significant differences were observed between seated and standing bioimpedance spectroscopy measurements, however they are regarded as small differences in a clinical setting.

Effects of Body Positioning When Assessing Lymphedema of the Lower Limb Using Bioimpedance Spectroscopy.

Background: Bioimpedance spectroscopy (BIS) measurements are conventionally performed in supine position with a lead device attached to gel-backed electrodes, and more recently, with a stand-on device that uses fixed stainless-steel electrodes under the hands and feet. The aim of this study was to assess and compare BIS measurements made in supine, sitting, and standing positions using lead and stand-on impedance devices in participants with and without unilateral leg lymphedema. Materials and Methods: Participants with self-ascribed unilateral leg lymphedema (n = 24) and healthy controls (n = 71) were recruited using a cross-sectional study design. Triplicate BIS measurements were taken for each device in each position. Results: Impedance measurements with either device were reliable with coefficient of variation of 0.6% or lower. The magnitude of mean differences in absolute impedance values between devices were between 1% and 6% dependent on condition. L-Dex scores between the two devices were highly correlated (r = 0.82) and ∼70% of participants in the lymphedema group were classified as having lymphedema using the recommended cut-off with either device. There was no significant interleg difference of controls using the lead device; however, small, but significant differences (p = 0.0001) were found when using the stand-on device. Conclusion: The findings demonstrate that reliable impedance measurements of the legs can be made with either device in lying, sitting, or standing positions. However, data between the devices were not directly interchangeable. Although the risk of misidentification was small, reference ranges appropriate to the device and measurement position should be used when converting data to L-Dex scores.

A New Technique to Estimate the Cole Model for Bio-impedance Spectroscopy with the High-Frequency Characteristics Estimation.

Bio-impedance spectroscopy (BIS) is a sophisticated testing technique used to analyze impedance changes at different frequencies. In this study, we investigated the estimation of the Cole Model for BIS measurements without the need for high-frequency resistance and reactance measurements, where they are inaccurate due to leakage capacitences. We employed a Texas Instruments evaluation kit (AFE4300) and compared the Cole plots of two different circuit models of tissue between the proposed configuration and a commercial impedance analyzer used as a reference. To enhance the performance of the AFE4300, we incorporated an external direct digital synthesis (DDS) to generate higher frequencies. The results demonstrated the reliability of the proposed theoretical estimation technique in accurately estimating the resistances and capacitance of the Cole Model.

Bioimpedance spectroscopy measurement method based on multisine excitation and integer-period undersampling

Bioimpedance spectroscopy (BIS) is a detection technology that uses the bioimpedance characteristics of human tissues and their changes to analyze their physiological and pathological status, and is widely used in clinical and scientific research applications. Traditional BIS measurement must satisfy the Nyquist sampling theorem so as to ensure that the measurement signal has no frequency aliasing, but at the same time the sampling frequency and the number of sampling points will be increased, which will increase the computation and hardware costs. This paper proposes a novel BIS measurement method based on multisine excitation and integer-period undersampling (IPUS) technology. Firstly, the multisine-based IPUS theory is deduced, and the BIS measurement principle based on multisine excitation and IPUS technology is introduced. Secondly, a BIS measurement system based on a field-programmable gate array + analog-to-digital converter + digital-to-analog converter architecture is designed, and multisine excitation with 32 pseudo-logarithmically distributed frequency components in the range of 2–997 kHz is generated. Comparative BIS measurement experiments on three RC three-element models are carried out under the Nyquist sampling condition (sampling frequency fs = 2.56 MHz) and under the IPUS condition (fs = 512 kHz), respectively. Experimental results show that the mean amplitude error of BIS measurement under the Nyquist sampling condition is 0.80% (±1.19% SD), while the mean amplitude error under the IPUS condition is 1.02% (±1.13% SD). Moreover, the signal-to-noise ratio (SNR z ) is calculated in 40 repeated BIS measurements, where the mean SNR z is 63.60 dB under the IPUS condition, similar to the value of 62.77 dB under the Nyquist sampling condition. The proposed multisine-based IPUS theory and its implementation method in this paper can complete a BIS measurement with only one fundamental period, and the sampling frequency and sampling point requirements are lower than for Nyquist sampling, laying a theoretical and technical foundation for a BIS measurement system with reduced hardware and computation requirements.

#4261 RELATIONSHIP BETWEEN FLUID OVERLOAD AND AVERAGE PLASMA REFILL RATE IN HEMODIALYSIS PATIENTS

Abstract Background and Aims Attaining the optimal balance between achieving adequate volume removal while preserving organ perfusion remains challenging in patients on maintenance hemodialysis (HD). Quantification of fluid status using bioimpedance spectroscopy (BIS) has become routine in many countries. Inadequate vascular space refill from the interstitial tissue (plasma refill rate, PRR) is the main contributing factor of hemodynamic instability during HD. We aimed to explore the association between fluid overload (FO) and plasma refill rate (PRR) in chronic HD patients. Method Pre-HD FO [l] was assessed once per subject by BIS (Body Composition Monitor; Fresenius Medical Care) in four urban HD dialysis clinics in the U.S. For each treatment within 30 days before and after the BIS measurement, we calculated the respective pre-HD FO by assuming that differences in pre-HD body weight were equivalent to differences in FO. We then used intradialytic hematocrit (measured with the Crit-Line® Monitor, Fresenius Medical Care) and ultrafiltration data to quantify the average PRR, normalized by body weight (Wang et al. Kidney360, 2023): To calculate the starting blood volume (BV), we first calculated the ending BV using the Nadler equation, followed by back-calculating the starting BV based on the cumulative change in relative BV. Plasma refill volume was calculated as the sum of the changes in blood volume and ultrafiltration volume; plasma refill volume was then divided by treatment time and estimated clinical dry weight to calculate the PRR [ml/kg/hr]. Results We analyzed 746 HD sessions from 79 patients (age 61 ± 15 years; 52 (66%) males; 41 (52%) black and 33 (42%) white). Across all HD sessions, PRR was positively associated with FO [slope estimate 0.92 (95% confidence interval 0.83 to 1.02) ml/kg/hr per 1 l of FO, P value < 0.0001] (Figure 1). This was also the case in subgroup analyses of fluid depleted (r = 0.94, P<0.001), normohydrated (r = 1.03, P<0.0001), and fluid overloaded subjects (r = 0.83, P<0.0001). Conclusion Across the entire fluid status spectrum, from fluid depletion to fluid overload, higher FO was associated with higher PRR on average (overall, an increase of 0.92 ml/kg/hr in PRR for each additional liter of FO). While patients with greater FO would be expected to better tolerate higher ultrafiltration rates, there is large inter-individual variability in PRR. Further investigation of the utility of PRR throughout HD may offer novel insights into fluid management and intradialytic symptom mitigation.

#4979 MORTALITY AND BIOIMPEDANCE SPECTROSCOPY–BASED DRY WEIGHT MEASUREMENT ERROR IN ELDERLY PATIENTS UNDERGOING HEMODIALYSIS

Abstract Background and Aims Dry weight (DW) estimation is important for patients undergoing hemodialysis. Although bioimpedance spectroscopy (BIS) is often employed to evaluate DW, BIS-based DW frequently differs from clinical DW. In this study, the characteristics of elderly patients were evaluated by separating them into groups based on the degree of disparity between the BIS-based DW and the clinically appropriate (DWGAP), and the mortality of each group was compared. Method This retrospective study included patients who underwent hemodialysis at Chungnam National University Hospital from January 1, 2016, to June 2020. All patients were aged ≥60 years. Patients with cancer, recipients of kidney transplant, and patients who dropped out of the study within 3 years were excluded. Body composition was assessed using a portable BIS device (Fresenius Medical Care, Bad Homburg, Germany). The BIS dataset includes extracellular water (ECW), intracellular water (ICW), and total body water level (TBW) as well as the lean tissue index (LTI), fat mass index (FTI), ECW/ICW ratio (E/I), lean tissue mass, fat mass (FAT), adipose tissue mass (ATM), and body cell mass (BCM). The absolute value of the gap between the BIS-based DW and the actual clinically appropriate dry weight was determined (DWGAP). To assess differences in blood chemistry and survival rate, four groups were classified based on the absolute value of DWGAP; Group 1: DWGAP < 0.5 kg, Group 2: 0.5 kg ≤ DWGAP < 1 kg, Group 3: 1 kg ≤ DWGAP < 2 kg, and Group 4: 2 kg < DWGAP. The mortality data of patients up to 3 years after BIS measurement were collected. Results There were 1024 patients in all. The study excluded 29 individuals with cancer, 31 patients with KT, and 249 participants with a loss of follow-up before 36 months. A total of 715 patients were analyzed: Group 1 (n = 236), Group 2 (n = 171), Group 3 (n = 137), and Group 4 (n = 171). The mean age for each group was 71.97, 70.73, 71.58, and 70.4 years, respectively. Groups 1 and 2 had the same survival rates (78%); however, Group 3 had a lower rate (73%) and Group 4 showed a significant decline (59%). In the laboratory test, Group 4 had lower hemoglobin, total protein, albumin, creatinine, and chloride levels than Groups 1, 2, and 3. In the BIS data, ECW and E/I were higher in Group 4 than in Groups 1, 2, and 3. Conclusion In the elderly patient group, mortality increased in the group where the DWGAP was >2 kg. Lower blood albumin levels, total protein levels, and E/I ratios of ≥1 were detected in the group with a gap of ≥2 kg, and these parameters are likely to adversely affect the survival of elderly patients requiring dialysis.

Early Detection of Breast Cancer-Related Lymphedema: Accuracy of Indocyanine Green Lymphography Compared with Bioimpedance Spectroscopy and Subclinical Lymphedema Symptoms.

Introduction: The reported incidences of breast cancer-related lymphedema (LE) affecting the arms vary greatly. Reason for this variability includes different diagnostic techniques used across studies. In the current study, we compared the accuracy of indocyanine green lymphography (ICG_L) and bioimpedance spectroscopy (BIS) in detecting LE before presentation of clinical signs. Methods and Results: Patients with no initial detectable signs of clinical LE of their arms after axillary lymph node dissection or removal of >5 lymph nodes on sentinel lymph node biopsy were included. Subclinical LE was defined as BIS values outside the normal range [(≥7 units (or >10 units)] or a 7-unit (or 10 unit) change between two measurements. We tracked ICG_L and BIS measurements for 133 potentially affected arms (n = 123). ICG_L detected signs of lymphatic flow disruption in 63 arms (47%). Based on the BIS value of 7 units, 60 arms (45%) had values outside the normal range. When using ICG_L-identified LE cases as true positives, BIS had a 54% accuracy (area under the curve [AUC] = 0.54) in detecting LE. Accuracy was 61% for subclinical LE symptoms when compared with ICG_L (AUC = 0.62). Both BIS and subclinical LE symptoms had <0.70 AUC-receiver characteristic operator curve, suggesting that BIS and development of subclinical LE symptoms are not adequate for identifying patients with subclinical LE. Conclusion: ICG_L is a reliable diagnostic tool for detecting early signs of lymphatic flow disruption in subclinical LE. Utilizing ICG_L to diagnose subclinical LE followed by a personalized treatment plan may provide patients the best chance of preventing disease progression.

Abstract P1-05-16: Bioimpedance Spectroscopy Monitoring Reduces Long-term Clinical Lymphedema Risk

Abstract Background: A prospective surveillance model (PSM) of care can reduce the risk of breast cancer related lymphedema (BCRL). Bioimpedance spectroscopy (BIS) devices can identify sub-clinical BCRL (sBCRL). A recent randomized controlled trial (RCT) demonstrated the benefit of a PSM model of care using BIS over tape measure (TM) but it did not look at the long-term risk following intervention. This work reports the actuarial risk of clinical lymphedema for those who have triggered an intervention for sBCRL by either BIS or TM. Materials and Methods: 879 women with breast cancer were randomized to lymphedema screening with either BIS (n=442) or TM (n=437). Following consent, patients underwent baseline pre-surgical measurements with BIS (L-Dex U400, ImpediMed) and volume (circumference) measurements (Gulick II tape) and randomized after surgery. Both the TM and BIS arms underwent planned post-operative assessments at 3, 6, 12, 18, 24, 30, and 36 months as well at the end of any intervention. Patients with a BIS change from baseline of ≥ 6.5 L-Dex units or TM volume change ≥ 5 and &amp;lt; 10% above pre-surgical baselines "triggered" for sBCRL form the basis of this study. Triggered patients underwent 4-weeks of wearing a class two (23–32 mmHg) compression sleeve and gauntlet for 12 hours per day. TM volume change ≥ 10% was considered clinical BCRL (cBCRL) for all patients who triggered by either BIS or TM. The cumulative incidence of cBCRL was calculated via the Kaplan-Meier method and compared by the Log-rank test. Results: 209 (23.8%) women triggered an intervention and completed treatment for sBCRL (BIS: 89 (20.1%), TM: 120 (27.5%)). The median follow up for the women who triggered was 32.2 months (IQR 17.0 – 33.9) with 30 women (14.4%) women developing cBCRL (BIS: 7 (7.9%), TM: 23 (19.2%)). There was a significant difference in risk between the groups over the follow up interval (log rank test p = 0.021) with the cumulative risk in the BIS group being lower compared to the TM group (Hazard Ratio = 0.38, 95%CI 0.19 – 0.79). The 2- year actuarial risk of cBCRL for triggered patients undergoing lymphedema screening by BIS was 5.0% versus 15.7% for TM screening (p = 0.021, HR = 0.30). The corresponding 3-year rates of cBCRL were 10.3% and 21.2%, (p = 0.031, HR = 0.40) respectively. Conclusions: BIS monitoring for sBCRL with subsequent intervention provides significantly lower risks of cBCRL. The lower triggering rates with BIS highlight its better discrimination of true sBCRL compared to TM and support its use for post-treatment surveillance to detect sBCRL and initiate early intervention. These data suggest that monitoring for sBCRL with BIS and subsequent intervention does not just delay the inevitable progression to cBCRL, but rather prevents it over the duration of the study. Citation Format: John Boyages, Frank Vicini, Chirag Shah. Bioimpedance Spectroscopy Monitoring Reduces Long-term Clinical Lymphedema Risk [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-16.

Differentiation of lipoedema from bilateral lower limb lymphoedema by imaging assessment of indocyanine green lymphography.

Lipoedema is characterized by disproportionate painful fat accumulation mostly in the lower limbs. The presence of lymphoedema in lipoedema remains controversial. This study aimed to assess the presence or absence of lymphoedema in the lower limbs of women with lipoedema using indocyanine green (ICG) lymphography. A cross-sectional retrospective study was undertaken in women with a clinical diagnosis of lipoedema whose lower limbs were examined with ICG lymphography. MD Anderson Cancer Center (MDACC) ICG staging was used to determine lymphoedema presence and severity. Patient characteristics, ICG lymphography findings, Stemmer sign, body mass index, waist-to-hip ratio, limb volume and bioimpedance spectroscopy measures were recorded. Forty women with lipoedema underwent ICG lymphography for the lower limbs from January 2018 to July 2022. Thirty-four women (85.0%) were determined by ICG lymphography as MDACC ICG Stage 0 representing normal lymphatics. Of the six women who demonstrated dermal backflow on ICG lymphography, all were determined as ICG Stage 1, four had localized traumatic dermal backflow area at their ankles, one had previously diagnosed with primary lymphoedema and one was classified as lipoedema stage 4. ICG lymphography findings suggested the absence of lymphoedema in a clear majority of women with lower limb lipoedema.

Evaluation of fluid overload markers in pediatric hemodialysis patients

Assessment of hydration status in children undergoing hemodialysis (HD) is crucial. This study aimed to identify the techniques that can be utilized to assess fluid overload in children with end-stage renal disease (ESRD) undergoing HD. The study included 9 patients aged &gt;5 years and &lt; 18 years who underwent 27 HD sessions and were followed up for ≥1 month. The median age of the patients was 16 years (IQR: 5-17.8 years) and the female/male ratio was 1.25:1. Symptoms of volume overload were clinically observed based on 5 (18.5%) of the 27 measurements. There was a significant positive linear correlation between fluid overload by weight and pre- and post-HD bioimpedance spectroscopy (BIS) measurements (OH) (r=0.95 [P=0.000]). There was a significant difference in median IVC diameter between pre-HD and after HD (P=0.029). The median pre-HD IVC collapsing index was 13.8% (IRQ: 4%-46%), versus 17.1% (IRQ: 4.5%-45%) after HD; the difference was significant (P=0.000). BIS is the most widely used body composition monitor for estimating fluid status in children undergoing HD. The present study investigated the sensitivity of markers of volume load in children on a routine HD program. The parameters that best indicate volume load are the differences between pre-HD and post-HD BIS measurements, physical examination findings, and heart rate measurements.

Clinical Characteristics and Implications of Indocyanine Green Lymphography-Identified Contralateral Inguinal Pathway of Lower-Limb Lymphedema

Background and Objectives: The contralateral inguinal pathway (CIP) to the inguinal nodal region of the contralateral limb has been described in lower-limb lymphedema (LLLE). This audit aimed to use indocyanine green (ICG) lymphography to determine characteristics of patients with CIP to inform conservative therapy. Methods: Patients with confirmed LLLE (n = 278) were categorized into secondary cancer-related (n = 82), secondary non–cancer-related (n = 86), or primary (n = 110). Patient characteristics, limb volume and bioimpedance spectroscopy (BIS) extracellular fluid ratio, and ICG lymphography of lymphatic pathways and dermal backflow areas were recorded. Results: Forty-seven patients (16.9%) had movement of ICG dye via CIP. Of these, 30 (63.8%) had secondary cancer-related, 8 (17.0%) had secondary non–cancer-related, and 9 (19.1%) had primary LLLE. Cancer-related LLE (P &lt; .001) and unilateral LLLE (P = .017) were significant indicators of CIP, with 36.6% of patients with cancer-related LLLE demonstrating this pathway. CIP was significantly associated with dermal backflow in shin (P = .016), calf (P = .006), thigh (P &lt; .001), inguinal (P &lt; .001), pubic (P &lt; .001), and abdominal regions (P = .001). Patients with CIP had significantly higher volume differences between limbs (P &lt; .001), severity of lymphedema (P &lt; .001), and BIS measurements (P &lt; .001) than patients without CIP. Conclusion: A compensatory lymphatic drainage pathway from the affected limb to the contralateral inguinal lymph node region was evident in 16.9% of patients with LLLE. This pathway was most observed in unilateral cancer-related lymphedema, particularly where edema was present in proximal thigh, inguinal, pubic, and lower abdominal regions. Directing manual lymphatic drainage to the contralateral inguinal drainage region should be considered especially for patients with cancer-related LLLE.

The Impact of Volume Overload on the Longitudinal Change of Adipose and Lean Tissue Mass in Incident Chinese Peritoneal Dialysis Patients.

Patients treated with peritoneal dialysis (PD) experience complex body composition changes that are not adequately reflected by traditional anthropometric parameters. While lean and adipose tissue mass can be readily assessed by bioimpedance spectroscopy (BIS), there is concern about the potential confounding effect of volume overload on these measurements. This study aimed to assess the influence of fluid status (by echocardiography) on body composition parameters measured by BIS and to describe the longitudinal changes in adipose and lean tissue mass. We conducted a prospective observational study in a tertiary hospital. Incident Chinese PD patients underwent baseline echocardiography and repeated BIS measurements at baseline and 12 months later. Among 101 PD patients, lean tissue index (LTI) or fat tissue index (FTI) was not associated with echocardiographic parameters that reflected left ventricular filling pressure (surrogate of volume status). Sixty-eight patients with repeated BIS had a significant increase in body weight and FTI, while LTI remained similar. Gains in fat mass were significantly associated with muscle wasting (beta = −0.71, p < 0.0001). Moreover, progressive fluid accumulation independently predicted decrease in FTI (beta = −0.35, p < 0.0001) but not LTI. Body composition assessments by BIS were not affected by fluid status and should be considered as part of comprehensive nutrition assessment in PD patients.

A new indocyanine green fluorescence lymphography protocol for diagnostic assessment of lower limb lymphoedema

The lower limbs are a common body site affected by chronic edema. Imaging examination of the lymphatic system is useful to diagnose lymphoedema, identify structural changes in individuals, and guide interventional strategies. In this study, we used a protocol combining indocyanine green (ICG) lymphography and ICG-guided manual lymphatic drainage (MLD) for the diagnostic assessment of lower limb lymphoedema. Patients with lower limb lymphoedema were divided into three groups by their medical history: primary, secondary cancer-related, or secondary non-cancer-related. ICG lymphography was conducted in three phases: initial observation, MLD to accelerate ICG dye transit and reduce imaging time, and imaging data collection. Lymphatic drainage regions were recorded, and the MD Anderson Cancer Center ICG staging was applied. We collected routine lymphoedema assessment data, including limb volume and bioimpedance spectroscopy measurements. Three hundred and twenty-six lower limbs that underwent ICG lymphography were analyzed. Eight drainage regions were identified. The ipsilateral inguinal and popliteal were recognized as the original regions, and the remaining six regions were considered compensatory regions that occur only in lymphoedema. More than half of the secondary cancer-related lower limb lymphoedema (57.6%) continued to drain to the ipsilateral inguinal region. The incidence of drainage to the ipsilateral inguinal region was even higher for the primary (82.8%) and secondary non-cancer-related (87.1%) groups. Significant associations were observed between cancer-related lymphoedema and the presence of compensatory drainage regions. We proposed a prospective ICG lymphography protocol for the diagnostic assessment of lower limb lymphoedema in combination with MLD. Eight drainage regions were identified, including two original and six compensatory regions.

Comparative Study of Measurement Methods for Embedded Bioimpedance Spectroscopy Systems

Bioimpedance spectroscopy (BIS) is an advanced measurement method for providing information on impedance changes at several frequencies by injecting a low current into a device under test and analyzing the response voltage. Several methods have been elaborated for BIS measurement, calculating impedance with a gain phase detector (GPD), IQ demodulation, and fast Fourier transform (FFT). Although the measurement method has a big influence on the measurement system performance, a systematical comparative study has not been performed yet. In this paper, we compare them based on simulations and experimental studies. To maintain similar conditions in the implementation of all methods, we use the same signal generator followed by a voltage-controlled current source (VCCS) as a signal generator. For performance analysis, three DUTs have been designed to imitate the typical behavior of biological tissues. A laboratory impedance analyzer is used as a reference. The comparison addresses magnitude measurement accuracy, phase measurement accuracy, signal processing, hardware complexity, and power consumption. The result shows that the FFT-based system excels with high accuracy for amplitude and phase measurement while providing the lowest hardware complexity, and power consumption, but it needs a much higher software complexity.

Risk factors for breast cancer-related lymphedema in patients undergoing 3 years of prospective surveillance with intervention.

BackgroundTo evaluate risk factors (treatment‐related, comorbidities, and lifestyle) for breast cancer–related lymphedema (BCRL) within the context of a Prospective Surveillance and Early Intervention (PSEI) model of care for subclinical BCRL.MethodsThe parent randomized clinical trial assigned patients newly diagnosed with breast cancer to PSEI with either bioimpedance spectroscopy (BIS) or tape measurement (TM). Surgical, systemic and radiation treatments, comorbidities, and lifestyle factors were recorded. Detection of subclinical BCRL (change from baseline of either BIS L‐Dex ≥6.5 or tape volume ≥ 5% and < 10%) triggered an intervention with compression therapy. Volume change from baseline ≥10% indicated progression to chronic lymphedema and need for complex decongestive physiotherapy. In this secondary analysis, multinomial logistic regressions including main and interaction effects of the study group and risk factors were used to test for factor associations with outcomes (no lymphedema, subclinical lymphedema, progression to chronic lymphedema after intervention, progression to chronic lymphedema without intervention). Post hoc tests of significant interaction effects were conducted using Bonferroni‐corrected alphas of .008; otherwise, an alpha of .05 was used for statistical significance.ResultsThe sample (n = 918; TM = 457; BIS = 461) was female with a median age of 58.4 years. Factors associated with BCRL risk included axillary lymph node dissection (ALND) (p < .001), taxane‐based chemotherapy (p < .001), regional nodal irradiation (RNI) (p ≤ .001), body mass index >30 (p = .002), and rurality (p = .037). Mastectomy, age, hypertension, diabetes, seroma, smoking, and air travel were not associated with BCRL risk.ConclusionsWithin the context of 3 years of PSEI for subclinical lymphedema, variables of ALND, taxane‐based chemotherapy, RNI, body mass index >30, and rurality increased risk.

Dual Fluorescent Tracers for Surgical Guidance: Preventing Donor-site Lymphedema in Vascularized Lymph Node Transfer.

Introduction:Vascularized lymph node transfer (VLNT) restores physiological lymphatic function. Although effective, postoperative impairment of donor-site lymphatic function and iatrogenic lymphedema following lymph node transfer remains a pressing concern.Methods:Prospective analysis of VLNT patients undergoing dual fluorescent tracers-assisted harvest was performed at our institution from September 2013 to April 2022. Reverse lymphatic mapping of the lower extremity was performed with indocyanine green (ICG). Blue dye was utilized in both white light and near-infrared spectra for visualization of donor-site lymphatic structures. Demographics, intraoperative details, and surgical outcomes were recorded.Results:Twenty-five patients were included. Median age was 52.9 years with a body mass index of 29.1 kg/m2 and mean follow-up of 44 months (range 24 to 90 months). Lymphedema stage ranged from Campisi 2 to 4. Inguinal VLNT was performed in 13 patients, and 12 patients received combined VLNT and free flap breast reconstruction. No patients required change in lymph node donor site intraoperatively. All ICG stained nodes were preserved in situ. No cases of iatrogenic lower extremity lymphedema were observed. Postoperative bioimpedance spectroscopy, circumferential, and volumetric measurements of the donor-site limb did not show evidence of subclinical or clinical lymphedema. The donor site healed appropriately in 92% of patients; one patient developed methylene blue-induced skin necrosis.Conclusion:Reverse lymphatic mapping and surgical guidance with dual ICG and blue dye fluorescent tracers provides surgeons with real-time surgical guidance without radioisotope, improves surgical visualization in both white light and near-infrared spectra, and avoids iatrogenic lymphatic dysfunction in the donor limb.

MO893: The Prognostic Value of Dysvolemia, Cardiac Biomarkers and Echocardiographic Parameters in Chronic Haemodialysis Patients

Abstract BACKGROUND AND AIMS Hypervolemia is one of the important risk factors for mortality in haemodialysis (HD) patients. The aim of this study is to determine the prognostic significance of volemia determined by bioimpedance spectroscopy (BIS), as well as cardiac biomarkers and echocardiographic (ECHO) measurements. METHOD A prospective single-centre observational study included 73 (42 m) chronic HD patients. The BIS and cardiac biomarkers were measured before the second weekly HD procedure. In addition, to overcome the problem of possible different pre-HD and post-HD fluid volume levels (`overhydration’, OH and post-HD or `dehydration’, DH, respectively) on different HD sessions of the week, the concept of Average Weekly hypervolemia (AVOH) or hypovolemia (AVDH) was implemented—the remaining two OH and DH values were calculated from pre-HD and post-HD weights and normal weight as suggested by BIS measurement. ECHO was performed 1 day after aforementioned measurements (i.e. 1 day after HD). RESULTS During observation period 11 subjects died (15%): seven (64%) directly due to cardiovascular (CV), two due to infective and due to malignant causes. Three-year cumulative survival was significantly lower (by Kaplan–Meier analysis) in those who had: 1) AVOH &amp;gt;13% extracellular fluid (ECV) (survival rate 73% versus 92% (P &amp;lt; 0.05); 2) average AVDH&amp;gt; -3% ECV (survival 69% versus 94%; P &amp;lt; 0.01); 3) value of serum N-terminal prohormone of brain natriuretic peptide (NT-proBNP)&amp;gt; 7350 pg/mL (survival 76% versus 93%; P &amp;lt; 0.05); 4) troponin T (TnT) value &amp;gt;0.067 ng/mL, (survival rate 68% versus 94%; P &amp;lt; 0.01). In addition, regarding just CV mortality, left ventricular ejection fraction according to Simpson (LVEF) &amp;lt;40% (survival rate 80% versus 93%; P &amp;lt; 0.05) and global longitudinal strain (GLS) &amp;lt;–8.5 (survival rate 81% versus 95%, P &amp;lt; 0.05) were markers of pure survival. CONCLUSION Determination of volemia by BIS, cardiac biomarkers and echocardiography has prognostic significance in HD patients. Further studies will show how much correction of dysvolemia affects their better survival.

MO671: Should We Undergo Peritoneal Dialysis in Malnourished Chronic Kidney Disease Patients?

Abstract BACKGROUND AND AIMS The implementation of peritoneal dialysis (PD) in end-stage renal disease has been associated with various long-term pathophysiologic changes, which result in adverse consequences, such as malnutrition, occurring in 30–50% of patients. Specific factors to PD might be associated with poor oral intake as continuous absorption of glucose from PD solutions and abdominal fullness induced by the dialysate can suppress appetite. There are several accepted strategies for stratifying malnutrition in PD, such as laboratory markers [serum albumin and normalized protein catabolic ratio (nPCR)] and the recent use of bioimpedance spectroscopy (BIS) (with low lean tissue index). We aimed to evaluate if PD patients with a poor nutritional status at the beginning of the technique had worse outcomes (peritonitis, PD failure, hospitalizations, and death). METHOD We studied a cohort of incident patients from a single PD unit between 1 July 2011 and 31 August 2021, who had one BIS measurement and a peritoneal equilibration test in the first 3 months after the start of PD. We also collect laboratory data within 6 months from the BIS evaluation (serum albumin). Besides demographic parameters, we evaluated established endpoints (peritonitis, PD failure, hospitalizations and death). RESULTS There were included 91 PD patients. The mean age of patients was 65.40 $ \pm $ 13.88 years with a median dialysis vintage of 24 (IQR 14–31.61) months; 59.3% were male and 28% had diabetes. During the follow-up period, 5.5% of the cohort died, 56% were hospitalized and 47.3% had at least one episode of peritonitis. Furthermore, the transfer to hemodialysis occurred in 18 cases (19.8%) and 15 (16.5%) received a renal transplant. There was no difference in nutritional markers median in patients that had clinical endpoints versus those who had not (Table 1). In a multivariable analysis, neither nPCR, nor albumin nor lean tissue index were predictors of peritonitis, PD failure or hospital admissions. CONCLUSION In this study, we found that malnourished patients, prevalent in PD, did not have worse clinical endpoints (higher rate of infections, hospital admissions and PD failure). Although adequate nutrition has been deemed vital to the success of PD, this modality of renal replacement therapy did not result in worse outcomes, despite the malnutrition markers at the beginning of PD. Further studies are warranted to evaluate the positive impact of PD in nutrition status.