Bioimpedance Spectroscopy Device Research Articles

Association of changes in body composition with all-cause mortality in patients undergoing hemodialysis: A prospective cohort study

ObjectivesThis study aimed to explore the effect of longitudinal body composition changes on mortality risk in patients undergoing hemodialysis and identify whether changes in body composition can more accurately predict mortality than baseline status. MethodsA prospective cohort study was conducted on 340 patients undergoing hemodialysis. Lean mass and body fat were determined using a bioimpedance spectroscopy (BIS) device and expressed as the lean tissue index (LTI) or fat tissue index (FTI), respectively. The patients were subjected to BIS at baseline and after 1 year. The hazard ratio (HR) for death was calculated using Cox regression analysis. ResultsAmong 340 patients, 289 were tested with a repeat BIS. LTI loss and FTI gain were observed in 51.2% and 47.1% of the patients, respectively. Low baseline LTI was a significant predictor of all-cause mortality after adjusting for demographic and biochemical parameters (HR, 2.41; P = 0.047), but not when comorbidities were included in the multivariate analysis. However, after adjusting for various confounding factors, LTI loss (HR, 3.40; P = 0.039) and FTI gain (HR, 4.06; P = 0.024) were independent risk factors for all-cause mortality, and the adjusted HR for LTI loss and FTI gain vs. no LTI loss and no FTI gain was 5.34 (P = 0.016). ConclusionsLTI loss and FTI gain, particularly their combination, are important predictors of survival in patients undergoing hemodialysis. Our results emphasize that longitudinal changes in LTI and FTI are more strongly associated with all-cause mortality than single-point values. Therefore, it is important to dynamically assess the muscle and fat tissues and develop potential targeted treatment strategies for this population.

Abstract PO3-12-07: Utility of Volumetric Measurement for Clinical Diagnosis of Breast Cancer-Related Lymphedema

Abstract Background: Early detection of Breast cancer-related lymphedema (BCRL) is crucial since it can significantly reduce the negative impact on a patient’s quality of life after breast cancer treatment. Several objective screening methods have been used in prior studies but have not proven accurate due to a lack of standardization. Bioimpedance spectroscopy (BIS), which assesses tissue resistance to an electric current and converts it into a score to measure interstitial fluid content, has proven to be an accurate tool in diagnosing lymphedema. SOZO® is a BIS device that generates quantitative results in real time and provides a Lymphedema Index (L-Dex) score by measuring the patient's extracellular fluid volume. However, there is a paucity of literature highlighting its clinical applicability. Thus, we aimed to evaluate the clinical utility of SOZO® in diagnosing BCRL in patients undergoing breast cancer surgery. Materials & Methods: A retrospective chart review was carried out of patients who underwent axillary surgery from January 2019 to December 2022. Demographic information such as age, body mass index (BMI), gender, ethnicity, disease pathology, cancer stage, type of axillary surgery, neoadjuvant and adjuvant treatment received was recorded. Patients undergoing sentinel lymph node biopsy (SLNB) and/or axillary lymph node dissection (ALND) were assessed for their preoperative L-Dex score, and they were followed up postoperatively with repeated measurements of their L-Dex score to diagnose lymphedema for a year at 3 months intervals. Clinical lymphedema was defined as those having an absolute L-Dex score of more than +10 and an increase in L-Dex score by 6.5 from the baseline. SOZO® scores measured at each follow-up were compared to their preoperative baseline scores. Results: A total of 200 patients’ data was evaluated whose mean age and BMI were 57.5+10.9 years and 29.6+5.6 kg/m2, respectively. Eighty-five percent of the patients belonged to ethnic minority groups. Furthermore, 84.5% (n=169) of the patients had SLNB, and 15.5% (n=31) had ALND. All the patients included in the study had their preoperative and postoperative quarterly L-Dex scores recorded. Pre- and post-operative L-Dex scores had a mean of -0.20+6.6 and 0.61+6.8, respectively. A total of 20 (10%) patients developed lymphedema without symptoms detected by SOZO®, with 19 (9.5%) resolving at their respective 3-month follow-up and 1 (0.5%) patient with persistent lymphedema at the end of the 24-month follow-up. All 20 patients were treated with a compression sleeve. Of the 20 patients with lymphedema, 4 patients underwent ALND, whereas 16 patients had SLNB. When compared to their preoperative baseline scores, all patients' SOZO® measurements had an absolute score of more than 10 and an increase of 6.5 from their baseline score. Additionally, 21 other patients had an increase in score of 6.5 from their baseline measurements but did not meet the cut-off range of an absolute score of +10. Therefore, we excluded them from the diagnosis of BCRL, and none of these patients later developed any signs of BCRL, such as swelling, pain, or discomfort. Conclusion: SOZO® procedure can accurately detect BCRL. In our study, 1 patient developed clinical lymphedema after undergoing SLNB and was diagnosed using SOZO®. Additionally, 19 patients who were initially diagnosed with lymphedema were later categorized as transient due to the resolution of lymphedema on follow-up. Early identification of transient lymphedema using SOZO® resulted in the prevention of a potentially life-long debilitation in our patients. Moreover, our findings underscore that an increase in SOZO® score from the baseline by > 6.5 with an absolute score of more than +10 should be the threshold to clinically diagnose lymphedema. Future studies with larger sample sizes and longer follow-up duration are necessary to understand better the utility of SOZO® in diagnosing BCRL. Table 1: Baseline characteristics and follow-up data of the patients included in the study. Citation Format: Fardeen Bhimani, Sheldon Feldman, Yu Chen, Anjuli Gupta, Jessica Pastoriza, Areej Shihabi, Maureen McEvoy. Utility of Volumetric Measurement for Clinical Diagnosis of Breast Cancer-Related Lymphedema [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-12-07.

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.

Fluids and body composition during anesthesia in children and adolescents: A pilot study

The purpose of this study is to evaluate the intracellular and extracellular volume before and after anesthesia in order to ascertain their variations and determine the potential utility of this information in optimizing intraoperative fluid administration practices. A bioimpedance spectroscopy device (body composition monitor, BCM) was used to measure total body fluid volume, extracellular volume, and intracellular volume. BCM measurements were performed before and after general anesthesia in unselected healthy children and adolescents visiting the Pediatric Institute of Southern Switzerland for low-risk surgical procedures hydrated with an isotonic solution. In 100 children and adolescents aged 7.0 (4.8–11) years (median and interquartile range), the average total body water increased perioperatively with a delta value of 182 (0–383) mL/m2 from pre- to postoperatively, as well as the extracellular water content, which had a similar increase with a delta value of 169 (19–307) mL/m2. The changes in total body water and extracellular water content significantly correlated with the amount of fluids administered. The intracellular water content did not significantly change. Conclusion: Intraoperative administration of isotonic solutions results in a significant fluid accumulation in low-risk schoolchildren during general anesthesia. The results suggest that children without major health problems undergoing short procedures do not need any perioperative intravenous fluid therapy, because they are allowed to take clear fluids up to 1 h prior anesthesia. In future studies, the use of BCM measurements has the potential to be valuable in guiding intraoperative fluid therapy.What is Known:• Most children who undergo common surgical interventions or investigations requiring anesthesia are nowadays hydrated at a rate of 1700 mL/m2/day with an isotonic solution.• The use bioimpedance spectroscopy for the assessment of fluid status in healthy children has already been successfully validated.• The bioimpedance spectroscopy is already currently widely used in various nephrological settings to calculate fluid overload and determine patient’s optimal fluid status.What is New:• Routine intraoperative fluid administration results in a significant fluid accumulation during general anesthesia in low-risk surgical procedures.• This observation might be relevant for children and adolescents with conditions predisposing to fluid retention.• In future studies, the use of BCM measurements has the potential to be valuable in guiding intraoperative fluid therapy.

Assessment of bioimpedance spectroscopy devices: a comparative study and error analysis of gold-plated copper electrodes

Objective. Bioimpedance spectroscopy (BIS) is a non-invasive diagnostic tool to derive fluid volume compartments from frequency dependent voltage drops in alternating currents by extrapolating to the extracellular resistance (R 0) and intracellular resistance (R i). Here we tested whether a novel BIS device with reusable and adhesive single-use electrodes produces results which are (in various body positions) equivalent to an established system employing only single-use adhesive electrodes. Approach. Two BIS devices (‘Cella’ and the ‘Body Composition Monitor’ [BCM]) were compared using four dedicated resistance testboxes and by measuring 40 healthy volunteers. In vivo comparisons included supine wrist-to-ankle (WA) reference measurements and wrist-to-wrist (WW) measurements with pre-gelled silver/silver-chloride (Ag/AgCl) electrodes and WW measurements with reusable gold-plated copper electrodes. Main results. Coefficient of variation were <1% for all testbox measurements with both BIS devices. Accuracy was within ±1% of true resistance variability, a threshold which was only exceeded by the Cella device for all resistances in a testbox designed with a low R 0/R i ratio. In vivo, WA-BIS differed significantly between BIS devices (p < 0.001). Reusable WW electrodes exhibited larger resistances than WW-BIS with Ag/AgCl electrodes (R 0: 738.36 and 628.69 Ω; R i: 1508.18 and 1390 Ω) and the relative error varied from 7.6% to 31.1% (R 0) and −15.6% to 37.3% (R i). Significance. Both BIS devices produced equivalent resistances measurements but different estimates of body composition both in silico and in WA setups in vivo, suggesting that the devices should not be used interchangeably. Employing WW reusable electrodes as opposed to WA and WW measurement setups with pre-gelled Ag/AgCl electrodes seems to be associated with measurement variations that are too large for safe clinical use. We recommend further investigations of measurement errors originating from electrode material and current path.

#4797 ASSOCIATION BETWEEN BLOOD PRESSURE AND SALT CONSUMPTION WITH FLUID STATUS USING BIOIMPEDANCE SPECTROSCOPY IN PERITONEAL DIALYSIS PATIENTS

Abstract Background and Aims Control of extracellular volume in peritoneal dialysis (PD) patients requires both removal of sodium and water. Hypervolemia occurs more frequently in PD patients and is associated with greater morbidity and mortality. Dietary salt restriction (Na+ &amp;lt; 2g) is recommended in all PD patients. Most patients do not comply with this recommendation (prevalence difficult to assess). Bioimpedance spectroscopy (BIS) devices can help assess volume overload in patients receiving maintenance PD. The aim of our study was to determine the association between fluid status as measured using BIS to BP and salt consumption in continuous ambulatory peritoneal dialysis (CAPD) patients. Method We performed a retrospective, longitudinal study, that included 60 PD patients followed at our unit. Demographic and clinical characteristics, such as age, gender, chronic kidney disease (CKD) etiology, time on PD program, dialytic efficacy (Kt/V), peritoneal equilibration test results, BIS results and episodes of peritonitis were registered from our unit database. We measured total sodium removal and estimated daily sodium intake using dietary recall for one day, during the assessment of dialysis adequacy. Based on a 2017 study of 87 patients on PD that sought a correlation between effective daily sodium intake (memory recollection) and urinary + peritoneal sodium sieving. It allowed, through logistic regression, the creation of equations for patients with and without renal residual function (RRF) (Pearson's 0.6). Statistical analyses were performed using SPSS statistics version 23.0. The statistical hypothesis tests with p-value &amp;lt;0.05 were considered significant. Results Sixty patients (male: 60%) with a mean age of 55,9 ± 9 years were selected. Mean time on dialysis was 24,8 months ± 11,9 (min. 2, max. 63). The most common etiology of CKD was glomerular diseases (n = 16, 26.7%), followed by uncertain etiology (n = 11, 18.3%) and diabetic kidney disease (n = 9, 15%). In total, 71,7% of patients were on continuous ambulatory peritoneal dialysis (CAPD). Mean Kt/V was 2,2 ± 0,6 and the majority of patients were high-average transporters. Previous comorbidities were arterial hypertension (n = 60, 100%), diabetes (n = 16, 26,7%), heart failure (n = 13, 21,7%), body mass index &amp;gt;30 kg/m2 (n = 22, 36,7%) and dyslipidemia (n = 40, 66,7%). According to European Society of Cardiology we define three stages of hypertension: stage 1 (140–159/90–99 mmHg) with 15 patients (25%), stage 2 (160–179/100–109 mmHg) with 14 patients (23,3%) and stage 3 (≥180/≥110 mmHg) with 4 patients (6,7%). In total, we have 27 patients (45%) with hypertension under control. A statistically significant positive correlation was found between a status of overhydration (≥2liters) with salt consumption (Na+ &amp;gt;2g) (p = 0,01) and also of hypertension stages 2 and 3 (p = 0,03). Conclusion In PD patients, BIS is a reliable method for evaluating volume status. We found that stable CAPD patients with uncontrolled BP had higher overhydration and salt consumption compared to patients whose BP was controlled. Control of hypervolemia and blood pressure is associated with better cardiac condition. Thus, it is important to encourage patients on peritoneal dialysis to significantly restrict salt intake.

#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 &amp;lt; 0.5 kg, Group 2: 0.5 kg ≤ DWGAP &amp;lt; 1 kg, Group 3: 1 kg ≤ DWGAP &amp;lt; 2 kg, and Group 4: 2 kg &amp;lt; 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 &amp;gt;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.

Abstract P3-05-29: Use of Bioimpedance Spectroscopy as a Surrogate for Bone Mineral Content in Oncology Patients: Practical Application of the SOZO Device

Abstract Background: Many cancer patients, particularly those with breast or prostate cancer, receive hormonal manipulation therapies that can significantly impact their bone mineral content (BMC), potentially leading to osteoporotic associated life-threatening fractures, particularly given the median age of patients diagnosed with these malignancies. Bioimpedance spectroscopy (BIS) is a non-invasive tool that measures fluid and body composition values including skeletal muscle mass (SMM) and fat free mass (FFM). BIS devices can be used easily and quickly at point-of-care at the time of vital signs, with the patient standing on the device placing their hands and feet on metal electrodes and a reading obtained in less than a minute. Multiple previous studies have shown strong correlation between SMM and BMC, suggesting that a BIS reading can provide a reproducible, simple and quick estimate of BMC. To that end, we present initial findings correlating BIS readings obtained with a SOZO device (ImpediMed) with dual x-ray absorptiometry (DXA) to determine if BIS readings can be applied as an accurate point of care surrogate measure of BMC. Materials and Methods: Concurrent BIS measures and DXA scans, were performed in 75 healthy volunteers and 93 cancer patients (during and after cancer treatment) Group 1: 75 healthy volunteers (32 male, 43 female), mean age 27.4 (18-66 years); Group 2: 44 patients undergoing cancer treatment (11 male, 33 female; 18 breast, 7 lung, 4 endometrial, 4 colorectal, 4 prostate, 7 other), mean age 61.3 (38-79 years); and Group 3: 49 patients participating in a 12-week exercise program after cancer treatment (15 males, 34 females; 22 breast, 6 prostate, 3 colorectal, 3 endometrial, 2 lung, 13 other), mean age 57.8 (19-79 years). The healthy volunteers in Group 1 were further randomized into two subsets. Group A was used to develop a BIS predicted BMC algorithm and Group B was used to validate the algorithm. Results: The Pearson correlation coefficients (R) for DXA BMC and SOZO SMM were strong for all 3 groups (R=0.92, 0.85, and 0.80 for Groups 1, 2, and 3, respectively). Stepwise multiple linear regression for BMC was performed for Group A based on BIS parameters. For Group A, SMM resulted in a multiple correlation coefficient of 0.94 (P&amp;lt; 0.0001). The correlation coefficient between the BIS predicted BMC and DXA BMC of Group B was 0.87 (P&amp;lt; 0.0001, 95%CI 0.78-0.93). For Groups 2 and 3 combined, the correlation coefficient between the BIS predicted BMC and DXA BMC was 0.82 (P&amp;lt; 0.0001, 95%CI 0.73-0.87). Conclusions: Concurrent measures of SMM obtained with BIS using SOZO correlated strongly with DXA BMC, demonstrating that SOZO SMM may be a useful surrogate in the clinic to provide a quick, easy, and reproducible indicator of change in BMC, particularly for those patients undergoing treatments that may affect BMC. Tracking SMM during or after cancer treatment with SOZO may provide an estimate of changes in BMC allowing clinicians to obtain additional diagnostic testing and/or consider treatment modifications. Citation Format: Frank Vicini, Chirag Shah. Use of Bioimpedance Spectroscopy as a Surrogate for Bone Mineral Content in Oncology Patients: Practical Application of the SOZO Device [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 P3-05-29.

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.

Importance of Bio-electrical Impedance for Measurement of Body Fluid Status in Chronic Kidney Disease Patients on Maintenance Haemodialysis: A Narrative Review

Assessing the precise body water status in patients with renal disorders is crucial for their health. It has been reported that chronic fluid overload is present even in the early stages of renal insufficiency. If volume overload in a patient with chronic renal failure is not controlled, serious problems such as pulmonary oedema, cardiac remodelling, and diastolic heart failure can develop. Bioelectrical Impedance Analysis (BIA) has emerged as one of the most useful tools, although randomised clinical studies are lacking to support its universal use. Early management of hydration may improve clinical outcomes, as it allows for personalised dialysis prescriptions and nutritional support. BIA practice is utilised as non invasive health monitoring for Body Composition (BC). BIA is a practical and inexpensive method. Moreover, BIA parameters estimated for disease prognosis analysis have been found to be reasonably predictable for both patient status and healthcare. Additionally, BIA is a simple, accurate, portable, quick, easy, and low-cost method. In patients with End-stage Renal Disease (ESRD) undergoing maintenance Haemodialysis (HD) treatment, excessive fluid volume is considered a risk factor for death. Furthermore, fluid elimination to achieve Dry Weight (DW) is a crucial component of HD treatment for ESRD patients. DW is an important concept related to patients undergoing HD. Conventional methods seem to be time-consuming and operator-dependent. BIA is a new and simple method that has been reported to accurately estimate DW. Estimating the dry weight of HD patients is a challenging task. Many tools are available, but not every HD centre has access to them. Several strategies have been used to develop a more standardised method of assessing dry weight in HD patients. The Bio-impedance Spectroscopy (BIS) device has been validated against gold standard methods of volume assessment. Body composition monitoring appears to be a helpful diagnostic tool that reasonably complements existing clinical methods in assessing the DW of HD patients. BIS identifies Fluid Overload (FO) as a virtual "Over Hydration (OH)" compartment, which is calculated from the difference between the measured extracellular volume and the predicted values based on a fixed hydration of lean and adipose tissue mass.

INTRACELLULAR WATER CONTENT IN LEAN MASS IS ASSOCIATED WITH MUSCLE FUNCTION AND PHYSICAL ACTIVITY AMONG OLDER ADULTS

Abstract High intracellular water (ICW) content in lean mass (LM) has been associated with better functional capacity and lower frailty risk in older adults and suggested to be a useful muscle quality indicator. However, limited research exists on the relationship of ICW to muscle function and physical activity among older adults. The purpose of this study is to examine the relationship between ICW/LM ratio and muscle function and physical activity among older adults. In a cross-sectional correlational study of older adults aged 70 years or older, a tetrapolar bioimpedance spectroscopy device (Impedimed SFB7, Australia) was used to assess both ICW and LM, and the ICW/LM ratio (mL/kg) was calculated. The Short Physical Performance Battery (SPPB) and Timed Up and Go (TUG) tests were used to measure muscle function. The Actigraph GT3X+ accelerometer (Actigraph, Inc., FL, USA) was used to measure light and moderate-vigorous physical activity and steps per day. Multiple regression analyses were used. For 96 recruited participants (mean age 82.5 ± 7.4 years; 79 [82.3%] were female), mean ICW/LM ratio was 245.1 ± 28.1 mL/kg. The ICW/LM ratio was positively associated with SPPB score, gait speed, moderate-vigorous physical activity, and steps per day, after adjusting for age, sex, and LM. The ICW/LM ratio was negatively associated with TUG score, after adjusting for age, sex, and LM. The findings suggest that intracellular water content in lean mass may affect muscle function and physical activity among older adults. Further studies are needed to verify these findings and determine any potential cause-and-effect relationships.

A Standardized Protocol for Measuring Bioelectrical Impedance in Green Turtles (Chelonia mydas).

AbstractBioelectrical impedance analysis (BIA) is gaining popularity in wildlife studies as a portable technology for immediate and nondestructive predictions of body composition components, such as fat-free and fat masses. Successful application of BIA for field-based research requires the identification and control of potential sources of error, as well as the creation of and adherence to a standardized protocol for measurement. The aim of our study was to determine sources of error and to provide a standardization protocol to improve measurement precision of BIA on juvenile green turtles (Chelonia mydas; ). We assessed the effects of altered environmental temperature (20°C-30°C), postprandial state (2-72 h), and time out of the water (2 h) on five impedance parameters (resistance at infinite frequency [Rinf], resistance at zero frequency [R0], resistance at 50 kHz [R50], phase angle at 50 kHz [PhA50], and intracellular resistance [Ri]) using a bioimpedance spectroscopy device. Technical reproducibility of measurements and interanimal variability were also assessed. We found an inverse exponential relationship between change in environmental temperature and impedance parameters Rinf, R0, and R50. Postprandial state significantly increased Rinf and Ri 72 h after feeding. BIA measurements were reproducible within individual juvenile green turtles at temperatures from 20°C to 30°C. Significant variation in impedance values was found between animals at all temperatures, sampling times, and postprandial states, but the relative differences (%) were small in magnitude. Our study suggests that measurement precision is improved by measuring animals at consistent environmental temperatures close to their preferred thermal range. We propose a standardized protocol of measurement conditions to facilitate laboratory and field use of BIA for body composition assessment studies in turtles.

The predictive value of bioimpedance-derived fluid parameters for cardiovascular events in patients undergoing hemodialysis

Background It is becoming increasingly evident that the accurate assessment of fluid status is critical to ensure optimal care in patients undergoing hemodialysis (HD). Various fluid parameters, including overhydration (OH) and overhydration/extracellular water (OH/ECW%), which can be obtained using a bioimpedance spectroscopy device have been used to indicate the hydration status in such patients. This study aimed to explore the effect of these fluid parameters on cardiovascular events and determine which parameter was a better predictor of cardiovascular events (CVEs). Methods A total of 227 patients who underwent HD at the Hangzhou Hospital of Traditional Chinese Medicine were enrolled in this prospective study between December 2017 and August 2018. Clinical data were collected, and the fluid status of patients was assessed using a body composition monitor. The patients were followed up until December 2020. The primary outcomes were CVEs. The association between fluid parameters and CVEs was analyzed using Cox proportional hazards models. The areas under the curve (AUCs) of receiver operating characteristic analysis and improvement in the global chi-squared value were used to compare the predictive values of fluid parameters for CVEs. Results During a median follow-up of 31 months, 66 CVEs were recorded. The patients with a higher absolute hydration index (OH) and a relative hydration index (OH/ECW%) exhibited an increased risk of developing CVEs. After adjusting for confounding factors, both OH [hazard ratio (HR) 1.279 per L, 95% confidence interval (CI) 1.047–1.562; p = 0.016] and OH/ECW% (HR 1.061 per %, 95% CI 1.017–1.108; p = 0.006) were independently associated with CVEs. The predictive ability of the absolute hydration index was superior to the relative hydration index based on AUC calculations for CVEs. Furthermore, a greater change in χ2 in predicting CVEs was noted for the absolute hydration index. Conclusions Both absolute hydration index and relative hydration index were found to be independent predictors of CVEs in univariate and multivariate analyses. Furthermore, the absolute hydration index had a better additive predictive value than the relative hydration index in predicting CVEs.

A Comparison of SARC-F, Calf Circumference, and Their Combination for Sarcopenia Screening among Patients Undergoing Peritoneal Dialysis.

Sarcopenia is frequently encountered in patients undergoing peritoneal dialysis (PD). We evaluated and compared the diagnostic performance of a strength, assistance walking, rise from a chair, climb stairs, and falls (SARC-F) questionnaire, SARC-F combined with calf circumference (SARC-CalF), and calf circumference (CC) for screening sarcopenia among patients undergoing PD. We measured the appendicular skeletal muscle mass, evaluated using a multifrequency bioimpedance spectroscopy device, handgrip strength, and 6-m gait speed. SARC-F, SARC-CalF, and CC were obtained in all participants. Sarcopenia was defined using four different diagnostic criteria, including the Asian Working Group for Sarcopenia (AWGS) 2019, revised European Working Group on Sarcopenia in Older People (EWGSOP2), Foundation for the National Institutes of Health (FNIH), and International Working Group on Sarcopenia (IWGS). Among 186 enrolled patients undergoing PD (mean age 57.5 ± 14.1 years), the sarcopenia prevalence was 25.8–38.2% using the four definitions. The discriminative powers of SARC-CalF (range 0.648–0.748) and CC (range 0.652–0.813) against the four definitions were better than those exhibited by SARC-F (range 0.587–0.625), which achieved significant difference, except when adopting the criteria of the FNIH. After stratification by gender, the superiority of SARC-CalF and CC over SARC-F was maintained when AWGS 2019, EWGSOP2, and IWGS were applied. In conclusion, CC and SARC-CalF outperformed SARC-F in the diagnostic accuracy of sarcopenia among patients undergoing PD.

Accuracy of Bioimpedance Spectroscopy in the Detection of Hydration Changes in Patients on Hemodialysis

The body composition monitor (BCM) is a bioimpedance spectroscopy device, specifically developed for patients on hemodialysis (HD) to improve ultrafiltration (UF) programming, based on an objective assessment of the degree of overhydration (OH) at the start of HD. However, its acceptance in clinical practice remains limited because of concerns about the accuracy at the individual level. The aim of this study is to examine the performance of the BCM and to identify means of improvement. Precision of the OH estimate was assessed by 6 consecutive measurements in 24 patients on HD. Accuracy was examined in 45 patients, by comparing the change in OH (ΔOH) during HD with UF volume. Accuracy was considered acceptable if the volume error in individual patients was ≤0.5L. The OH estimate had an analytical precision of 1.0±0.4%. The correlation between UF volume and ΔOH was moderate (Slope=0.66, R2=0.44, P<.001) and indicated underestimation of UF volume, in particular for high UF volumes. Accuracy at individual level was highly variable. A volume error >0.5L occurred in 44% of patients. Accuracy improved over the course of HD, with a decrease in total error range from 2.3L in the first hour to 1.1L in the final hour of HD. The accuracy of BCM volume change estimates is highly variable and below requirements of daily practice. Improvement may be achieved by a switch to an end-of-HD measurement.

Prevalence of fluid overload in an urban US hemodialysis population: A cross-sectional study.

Inadequate fluid status remains a key driver of cardiovascular morbidity and mortality in chronic hemodialysis (HD) patients. Quantification of fluid overload (FO) using bioimpedance spectroscopy (BIS) has become standard in many countries. To date, no BIS device has been approved in the United States for fluid status assessment in kidney patients. Therefore, no previous quantification of fluid status in US kidney patients using BIS has been reported. Our aim was to conduct a cross-sectional BIS-based assessment of fluid status in an urban US HD population. We determined fluid status in chronic HD patients using whole body BIS (Body Composition Monitor, BCM). The BCM reports FO in liters; negative FO denotes fluid depletion. Measurements were performed before dialysis. Post-HD FO was estimated by subtracting the intradialytic weight loss from the pre-HD FO. We studied 170 urban HD patients (age 61 ± 14 years, 60% male). Pre- and post-HD FO (mean ± SD), were 2.2 ± 2.4 and -0.2 ± 2.7L, respectively. Pre-HD, 43% of patients were fluid overloaded, 53% normally hydrated, and 4% fluid depleted. Post-HD, 12% were fluid overloaded, 55% normohydrated and 32% fluid depleted. Only 48% of fluid overloaded patients were hypertensive, while 38% were normotensive and 14% hypotensive. Fluid status did not differ significantly between African Americans (N=90) and Caucasians (N=61). While about half of the patients had normal fluid status pre-HD, a considerable proportion of patients was either fluid overloaded or depleted, indicating the need for tools to objectively quantify fluid status.

Multi-channel bioimpedance spectroscopy based on orthogonal baseband shifting

Objective. Multi-channel bioimpedance spectroscopy (BIS) systems typically sample each channel’s impedance sequentially using multiplexers and a single analog-to-digital converter. These systems may lose their real-time capability with an increasing number of channels, especially for low excitation frequencies. We propose a new method, called orthogonal baseband shifting (OBS), for high-speed parallel BIS data acquisition at multiple excitation frequencies with low hardware and computational effort. Approach. Similar to orthogonal frequency-division multiplexing, used for digital data transmission, OBS systems use channel-specific orthogonal carrier frequencies to modulate the voltage response of the tissue. Given a suitable choice of carrier frequencies, the modulated signals of all channels sum up without loss of information and cross-talk. The fast Fourier transform (FFT) of the summed signal reveals a spectrum of non-overlapping, interleaved BIS data from which the corresponding BIS data of each channel can be calculated. Main results. In simulations, the system design requires a minimum signal-to-noise ratio of 30 dB to achieve amplitude errors below 1% and phase errors below 0.8°. The hardware realization, called ‘AixBIS’, has been evaluated for impedance measurements between 0.1 and 10 Ω with multi-frequency excitations between 45 and 180 kHz. The impedance values acquired had an averaged precision of 3.67 mΩ, which is only 0.65‰ in relation to the measured impedance. The phase had a mean precision of 0.46°. Moreover, in vitro measurements achieved 140 full spectrum acquisitions per second. The impedance change measured in a silicone heart phantom showed a high correlation of 0.83 with the ventricles volume change (flow). Significance. The proposed method enables very fast impedance acquisition of all channels. A complete measurement is performed in the time of a single FFT acquisition, which is equal to the resolution bandwidth of the FFT. In addition, portable and low-power multi-channel BIS devices profit from highly reduced hardware effort. The outstanding performance of OBS measurements with the AixBIS system have the potential for in vivo BIS measurements in real-time.

Cole-Impedance Model Representations of Right-Side Segmental Arm, Leg, and Full-Body Bioimpedances of Healthy Adults: Comparison of Fractional-Order

The passive electrical properties of a biological tissue, referred to as the tissue bioimpedance, are related to the underlying tissue physiology. These measurements are often well-represented by a fractional-order equivalent circuit model, referred to as the Cole-impedance model. Objective: Identify if there are differences in the fractional-order (α) of the Cole-impedance parameters that represent the segmental right-body, right-arm, and right-leg of adult participants. Hypothesis: Cole-impedance model parameters often associated with tissue geometry and fluid (R∞, R1, C) will be different between body segments, but parameters often associated with tissue type (α) will not show any statistical differences. Approach: A secondary analysis was applied to a dataset collected for an agreement study between bioimpedance spectroscopy devices and dual-energy X-ray absoptiometry, identifying the Cole-model parameters of the right-side body segments of N=174 participants using a particle swarm optimization approach. Statistical testing was applied to the different groups of Cole-model parameters to evaluate group differences and correlations of parameters with tissue features. Results: All Cole-impedance model parameters showed statistically significant differences between body segments. Significance: The physiological or geometric features of biological tissues that are linked with the fractional-order (α) of data represented by the Cole-impedance model requires further study to elucidate.

Application of survival classification and regression tree analysis for identification of subgroups of risk in patients with heart failure and reduced left ventricular ejection fraction.

The aim of this study was to identify by classification and regression tree (CART) analysis groups of patients with different survival patterns in a population of patients with heart failure and reduced left ventricular ejection fraction (HFrEF) by using standard methods of heart function assessment, as well as well as utilizing non-traditional approaches for determining hydration and nutritional status in HF patients-lung ultrasonography (LUS) and bioimpedance spectroscopy (BIS) analysis. Eligible patients with a left ventricular ejection fraction (LVEF) below 45% were identified via the daily echocardiography assessments. LUS was performed with patients in the supine position, for a total of 28 sites per complete examination. The hydration state and the body composition were assessed using a portable whole-body BIS device. Our study included 151 patients (69.2% males) with a mean age of 67.1years. During the follow-up 53 (35.1%) patients died. Using the CART algorithm, we identified five groups based on serum sodium, the severity of NYHA class, serum urea and systolic blood pressure. When comparing the two models, the model derived from the CART analysis showed better predictive power than the conventional Cox model (c-index 0.790, 95% CI 0.723-0.857 vs. 0.736, 95%CI 0.664-0.807, p < 0.05). The application of CART analysis allowed us to identify different groups of risk for all-cause mortality in patients with HFrEF. The use of this type of modelling showed better prediction capabilities over that of using more conventional statistical approach.ClinicalTrials.gov Identifier: NCT02764073.

Assessment of volume status with bioimpendance prior to hemodialysis and its importance for predicting survival in hemodialysis patients.

Optimal fluid management is a physician's everyday challenge in patients on maintenance hemodialysis (HD). Bioimpedance spectroscopy (BIS) is a non-invasive method to estimate body composition, including estimates of fluid overload (FO). Our study aimed to analyze the association between FO and the mortality rate in HD patients. We performed a retrospective single-center cohort study in 92 HD patients. The body composition was measured before HD using the portable whole-body BIS device Body Composition Monitor (BCM). We have analyzed the mortality rates of HD patients in two FO groups, a standard definition FO group (> 1.1 L), and a severe FO group (> 2.5 L) and compared them to mortality rates of patients without FO or without severe FO, respectively. The mean age of patients was 64.3 ± 13.0 years, mean dialysis vintage 64 months, 60.9% were men. 68 (73.9%) patients had FO of > 1.1 L and 30 (32.6%) had FO of > 2.5 L. During the follow-up period of 1,020 ± 417 days, 29 (31.5%) patients died. Kaplan-Meier survival analysis showed that patients with FO > 2.5 L had worse survival (p = 0.039). In a Cox regression model, which included FO > 2.5 L, age, dialysis vintage, hemoglobin, C-reactive protein, and albumin, only FO > 2.5 L and advanced age turned out to be predictors of death (p = 0.044 and p = 0.001, respectively). HD patients with FO > 2.5 L before HD have poorer survival than patients with normohydration or lower overhydration.