Phase angle as an index of physiological status: validating bioelectrical assessments of hydration and cell mass in health and disease

Assessment of phase angle as a novel indicator for sarcopenic obesity according to the ESPEN/EASO criteria in older adults with diabetes mellitus

BACKGROUND

Sarcopenic obesity (SO) is a clinical condition in which sarcopenia and obesity occur together, and is associated with more poor clinical outcomes, increased mortality, and morbidity than sarcopenia. Phase angle (PhA), a parameter derived from bioimpedance analysis (BIA), provides data on cellular health, membrane integrity, and cellular function. This study aimed to evaluate the relationship between SO and PhA among older adults with type 2 diabetes mellitus (DM).

METHODS

We performed a cross-sectional study in a tertiary hospital, and all participants underwent a comprehensive geriatric assessment, the hand-grip strength test (HGST), the chair stand test (CST) for muscle strength evaluation, the 4-meter walking test, and the timed up-and-go (TUG) test for physical performance assessment. The diagnosis of SO was made according to the ESPEN/EASO criteria. The PhA was determined automatically by the BIA using resistance and reactance at 50 kHz for each participant.

RESULTS

A total of 322 participants were included in the study. The mean age of the participants was 72.5 ±5.8, and 203 (63%) of them were female; 63 (19.6%) of them were sarcopenic obese. In multivariable logistic regression analyses, a significant relationship was found when the model was adjusted for age, female gender, MNA-sf scores, HbA1c level, and CCI scores (OR: 0.53, 95%CI: 0.29-0.98, P = 0.04). In ROC analyses, for PhA in predicting SO diagnosis, the AUC was 0.586 (95%CI: 0.505-0.678, P = 0.033). At the cut-off score 4.4, sensitivity was 57.1% and specificity was 61.4%; positive predictive value (PPV) was 26.5%; negative predictive value (NPV) was 85.5%.

CONCLUSIONS

The study identified a significant relationship between SO and PhA among older adults with type 2 DM. However, larger prospective studies are needed to confirm the potential utility of PhA as a biomarker for SO.

The severity of early fluid overload assessed by bioelectrical vector impedance as an independent risk factor for longer patient care after cardiac surgery

BACKGROUND AND AIMS

Fluid overload is a common postoperative complication in patients undergoing cardiac surgery. Although this condition is notably associated with relevant adverse outcomes, assessment of hydration status in clinical practice is challenging. Bioelectrical impedance vector analysis (BIVA) has emerged as a potentially effective method to monitor hydration changes, but the available evidence in critically ill patients undergoing cardiac surgery is limited and sometimes conflicting. The aim of this study was to explore by mean of BIVA the evolution over time of hydration status and its impact on relevant outcomes.

METHODS

Prospective observational study enrolling 130 patients undergoing cardiac surgery. Height normalized impedance was calculated both before surgery (baseline) and in the first five postoperative days. Relevant clinical and laboratory data were collected daily close to BIVA measurements. Length of mechanical ventilation (MV), intensive care unit (ICU) and hospital stay exceeding the 75th percentile of the study population were considered as study endpoints.

RESULTS

Compared to baseline, a significant reduction in impedance was found at first postoperative day, demonstrating a relevant fluid overload. An adjusted impedance at first postoperative day shorter than the best respective threshold was associated to longer MV (7.4 times), ICU stay (4.7 times) and hospital stay (5.6 times). A significant change in impedance and phase angle was documented throughout the observation days (p < 0.001), without returning to the baseline value. The co-existence of low impedance and high plasma osmolarity increased significantly the risk of incurring the study outcomes.

CONCLUSIONS

In patients with cardiac surgery-induced fluid overload, recovery to baseline conditions occurs slowly. A relevant early fluid overload should be considered predictive for longer time of MV, ICU and total hospital stay.

Limb-specific isometric and isokinetic strength in adults: The potential role of regional bioelectrical impedance analysis-derived phase angle

BACKGROUND & AIMS

It is not yet known whether regional bioelectrical impedance (BIA) phase angle (PhA) may be informative of different types of strength performed by the lower and upper limbs, independently of lean soft tissue mass (LSTM). Using a sample of healthy adults, we aimed to examine the association and relevance of regional PhA relative to isometric and isokinetic strength of each limb.

METHODS

A total of 57 participants (32.7 ± 12.9 years; 24.7 ± 3.5 kg/m2) were included in the present investigation. Regional raw BIA variables were determined using a phase-sensitive BIA device. Dual-energy X-ray absorptiometry was used to evaluate LSTM. Absolute isometric and isokinetic (i.e., 60°/s and 180°/s) strength of each limb (extension and flexion) was assessed using an isokinetic dynamometer and used to calculate relative strength.

RESULTS

In absolute strength, only dominant leg PhA was associated with isometric extension strength (β = 0.283) and isokinetic 180°/s flexion strength (β = 0.354), regardless of LSTM (p < 0.05). In relative strength, a significant association of regional PhA was found for dominant arm flexion isometric strength (β = 0.336), and non-dominant arm and dominant leg extension isometric strength (β = 0.377, β = 0.565, respectively; p < 0.05), independently of LSTM. Similarly, for isokinetic 180°/s strength, regional PhA significantly explained the variance in the relative strength of both arms and dominant leg (β = 0.350 to 0.506), regardless of LSTM (p < 0.05). Relative isokinetic 60°/s strength was not consistently associated with regional PhA (p ≥ 0.05).

CONCLUSIONS

Regional PhA significantly explained relative (isometric and 180°/s isokinetic strength of both arms and dominant leg), but not absolute muscle strength, independently of regional LSTM. Thus, after accounting for body size, regional PhA seems to have its own characteristics that explain relative strength independently of LSTM.

Muscle quality improvement in subacute post-stroke patients after rehabilitation: Usefulness of segmental phase angle from bioelectrical impedance analysis

BACKGROUND & AIMS

During stroke rehabilitation, the whole-body Phase Angle (PhA) from Bioelectrical Impedance Analysis (BIA) is measured to assess whole-body muscle quality, which reflects cellular integrity and function. The segmental BIA is a valuable method for assessing the body composition of specific body segments, such as the arms, legs, and hemisoma. After a stroke insult, patients frequently experience hemiparesis, and segmental PhA from segmental BIA appears to be an appropriate parameter for examining the muscle quality of affected and unaffected limbs separately. This study aims to investigate whether segmental PhA is more informative than whole-body PhA in (a) assessing the deterioration of muscle quality in post-stroke patients and (b) monitoring its recovery following rehabilitative treatment.

METHODS

This longitudinal study recruited subacute post-stroke patients who were admitted to our rehabilitation center. At admission, demographic, anamnestic, and clinical information, such as the presence of comorbidities, were recorded. BIA was used to evaluate the whole-body PhA and segmental PhA of the affected and unaffected hemisoma, arms, and legs at admission (T0) and after a six-week rehabilitation program (T1). The modified Barthel Index (mBI), Fugl-Meyer Assessment for the Upper Extremity (FMA-UE), and Motricity Index of the Upper (MI-UE) and Lower (MI-LE) Extremities were evaluated at T0 and T1 to determine the patient's Activity of Daily Living (ADL) performance, upper limb motor performance, and upper and lower limb muscle strength, respectively.

RESULTS

We evaluated segmental and whole-body BIA in 70 subacute post-stroke patients (women n = 34, ischemic n = 56, mean age 70 ± 11) at T0 and T1. Whole-body PhA values of the patients were below the normal range. Considering segmental data, the affected hemisoma, arm, and leg had considerably lower PhA values as compared to the unaffected body segments. Furthermore, at T1, the PhA values of all affected body segments improved, while those of the unaffected ones and whole-body PhA did not. At both T0 and T1, the segmental PhA values of the affected body segments showed to be related with all clinical outcome measures, while whole-body PhA correlated only with mBI.

CONCLUSIONS

This study emphasizes the significance of measuring segmental PhA in hemiparetic subacute stroke patients undergoing rehabilitation treatment. Segmental PhA is a more accurate parameter to evaluate rehabilitation treatment in patients with hemiparesis because it can distinguish affected from unaffected body segments, hence facilitating accurate monitoring of muscle quality improvements resulting from a rehabilitation program.

Is muscle localized phase angle an indicator of muscle power and strength in young women?

Objective. This study aimed to investigate the capacity of the bioelectrical muscle localized phase angle (ML-PhA) as an indicator of muscle power and strength compared to whole body PhA (WB-PhA).Approach. This study assessed 30 young women (22.1 ± 3.2 years) for muscle power and strength using the Wingate test and isokinetic dynamometer, respectively. Bioimpedance analysis at 50 kHz was employed to assess WB-PhA and ML-PhA. Lean soft tissue (LST) and fat mass (FM) were quantified using dual x-ray absorptiometry. Performance values were stratified into tertiles for comparisons. Regression and mediation analysis were used to test WB-PhA and ML-PhA as performance predictors.Main results. Women in the second tertile of maximum muscle power demonstrated higher ML-PhA values than those in first tertile (13.6° ± 1.5° versus 11.5° ± 1.5°,p= 0.031). WB-PhA was a predictor of maximum muscle power even after adjusting for LST and FM (β= 0.40,p= 0.039). ML-PhA alone predicted average muscle power (β= 0.47,p= 0.008). FM percentage was negatively related to ML-PhA and average muscle power, and it mediated their relationship (b= 0.14; bias-corrected and accelerated 95% confidence interval: 0.007-0.269).Significance. PhA values among tertiles demonstrated no differences and no correlation for strength variables. The results revealed that both WB and ML-PhA may be markers of muscle power in active young women.

Rectus Femoris Cross-Sectional Area and Phase Angle asPredictors of 12-Month Mortality in Idiopathic Pulmonary Fibrosis Patients

BACKGROUND

The value of the phase angle (PhA), measured via bioelectrical impedance analysis (BIA), could be considered a good marker of the cell mass and the cell damage of a patient; however, there are new techniques, such as muscle ultrasonography, that allow the quantity and quality of muscle to be assessed in a minimally invasive way. The aim of this study is to determine the prognostic value of morphofunctional techniques in the prognosis of mortality in patients with idiopathic pulmonary fibrosis (IPF).

METHODS

This multicenter, cross-sectional study included 86 patients with idiopathic pulmonary fibrosis with a mean age of 71 years, 82.7% of whom were male. The nutritional risk of the patients was assessed by means of questionnaires, such as the Subjective Global Assessment (SGA), and non-invasive functional techniques, including BIA, nutritional ultrasound, and hand grip strength (HGS). Statistical analysis of the sample was performed using JAMOVI version 2.3.22.

RESULTS

Correlations were made between the RF-CSA techniques with PhA (r = 0.48, p < 0.001), BCM (r = 0.70, p < 0.001), SMI (r = 0.64, p < 0.001), and HGS (r = 0.54, p < 0.001). The cut-off points for 12-month mortality were PhA = 4.5° (AUC = 0.722, sensitivity of 72.7% and specificity of 66.6%), BCM = 28.8 kg (AUC = 0.609, sensitivity of 32.4% and specificity of 100.0%), RF-CSA = 3.00 cm2 (AUC = 0.857, sensitivity of 64.4% and specificity of 100.0%), 6MMW = 420 m (AUC = 0.830, sensitivity of 63.27% and specificity of 100.0%), and TUG = 7.2 s (AUC = 0.771, sensitivity of 100.0% and specificity of 56.67%). In addition, a multivariate analysis was performed with RF-CSA, HR = 8.11 (1.39-47.16, p = 0.020), and PhA of 6.35 (1.29-31.15, p = 0.023), taking into account age, sex, and BMI to determine mortality. Finally, a Kaplan-Meier survival analysis was conducted with low or normal values for classical parameters (GAP and T6MM) and new parameters (PhA, BCM, RF-CSA, and TUG).

CONCLUSION

RF-CSA and PhA were shown to be good prognostic markers of 12-month mortality and could, therefore, be useful screening tools to complement the nutritional assessment of IPF patients.

Prediction of body water compartments by raw bioelectrical impedance parameters in athletes: Comparison between series and parallel measurements

BACKGROUND

The aim of this study was to determine the predictive role of series and parallel bioelectrical impedance-derived parameters in predicting total body (TBW), intracellular (ICW), and extracellular water (ECW) in athletes.

METHODS

This cross-sectional study analyzed 134 male (21.33 ± 5.11 years) and 64 female (20.45 ± 5.46 years) athletes. Using dilution techniques, TBW and ECW were determined while ICW was the difference between both. Raw and standardized for height (/H) bioelectrical resistance (R), reactance (Xc), and impedance (Z) values were obtained using a phase-sensitive device at a single frequency in a series array (s). These were mathematically transformed in a parallel array (p) and capacitance (CAP). Fat-free mass (FFM) was assessed by dual-energy X-ray absorptiometry.

RESULTS

Multiple regressions adjusted for age and FFM show that R/Hs, Z/Hs, R/Hp, and Z/Hp were significant predictors of TBW (p < 0.001 in females and males). While Xc/Hs did not predict ICW, Xc/Hp was a predictor (p < 0.001 in females and Males). In females, R/H and Z/H predicted similarly TBW, ICW, and ECW. In males, R/Hs was considered a better predictor than R/Hp for TBW and ICW, and the Xc/Hp was considered the best predictor for ICW. Another significant predictor of ICW was CAP (p < 0.001 in females and males).

CONCLUSION

This study highlights the potential value of parallel bioelectrical impedance values to identify fluid compartments in athletes as an alternative to the regularly used series measurements. Moreover, this study supports Xc in parallel, and ultimately CAP, as valid indicators of cell volume.

Association between Phase Angle and Body Composition of Children and Adolescents Diagnosed with HIV Infection

The aim of the study was to investigate how phase angle (PhA) is associated with subtotal and lumbar spine bone mineral density [BMD], lean soft tissue mass [LSTM], total body fat mass, android and gynoid in children and adolescents with HIV according to sex. A cross-sectional study was conducted in Florianópolis, Brazil, involving 64 children and adolescents vertically transmitted with HIV. Resistance and reactance values were obtained using bioelectrical impedance analysis, and PhA was subsequently calculated. Dual emission X-ray absorptiometry was used to assess body composition. Antiretroviral medication, physical activity (accelerometers) and skeletal maturation (wrist-carpal radiography) were used in the adjusted model. In males, PhA was directly associated with subtotal BMD (βadj: 0.65; R²: 0.38, p < 0.01) and lumbar spine BMD (βadj: 0.53; R²: 0.22, p = 0.01), directly associated with LSTM (βadj: 0.76; R²: 0.46, p < 0.01), and inversely associated with gynoid fat (βadj: -0.47; R²: 0.2, p = 0.01), in adjusted models. In females, PhA was directly associated with subtotal BMD (βadj: 0.46; R²: 0.17, p < 0.01) and lumbar spine BMD (βadj: 0.48; R²: 0.19, p < 0.01). It is concluded that PhA was directly associated with subtotal and regional BMD, LSTM, and inversely with gynoid fat in boys with HIV. In girls, PA was directly associated only with subtotal and regional BMD.

Hydration Status in Older Adults: Current Knowledge and Future Challenges

Adequate hydration is essential for the maintenance of health and physiological functions in humans. However, many older adults do not maintain adequate hydration, which is under-recognized and poorly managed. Older adults are more vulnerable to dehydration, especially those living with multiple chronic diseases. Dehydration is associated with adverse health outcomes in older adults, and acts as an independent factor of the hospital length of stay, readmission, intensive care, in-hospital mortality, and poor prognosis. Dehydration is a prevalent health problem in older adults, accounting for substantial economic and social burden. This review attempts to provide current knowledge of hydration including patterns of body water turnover, the complex mechanisms behind water homeostasis, the effects of dehydration on the health of the body, and practical guidance for low-intake dehydration in older adults.

Phase angle, muscle tissue, and resistance training

The biophysical response of the human body to electric current is widely appreciated as a barometer of fluid distribution and cell function. From distinct raw bioelectrical impedance (BIA) variables assessed in the field of body composition, phase angle (PhA) has been repeatedly indicated as a functional marker of the cell's health and mass. Although resistance training (RT) programs have demonstrated to be effective to improve PhA, with varying degrees of change depending on other raw BIA variables, there is still limited research explaining the biological mechanisms behind these changes. Here, we aim to provide the rationale for the responsiveness of PhA determinants to RT, as well as to summarize all available evidence addressing the effect of varied RT programs on PhA of different age groups. Available data led us to conclude that RT modulates the cell volume by increasing the levels of intracellular glycogen and water, thus triggering structural and functional changes in different cell organelles. These alterations lead, respectively, to shifts in the resistive path of the electric current (resistance, R) and capacitive properties of the human body (reactance, Xc), which ultimately impact PhA, considering that it is the angular transformation of the ratio between Xc and R. Evidence drawn from experimental research suggests that RT is highly effective for enhancing PhA, especially when adopting high-intensity, volume, and duration RT programs combining other types of exercise. Still, additional research exploring the effects of RT on whole-body and regional BIA variables of alternative population groups is recommended for further knowledge development.

Phase angle (PhA) in overweight and obesity: evidence of applicability from diagnosis to weight changes in obesity treatment

Phase angle (PhA) is a recently proposed marker of nutritional status in many clinical conditions. Its use in patients with obesity presents different critical concerns due to the higher variability of the two measured parameters (resistance, R, and reactance, Xc) that contribute to the determination of PhA. Controversial is the relation between PhA and BMI that might vary with graded levels of obesity due to the variation in fat and free fat mass. Obesity is frequently associated with metabolic, hepatic, cardiovascular and kidney diseases that introduce variations in PhA values, in relation to multimorbidity and severity degree of these diseases. It is reported that the improvement of clinical condition is associated with a positive change in PhA. Also, the treatment of obesity with weight loss might confirm this effect, but with different responses in relation to the type and duration of the intervention applied. In fact, the effect appears not only related to the percentage of weight loss but also the possible loss of free fat mass and the nutritional, metabolic and structural modifications that might follow each therapeutic approach to decrease body weight. We can conclude that the PhA could be used as marker of health status in patients with obesity supporting an appropriate weight loss intervention to monitor efficacy and fat free mass preservation.