Bioelectrical Impedance Analysis (BIA)- Derived Phase Angle in Children and Adolescents: A Systematic Review

Bioimpedance formalism: A new approach for accessing the health status of cell and tissues

This manuscript describes a novel methodology for studying relaxation dynamics in tissues and cells using characteristic frequency of bioimpedance spectroscopy measurements. The Bioimpedance Formalism allows for the simultaneous study of bioelectrical parameters in the frequency and time domains, providing insight into possible relaxation processes occurring in the tissue or cell of interest. Results from the Cole-Cole analysis showed no multiple relaxation processes associated with heterogeneity, with a visible age group separation in males compared with females. The study of the relaxation dynamic in the time domain revealed that the β parameter can be used to analyse the charge carriers in tissues, cells, or cancer cells, potentially leading to new diagnostic and therapeutic approaches for cancer and other diseases. Overall, this approach presents a promising area of research for gaining insights into the electrical properties of tissues and cells using bioimpedance methods.

Postoperative complications in the pediatric population. Malnutrition or phase angle? Which one do we use?

Background and Aims

Malnutrition increases post-operative risks like infections and prolonged stays. Pediatric assessment challenges require using anthropometric measurements and phase angle, which reflects body cell mass and health outcomes. Phase angle varies by maturation stages, making it crucial for pre-surgical evaluations alongside BMI. This study aimed to determine the relationship between nutritional status, phase angle, and postoperative complications in pediatric patients who underwent surgery.

Methods

Prospective study with patients aged 3-17 undergoing major non-ambulatory surgery. Anthropometric measurements (weight, height, BMI Z-scores) hand grip strength, dietary intake and body composition via bioimpedance to assess phase angle were recorded. Postoperative complications were monitored, including surgical site infections, morbidity (pneumonia, inotropic support, infections, thromboembolism), and mortality. Surgical risks and pre- and postoperative conditions were documented.

Results

After the application of the selection criteria, a total of 391 patients who underwent surgery were included; 60% (n = 235) were within the range of the preschool and school-age groups. During the follow-up period, 51 (13%) patients developed at least one postoperative complication, with surgical site infections being the most common. Moreover, as phase angle decreased, the length of stay (LOS) increased in all the participants. Among children aged ≤12 years old, malnutrition was a risk factor for complications [OR 3.86 (1.61-9.27 95%CI)], whereas among adolescents, phase angle served as a protective factor [OR 0.63 (0.42-0.94 95%CI)].

Conclusion

Significant associations were observed between nutritional status, by BMI z-score, and post-surgical complications in younger patients. Additionally, in adolescents, the phase angle emerged as a protective factor against these complications.

Bioelectrical impedance phase angle and nutritional status in children with intestinal failure on prolonged parenteral nutrition

OBJECTIVE

To compare the phase angle (PhA) through bioelectrical impedance (BIA) of children with intestinal failure (IF) using prolonged parenteral nutrition (PN) followed by an Intestinal Rehabilitation Program, with a control group.

METHODS

Children under 10 years of age with IF using prolonged PN for >60 days (study group) were included. The control group consisted of healthy children without chronic pathologies, matched by sex and age. Anthropometric parameters evaluated were: weight, height, weight/age z-score (W/A), height/age z-score (H/A), BMI, BMI/A z-score, arm circumference, triceps skinfold, subscapular skinfold, mid-arm muscle circumference. BIA parameters were resistance (R), reactance (Xc), and phase angle (PhA).

RESULTS

Twenty-eight children were included in the study group, median (IQR) age was 11 (8-27) months, 53.6 % were male. In the control group, 28 children were included, median (IQR) age was 12.5 (8-24.7) months, 50 % were male. Children from the study group had W/A z-scores and H/A z-scores significantly lower than controls. There was no significant difference between PhA in the study group and controls, [median (IQR) 4.3° (3.8;4.6) vs 4.0° (3.8;5.4) respectively, p = 0.980]. Prematurity was significantly higher in the study group than in the controls, but there was no significant correlation between gestational age at birth and PhA of the children from the study group.

CONCLUSION

Children with IF using prolonged PN showed lower W/A and H/A compared to the control group, but without significant difference between the PhA of children with IF compared to controls.

Bioelectrical impedance phase angle and the mortality in critically ill children

Background

Phase angle (PhA) is a variable obtained from bioelectrical impedance analysis (BIA). It is highly sensitive and specific and is commonly used in clinical nutrition assessment. Recently, PhA has shown promise in predicting clinical outcomes, especially as a new indicator of mortality, but its use in pediatric research is limited. This study aims to investigate the association between PhA measured at admission using BIA and PICU length of stay (LOS) and 60-day mortality in critically ill children and adolescents.

Methods

A consecutive series of pediatric patients in the PICU underwent BIA measurements within 72 h of admission. All patients met the inclusion and exclusion criteria. Patient demographics, anthropometric measurements, pediatric index of mortality 2 score (PIM-2), and laboratory exams were recorded. Kaplan-Meier (K-M) survival curves were constructed based on the critical PhA value to assess differences in survival status within the 60-day window. Multivariate cox regression model was employed to illustrate the relationship between PhA and 60-day mortality rates. The Youden's index method was used to identify the critical cut-off value for PhA in relation to mortality rates. ROC curves provided the area under the curve (AUC) and a 95% confidence interval (CI).

Results

A total of 205 pediatric patients (118 boys) were included, with a mean age of 9.2 years (±6.0). Survival curves indicated a cutoff value of 3.1°, with higher survival in patients with PhA ≥3.1° compared to those with PhA <3.1° (F = 10.51, p < 0.0001). The area under the ROC curve was 0.70, with a sensitivity of 0.65 and specificity of 0.72. Total hospital LOS was longer in the PhA <3.1° group compared to the PhA ≥3.1° group (p = 0.000). The PhA <3.1° group had a longer PICU LOS (adjusted for age and sex, HR 1.871, p = 0.000, log-rank test, p = 0.000). PhA and PIM-2 were two independently significant correlated variables (p < 0.05) for the 60-day mortality rate in this study.

Conclusion

Low PhA in patients is associated with longer PICU LOS and an increased risk of PICU patient mortality. PhA not only serves as an indicator for monitoring pediatric nutrition but also as a prognostic indicator for PICU patients.

Phase angle and anthropometric indicators of cardiometabolic risk in children and adolescents

RATIONALE/OBJECTIVE

The phase angle (PhA) is a measurement obtained from the resistance and reactance found in the bioelectrical impedance examination and is useful in assessing nutritional status and in assessing cardiometabolic diseases. Therefore, the objective was to correlate the phase angle to the anthropometric variables of cardiometabolic risk (CMR) in children and adolescents.

SUBJECTS/METHODS

Weight, height, body mass index (BMI), waist circumference (WC) and neck circumference (NC), waist-to-height ratio (WHtR), and PhA of 1231 children and adolescents aged between 5 and 18 years were assessed. PhA was assessed in tertiles and CMR was identified using the anthropometric variables BMI, WC, NC, and WHtR. Linear regression models were used to verify the association between PhA tertiles and CMR anthropometric variables, stratified by sex.

RESULTS

No relationship was found between PhA and CMR variables in children. In adolescents, lower values of NC (β = -0.019, p = 0.005) and BMI (β = -0.025, p = 0.023) were found in boys, WC (β = -0.017, p = 0.020), WHtR (β = -0.017, p = 0.020), NC (β = -0.011, p = 0.027) and BMI (β = -0.026, p = 0.009) in girls when they were in tertile 1 when compared to tertile 3 of the PhA, even after adjusting for age.

CONCLUSION

The PhA was directly associated with CMR in the assessed adolescents.

Could BIA-derived phase angle predict health-related musculoskeletal fitness? A cross-sectional study in young adults

OBJECTIVES

To our knowledge, little evidence exists on the relationships between body composition and health-related physical fitness; in particular, musculoskeletal fitness. Bioimpedance index phase angle (bioelectrical impedance analysis raw variables) is a candidate predictor of health-related fitness, a marker of fat-free and body cell mass, respectively. The aim of this study was to evaluate body composition, raw bioelectrical impedance analysis variables, and health-related fitness in young adults and investigate their mutual relationships to identify predictors of muscle strength.

METHODS

The study included 229 young adults (115 men and 114 women; 24.2 ± 3 y; body mass index 19-30 kg/m²). Anthropometry was measured with standardized procedures. Whole-body BIA (50 kHz) was performed for impedance and phase angle. Predictive equations estimated fat-free mass and percentage body fat. The bioimpedance index was calculated as stature²/impedance. Musculoskeletal fitness was assessed by handgrip strength, standing broad jump, squat jump, and countermovement jump.

RESULTS

In both sexes, health-related fitness had stronger associations with body composition than stature or weight. Handgrip strength was related to fat-free mass and bioimpedance index, while an inverse association with percent body fat emerged for standing broad jump, squat jump and countermovement jump. Phase angle is directly correlated with handgrip strength, standing broad jump, squat jump, and countermovement jump. In multiple regression analysis phase angle was an independent predictor of all health-related fitness tests, along with fat-free mass (or bioimpedance index) for handgrip strength, and with sex and percent body fat for the three jump tests.

CONCLUSIONS

The present study provided consistent information on the relationships between body composition and health-related fitness in young adults. Phase angle emerged as a significant predictor of all health-related fitness measures and might be useful for a more consistent assessment of musculoskeletal fitness.

Phase angle as a prognostic indicator in critically ill children: A systematic review

Phase angle (PhA) may reflect the integrity of cellular membranes, hydration status, and total body cell mass. Studies have shown that PhA can be used as a good predictor for evaluation of disease severity in critically ill adults. However, there is a lack of studies assessing the association between PhA and clinical outcomes in critically ill children. This systematic review described the association between PhA at pediatric intensive care unit (PICU) admission with clinical outcomes in critically ill children. The search was conducted using PubMed/Medline, Scopus, Web of Science, EMBASE and LILACS until July 22, 2022. Studies that evaluate the association between PhA at PICU admission in critically ill children and clinical outcomes were eligible. Data regarding population, study design, setting, bioelectrical impedance analysis (BIA) protocol used, PhA classification, and outcome analysis were extracted. Risk of bias was assessed by Newcastle-Ottawa Scale. Among the 4669 articles screened, five prospective studies were included. The studies have shown association between lower values of PhA at PICU admission with longer PICU and hospital length of stay, duration of mechanical ventilation, septic shock, and higher mortality risk. Small sample size, different clinical conditions, and methodological differences of the studies regarding BIA equipment and cutoffs of PhA were observed. Although the studies have limitations, the PhA has a potential role in predicting clinical outcomes in critically ill children. Larger studies with standardized PhA protocols and other relevant clinical outcomes are necessary.

One-Year Changes in Bioelectrical Impedance Data in Adolescent Athletes

Raw bioelectrical impedance (BI) data and vector analysis (BIVA) have been used to evaluate fat-free mass (FFM) cross-sectionally in adolescent athletes; however, there have been no longitudinal studies about it. This study aimed to assess the magnitude of changes in raw BI data (resistance [R], reactance [Xc], and phase angle [PhA]), BIVA, and FFM in adolescent athletes (n = 137, 40% female). BI data were collected using a single-frequency device at baseline and after one year of sports practice. Baseline chronological age categorized the participants (11, 12, or 13 years [y]). In females, Xc/H increased (13 to 14 y, p = 0.04) while R/H decreased in all age groups (p = 0.001). PhA (11 to 12 y, p = 0.048) and FFM (11 to 12 y and 12 to 13 y groups p = 0.001) increased and showed the lowest magnitude of changes in the 13 to 14 y group (p = 0.05). In males, Xc/H decreased (11 to 12 and 12 to 13 y groups, p = 0.001) with a higher magnitude of changes in the 13 to 14 y group (p = 0.004); R/H decreased (p = 0.001); FFM increased in all groups (p = 0.001); however, no magnitude of changes was observed. PhA increased in the 13 to 14 y group (p = 0.004). BIVA showed no differences among ellipse distances in females. In males, a high distance was observed in the 11 to 12 y group. "Time interval" influenced PhA and Xc/H in the female group and R/H and Xc/H in the male group. "Initial age" and "time interval" influenced the increase in PhA in the male group. Raw BI data and BIVA patterns can detect the magnitude of the changes in a sex-dependent manner.

Utilization of bioelectrical impedance vector analysis (BIVA) in children and adolescents without diagnosed diseases: a systematic review

Introduction. Bioelectrical impedance vector analysis (BIVA) emerges as a technique that utilizes raw parameters of bioelectrical impedance analysis and assumes the use of a reference population for information analysis.Objective. To summarize the reference values, main studies objectives, approaches, pre-test recommendations and technical characteristics of the devices employed in studies utilizing BIVA among children and adolescents without diagnosed diseases.Methods. A systematic search was conducted in nine electronic databases (CINAHL, LILACS, PubMed, SciELO, Scopus, SPORTDiscus, Science Direct, MEDLINE, and Web of Science). Studies with different designs which allowed extracting information regarding reference values of BIVA in children and adolescents without diagnosed diseases, aged 19 years or younger, were included. The systematic review followed PRISMA procedures and was registered in PROSPERO (registration: CRD42023391069).Results. After applying the eligibility criteria, 36 studies were included. Twenty studies (55.6%) analyzed body composition using BIVA, thirteen studies (36.1%) aimed to establish reference values for BIVA, and three studies (8.3%) investigated the association of physical performance with BIVA. There was heterogeneity regarding the reference populations employed by the studies. Fifteen studies used their own sample as a reference (41.6%), four studies used the adult population as a reference (11.1%), and five studies used reference values from athletes (13.9%).Conclusion. Nutricional status and body composition were the main studies objectives. References values were not always adequate or specific for the sample and population. Furthermore, there was no pattern of pre-test recommendations among the studies.

Body composition in pediatric patients

Undernutrition is highly prevalent in children who are critically ill and is associated with increased morbidity and mortality, including a higher risk of infection due to transitory immunological disorders, inadequate wound healing, reduced gut function, longer dependency on mechanical ventilation, and longer hospital stays compared with eutrophic children who are critically ill. Nutrition care studies have proposed that early interventions targeting nutrition assessment can prevent or minimize the complications of undernutrition. Stress promotes an acute inflammatory response mediated by cytokines, resulting in increased basal metabolism and nitrogen excretion and leading to muscle loss and changes in body composition. Therefore, the inclusion of body composition assessment is important in the evaluation of these patients because, in addition to the nutrition aspect, body composition seems to predict clinical prognosis. Several techniques can be used to assess body composition, such as arm measurements, calf circumference, grip strength, bioelectrical impedance analysis, and imaging examinations, including computed tomography and dual-energy x-ray absorptiometry. This review of available evidence suggests that arm measurements seem to be well-established in assessing body composition in children who are critically ill, and that bioelectrical impedance analysis with phase angle, handgrip strength, calf circumference and ultrasound seem to be promising in this evaluation. However, further robust studies based on scientific evidence are necessary.

Phase angle as a marker of outcome in hospitalized pediatric patients. A systematic review of the evidence (GRADE) with meta-analysis

Phase angle (PhA) is a valuable tool for evaluating the nutritional and inflammatory status, which can accompany acute and severe disorders. PhA is a cellular health biomarker, whose value is particularly substantial due to the negative consequences of these situations in the pediatric population. Relevant literature was collected with the aim of comprehensively analysing the evidence on the association between an altered PhA can serve as a predictive-marker for mortality and poor-outcomes in at-risk-pediatric patients. Understanding this relationship could have significant implications for identifying high-risk individuals and implementing timely interventions. A systematic review with meta-analysis was conducted in the primary electronic databases from inception until January 2023. Overall, four studies with a total of 740 patients were eligible for our analysis. Evidence demonstrates that PhA is associated with nutritional status, reflecting undernutrition and changes in body composition related to illness. This review suggests that PhA can indeed be used as an indicator of nutritional status and a tool for predicting prognosis, including mortality and poor-outcomes, in hospitalized pediatric patients. A low PhA was associated with a significant mortality risk [RR:1.51;95%CI (1.22-1.88),p = 0.0002;I2 = 0%,(p = 0.99)] and an increased complications risk [OR:8.17;95%CI (2.44-27.4),p = 0.0007;I2 = 44%,(p = 0.18)]. These findings highlight the importance of taking a comprehensive approach to clinical nutrition, integrating multiple evaluation aspects to establish an accurate diagnosis and personalized therapeutic plans. While PhA emerges as a valuable tool for assessing the risk of malnutrition and as a prognostic-indicator for poor-outcomes in pediatric patients. Further future studies are needed to focus on investigating this relationship in larger and diverse population to strengthen the evidence base.

Comparison of bioelectrical impedance analysis-derived phase angle in individuals with different weight status

OBJECTIVE

Obesity is characterized not only by an increase of fat mass but also by alterations in skeletal muscle. Bioimpedance analysis (BIA)-derived phase angle (PhA) may provide specific information on the inherent characteristics of fat-free mass, and is widely used as an index of poor nutritional status. The aim of this study was to describe whether and to what extent PhA varies depending on age, sex, and body mass index (BMI) in individuals with different weight status.

METHODS

We selected 1877 participants for this retrospective study (two weight status groups): 983 individuals with obesity (age 40 ± 13.9 y; BMI 39.5 ± 7.2 kg/m²) and 894 controls (age 40 ± 13.3 y; BMI 24.6 ± 2.7 kg/m²). Anthropometry and PhA at 50 kHz for the whole body were performed in all participants.

RESULTS

PhA was greater in men than in women, although a decline of PhA was observed with age, which was linear in women and occurred in men after 40 y of age. On the other hand, no significant differences were observed with increasing BMI in either sex; lower values might be observed when BMI >50 kg/m².

CONCLUSIONS

A more detailed appraisal of BIA-derived PhA in obesity is reported in the present study, providing basic data that might be taken into consideration in prevention and clinical nutrition. Further studies are needed to explore differences of PhA in individuals with different weight status.

The Efficacy of Pulmonary Rehabilitation in Patients with Idiopathic Pulmonary Fibrosis

Background: This study evaluated the efficacy and safety of pulmonary rehabilitation (PR) on functional performance, exercise-related oxygen saturation, and health-related quality of life among patients with idiopathic pulmonary fibrosis (IPF). Methods: A total of 25 patients with IPF (13 in the PR group and 12 in the non-PR group) were enrolled between August 2019 and October 2021 at Haeundae-Paik Hospital in the Republic of Korea. A cardiopulmonary exercise test (CPET), six-minute walk test (6MWT), pulmonary function test (PFT), Saint George's Respiratory Questionnaire (SGRQ), muscle strength test, and bioelectrical impedance analysis were performed in each group at baseline and after eight weeks of PR. Results: The mean age was 68 years of age and most subjects were male. Baseline characteristics were similar between the two groups. The distance during 6MWT after PR was significantly improved in the PR group (inter-group p-value = 0.002). VO₂max and VE/VCO₂ slopes showed a significant difference after eight weeks only in the PR group, but the rate of change did not differ significantly from the non-PR group. Total skeletal muscle mass, PFT variables, and SGRQ scores did not differ significantly between the groups. Conclusions: PR improved exercise capacity, as measured using CPET and 6 MWT. Further studies in larger samples are needed to evaluate the long-term efficacy of PR in IPF patients.