Standardized phase angle: relationship with functionality, muscle mass and postoperative outcomes in surgical cancer patients

To evaluate the association of standardized phase angle (SPA) with nutritional status, functional parameters, and postoperative outcomes in surgical cancer patients. This prospective study includes 59 cancer patients from Pelotas (Brazil) admitted for elective cancer surgery. We obtained the phase angle through Bioelectrical Impedance Analysis (BIA) and standardized it according to the population's reference values. We estimated the muscle mass using BIA for later calculation of the Skeletal Muscle Index (SMI) and performed handgrip strength (HGS) and gait speed (GS) tests. We used the Patient-Generated Subjective Global Assessment (PG-SGA) to assess the nutritional status. Postoperative complications and duration of hospital stay were evaluated as the outcomes. The prevalence of malnutrition in the sample was 28.8%, according to ASG-PPP. SPA was statistically lower in patients with malnutrition, with lower HGS and reduced GS. For postoperative outcomes, patients with severe complications and those with prolonged hospitalization also had lower SPA values. The greater the number of functional alterations in patients, the lower the SPA value, mainly when associated with reduced muscle mass assessed by BIA, suggesting that muscle mass reduction plays an important role in the association between functional alterations and phase angle in patients with cancer. According to the parameters used in this study, low SPA value was associated with impaired nutritional and functional status and negative outcomes in the analyzed sample.

Electrical bioimpedance analysis and comparison in biological tissues through crystalloid solutions implementation

Electrical bioimpedance is a non-invasive and radiation-free technique that was proposed to be used in different clinical areas, however, its practical use is limited due to its low capacity to discriminate between tissues. In order to overcome this limitation, our research group proposes to incorporate the contrast media into the electrical bioimpedance procedure. The main objective of the present study was to assess the crystalloid solutions as a possible contrast media to discriminate between different tissue types in the bioimpedance technique. Two medical-grade crystalloid solutions (Hartmann and NaCl 0.9%) were injected into three biological ex vivo models: kidney, liver, and brain. BIOPAC system was used to acquire bioimpedance data before and after the injections. The data was adjusted to the Debye electrical model. The analysis of measured values showed substantial bioimpedance disparities in tissues subjected to isotonic solutions. The NaCl solution exhibited more pronounced changes in electrical parameters compared to the Hartmann solution. Similarly, NaCl solution displayed superior discriminatory capabilities among tissues, with variations of 465%, 157%, and 206%. Distinct spectral modifications were identified, with tissues demonstrating unique responses at each frequency of analysis relative to untreated tissue. Variations in bandwidth alterations were discernible among tissues, providing clear distinctions. In conclusion, the research showed that the crystalloid solution exhibited greater sensitivity and superior tissue contrast at specific frequencies. This study's findings underscore the feasibility of implementing crystalloid solutions to enhance tissue discrimination, similar to the effects of contrast agents.

Sensitivity study of a locally developed six electrode focused impedance method

The Focused Impedance Method (FIM) is a new technique of electrical bioimpedance measurements in the human body. The idea originated in Bangladesh and provides an opportunity for localized measurement of bioimpedance down to reasonable depths from the body surface using skin surface electrodes. This has potential applications for physiological studies of targeted organs in the body and in detecting or diagnosing diseases and disorders. FIM is based on the age-old Tetra-Polar Impedance Measurement (TPIM) but provides a few significant improvements. Technology must be developed indigenously to obtain long-term benefits, particularly in Low and Medium Income countries (LMIC). This paper presents an experimental sensitivity study of the six-electrode version of the Focused Impedance method (FIM-6) with the circuit and phantom indigenously designed in Nepal. The work involved sensitivity studies of both FIM-6 and TPIM with the necessary circuit blocks developed through experimental validation. The sensitivity studies were performed on a simple 2D phantom with different electrode arrangements for FIM-6 and linear TPIM. A cylindrical object was placed at different positions for this study. The FIM-6 gave a high sensitivity in the central part, which remained almost constant within a small region that may be termed as the focused region. On the other hand, TPIM results fell off sharply away from the central point, making it unsuitable for practical measurements on target organs. Besides, there were areas with large negative sensitivities in TPIM, which were much smaller in FIM. The results obtained through this work clearly show the improvement offered by FIM over TPIM.

Role of the phase angle in the prognosis of the cirrhotic patient: 15 years of follow-up

BACKGROUND

In 2019, cirrhosis accounted for 2.4% of global deaths. The projection for 2030 is an increase in this index. In recent years, hospitalization costs have escalated by 36% for compensated cirrhosis and 24% for decompensated cirrhosis. Therefore, it is necessary to identify a tool capable of predicting the mortality of these patients according to their clinical condition and consequently extending their survival time. Different studies have shown that the phase angle (PA) can be a feasible method in clinical practice, with the potential to guide assertive patient management in the therapeutic of chronic liver disease.

AIM

To evaluate the prognostic role of PA in cirrhotic patients over a 15-year follow-up period.

METHODS

Retrospective cohort study with 129 cirrhotic patients of both sexes over 18 years old. Diagnosis of cirrhosis by liver biopsy. The first year of data collection was 2007, and data regarding outcomes was collected in 2023. Data were gathered from medical records, such as esophageal varices (EV), EV bleeding, ascites, spontaneous bacterial peritonitis (SBP), encephalopathy, laboratory findings and PA. The cut-off value for the PA was 5.4°, a value described in 2012 by Fernandes et al for 129 patients evaluated in this study and the cut-off points for the Brazilian population presented in percentiles (P), as described by Mattiello et al. The mortality was assessed using the PA percentile through Kaplan-Meier curves and multivariate binary logistic regression models.

RESULTS

Patients were divided into two groups according to the PA 5.4th (PA > 5.4°, n = 40; PA ≤ 5.4°, n = 89) PA percentile (< P50, n = 56; ≥ P50 n = 73). The percentile classification was more accurate in identifying long-term deaths than the 5.4º PA. Patients with < P50 had a higher number of relevant complications such as ascites, SBP, liver encephalopathy and HCC. PA is strongly correlated with serum albumin (P < 0.001), International Normalized Ratio (P = 0.01), total bilirubin (P = 0.02) and direct bilirubin (P = 0.003). PA is correlated with survival time (P < 0.001) and length of stay (P = 0.02). Logistic regression analysis shows that an increase of 1° in PA enlarges the cirrhotic patient's chance of survival by 17.7%.

CONCLUSION

PA is a good predictor of morbidity and mortality for cirrhotic patients. The PA by percentile showed greater sensitivity in predicting mortality compared to the cut-off point of 5.4º.

A non-invasive, concealed electrocardiogram and bioimpedance measurement system for captive primates

Captive housed non-human primates, specifically great apes such as chimpanzees (Pan troglodytes) are frequently reported to have died from or are diagnosed with potentially fatal heart conditions that require the monitoring of physiological signals such as electrocardiogram (ECG) or respiratory rate. ECG screening must be conducted after applying full anaesthesia, causing potential physical and emotional stress as well as risk for the animal. Here, we present an electronic system that simultaneously measures the ECG and the electrical bioimpedance for the early detection of abnormal cardiovascular activity. Modified gloves whose fingers are equipped with electrodes enable the caregiver to obtain three cardiovascular signals (ECG, pulse rate and respiratory rate) by placing the fingertips on specific parts of the non-human primate without needing any prior physical preparations. Validation (ECG and bioimpedance) was performed both on humans and on captive housed chimpanzees, where all the signals of interest were correctly acquired.

Relationship of circulating resistin levels with muscle mass determined by bioelectrical impedance in females with obesity

INTRODUCTION

Serum resistin levels have been associated with obesity, visceral fat, and insulin resistance. Its relationship with muscle mass has been less evaluated.

OBJECTIVES

to evaluate the relationship between muscle mass determined by electrical bioimpedance and circulating resistin levels in obese women over 60 years of age.

METHODS

We conducted a cross-sectional study in 313 obese women. Anthropometric data (weight, height, body mass index (BMI) and waist circumference), BIA parameters (total fat mass (TFM), fat-free mass (FFM), fat-free mass index (FFMI)), skeletal muscle mass (SMM) and skeletal muscle mass index (SMI)), blood pressure and laboratory tests were recorded.

RESULTS

Patients were divided into two different groups according to the mean value of SMI (11.93 kg/m2): low SMI versus high SMI. In the low SMI group, the resistin levels were higher than the resistin levels in the high SMI group (delta value: 2.8 + 0.3 ng/dl:p = 0.01). Serum resistin levels are inversely correlated with FFM, FFMI, SMM, and SMI. This adipokine shows a positive correlation with insulin, HOMA-IR and PCR levels. In the model with SMI as the dependent variable, resistin levels explained 12% of the variability in muscle mass (Beta -0.38, 95% CI -0.91 to -0.11).

CONCLUSIONS

Serum resistin levels are associated with low skeletal muscle mass in obese women over 60 years of age.

Piezoresistivity modeling of soft tissue electrical-mechanical properties: A validation study

In general, the electrical property of soft tissues is sensitive to the force applied to their surface. To further study the relationship between the force and the electrical property of soft tissues, this paper attempts to investigate the effect of static and higher-order stresses on electrical properties. Overall, a practical experimental platform is designed to acquire the force information and the electrical property of soft tissues during a contact procedure, which is featured different compression stimuli, such as constant pressing force, constant pressing speed, and step-force compression, etc. Furthermore, the piezoresistive characteristic is innovatively introduced to model the mechanical-electrical properties of soft tissue. Finite Element Modeling (FEM) is adopted to fit the static piezoresistivity of the soft tissue. Finally, experimental studies were performed to demonstrate the effect of stress on the electrical properties and the feasibility of the proposed piezoresistive model to describe soft tissues' mechanical and electrical properties.

Detrusor pressure monitoring by electrical bioimpedance in the neurogenic bladder of adult patients

PURPOSE

Detrusor pressure-volume relationship evaluation by urodynamics provides useful clinical information; however, it is invasive, and requires specific installations. An alternative technique proposed by our research group is the electrical bioimpedance (BI) which is an easily performed and non-invasive method. In this work, we assess the relationship between BI and detrusor bladder pressure in adults with neurogenic lower urinary tract dysfunction.

METHODS

A prospective observational study was conducted. 20 patients (11 females and 9 male) previously diagnosed with neurogenic bladder were included. All participants underwent simultaneously a urodynamic evaluation (UDS) and BI determination, and both examination signals were recorded and subjected to Shapiro-Wilks statistical test. A correlational statistical test was used to compare the pressure parameters (detrusor, vesical and abdominal) with their respective BI determinations. Subsequently, a linear regression test was performed to evaluate the concordance between BI and their respective pressure values.

RESULTS

From the 20 correlations, between detrusor bladder pressure (PDET) and abdominal bioimpedance determinations (ZABD), obtained for all participants, 16 evidenced significant results over 90% (p < 0.05).

CONCLUSIONS

A significantly high correlation between abdominal bioimpedance determinations and the detrusor bladder pressures was evidenced. These results should be confirmed in a larger group of participants.

A low-cost, portable, two-dimensional bioimpedance distribution estimation system based on the AD5933 impedance converter

This study proposes a low-cost, portable, eight-channel electrical impedance tomograph based on the AD5933 impedance converter. The patterns for current injection and voltage measurement are managed by an Arduino Mega 2560 board and four 74HC4067 Texas Instruments multiplexers. Regarding the experimental results, the errors in the impedance estimates of an electrical circuit that represents a Cole model were less than 1.14% for the magnitude and 4.15% for the phase. Furthermore, the signal-to-noise ratio measured in a resistive phantom was 55.23 dB. Additional experiments consisted of placing five spheres of different size and conductivity in a saline tank, measuring their impedance through eight electrodes, and then generating impedance maps using the Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software (EIDORS). These maps were different for each sphere, suggesting the proposed prototype as a promising alternative for medical applications.

Association of phase angle with muscle strength and aerobic fitness in different populations: A systematic review

OBJECTIVES

The aim of this study was to summarize the evidence on the association of phase angle (PhA) with muscle strength and aerobic fitness in different populations.

METHODS

A systematic search on this topic was performed in nine electronic databases (CINAHL, LILACS, PubMed, SciELO, Scopus, SPORTDiscus, ScienceDirect, MEDLINE, and Web of Science) in January 2021. Studies with different designs that permitted extraction of information about the relationships between PhA and muscle strength and between PhA and aerobic fitness were included. A total of 4446 studies were initially identified; 34 were included after reading of the title, abstract, full text, and references. Four of the studies included had a longitudinal design, with samples consisting of participants ages 6 to 92 years. Thirty-two of the 34 studies evaluated the relationship between PhA and muscle strength, two cross-sectional studies investigated only PhA and aerobic fitness, and three cross-sectional studies evaluated both components (muscle strength and aerobic fitness).

RESULTS

PhA was directly associated with muscle strength in 30 cross-sectional studies and two longitudinal studies; the two studies that did not find a direct relationship had a cross-sectional design. For aerobic fitness, the five studies identified reported a direct relationship with PhA.

CONCLUSIONS

PhA is directly associated with muscle strength and aerobic fitness in different age groups (children, adolescents, adults, and older adults) and in people with different health conditions (human immunodeficiency virus, Crohn's disease, chronic obstructive pulmonary disease, bariatric surgery, kidney transplant, cancer, hemodialysis, and sarcopenia).

Regional pulmonary effects of bronchoalveolar lavage procedure determined by electrical impedance tomography

Background

The provision of guidance in ventilator therapy by continuous monitoring of regional lung ventilation, aeration and respiratory system mechanics is the main clinical benefit of electrical impedance tomography (EIT). A new application was recently described in critically ill patients undergoing diagnostic bronchoalveolar lavage (BAL) with the intention of using EIT to identify the region where sampling was performed. Increased electrical bioimpedance was reported after fluid instillation. To verify the accuracy of these findings, contradicting the current EIT knowledge, we have systematically analysed chest EIT data acquired under controlled experimental conditions in animals undergoing a large number of BAL procedures.

Methods

One hundred thirteen BAL procedures were performed in 13 newborn piglets positioned both supine and prone. EIT data was obtained at 13 images before, during and after each BAL. The data was analysed at three time points: (1) after disconnection from the ventilator before the fluid instillation and by the ends of fluid (2) instillation and (3) recovery by suction and compared with the baseline measurements before the procedure. Functional EIT images were generated, and changes in pixel electrical bioimpedance were calculated relative to baseline. The data was examined in the whole image and in three (ventral, middle, dorsal) regions-of-interest per lung.

Results

Compared with the baseline phase, chest electrical bioimpedance fell after the disconnection from the ventilator in all animals in both postures during all procedures. The fluid instillation further decreased electrical bioimpedance. During fluid recovery, electrical bioimpedance increased, but not to baseline values. All effects were highly significant (p < 0.001). The fractional changes in individual regions-of-interest were posture-dependent. The regional fall in electrical bioimpedance was smaller in the ventral and larger in the dorsal regions after the fluid instillation than after the initial disconnection to ambient pressure in supine animals (p < 0.001) whereas these changes were of comparable amplitude in prone position.

Conclusions

The results of this study show a regionally dissimilar initial fall in electrical bioimpedance caused by non-uniform aeration loss at the beginning of the BAL procedure. They also confirm a further pronounced fall in bioimpedance during fluid instillation, incomplete recovery after suction and a posture-dependent distribution pattern of these effects.

Electronic supplementary material

The online version of this article (10.1186/s40635-019-0225-6) contains supplementary material, which is available to authorized users.

Gastric motility measurement and evaluation based on electrical-mechanical composite mechanism

Gastric motility and emptying are a composite course involving electrical activity and mechanical contraction. In the research of gastric motility, the electrical activity should be closely connected to the subsequent mechanical contraction based on the understanding of electrical-mechanical composite mechanism. Existing simulation research and clinical research suggest that electrogastrogram (EGG) signals can provide physiological time scales, and gastric motility can be extracted from impedance signals. According to the coupling of the myoelectric activity and the mechanical contraction of the stomach, the correlation analysis of multiple signals can be performed. And then the influence of various factors such as the range, time and transmission distance of the gastric contraction can be deeply explored. The method combining gastric impedance and synchronous EGG measurements is effective and promising for evaluating gastric motility.

Electrical bioimpedance gastric motility measurement based on an electrical-mechanical composite mechanism

AIM: To introduce a bioimpedance gastric motility measurement method based on an electrical-mechanical composite concept and a preliminary clinical application.

METHODS: A noninvasive gastric motility measurement method combining electrogastrogram (EGG) and impedance gastric motility (IGM) test was used. Preliminary clinical application studies of patients with functional dyspepsia (FD) and gastritis, as well as healthy controls, were carried out. Twenty-eight FD patients (mean age 40.9 ± 9.7 years) and 40 healthy volunteers (mean age 30.9 ± 7.9 years) were involved. IGM spectrum was measured for both the healthy subjects and FD patients, and outcomes were compared in the FD patients before treatment and 1 wk and 3 wk after treatment. IGM parameters were obtained from 30 erosive gastritis patients (mean age 50.5 ± 13.0 years) and 40 healthy adults, and IGM and EGG results were compared in the gastritis patients before treatment and 1 wk after treatment.

RESULTS: There were significant differences in the IGM parameters between the FD patients and healthy subjects, and FD patients had a poorer gastric motility [percentage of normal frequency (PNF) 70.8 ± 25.5 in healthy subjects and 28.3 ± 16.9 in FD patients, P < 0.01]. After 1 wk administration of domperidone 10 mg, tid, the gastric motility of FD patients was not improved, although the EGG of the patients had returned to normal. After 3 wk of treatment, the IGM rhythm of the FD patients became normal. There was a significant difference in IGM parameters between the two groups (PNF 70.4 ± 25.5 for healthy subjects and 36.1 ± 21.8 for gastritis patients, P < 0.05). The EGG rhythm of the gastritis patients returned to normal (frequency instability coefficient 2.22 ± 0.43 before treatment and 1.77 ± 0.19 one wk after treatment, P < 0.05) after 1 wk of treatment with sodium rabeprazole tablets, 10 mg, qd, po, qm, while some IGM parameters showed a tendency toward improvement but had not reached statistical significance.

CONCLUSION: The electrical-mechanical composite measurement method showed an attractive clinical application prospect in gastric motility research and evaluation.

Invasive electrical impedance tomography for blood vessel detection

We present a novel method for localization of large blood vessels using a bioimpedance based needle positioning system on an array of ten monopolar needle electrodes. The purpose of the study is to develop a portable, low cost tool for rapid vascular access for cooling and controlled reperfusion of cardiac arrest patients. Preliminary results show that localization of blood vessels is feasible with this method, but larger studies are necessary to improve the technology.

Use of electrical bioimpedance for gastric motility measurement and evaluation

Electrical bioimpedance technology is a measurement method to extract biomedical information associated with the physiological and pathological states of human body according to the electrical properties of tissue and organs. It has many outstanding advantages such as noninvasiveness, cheapness, convenience and rich function information. According to the electrical properties of the stomach tissue or the food in the stomach and the characteristics of food digestion, electrical bioimpedance methods permit to extract physiological and pathological information associated with gastric motility, investigate gastric contraction, peristalsis, transmission and emptying, and measure and evaluate gastric motility function noninvasively. In this article, we reveiw the development history of electrical bioimpedance technology and the characteristics of gastric motility impedance signal, and introduce the bioimpedance methods for measurement of gastric motility based on the concept of electrical-mechanical coupling. Besides, we also summarize the application of bioimpedance methods in the basic research of gastric motility, in the measurement of gastric motility in patients with functional dyspepsia, in the evaluation of gastric motility in patients with erosive gastritis, and in the detection and screening of gastric cancer. Moreover, we put forward some suggestions on the future development directions of bioimpedance methods for measurement of gastric motility.

Electrical impedance tomography measuring gastric emptying and gastric motility

Electrical impedance tomography (EIT) is a novel medical imaging technology, which comes forth in recent 20 years following morphology imaging and structure imaging. EIT has the outstanding advantages of noninvasive, functional imaging and medical image monitoring. It has been mostly used in gastroenterology to assess flow of ingesta through the gastric region as an alternative to radionuclide studies. In vitro, EIT can accurately measure the volume of glass rods/balloons in a phantom. In humans, EIT can accurately measure gastric volume (balloons) in experimental conditions. Gastric emptying measurement of EIT has good correlations with dye dilution, gastric residuals and scintigraphy. By electrode array located on body surface, gastric motility measurement using EIT realizes noninvasive measurement and directly displays shrink and motility conditions of stomach in body by images of real time. This is going to be a great progress of gastric motility measurement and evaluation method. EIT gastric motility measurement has shown seductive application prospect.