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Bioelectrical impedance vector analysis in haemodialysis patients: relation between oedema and mortality

In this work, bioelectrical impedance vector analysis (BIVA) method is used in a sample of haemodialysis patients in stable (without oedema) and critical (hyperhydrated and malnutrition) states, in order to establish the relation between hyperhydration (oedema) and mortality. The measurements obtained were single frequency (50 kHz), tetrapolar (hand-foot) complex impedance measurements (vector components are: resistance R and reactance Xc). The impedance components were standardized by the height H of the subjects, (R/H and Xc/H) to obtain de impedance vector Z/H, that is represented in the RXc plot (abscise R/H, ordinate Xc/H). Measurements were performed on a sample of 74 patients (30 men and 44 women, 18-70 year, body mass index (BMI), 19-30 kg m(-2)) at the Saturnino Lora University Hospital in Santiago de Cuba. The 46 stable patients comprised 28 men and 18 women; the 28 critical patients 16 men and 12 women. The reference population consisted of 1196 healthy adult subjects living in Santiago de Cuba (689 men and 507 women, 18-70 year, BMI 19-30 kg m(-2)). We used the RXc plot with the BIVA method to characterize the reference population using the 50%, 75% and 95% tolerance ellipses. Students t-test and Hotellings T2-test were used to analyse the separation of groups obtained by means of clinical diagnosis and those obtained by BIVA. We obtained a significant difference (P < 0.05) in R/H, Xc/H and phase angle (PA) in men as in women between the location of Z/H vectors in the RXc graph and the separation made by the doctors between stable and critical patients. Critical (hyperhydrated) patients were located below the inferior pole of the 75% tolerance ellipse, whereas stable patients were within the tolerance ellipses. Some cases classified as stable by the clinic were classified as hyperhydrated by BIVA with 100% sensitivity and 48% specificity. In conclusion, the BIVA method could be used to classify patients by hydration state and to predict survival. Advantages of the method are its simplicity, objectivity and that it does not require the definition of patient dry weight.

Localized bioimpedance to assess muscle injury.

Injuries to lower limb muscles are common among football players. Localized bioimpedance analysis (BIA) utilizes electrical measurements to assess soft tissue hydration and cell membrane integrity non-invasively. This study reports the effects of the severity of muscle injury and recovery on BIA variables. We made serial tetra-polar, phase-sensitive 50 kHz localized BIA measurements of quadriceps, hamstring and calf muscles of three male football players before and after injury and during recovery until return-to-play, to determine changes in BIA variables (resistance (R), reactance (Xc) and phase angle (PA)) in different degrees of muscle injury. Compared to non-injury values, R, Xc and PA decreased with increasing muscle injury severity: grade III (23.1%, 45.1% and 27.6%), grade II (20.6%, 31.6% and 13.3%) and grade I (11.9%, 23.5% and 12.1%). These findings indicate that decreases in R reflect localized fluid accumulation, and reductions in Xc and PA highlight disruption of cellular membrane integrity and injury. Localized BIA measurements of muscle groups enable the practical detection of soft tissue injury and its severity.

Measurement errors in multifrequency bioelectrical impedance analyzers with and without impedance electrode mismatch.

The purpose of this study is to compare measurement errors in two commercially available multi-frequency bioimpedance analyzers, a Xitron 4000B and an ImpediMed SFB7, including electrode impedance mismatch. The comparison was made using resistive electrical models and in ten human volunteers. We used three different electrical models simulating three different body segments: the right-side, leg and thorax. In the electrical models, we tested the effect of the capacitive coupling of the patient to ground and the skin-electrode impedance mismatch. Results showed that both sets of equipment are optimized for right-side measurements and for moderate skin-electrode impedance mismatch. In right-side measurements with mismatch electrode, 4000B is more accurate than SFB7. When an electrode impedance mismatch was simulated, errors increased in both bioimpedance analyzers and the effect of the mismatch in the voltage detection leads was greater than that in current injection leads. For segments with lower impedance as the leg and thorax, SFB7 is more accurate than 4000B and also shows less dependence on electrode mismatch. In both devices, impedance measurements were not significantly affected (p > 0.05) by the capacitive coupling to ground.

Bioelectrical impedance vector analysis (BIVA) in stable and non-stable heart failure patients: A pilot study

a ICREC Research Group, Health Research Institute Germans Trias i Pujol, Badalona, Spain b Department of Electronic Engineering, Technical University of Catalonia, Barcelona, Spain c Cardiology Service, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain d Cardiology Service, Hospital Universitari Germans Trias i Pujol, Badalona, Spain e Department of Medicine, Universitat Autonoma de Barcelona, Barcelona, Spain

Assessment and follow-up of muscle injuries in athletes by bioimpedance: Preliminary results

Mono-frequency (50 kHz) whole-body and segmental bioimpedance is measured before sport training in 14 high performance athletes. The athletes are classified in two groups according to the team sport: football and basketball. Bioelectrical impedance vector analysis (BIVA) method is used to obtain the individual whole-body impedance and 6 segmental impedance vectors in the main muscular groups in the lower-limbs. The whole-body vector is analyzed in the tolerance ellipses of the reference population. Individual impedance vector components are standardized by the height H of the subject, (R/H and Xc/H) to obtain the impedance vector (Z/H) of each segment. The hypotheses of the study are: 1) Not all the sports have the same pattern of bioimpedance vector by muscle group. 2) In elite well trained athletes their muscle groups are symmetrical (right and left sides), thus each athlete is its own reference for future comparisons. 3) We expect a change in the two components of bioimpedance vector (R/H and Xc/H) in front of a muscle injury. In order to compare the differences between the complex Z/H vector (R/H, Xc/H) we use Hotellings T2 test. Preliminary results show a significant difference (P < 0.05) in bioimpedance vectors between groups according to the team sport, and also between normal muscle condition and after muscle injury producing hyper-hydration.

Thoracic versus whole body bioimpedance measurements: the relation to hydration status and hypertension in peritoneal dialysis patients.

The whole body bioimpedance technique is a highly promising non-invasive, reproducible, fast and inexpensive bed-side method for monitoring hydration status. Using segmental bioimpedance measurements, it is possible to obtain information about the fluid change in each body segment (Song, Lee, Kim and Kim 1999 Perit. Dial. Int. 19 386-90). In this pilot study we have measured 25 male patients (30-65 yr, BMI 20-32 kg m(-2)) undergoing continuous ambulatory peritoneal dialysis (CAPD). Tetrapolar impedance measurements were obtained using the right-side technique (whole body), and a segmental impedance method focused in the thorax region. Blood pressure (BP) measurements were taken manually with a sphygmomanometer. Patients were classified as either stable (group 0) or unstable (group 1) using clinical parameters of overall cardiovascular risk. The Mahalanobis distance (dM2) was calculated for the mean blood pressure (BP(mean)), and the impedance parameter R normalized by body height H for the right-side (R(RS)/H) and the thorax segment (R(TH)/H). Differences between groups were significant (p < 0.0001) for R(TH)/H and for BP(mean), and less significant (p = 0.016) for R(RS)/H. Group 1 patients showed a small dM2 as compared with a reference patient (a critical patient with acute lung edema) with high BP(mean) and low values of R(TH)/H and R(RS)/H. Moreover, Group 0 patients showed a larger dM2 with respect to the reference patient, with lower BP(mean) and higher values of R(TH)/H and R(RS)/H. All patients classified as unstable by clinical assessment were correctly classified using R(TH)/H in conjunction with BP(mean) using dM2. Segmental-monofrequency non-invasive bioimpedance of the thoracic region could provide a simple, objective non-invasive method of support for facilitating the clinical assessment of CAPD patients.

Influence of electrode mismatch on Cole parameter estimation from Total Right Side Electrical Bioimpedance Spectroscopy measurements

Applications based on measurements of Electrical Bioimpedance (EBI) spectroscopy analysis, like assessment of body composition, have proliferated in the past years. Currently Body Composition Assessment (BCA) based in Bioimpedance Spectroscopy (BIS) analysis relays on an accurate estimation of the Cole parameters R(0) and R(∞). A recent study by Bogonez-Franco et al. has proposed electrode mismatch as source of remarkable artefacts in BIS measurements. Using Total Right Side BIS measurements from the aforementioned study, this work has focused on the influence of electrode mismatch on the estimation of R(0) and R(∞) using the Non-Linear Least Square curve fitting technique on the modulus of the impedance. The results show that electrode mismatch on the voltage sensing electrodes produces an overestimation of the impedance spectrum leading to a wrong estimation of the parameters R(0) and R(∞), and consequently obtaining values around 4% larger that the values obtained from BIS without electrode mismatch. The specific key factors behind electrode mismatch or its influence on the analysis of single and spectroscopy measurements have not been investigated yet, no compensation or correction technique is available to overcome the deviation produced on the EBI measurement. Since textile-enabled EBI applications using dry textrodes, i.e. textile electrodes with dry skin-electrode interfaces and potentially large values of electrode polarization impedance are more prone to produce electrode mismatch, the lack of a correction or compensation technique might hinder the proliferation of textile-enabled EBI applications for personalized healthcare monitoring.

Whole-body and Thoracic Bioimpedance Measurement: Hypertension and hyperhydration in Hemodialyisis patients

Mono-frequency (50 kHz) and multi-frequency (3 kHz - 1 MHz) whole-body and thoracic segment bioimpedance measurement were doing before and after hemodialysis session in 20 patients. The patients were classified in hypertensive or non-hypertensive according to the mean blood pressure, BPmean. The relation between hyperhydration in thorax segment through real part of impedance and mean blood pressure was analyzed. Also the bioelectrical impedance vector analysis method was used to analyze the displacement of Z/H vector in order to establish the relation with hyper-hydration (edema). Finally we made multi- frequency measurements with the objective to find a significative change in high and low frequency. We obtained a significant difference (P<0.05) in impedance parameters before and after HD session. Some patients are located in hyper-hydration zone, below the inferior pole of the 75% tolerance ellipse, whereas others patients were within the tolerance ellipses. The real part of the impedance in thorax region can identify over-hydrated patients with an increased risk for cardiovascular disease associate to hypertension. Multi-frequency bioimpedance measurement show an important change at low and high frequency and indicate that is possible to obtain more information about extra-cellular or intra-cellular fluid status, to find the relation between fluid loads, bioimpedance parameters, extra-cellular water, and blood pressure.

Detection of muscle gap by L-BIA in muscle injuries: clinical prognosis

Sport-related muscle injury classifications are based basically on imaging criteria such as ultrasound (US) and magnetic resonance imaging (MRI) without consensus because of a lack of clinical prognostics for return-to-play (RTP), which is conditioned upon the severity of the injury, and this in turn with the muscle gap (muscular fibers retraction). Recently, Futbol Club Barcelonas medical department proposed a new muscle injury classification in which muscle gap plays an important role, with the drawback that it is not always possible to identify by MRI. Localized bioimpedance measurement (L-BIA) has emerged as a non-invasive technique for supporting US and MRI to quantify the disrupted soft tissue structure in injured muscles. OBJECTIVE To correlate the severity of the injury according to the gap with the RTP, through the percent of change in resistance (R), reactance (Xc) and phase-angle (PA) by L-BIA measurements in 22 muscle injuries. MAIN RESULTS After grouping the data according to the muscle gap (by MRI exam), there were significant differences in R between grade 1 and grade 2f (myotendinous or myofascial muscle injury with feather-like appearance), as well as between grade 2f and grade 2g (myotendinous or myofascial muscle injury with feather and gap). The Xc and PA values decrease significantly between each grade (i.e. 1 versus 2f, 1 versus 2g and 2f versus 2g). In addition, the severity of the muscle gap adversely affected the RTP with significant differences observed between 1 and 2g as well as between 2f and 2g. SIGNIFICANCE These results show that L-BIA could aid MRI and US in identifying the severity of an injured muscle according to muscle gap and therefore to accurately predict the RTP.

The Dynamics of Cardiovascular Biomarkers in non-Elite Marathon Runners

The number of recreational/non-elite athletes participating in marathons is increasing, but data regarding impact of endurance exercise on cardiovascular health are conflicting. This study evaluated 79 recreational athletes of the 2016 Barcelona Marathon (72% men; mean age 39 ± 6 years; 71% ≥35 years). Blood samples were collected at baseline (24–48 h before the race), immediately after the race (1–2 h after the race), and 48-h post-race. Amino-terminal pro-B type natriuretic peptide (NT-proBNP, a marker of myocardial strain), ST2 (a marker of extracellular matrix remodeling and fibrosis, inflammation, and myocardial strain), and high-sensitivity troponin T (hs-TnT, a marker of myocyte stress/injury) were assayed. The median (interquartile range, IQR) years of training was 7 (5–11) years and median (IQR) weekly training hours was 6 (5–8) h/week, respectively. The median (IQR) race time (h:min:s) was 3:32:44 (3:18:50–3:51:46). Echocardiographic indices were within normal ranges. Immediately after the race, blood concentration of the three cardiac biomarkers increased significantly, with 1.3-, 1.6-, and 16-fold increases in NT-proBNP, ST2, and hs-TnT, respectively. We found an inverse relationship between weekly training hours and increased ST2 (p = 0.007), and a direct relationship between race time and increased hs-TnT (p < 0.001) and ST2 (p = 0.05). Our findings indicate that preparation for and participation in marathon running may affect multiple pathways affecting the cardiovascular system. More data and long-term follow-up studies in non-elite and elite athletes are needed.