Tolerance Ellipses Research Articles

Modeling the short wavelength infrared laser radiance reflection on the sea surface.

The sea surface is a complex dynamic structure dependent on atmospheric conditions, and for which physical and chemical properties change from water to foam. Its roughness determines how the surface reflects, absorbs, and emits radiance, and depends on multiple parameters such as wind speed and direction, and foam and turbulence induced from natural waves or from object displacement. In this paper, a model description is given for laser reflection on the sea surface in open water driven by the wind. The model allows calculation of the reflected laser radiance from the sea surface toward a receiver as a function of the incoming laser radiance with a known beam intensity profile. Each subarea of the sea surface seen by one pixel of the receiver is considered as an ensemble of facets, where each facet is defined by its x and y directional slopes. The wind speed and orientation determine the probability density function of the sea surface facet slope occurrence. In this paper, we have analytically expressed the reflected radiance on the sea surface as a function of the wind speed, receiver range, receiver heading, laser position, laser output aperture, and laser incoming radiance. Using the tolerance ellipse, the reflected radiance expression was approximated, and both direct and approximated results were compared. The richness in behavior of the reflected radiance and its dependence on the geometry of the problem were studied showing the impact of the receiver position, the laser position, heading, and beam divergence.

Distinguishing Different Varieties of Oolong Tea by Fluorescence Hyperspectral Technology Combined with Chemometrics.

Oolong tea is a semi-fermented tea that is popular among people. This study aims to establish a classification method for oolong tea based on fluorescence hyperspectral technology(FHSI) combined with chemometrics. First, the spectral data of Tieguanyin, Benshan, Maoxie and Huangjingui were obtained. Then, standard normal variation (SNV) and multiple scatter correction (MSC) were used for preprocessing. Principal component analysis (PCA) was used for data visualization, and with tolerance ellipses that were drawn according to Hotelling, outliers in the spectra were removed. Variable importance for the projection (VIP) > 1 in partial least squares discriminant analysis (PLS–DA) was used for feature selection. Finally, the processed spectral data was entered into the support vector machine (SVM) and PLS–DA. MSC_VIP_PLS–DA was the best model for the classification of oolong tea. The results showed that the use of FHSI could accurately distinguish these four types of oolong tea and was able to identify the key wavelengths affecting the tea classification, which were 650.11, 660.29, 665.39, 675.6, 701.17, 706.31, 742.34 and 747.5 nm. In these wavelengths, different kinds of tea have significant differences (p < 0.05). This study could provide a non-destructive and rapid method for future tea identification.

Computation of tolerance ellipses for bivariate and trivariate normal populations

We consider the computation of the critical constants c of a p-content -confidence tolerance ellipse for bivariate and trivariate normal populations which are probably the most used multivariate normal distributions in applications. There are only approximation methods available in the statistical literature for computing c. Without knowing the accurate value of c, it is impossible to assess the accuracy of the approximation methods. In this paper, a new method is given to compute c. Although the method is also based on Monte-Carlo simulation, it allows c to be computed as accurate as required if the number of simulation replications is sufficiently large. The R codes provided allow easy implementation of the method. Furthermore, the method allows the accuracy of the available approximation methods for bivariate and trivariate normal distributions to be assessed.

Preferred skin tones on mobile displays under illuminants having different correlated colour temperatures

A psychophysical experiment was conducted to investigate preferred skin tones of 4 skin types under 5 illuminants varying in correlated colour temperatures. The experiments were performed on calibrated mobile display devices. Four facial skin tone images representing each skin type were captured and were rendered to 25 skin tone images to cover a large colour region. The facial skin tone images were assessed by a panel of 28 Chinese observers using an alternative forced choice psychophysical method. The ellipses based on observer preference rate were derived, and the preferred skin tone centres and 50% tolerance ellipse of different skin types under each test illuminants were obtained. According to the colour appearance shift of preferred skin tones under illuminants with varying CCTs, all data were transformed and compared in the a*b* plane under D65 and CIE 1931 Standard Colorimetric Observer condition. The results on the impact of illuminants on preferred skin tones were reported here. All types of skin tones had a good agreement under different illuminants.

Association of electrical bioimpedance vectors with the nutritional classification of vulnerable multiethnic children.

Monitoring growth and body composition in childhood is vital for early detection of health and nutrition problems during child development. The bioelectrical impedance vector analysis (BIVA) revealed its effectiveness as an indicator of nutritional status. This study aimed to measure the bioimpedance vectors of a sample of multiethnic children and evaluate the utility of BIVA for the classification of the nutritional status in a group of children with greater vulnerability, including in the presence of obesity. This is a cross-sectional study that analyzed the bioelectrical impedance of a sample of 321 children from public daycare centers, aged 1-4 years, using the RXc graph method (tetrapolar analysis at 50kHz frequency). The 95%, 75%, and 50% tolerance ellipses were plotted by age group. The Z-scores of bioimpedance parameters (Xc/H-Z and R/H-Z) were calculated regarding age, which were used to build reference tolerance ellipses for a single group, regardless of age. Such ellipses were evaluated for their ability to recognize the pattern and classify the deviations, using individual vectors of obese children. The mean impedance vectors showed progressively higher reactances and lower resistances with age. In the group of obese children, the individual vectors located outside the 95% baseline tolerance ellipse were 12.5%, 18.75%, and 11.1% of the cases for the WHZ, WAZ, and BMIZ criteria, respectively, all above the expected 5%, but much below expectations. This may be a problem with the obesity criteria used, as WHZ, WAZ, and BMIZ do not differentiate fat from lean mass. Bioimpedance vector analysis reflects differences in the bioelectric patterns of children classified as obese. Provided the obesity criteria are constructed based on fat measurements, rather than lean mass, the use of tolerance ellipses in the BIVA chart is promising as a tool for monitoring nutritional status where measuring body composition is difficult, because constant tissue hydration cannot be assumed.

A balanced total-variation-Chambolle-Pock algorithm for EPR imaging

Total variation (TV) minimization algorithm is an effective algorithm capable of accurately reconstructing images from sparse projection data in a variety of imaging modalities including computed tomography (CT) and electron paramagnetic resonance imaging (EPRI). The data divergence constrained, TV minimization (DDcTV) model and its Chambolle-Pock (CP) solving algorithm have been proposed for CT. However, when the DDcTV-CP algorithm is applied to 3D EPRI, it suffers from slow convergence rate or divergence. We hypothesize that this is due to the magnitude imbalance between the data fidelity term and the TV regularization term. In this work, we propose a balanced TV (bTV) model incorporating a balance parameter and demonstrate its capability to avoid convergence issues for the 3D EPRI application. Simulation and real experiments show that the DDcTV-CP algorithm cannot guarantee convergence but the bTV-CP algorithm may guarantee convergence and achieve fast convergence by use of an appropriate balance parameter. Experiments also show that underweighting the balance parameter leads to slow convergence, whereas overweighting the balance parameter leads to divergence. The iteration-behavior change-law with the variation of the balance parameter is explained by use of the data tolerance ellipse and gradient descent principle. The findings and insights gained in this work may be applied to other imaging modalities and other constrained optimization problems.

Phase Angle Is Related to 10 m and 30 m Sprint Time and Repeated-Sprint Ability in Young Male Soccer Players.

Objective: To examine the association between phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) and components of physical performance in male youth soccer players. Design: Cross-sectional. Methods: Sixty-two players from two professional soccer academies were recruited. Electrical bioimpedance was used to obtain the PhA and BIVA. Body fat (BF) and lean soft tissue mass (LSTM) were measured by dual-energy X-ray absorptiometry. All players completed physical tests including the standing long jump (SLJ), Carminatti’s test (peak speed at the end of the test, PST-CAR), 10 m and 30 m straight-line sprints, and repeated-sprint ability (RSA) test (RSAbest and RSAmean times). Results: Adjusting for chronological age, BF, and LSTM, multiple regression analysis outputs showed that PhA remained inversely related to RSAmean (β = −0.362; p < 0.001), RSAbest (β = −0.239; p = 0.020), 10 m (β = −0.379; p = 0.012), and 30 m (β = −0.438; p < 0.001) sprint times, while the association with PST-CAR and SLJ performance were statistically non-significant. In addition, BIVA showed that differences in confidence ellipses were found between athletes in the reference population and the study sample (p < 0.05). The tolerance ellipses indicated that the athletes in the present study had more total body water (TCW) and lower proportions of intracellular water (ICW) to extracellular water (ECW). The reference population had more TCW and ICW/ECW. Conclusions: Our results suggest that young soccer players with higher PhA values, indicating better cell integrity and functionality, have better performance in typical anaerobic running activities, such as sprinting speed and RSA performance, adjusted to age and body composition characteristics.

POS-654 ASSESSMENT OF OVERHYDRATION IN CHILDREN ON CONTINUOUS AMBULATORY PERITONEAL DIALYSIS BY BIOIMPEDANCE VECTOR ANALYSIS – A LONGITUDINAL OBSERVATIONAL STUDY

Detecting overhydration in children on chronic ambulatory peritoneal dialysis (CAPD) is critical as it contributes to cardiovascular morbidity and mortality. However, precise clinical assessment of overhydration is challenging. Bio-impedance vector analysis (BIVA) is a bedside body composition tool that can estimate overhydration with a potential role of guiding the clinician on fluid management. This study aimed to longitudinally assess and compare the overhydration status detected using clinical assessment and BIVA in children on CAPD. A longitudinal observational study was undertaken in clinically stable children (age 4-18years) on CAPD (minimum duration of 6 months) from May 2017 to January 2020 at the pediatric chronic kidney disease clinic of a tertiary hospital. Presence of overhydration was assessed by clinical signs, bioimpedance measures and BIVA at enrollment, 3 and 6 months of follow up. Modifications to CAPD prescriptions and antihypertensive medications were based only on clinical assessment. Children were categorized as having clinical overhydration if they fulfilled 2 of 3 criteria of weight gain (>7% of body weight), uncontrolled hypertension (office BP ≥95thcentiles despite being on anti-hypertensive medications) and presence of signs of fluid overload. Based on a normative reference R-Xc graph, derived from z-scores of 20 healthy controls, bioimpedance vectors were plotted. The position of the vector in the left lower quadrant beyond the 95% tolerance ellipse was regarded as overhydration. Differences in the longitudinal vector displacement were analyzed using Hotelling’s T2 test. Twenty six children [18 boys, median age 9.5(4,16)years] on CAPD for 21(12,72) months were enrolled. Non-glomerular etiology was noted in 69% and 58% had residual kidney function. At enrollment, the proportion of children with overhydration assessed clinically and by BIVA was 34.6% and 30.7% respectively. There was poor agreement between measures of overhydration by clinical assessment and BIVA at all three time points. Among those detected to be overhydrated at enrollment, 9/11 (82%) and 4/9 (44%) remained overhydrated at 6 months by BIVA and clinical assessment respectively. The BIVA plots on the reference RXc graph (Figure) revealed a significant difference in the vector displacement towards the quadrant of overhydration at all time points, with the maximum difference seen between enrollment and 6 months (T2 = 32.58, p <0.001). In children on CAPD, there is poor agreement between measures of overhydration detected clinically and by BIVA. Longitudinal vector plots over 6 months reflect persistence of overhydration in a majority, as compared to clinical assessment. Further studies to explore the utility of BIVA in guiding the clinician with fluid management in these children are warranted.

Bioelectrical impedance vector analysis (BIVA) in university athletes

BackgroundBioelectrical impedance vector analysis (BIVA) is able to identify differences in hydration status and body composition components, such as body cell mass (BCM) by means of plotting individuals in ellipses, when comparing groups with different characteristics.ObjectiveCompare the confidence and tolerance ellipses of BIVA in individual and team sports athletes with a non-athlete reference population.Design and participantsOne hundred sixty-seven college athletes (team sports: 117 athletes, individual sports: 50 athletes) aged between 18 and 35 years. Bioelectrical impedance was used to measure resistance (R) and reactance (Xc) values that were used in the BIVA analysis to identify hydration status and BCM, respectively. Hotelling’s t-test was used to identify differences between groups in the confidence ellipses and the comparison was made with a non-athlete Italian reference population.ResultsThere were no differences between male team sports and individual athletes (p = 0.151) and for female athletes (p = 0.624). Most athletes were located in the 50% tolerance ellipses, indicating adequate hydration. Compared to the Italian a non-athlete population, athletes of both sexes presented left impedance vector deviation in the minor axis (Xc) of the tolerance ellipses, indicating higher BCM.ConclusionThere were no differences in BIVA between team and individual sports athletes, but most athletes presented an adequate hydration state and, compared to a non-athlete population, the athletes of the present study presented higher BCM.

Technology of Two-dimensional Bioimpedance Analysis of the Human Body Composition.

The BIA primary result sheets as a rule contain one-dimensional graphical scales with a selected area of normal values. In 1994, Piccoli et al. proposed BIVA, an alternative form of BIA data presentation, where two bioimpedance parameters are considered simultaneously as tolerance ellipses: resistance and reactance normalized to height.The purpose of this study is to develop an approach to data analysis in body composition bioimpedance research in two-dimensional representations.The data of 1.124.668 patients aged 5 to 85 years who underwent a bioimpedance study in Russian Health Centers from 2009 to 2015 were used. Statistical programming in the R Studio environment was carried out to estimate two-dimensional distribution densities of pairs of body composition parameters for each year of life.The non-Gaussian distribution is found in most parameters of bioimpedance analysis of body composition for most ages (Lilliefors test, p-value << 0.0001). The slices of the actual two-dimensional distribution pairs of body composition parameters had an irregular shape. The authors of the article propose using the actually observed distribution for populations where numerous bioimpedance studies have already been carried out. Such technology can be called two-dimensional bioimpedance analysis of human body composition (2DBIA). The 2DBIA approach is clearer for practitioners and their patients due to the use of body composition parameters in addition to electrical impedance parameters.

Utility of bio-electrical impedance vector analysis for monitoring treatment of severe acute malnutrition in children.

Change in hydration is common in children with severe acute malnutrition (SAM) including during treatment, but is difficult to assess. We investigated the utility of bio-electrical impedance vector analysis (BIVA), a quick non-invasive method, for indexing hydration during treatment. We studied 350 children 0·5-14 years of age with SAM (mid-upper arm circumference <11·0cm or weight-for-height <70% of median, and/or nutritional oedema) admitted to a hospital nutrition unit, but excluded medically unstable patients. Weight, height (H), resistance (R), reactance (Xc) and phase angle (PA) were measured and oedema assessed. Similar data were collected from 120 healthy infants and preschool/school children for comparison. Means of height-adjusted vectors (R/H, Xc/H) from SAM children were interpreted using tolerance and confidence ellipses of corresponding parameters from the healthy children. SAM children with oedema were less wasted than those without (p<0·001), but had BIVA parameters that differed more from those of healthy children (P<0·05) than those non-oedematous. Initially, both oedematous and non-oedematous SAM children had mean vectors outside the reference 95% tolerance ellipse. During treatment, mean vectors migrated differently in the two SAM groups, indicating fluid loss in oedematous patients, and tissue accretion in non-oedematous patients. At admission, R/H was lower (oedematous) or higher (non-oedematous) among children who died than those who exited the hospital alive. BIVA can be used in children with SAM to distinguish tissue-vs. hydration-related weight changes during treatment, and also identify children at high risk of death enabling early clinical interventions.

Bioelectrical impedance vector values in a Spanish healthy newborn population for nutritional assessment.

Vector bioimpedance analysis (BIVA) can be very useful for the evaluation of body composition, hydration, and nutritional status in infants and newborns. The objective of this study was to determine the impedance vector distribution for a group of healthy newborn Spanish children. This was a cross-sectional, descriptive study conducted with 154 healthy, Spanish newborns (gestational age: 37-41 weeks) aged 24 to 72 hours (79 males, 75 females). Weight, height, and cephalic-circumference were determined. Resistance and reactance were measured with a single-frequency impedance analyzer at 50 kHz (tetrapolar analysis). The newborns' specific 95% confidence intervals of the mean vectors and the 95%, 75%, and 50% tolerance intervals for the individual vector measurements were plotted using R and Xc components standardized by the subjects' lengths. The mean impedance vectors were compared with Hotelling's-T2 test for vector analysis (significance level: P < .05). The newborns exhibited gender-related differences in the mean impedance vector (mean [SD] R/H: 833.6 [97.5] Ohm/m in males vs 918.2 [107.7] Ohm/m in females; mean [SD] Xc/H: 91.3 [34.7] Ohm/m in males vs 95.6 [23.2] Ohm/m in females). No statistically significant differences in the mean impedance vectors were observed according to days of life. Lower values of resistance and slightly higher reactance values were observed in the healthy Spanish newborns compared to Italian newborns. New tolerance ellipses were constructed for healthy Spanish newborns. These data allow detecting alterations in the hydration status and cell mass in term newborns in the first 3 days of life.

Bioelectrical impedance vector analysis and phase angle in boys with Duchenne muscular dystrophy.

BackgroundDuchenne muscular dystrophy (DMD) is a disease characterized by progressive loss of functional muscle mass followed by changes in body composition.ObjectiveThis study aimed to describe and evaluate bioimpedance parameters in boys with DMD.DesignThis cross-sectional, descriptive study investigated children and adolescents diagnosed with DMD. Age, weight, height, resistance, and reactance data were collected. Phase angle and bioelectrical impedance vector analysis were calculated based on resistance and reactance values.ResultsWe analyzed 43 boys aged between 2.7 and 19.8 years. Low-phase angle values were observed during the investigation of bioimpedance parameters. Bioelectrical impedance vector analysis showed that approximately 87% of the subjects presented vectors outside the tolerance ellipses, and only one patient presented vectors located within the 50% tolerance ellipse, indicating normally hydrated and a good body cell mass. Compared with the reference population, boys with DMD had lower levels of body cell mass.ConclusionBased on the evidence, compared with the reference population, patients with DMD had lower levels of body cell mass. This evidence points to bioimpedance parameters as useful tools for the nutritional evaluation and clinical management of patients with DMD.

Dynamics of Bioimpedance Parameters on Three Frequencies During Ultrafiltration

Background/Aim. At present, methods based on the analysis of non-invasively measured parameters of electrical bioimpedance for the diagnosis of the patient's biohydrality are of interest. The purpose of this article is to investigate the dynamics of electrical impedance parameters (module, phase angle, active and reactive components) of the human body during ultrafiltration of programmed hemodialysis at three frequencies of 20 kHz, 100 kHz, 500 kHz. Equipment and Methods. For the research was used the hemodialysis system Fresenius Medical Care 5008C. This system provided the implementation of the ultrafiltration procedure profile. Also was used the hardware and software complex of monitoring bioimpedasometry TOR-M-1, adapted for hemodialysis procedure and conditions. Using these equipment the dependences of the modulus Z, the phase angle $ \varphi $, active R and the reactive X impedance components corrected to the body length of the patient H, the region of distribution of the bioimpedance vector relative to the tolerance ellipses and the dynamics of these parameters, depending on the volume of the ultrafiltrate and the profile of the ultrafiltration procedure were studied. Dynamics of bioimpedance parameters. It was found that during the ultrafiltration has a characteristic complex nonlinear behavior of the impedance parameters for each individual patient. The intensity of this nonlinearity increases with increasing frequency. It is expressively observed at higher frequencies of 100 kHz and 500 kHz. Interpretation of Impedance Dynamics with Tolerance Ellipses. The non-stationary oscillatory character of the parameter dynamics testifies to the complexity of the individual transient processes of redistribution of volumes of human water sectors in the process of hemodialysis and associated with changes in the ratio of intracellular, extracellular fluids and blood, the structural composition of the liquid. This causes fast flowing changes in active conductivity in the intercellular environment and reactive conductivity due to the action of polarization processes on the dielectric structures of biological tissues. Discussion and Conclusion. Measurements and cumulative analysis of the parameters of electrical impedance directly in the process of hemodialysis allows to objectively monitor the progress of the patient's functional state in real time with an assessment of the presence or absence of a `dry weight 'level, evaluate the nature of the processes of redistribution of intracellular and extracellular sectors of the body and blood, and the differences in the course of the process of ultrafiltration of patients. This can be the basis, if necessary, for promptly adjusting the ultrafiltration process. Widening of the impedance measurement bandwidth enhances the diagnostic capabilities of such monitoring and the timely correction of the ultrafiltration procedure.

Bioelectrical impedance vector reference values for assessing body composition in a Spanish child and adolescent population.

Reference values of the bioelectrical impedance vector for the Spanish child and adolescent population are needed for assessing body composition and hydration status in this population. The aim of this study is to provide reference values of the bioelectrical impedance vector in Spanish children and adolescents aged 4-18years from Castilla y León. This was a cross-sectional descriptive study conducted in 4401 Spanish healthy children and adolescents aged 4-18years (2265 boys and 2136 girls). Resistance and reactance were measured with a single-frequency impedance analyzer at 50kHz (tetrapolar analysis). The values of resistance and reactance normalized by height were used to plot the bivariate 50th, 75th, and 95th percentiles of the population by age group. Mean impedance vectors were compared with Hotelling's T2 test for vector analysis (differences being considered significant if p<.05). Tolerance ellipses were drawn for the Spanish child and adolescent population studied. The mean impedance vector showed displacement across all age groups except for (1) girls aged 12-13years, (2) girls aged 15-18years, and (3) boys aged 16-18years. There were sex-related differences in the mean impedance vector in all age ranges, even in prepubertal children. Among adolescents, the patterns of the vector displacement were consistent with the timing of normal growth and development in all groups and are attributable to the maturation process. New tolerance ellipses have been constructed for Spanish children and adolescents by sex and age. These ellipses reflect the timing of normal childhood growth and development.

Qualitative body composition of cyclists: bioimpedance vector analysis discriminates different categories of cyclists

Introduction: Bioelectrical impedance vector analysis (BIVA) and the phase-angle (PA), derived from bioelectrical impedance raw values (i.e., resistance, R, and reactance, Xc) allow qualitative and descriptive assessments of body composition and hydration status, independent of prediction equations, body weight and body composition models [3,4,5]. Bioelectrical impedance reference values for the healthy normal population, soccer players [6] and several clinical settings are well established [1,2], but are lacking for male cyclists. Therefore, the aim of the present study was to obtain reference bioelectrical impedance data characterizing professional, elite, junior, and amateur male road cyclists.  Methods: The study included 102 male professional riders (age: 25.6±4.7 yr, height: 178.3±5.9 cm, weight: 68.5±5.9 kg), 225 male amateur riders (age: 39±2 yr, height: 176.1±6.4 cm, weight: 71.1±9.5 kg), 46 male junior cyclists (age: 16.9±1.2 yr, height 176.60±5.94 cm, weight 65.62±7.27 kg) and 69 male elite road cyclists (age: 21±2.9 yr, height: 178.2±5.7 cm, weight: 69.03±7.6 kg). The controls were represented by normal values of healthy male Italian population (age: 48±17 yr, height: 170.4±8 cm, weight: 72.6±11.5 kg) [2]. Professional cyclists were classified into 3 groups according to their team role (sprinter, n=16; climber, n=35; all-rounder, n=51), whereas the juniors, amateurs and elite cyclists were all considered all-rounder. Whole-body impedance measurements (BIA- 101 Anniversary AKERN/RJL-Systems) were performed during the peak performance period of the cyclists. All measurements were obtained in compliance with the manufacturer’s guidelines and analyzed according to the BIVA method [1]. BIVA, compared to the estimated fat and fat-free masses with conventional BIA, does not use regression prediction equations, and was shown to adequately display differences in hydration and soft tissue mass in healthy people and athletes [7]. Furthermore, BIVA allows establishing population- specific norms (50, 75 and 95% tolerance ellipses).  Results: Compared to the amateur cyclists and the normal population, the group vector and the tolerance ellipses of the professional cyclists was displaced to the upper left (p<0.001) as well as the comparison of the amateurs and juniors (p<0.001), amateurs and elite cyclists (p<0.001) (fig. 1). Also, all categories showed a shift to the upper left in comparison of controls. Comparisons of professional cyclists to amateurs and elite cyclists to amateurs showed a higher phase-angle (7.1°±0.1 vs 6.5°±0.8 (p<0.001) and 7.0°±0.7 vs 6.5°±0 (p<0.001), respectively). Significant differences in vector position were found between sprinters and climbers (p<0.05) and between allrounders and climbers (p<0.02) (fig. 2).  Conclusion: The main finding of the present study is that road cyclists in general and specialists have specific bioimpedance values compared to non-cyclists. Muscle mass and function, as indicated by the left shifted vector and the phase-angle, increased with increasing performance level. The specific tolerance ellipses of the professionals might be used for classifying individual vectors of professional cyclists and to define target regions for lower level cyclists.

Accuracy of bioimpedance vector analysis and brain natriuretic peptide in detection of peripheral edema in acute and chronic heart failure

ObjectiveTo evaluate the role of bioelectrical impedance vector analysis (BIVA) and brain natriuretic peptide (BNP) in detecting peripheral congestion in heart failure (HF). BackgroundBIVA/BNP are biomarkers for congestion in acute (ADHF) and chronic HF. Methods487 ADHF and 413 chronic HF patients underwent BIVA and BNP tests. ResultsBIVA was more accurate than BNP in detecting peripheral congestion both in ADHF (AUC 0.88 vs 0.57 respectively; p < 0.001) and chronic HF patients (AUC 0.89 vs 0.68, respectively; p < 0.001). In ADHF patients, the optimal BNP cut-off for discriminating presence or absence of edema was >870 pg/mL (PPV = 48% and NPV = 58%) whereas in chronic HF it was >216 pg/mL (PPV = 18% and NPV = 95%). The BIVA detected edema when the vector fell into the lower pole of 75th percentile tolerance ellipse (PPV = 84% and NPV = 78%) in ADHF, the lower pole of 50% (PPV = 68% and NPV = 95%) in chronic HF. ConclusionsIn HF patients, BIVA is an easy, fast technique to assess peripheral congestion, and is even more accurate than BNP.

Noninvasive assessment of extracellular and intracellular dehydration in healthy humans using the resistance-reactance–score graph method

AbstractBackground: Few dehydration assessment measures provide accurate information; most are based on reference change values and very few are diagnostically accurate from a single observation or measure. Bioelectrical impedance may lack the precision to detect common forms of dehydration in healthy individuals. Limitations in bioimpedance may be addressed by a unique resistance-reactance (RXc)–score graph method, which transforms vector components into z scores for use with any impedance analyzer in any population.Objective: We tested whether the RXc-score graph method provides accurate single or serial assessments of dehydration when compared with gold-standard measures of total body water by using stable isotope dilution (deuterium oxide) combined with body-weight changes.Design: We retrospectively analyzed data from a previous study in which 9 healthy young men participated in 3 trials: euhydration (EUH), extracellular dehydration (ED; via a diuretic), and intracellular dehydration (ID; via exercise in the heat).Results: Participants lost 4–5% of their body weight during the dehydration trials; volume loss was similar between trials (ID compared with ED group: 3.5 ± 0.8 compared with 3.0 ± 0.6 L; P > 0.05). Despite significant losses of body water, most RXc vector scores for ED and ID groups were classified as “normal” (within the 75% population tolerance ellipse). However, directional displacement of vectors was consistent with loss of volume in both ED and ID conditions compared with the EUH condition and tended to be longer in ED than in ID conditions (P = 0.054).Conclusions: We conclude that, whereas individual RXc-score graph values do not provide accurate detection of dehydration from single measurements, directional changes in vector values from serial measurements are consistent with fluid loss for both ED and ID conditions. The RXc-score graph method may therefore alert clinicians to changes in hydration state, which may bolster the interpretation of other recognized change measures of hydration.

Investigation of Memory Colours across Cultures

Memory colours have been extensively investigated. They are important for different image applications, such as colour image reproduction. However, it is possible memory colours vary according to different cultures. The present experiments were conducted to investigate 22 memory colours, which are divided into three types: 12 common colours such as vegetables, fruits and flowers, 6 natural colours such as sky blue, grass, and skin colours, and 4 culture specific colours. Each colour was assessed by 25 Chinese observers and 30 German observers in each country. The inter-observer variations between two groups were compared in terms of mean of CIELAB colour differences in terms of MCDM measure and tolerance ellipses. Also, the colour centers are plotted in CIELAB a*b* diagram to show the culture differences. The intention here is to establish a methodology to study memory colours across different countries based on homogeneous colour patches.

Bioimpedance identifies body fluid loss after exercise in the heat: a pilot study with body cooling.

PurposeAssessment of post-exercise changes in hydration with bioimpedance (BI) is complicated by physiological adaptations that affect resistance (R) and reactance (Xc) values. This study investigated exercise-induced changes in R and Xc, independently and in bioelectrical impedance vector analysis, when factors such as increased skin temperature and blood flow and surface electrolyte accumulation are eliminated with a cold shower.MethodsHealthy males (n = 14, 24.1±1.7 yr; height (H): 182.4±5.6 cm, body mass: 72.3±6.3 kg) exercised for 1 hr at a self-rated intensity (15 BORG) in an environmental chamber (33°C and 50% relative humidity), then had a cold shower (15 min). Before the run BI, body mass, hematocrit and Posm were measured. After the shower body mass was measured; BI measurements were performed continuously every 20 minutes until R reached a stable level, then hematocrit and Posm were measured again.ResultsCompared to pre-trial measurements body mass decreased after the run and Posm, Hct, R/H and Xc/H increased (p<0.05) with a corresponding lengthening of the impedance vector along the major axis of the tolerance ellipse (p<0.001). Changes in Posm were negatively related to changes in body mass (r = −0.564, p = 0.036) and changes in Xc/H (r = −0.577, p = 0.041).ConclusionsPresent findings showed that after a bout of exercise-induced dehydration followed by cold shower the impedance vector lengthened that indicates fluid loss. Additionally, BI values might be useful to evaluate fluid shifts between compartments as lower intracellular fluid loss (changed Xc/R) indicated greater Posm increase.