A Bedside Measure of Body Composition in Duchenne Muscular Dystrophy

Background In clinical practice, monitoring body composition is a critical component of nutritional assessment and weight management in boys with Duchenne muscular dystrophy. We aimed to evaluate the accuracy of a simple bedside measurement tool for body composition, namely bioelectrical impedance analysis, in boys with Duchenne muscular dystrophy. Methods Measures of fat-free mass were determined using a bioelectrical impedance analysis machine and compared against estimations obtained from a reference body composition model. Additionally, the use of raw impedance values was analyzed using three existing predictive equations for the estimation of fat-free mass. Accuracy of bioelectrical impedance analysis was assessed by comparison against the reference model by calculation of biases and limits of agreement. Results Body composition was measured in 10 boys with Duchenne muscular dystrophy, mean age 9.01 ± 2.34 years. The bioelectrical impedance analysis machine values of fat-free mass were on average 2.3 ± 14.1 kg higher than reference values. Limits of agreement (based on 95% confidence interval of the mean) were -7.4 to 2.9 kg. There was a significant correlation between the mean fat-free mass and difference in fat-free mass between the bioelectrical impedance analysis machine and the reference model (r = -0.86; P = 0.02) suggesting that the bias was not consistent across the range of measurements. The most accurate predictive equation for the estimation of fat-free mass using raw impedance values was the equation by Pietrobelli et al. (mean difference, -0.7 kg; 95% limits of agreement, -3.5 to 2.0 kg). Conclusions In a clinical setting, where a rapid assessment of body composition is advantageous, the use of raw impedance values, combined with the equation by Pietrobelli et al., is recommended for the accurate estimation of fat-free mass, in boys with Duchenne muscular dystrophy

Body cell mass index in children: interpretation of total body potassium results

Body cell mass (BCM) is a valuable measure of functional nutritional status in children. As BCM is related to body size, it is essential that BCM is adjusted for stature when interpreting BCM data in children. Our aim was to examine the relationship between height and BCM in healthy children to determine the power by which height should be raised to adjust BCM for stature. This cross-sectional study calculated BCM by K-40 counting in 146 healthy children aged between 5 and 18 years. The relationship between BCM and height was explored using log-log regression. The present results demonstrate that the power by which height should be raised to adjust for BCM in females is 2.39 (SE 0.09) and for males is 2.92 (SE 0.10). A simplified sex-specific version of the index, BCM/height(2.5) for females and BCM/height(3) for males, was found to be statistically valid and numerically convenient. with the proportion of variation that could be attributed to height being less than 2 %. The present study shows that there is a difference in the relationship between height and BCM for males and females and that BCM can be adjusted in children using the BCM index of BCM/height(2.5) for females and BCM/height(3) for males

Stable isotopes and bioelectrical impedance for measuring body composition in infants born small for gestational age

The assessment of body composition in infants born small for gestational age (SGA) is required primarily to evaluate nutritional status and to monitor growth in the neonatal period. Measurement of total body water, using stable isotopes of hydrogen (H-2) and oxygen (O-18), offers a potential method by which body composition can be assessed. This technique is non-invasive and recently has been used successfully in a cohort of 5-week-old infants born SGA. Nevertheless, the assessment of total body water using stable isotopes requires specialized laboratories and equipment, which may limit its use. Prediction of total body water by bioelectrical impedance is a possible alternative. This technique uses electrical theory to predict the volume of the conducting medium in the body, namely, water. A potential limitation of bioelectrical impedance analysis is the accuracy, which may impinge on its usefulness in small infants

Estimates of body fatness in infancy and childhood

Body composition estimates in infants and children are difficult, largely due to ethical and practical reasons. However, the use of (H2O)-O-18 as a tracer for the calculation of total body water allows the noninvasive estimation of fat-free mass (FFM) and fat mass (FM) in the pediatric population. Body fatness was estimated on 244 occasions in infants and children 0.1 to 3.99 years of age. The mean percentage body fatness in the first year of life is similar to previously published theoretical reference data. During childhood, however, the reference data were considerably below current estimates of body fatness. This may be evidence to support the hypothesis that there has been a secular trend in levels of body fatness in children in recent years

Energy metabolism and obesity in childhood

Obesity in childhood often leads to obesity in adulthood, with the resulting potential risks to health. It has been suggested that in some cases, obesity develops because of a reduction in energy expenditure rather than excessive energy intake. While it is possible that this mechanism contributes to the development of obesity in specific cases, there is little evidence to suggest that it is an important contributory factor in the general population

Reply - Clinical longitudinal standards for height and height velocity for North American children

Longitudinally-based height and height velocity charts for North American children are presented. Centiles are given for early, middle, and late maturers. The shape of the curves is taken from a review of longitudinal studies, and the prepubertal and adult centiles for height attained are taken from National Center for Health Statistics data. The charts are suitable for following an individual child's progress during observation or treatment throughout the growth period, including puberty

Energy cost of activity assessed by indirect calorimetry and a (CO2)-C-13 breath test

Purpose: The aim of this study was to assess the accuracy of a (CO2)-C-13 breath test for the prediction of short-duration energy expenditure. Methods: Eight healthy volunteers walked at 1.5 km.h(-1) for 60 min followed by 60-min recovery. During this time, the energy cost of physical activity was measured via respiratory calorimetry and a C-13 bicarbonate breath test. A further eight subjects were tested using the same two methods during a 60-min cycle at 0.5 kp. 30 ipm followed by a 60-min recovery. The rate of appearance of (CO2)-C-13, (RaCO2) was measured and the mean ratio, (V) over dot CO2/RaCO2 was used to calculate energy expenditure using the isotopic approach. Results: As would be expected, there was a significant difference in the energy cost of walking and cycling using both methods (P < 0.05). However. no significant differences were observed between respiratory calorimetry and the isotope method for measurement of energy expenditure while walking or cycling. Conclusions: These data suggest that the C-13 breath test is a valid method that can be used to measure the energy cost of short duration physical activity in a field setting