The following is a summary of “Air Displacement Plethysmography is an Accurate and Feasible Noninvasive Measure of Fat-Free Mass in Children With Intestinal Failure,” published in the October 2023 issue of Pediatrics by Carey, et al.
Assessing the nutritional status of children with intestinal failure (IF) is challenging using conventional methods. Air displacement plethysmography (ADP) provides a noninvasive approach to measure body composition, including body mass, volume, percent body fat (%BF), and fat-free mass (FFM), potentially enhancing the evaluation of specialized nutrition. For a study, researchers sought to evaluate the validity and feasibility of using ADP to measure body composition in children with IF, comparing it with deuterium dilution (DD), bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA), and four-site skinfold anthropometry.
A prospective cohort study enrolled 18 children (2–17 years) with IF dependent on parenteral nutrition for over 90 days. Spearman rank correlation and Bland-Altman analysis were employed to compare ADP with alternative body composition measures.
In the study, 18 children with intestinal failure (IF) participated, with a median age of 7.1 years (interquartile range [IQR] 5.4–9.3), and 50% were female. The median residual bowel length was 31 cm (IQR 22–85). The median parenteral nutrition (PN) energy intake was 46 kcal/kg/day (IQR 39–49). In four subjects, incomplete bladder emptying led to invalid deuterium dilution (DD) measures. Spearman correlation coefficients for percent body fat (%BF) showed low to moderate associations between ADP and DD (r = 0.29), dual-energy X-ray absorptiometry (DXA) (r = 0.62), bioelectrical impedance analysis (BIA) (r = 0.50), and skinfold measurements (r = 0.40). High correlations for fat-free mass (FFM) were observed between ADP and these measures, ranging from 0.95 to 0.98. Comparing ADP with DD and skinfold measures using Bland-Altman analysis revealed small mean biases (-1.9 and +1.5 kg) and acceptable 95% limits of agreement (LOA) ranges (10.7 and 22.9 kg), respectively. However, larger biases (-10.7 and -7.7 kg) and wider LOA ranges (38.7 and 45.2 kg) were observed compared to DXA and BIA. The correlation between %BF measured by ADP and skinfold thickness was moderate (r = 0.43), with a low bias (-0.2%) but very wide LOA (25.7%).
ADP is feasible and valid in children with IF for measuring FFM but may be less suitable for %BF. While holding promise for assessing interventions, further research was needed to optimize its application in the population.