The use of air displacement plethysmography in children and adolescents with cystic fibrosis

Abstract

Objectives: The purpose of this paper was to evaluate the use of air displacement plethysmography (ADP) in children and adolescents with cystic fibrosis (CF). Specifically, the primary aim of this study was to compare estimates of fat-free mass (FFM) measured from ADP and dual energy X-ray absorptiometry (DEXA) in children and adolescents with CF. The secondary aim was to compare the effect of using predicted thoracic gas volume (V TG ) and measured V TG for the calculation of FFM by ADP in this population. Methods: Cross-sectional FFM measurements were taken using ADP and DEXA in 52 children and adolescents with CF, ranging in age from 6.3 to 16.6 y. Results: Bland-Altman analysis showed that ADP values of FFM were on average 0.59 kg higher than DEXA values (95% limits of agreement ¼ 3.61 to À2.43 kg); however this difference was not significant. There was no significant correlation (r ¼ À0.26, P ¼ 0.07) between the mean FFM and difference in FFM between ADP and DEXA. Using either predicted or measured V TG did not significantly affect FFM estimates in individuals with CF who had normal lung function (bias ¼ À0.3970.86 kg; r ¼ À0.02, P ¼ 0.93). Conclusions: ADP is an appropriate technique for use in children and adolescents with CF.

Body composition and lung function in cystic fibrosis and their association with adiposity and normal-weight obesity

“…This method has been shown to provide similar fat-free mass estimates as dual-energy X-ray absorptiometry in children and adolescents with CF 30 . However, air displacement plethysmography is based on the two-component model of body composition which partitions body weight into fat mass and fat-free mass and is dependent on the assumption that the density of fat-free mass is constant, regardless of age, sex, race, or disease state 31 .…”

Validation of Percent Body Fat Indicators in Pediatric Oncology Nutrition Assessment

“…9 Few studies have used ADP in pediatric clinical conditions, but one study in children with cystic fibrosis found that ADP was inappropriate when compared with dual energy x-ray absorptiometry. 24 It is recommended that further validation of ADP methodology in the pediatric oncology population is done via the 4 compartment model. Malnutrition is a loss of functional tissues, which is impossible to determine from general anthropometric measurements.…”

Malnutrition in Children With Chronic Disease

“…One study using DEXA as a reference showed that 14% of children had normal BMI but low fat‐free mass, and another study showed that 24% of patients were classified as well‐nourished based on weight but had low fat‐free mass based on total‐body potassium assessment . One study of ADP in patients with CF showed fair agreement with DEXA in assessing body composition, although there was a trend toward ADP overestimating fat‐free mass in younger children and underestimating it in older children . Once validated in a larger population, BIA using CF‐specific equations may be a more practical and reliable method for clinically assessing body composition in children with CF that better reflects overall nutrition status …”