title: Biological and technological variability of residual lung volume and the effect on body fat calculations.
abstract: Ten subjects were studied to determine within-subject variance (Swi2), and its components, biovariability (Si2) and technological error (Se2) of residual lung volume (RLV). Each subject's RLV was determined 18 times using the oxygen dilution method (O2D) over a 5-day period. Se2 was measured using a 9.0 l spirometer as a simulated subject and estimating its added space by the O2D method for 20 repeat trials. The mean +/- SD of RLV across subjects was 1.408 +/- 0.3143 l. The average Swi2 for the 18 trials was 0.0054 (Swi = +/- 0.0735 l). The variance associated with a trend effect (variance of mean trial scores, Sc2) was 0.00050 (Sc = +/- 0.0224 l). Se2 was found to be 0.00104 (Se = +/- 0.0323 l). Si2 calculated by subtracting Se2 and Sc2 from Swi2, was 0.0039 (Si = +/- 0.0621 l). It was demonstrated that body fat weight calculations can vary because of the within-subject variability in RLV. The calculated reliability of RLV across subjects was r = 0.95. It is concluded that RLV determined by the O2D method is very reliable. Moreover, biological variance accounts for 72% of Swi2 while technological variance and trend effect variance account for 19 and 9% of Swi2 respectively.
mesh_terms: D000328:Adult; D000886:Anthropometry / Q000379:methods; D001823:Body Composition; D001835:Body Weight; D005260:Female; D014644:Genetic Variation; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D012115:Residual Volume