title: Maximal expiratory flow at FRC (V'maxFRC): Methods of selection and differences in reported values.
abstract: We compared three methods of reporting maximal expiratory flow (V'maxFRC) measured in partial expiratory flow-volume curves (PEFVCs) at the point of functional residual capacity (FRC). PEFVCs were obtained with the rapid thoracoabdominal compression technique (RTC) on a total of 446 occasions in 281 HIV-negative, asymptomatic infants (4.8-28.1 months old). Three different expressions of V'maxFRC were recorded: 1) the highest measured flow (maxV'FRC), 2) the mean of the three highest flows (mean3V'FRC), and 3) the flow at FRC in a composite curve (compV'FRC) consisting of PEFVCs, obtained at different jacket pressures and superimposed at their distal limb. The numerical value of maxV'FRC was 7.4% (+/-5.6%) higher than the mean3V'FRC, and 11.9% (+/-17.7%) higher than the compV'FRC; the mean3V'FRC was 5% (+/-18.3%) higher than the compV'FRC. Bland-Altman analysis was used to evaluate the agreement between the three indices. The mean difference and 95% limits of agreement were: maxV'FRC -mean3V'FRC, 14 +/- 18 ml/sec; maxV'FRC - compV'(FRC), 23 +/- 58 ml/sec; and mean3V'(FRC) - compV'(FRC), 10 +/- 52 ml/sec. The differences between the slopes of the three indices (regressed against height) were statistically significant, although clinically unimportant. We conclude that despite their high correlation, the mean3V'FRC and maxV'FRC should not be used interchangeably, and that the composite analysis, although useful, does not improve the reproducibility of V'maxFRC, and thus it cannot be recommended for routine use in its current form.
authors.affiliation: Pediatric Pulmonary Division, Columbia-Presbyterian Medical Center, New York, New York, USA. akoumbou@LIJ.edu
authors.forename: Anastassios C
authors.initials: AC
authors.lastname: Koumbourlis
authors.forename: Xin C
authors.initials: XC
authors.lastname: Chen
authors.forename: J Sunil
authors.initials: JS
authors.lastname: Rao
authors.forename: Mark D
authors.initials: MD
authors.lastname: Schluchter
authors.forename: Kirk
authors.initials: K
authors.lastname: Easley
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Colin
authors.forename: Peter
authors.initials: P
authors.lastname: Hiatt
authors.forename: Meyer
authors.initials: M
authors.lastname: Kattan
authors.forename: Kevin
authors.initials: K
authors.lastname: McCarthy
authors.forename: Robert B
authors.initials: RB
authors.lastname: Mellins
authors.forename: Hannah
authors.initials: H
authors.lastname: Peavy
authors.forename: Arnold C G
authors.initials: AC
authors.lastname: Platzker
authors.forename: Suzanne
authors.initials: S
authors.lastname: Steinbach
authors.forename: Andrew
authors.initials: A
authors.lastname: Ting
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weisner
authors.forename: Mary Ellen B
authors.initials: ME
authors.lastname: Wohl
mesh_terms: D002675:Child, Preschool; D019992:Databases as Topic; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology; D006801:Humans; D007223:Infant; D008297:Male; D008448:Maximal Expiratory Flow Rate / Q000502:physiology*; D008449:Maximal Expiratory Flow-Volume Curves / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D012044:Regression Analysis