Variability of the computerized single-breath nitrogen washout test in healthy adults. Results from a field survey in a French rural area.
Within-subject (difference between paired tests, or coefficient of variation [c. var.] of three consecutive measurements) and between-subjects (standard deviation of the mean group) variability were assessed for the variables derived from the single-breath nitrogen (SBN2) test in a group of healthy, asymptomatic subjects (n = 289) aged 20-64 years, from a rural area in North-East France. Duplicate measurements in 99 subjects showed excellent agreement between the two attempts (correlation coefficients between 0.94 and 0.98) for static lung volumes and the alveolar N2 slope (PIII); closing volumes (CV) were more variable (r = 0.77 for absolute value, 0.79 for % VC) while closing capacities (CC) were in intermediate position (r = 0.86 for absolute value, and 0.88 for % TLC). The variability of three consecutive measures in 190 subjects showed the coefficients of variation to be low for static volumes and closing capacity (2.4-7.4%) and higher for PIII (15.1%) and CV or CV/VC (18.2 and 17.8%). The analysis of variance did not detect significant differences between the three sets of measurements, with the exception of a progressive increase of vital capacity (VC), and decrease in residual volume (RV) from test 1 to test 3, the total lung capacity being the same. Variability was uninfluenced by age or sex, except a higher c. var. for female VC as compared to males (2.8 vs. 2.2%, P = 0.02) and a higher variability of TLC (2.9 vs. 2.3%, P = 0.03) and VC (2.8 vs. 1.9%, P = 0.003) in people older than 40 years as opposed to those younger than 40 years.
Teculescu
D B
DB
INSERM-Unité 115, Vandoeuvre-lès-Nancy, France.
Rebstock
E
E
Caillier
I
I
Pham
Q T
QT
Costantino
E
E
Bouchy
O
O
D000293:Adolescent; D000328:Adult; D000368:Aged; D001944:Breath Tests; D003201:Computers; D005260:Female; D005602:France; D006801:Humans; D008297:Male; D008875:Middle Aged; D009584:Nitrogen; D011650:Pulmonary Alveoli / Q000502:physiology; D012016:Reference Values; D012129:Respiratory Function Tests / Q000592:standards*; D012424:Rural Population
D009584:Nitrogen