Abstract
Moment analysis (MA) of MBNW could in theory be a good method of quantifying ventilation inhomogeneity in young children since it requires only quiet breathing of oxygen for <2 minutes and the results are independent of breathing pattern or lung volume. We have developed the software required for on-line MA of MBNW and have performed duplicate studies on 36 healthy children (H) and 10 with cystic fibrosis (CF) ages 3-6 years. Outcome variables included FRC, moments 0,1,2 and moment ratios M1/M0 and M2/M0. In H there were no sex related differences in FRC or moment ratios while absolute moments tended to be higher in boys (p<.05,M0). Intrasubject coefficient of variation (CV%) was <10% for all variables. Intersubject CV% for M1/M0=8%, M2/M0=13%, and FRC=18%. A modified Shwachman (S) score was used to quantify lung involvement in CF with a score of 75 being the best possible. The CF group varied from no lung involvement to severe disease, S score 30-75. Mean FRC was no different in CF vs H while mean M1/M0 and M2/M0 were both higher in CF, 2.59 vs 2.32 and 13.04 vs 9.31, p< .001. 7 of 10 CF had moment ratios >95th percentile of H. The 3 with values in the normal range had higher S scores than the 7 with abnormal values, mean 65 vs 47, p<.001. Moment ratios in CF showed a good correlation with S scores; for instance M1/M0=3.35 -.01·S score r=.67, p<.01. We conclude that MA of MBNW has promise as a test of lung function in young children since the method is non-invasive, low in variability, and appears to have the sensitivity required to detect mild ventilation inhomogeneity.
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