Reproducibility of forced expiratory flow and volume measurements in infants with bronchiolitis

The end-tidal rapid thoracoabdominal compression (ETRTC) technique is an es tablished method for lung function testing in infancy. Previous work in hea lthy infants, however, has shown that measurements with the newly developed raised volume rapid thoracoabdominal compression (RVRTC) technique are mor e reproducible than those with the ETRTC technique. So far, reproducibility of the two techniques has not been compared in infants with acute airway d isease. Twenty-three infants with acute viral bronchiolitis underwent lung function assessment with both the ETRTC and the RVRTC technique. A series o f 8-10 measurements with each technique was done in randomized order. Force d expired volumes at 0.5, 0.75, and 1 sec after chest compression (FEV0.5, FEV0.75, and FEV1.0) were measured with the RVRTC technique; maximum expira tory flow at functional residual capacity (V'(maxFRC)) was measured with th e ETRTC technique. Group mean intrasubject coefficients of variation (CV) w ere 4.84% for FEV0.5, 5.01% for FEV0.75, 5.43% for FEV1.0, and 13.79% for V '(maxFRC), respectively. Differences between FEV parameters were statistically insignificant, wherea s the difference between each FEV parameter and V'(maxFRC) was highly signi ficant (P < 0.001). In infants with acute viral bronchiolitis, RVRTC measur ements have significantly less intraindividual variability than flow rates assessed with the conventional ETRTC technique. This finding provides the b asis for assessing disease course and effects of therapeutic interventions on an individual basis. (C) 1999 Wiley-Liss, Inc.