Assessment of bronchodilator responsiveness in infants with bronchiolitis - A comparison of the tidal and the raised volume rapid thoracoabdominal compression technique

Whether bronchodilators should be used for the treatment of infants with br onchiolitis is subject to debate, partly because of the low sensitivity of the methods for assessing lung function changes in infants. In the present study, we compared the recently introduced raised volume (RVRTC) with the c onventional end-tidal rapid thoracoabdominal compression (ETRTC) technique in infants with acute viral bronchiolitis. In 17 infants lung function was assessed by both methods, at baseline values and after salbutamol inhalatio n. Forced expiratory volumes (FEV0.5, FEV0.75, FEV1.0) were used for the qu antification of RVRTC measurement, and maximal expiratory flow at functiona l residual capacity ((V) over dot max(FRC)) for ETRTC measurements. A signi ficant individual change was defined by a mean post-bronchodilator value th at differed from baseline value by more than twice the within-subject coeff icient of variation (CV). Group mean intrasubject CVs ranged from 4.7% to 5 .3% for FEV parameters; it was 14.0% for (V) over dot max(FRC). For the gro up, postbronchodilator measurements did not differ significantly from basel ine measurements. For the majority of infants, however, the within-subject comparison of responses revealed substantial differences between both techn iques; while no infant demonstrated a significant increase in (V) over dot max(FRC), eight (47%) infants responded with significantly improved timed v olumes. The RVRTC technique provides the investigator with a more sensitive diagnostic tool for documenting the effectiveness of therapeutic intervent ions on an individual basis. Furthermore, the findings of the present study provide a rationale for the application of bronchodilators in a subgroup o f infants with acute bronchiolitis.