Baseline PFTs
Initial PFTs were accomplished at the age that each patient could perform the maneuver (median:78 months; range: 59-110) according to the guidelines established by the ATS/ERS. The median duration of the PIBO disease at the time of initial PFTs was 43 months. All PFT data of patients showed consistent with moderate to severe obstruction. At baseline, the median PFT values (based on percentage of predicted value for a given age) for FEV1, FVC, FEV1/FVC ratio and MMEF25% -75% were 39.75%, 41.6%, 90.7% and 22.2% respectively (Table 2).
Post-bronchodilator improvements were significant in expiratory flows, although the values didn’t reach normality for age. Of the 12 pediatric PIBO patients, 10 (83.3%) demonstrated a significant bronchodilator response when the cut-off point was a percent change of 12%, as recommended by the ATS/ERS (data was not given). As showed in Table 3, FEV1 was significantly improved after inhalation of bronchodilators, and MMEF25%-75% alike. The mean percent variation and the mean absolute volume change from the previous measurement were 23.01% and 0.15 L for FEV1, 46.92% and 0.28L/s for MMEF25%-75% respectively. In the multivariate analysis of the outcome variables, we found that the predictor variables (age at diagnosis, allergy factors) had no significant effect on the bronchodilator response, although the higher diagnosis age will reduce the improvement value of MMEF25%-75%(P<0.05) (Table 4).