Post-bronchodilator changes in volumes and airway caliber according to Peak flow and FEV1 reversibility

Abstract

Background: The possible negative effect of Peak Expiratory Flow (PEF) increase on Forced Expiratory Volume in 1s (FEV1) has been related to enhanced intra-thoracic gas compression or to decreased Forced Vital Capacity (FVC). Objectives: To disentangle which mechanism can be acknowledged for a significant post-bronchodilator (BD) PEF increase without FEV1 reversibility Methods: Eight-year monocentric retrospective study of all asthmatic children’s records including baseline and post-BD spirometry, plethysmography (specific airway resistance, sRaw) or interrupter resistance (Rint) measurements. Changes were described as reversible (R) or non-reversible (NR) for PEF (≥15%), FEV1 (≥12%), sRaw (≤-42%) or Rint (≤-35%). Results: We retrieved 3169 records in 2260 children (856 females, median age 10.4 years, 4.7 to 22). Bronchial obstruction was similar in the two FEV1_NR groups (14% vs 18%; P=0.13) but sRaw and Rint were more frequently reversible in case of PEF_R than PEF_NR (difference significant for sRaw; P In PEF_R FEV1_NR group post-BD changes in FVC were not significant and small (median 0.3%)(P>0.05) but correlated to these of FEV1 (median 7%)(r=0.53). Conclusion: Lack of FEV1 post-BD reversibility in children with PEF_R was not explained by significant change in FVC but respiratory mechanics improvement was frequent.