Longitudinal Assessment of Pulmonary Function and Bronchodilator Responses in Pediatric Patients with Post-Infectious Bronchiolitis Obliterans

Abstract Objective: We aimed to further assess the evolution of pulmonary function and bronchodilator response in the Chinese case series with post-infectious bronchiolitis obliterans (PIBO). Methods:  Twelve children with PIBO, aged 59-110 months, were retrospectively studied between 2011 and 2019. According to the ATS/ERS recommendations, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC and maximal midexpiratory flow velocity 25%-75% (MMEF25%-75%) were collected at each pulmonary function tests (PFTs), as well as bronchodilator responses were evaluated. Spirometric parameters were monitored over time, and generalized linear mixed models were used to analyze longitudinal panel data. Results:  The median baseline PFT values for FVC, FEV1, FEV1/FVC ratio and MMEF25% -75% were 41.6%, 39.75%, 90.7% and 22.2% respectively. At the initial PFTs, 10 (83.3%) patients demonstrated a significant bronchodilator response. FVC and FEV1 increased by a mean of 8.212%/year and 5.007%/year, and FEV1/FVC ratio with an average decrease of 3.537%/year. MMEF25-75% showed an average increase of 1.583% per year. Over all, FEV1 and MMEF25%-75% showed different degrees of improvement after inhaled bronchodilators at each PFT sessions for ten patients, and FEV1 was with significant (>12%) β2-bronchodilation in 53% of PFT sessions. Conclusions:  Pediatric patients with PIBO showed an obstructive defect of pulmonary function. The FVC, FEV1 and MMEF25%-75% improved as they grew old, while FEV1/FVC ratio decreased. It may be due to the development of lung parenchyma more than airway growth. Airway obstruction of some patients improved with the use of β2 agonists.