Small airways impairment and air-trapping in patients with chronic hypersensitivity pneumonitis (CHP) of different severity

Introduction: CHP is a heterogeneous disease associated with multi-compartmental involvement of the distal lung. Bronchiolitis is a key pathologic component that accounts for characteristic clinical-radiological abnormalities. The extent to which small airway (SA) function changes as CHP progresses is incompletely understood. Aim: To evaluate SA dysfunction in patients with CHP of varying severity. Methods: Pulmonary function tests of patients with a multidisciplinary panel-agreed diagnosis of CHP (n=118) at the Royal Brompton Hospital were retrospectively studied. Subjects were divided into 3 groups of disease severity. Parameters related to SA and air-trapping (AT) were assessed. Data were analyzed through linear regression models and expressed as mean±SD. Results: Changes in indices of SA function (MEF75/50/25, FEV3 and inspiratory airway resistance) and of AT (RV/TLC ratio) correlated with the severity of CHP. Values were significantly different between the severe and mild disease groups (Table 1). Conclusions Patients with more severe CHP have significantly impaired SA flow, increased airway resistance and higher AT. Analysis of airway function in CHP might broaden its clinical phenotyping by highlighting measurable indices relating to specific pathological abnormalities.