S83 Pigeon fanciers with normal spirometry and no known ILD, display forced oscillometry findings suggestive of sub-clinical interstitial lung disease

Introduction Pigeon fanciers are recognised to suffer from acute through to chronic hypersensitivity pneumonitis (HP), and given their HP is driven by a known antigen, provide a potentially useful group to identify novel causative mechanisms for HP. The forced oscillation technique (FOT) employs sound waves to examine the relationships between pressure and flow during tidal respiration, and has been advocated as an approach to assess the small airways and lung parenchyma. It is also simple to perform, as it requires tidal breathing only. Given this we examined FOT in a group of pigeon fanciers at a recent national meeting. Methods Volunteers were recruited from among the attendees at the National Royal Pigeon Fancier’s Meeting Blackpool, 2019. Participants completed a questionnaire with experienced clinicians, which focused on; presence of a diagnosis of interstitial lung or connective tissue disease, current medication, symptoms post pigeon exposure, number of pigeons kept and occupational dust exposure. All subjects provided blood for genetic and immunological assessment, and performed spirometry. An unselected subgroup performed FOT using the Resmon Pro (Intermedical UK Ltd). Results 178 subjects participated over two days. Of these 94 performed FOT. 51 participant’s FOT results were analyzed, after exclusion of those with known interstitial lung disease, abnormal spirometry or no result due to inadequate spirometry technique. 23 subjects (45%) demonstrated abnormal FOT results, with the consistent finding being high expiratory reactance at 5Hz (exp Xrs5). Median exp Xrs5 was -3.5 cmH2O (-6.3 to -2.5), equating to 244% predicted (204 to 446) (both median (IQR)). Discussion FOT, specifically elevated expiratory Xrs at 5Hz, is abnormal in a large proportion of pigeon fanciers who have no known ILD and normal spirometry. Given this we suggest that exp Xrs5 may be able to detect sub-clinical lung inflammation in otherwise healthy subjects with known exposure to a risk factor for development of HP. Further research is required to determine how exp Xrs5 relates to interstitial changes on CT, and whether changes in FOT can predict subsequent progression to chronic fibrosis in subjects with ongoing antigen exposure.