The impact of tracheobronchomalacia on lung disease, microbiology and inflammation in children with cystic fibrosis

<bold>Background:</bold> Tracheobronchomalacia (TBM) is common in children with cystic fibrosis (CF). The clinical implications of TBM remain unclear as the impact on CF lung disease is unknown. <bold>Aim:</bold> To determine if presence of TBM in young children with CF impacts lung disease imaging scores, airway microbiology and inflammatory markers. <bold>Method:</bold> Reports from bronchoscopies performed between 2001-2016 for children (<4 years old) with CF were retrospectively reviewed to determine presence of TBM. Airway microbiology and inflammatory markers were determined from bronchoalveolar lavage fluid. Lung imaging scores (PRAGMA and CF-CT) were calculated from computerised tomography scans from an annual clinical surveillance program. <bold>Results:</bold> Data was available for 167/181 (92%) participants. TBM was seen at least once in 41%. There was no differences in the number or type of bacterial pathogens present in lavage fluid of those with and without TBM. Presence of neutrophil elastase was significant in those with moderate to severe TBM (p=.02) or when TBM was seen on mulitple bronchoscopies (p=.04). Children with TBM had significantly higher PRAGMA %disease (p=.01) and PRAGMA %trapped air scores (p=.02) but not PRAGMA %bronchiectasis score. Increase in CF-CT mucus plugging score was associated with TBM (p<.01). <bold>Conclusion:</bold> Children with CF and TBM have higher neutrophil elastase and evidence of lung disease on imaging in early life which is associated with mucus plugging but not bronchiectasis. These children may require treatment modification to imporve airway clearance and reduce risk of mucus plugging that could lead to airway inflammation and disease progression.