Peripheral airway abnormalities are common in children post bone marrow transplantation

Aim: Pulmonary complications are common following Bone Marrow Transplantation (BMT) but peripheral airway involvement may be underestimated by conventional lung function measures, such as spirometry. This study aimed to characterize peripheral airway function in children post BMT using Multiple Breath Washout (MBW) in comparison to standard lung function. Methods: Cross sectional study of children following BMT at a single tertiary centre. Inclusion criteria included age ≥3 years, allogenoeic BMT, similar conditioning regimens and stability at the time of testing. Assessment included MBW (performed using simultaneous inert gas washout with SF 6 and Helium) and conventional lung function. Non-parametric data displayed as median (range). Results: 24 subjects have been recruited to date: 16 (67%) male, age 14.3 (4.3-18.6) years, tested at 4.8 (0.7-12.1) years post BMT. Spirometry was feasible in 15/24 (63%) of the cohort, with abnormal values present in 5/24 (21%) for FEV 1 and 4/15 (17%) for FEF 25-75 . MBW was feasible in all subjects. Abnormal MBW parameters were observed in a greater proportion (18/24, 75%) vs. either FEV 1 or FEF 25-75 (p 6 MBW indices was greatest with S cond (0.034 (0.004-0.089), Upper limit of normal (ULN) 0.023, abnormal in 18/24, (75%) followed by LCI (7.52 (5.03-23.59), ULN 7.35, abnormal in 14/24, 58%) and S acin (0.105 (0.056-0.463), ULN 0.121, abnormal in 8/24, 33%). Conclusion: MBW offered improved feasibility, compared to spirometry, for lung function assessment. Peripheral airway involvement was present in the majority of the cohort, and was underappreciated by spirometry.