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Fixed obstruction – BOS — RACP Paediatrics MCQ

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HardRespiratoryFixed obstruction – BOSRACP Paediatrics

A 14-year-old post-lung transplant patient has spirometry showing FEV1 45% predicted, FVC 80% predicted, FEV1/FVC 0.48. There is no bronchodilator response. Flow-volume loop shows a concave expiratory curve. Previous spirometry 6 months ago was normal. What is the most likely interpretation?

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Correct answer: D — Fixed obstruction

Fixed obstruction (reduced FEV1/FVC without bronchodilator reversibility) with a concave expiratory loop in a post-transplant patient with rapidly declining FEV1 suggests bronchiolitis obliterans syndrome (BOS/chronic lung allograft dysfunction). This is the most common cause of late graft loss after lung transplantation.

Reference: RACP Paediatric Curriculum – Respiratory; RCH Melbourne – 2023