Defining and classifying airway malacia
Airway malacia was defined as greater than 25% expiratory reduction in the cross-sectional luminal area during quiet respiration on the visual inspection at bronchoscopy 4. Lower airway malacia was classified as TM, if the collapsibility was located on trachea, or BM, if the collapsibility was restricted to one or both of the mainstem bronchi and/or their divisions at the lobar or segmental level. When at least one of the bronchi affected with trachea, the condition was called TBM 1. In cases in where TBM didn’t exist, the malacia was defined as isolated TM or isolated BM. The localization and severity of TM were assessed with bronchoscopy. Trachea was divided into three regions and classified as upper (from the cricoid to the thoracic inlet), middle (from the thoracic inlet to the mid portion to the intrathoracic trachea) and lower (from the middle of the intrathoracic trachea to the carina) trachea 1. The severity of TM was described as mild (25 – 50% reduction), moderate (50 – 90% reduction) and severe (>90% reduction). The causes of airway malacias were classified according to ERS guideline1.