Tracheobronchomalacia is characterised by excessive airway collapsiibility due to weakness of airway walls and supporting cartilage. Given that the criteria used to make the daignosis of tracheobronchomalacia are poorly validated, further studies with larger patient samples are required to define the threshold for pathalogical airway collapse.
Tan, J. Z. Y., Ditchfield, M., & Freezer, N. (2012). Tracheobronchomalacia in children: review of diagnosis and definition. Pediatric Radiology, 42(8), 906 - 915. https://doi.org/10.1007/s00247-012-2367-5