Wikipedia
Tracheomalacia
Tracheomalacia (from trachea and the Greek μαλακία, softening) is a condition characterized by flaccidity of the tracheal support cartilage which leads to tracheal collapse especially when increased airflow is demanded.
The trachea normally dilates slightly during inspiration and narrows slightly during expiration. These processes are exaggerated in tracheomalacia, leading to airway collapse on expiration. The usual symptom of tracheomalacia is expiratory stridor or laryngeal crow.
If the condition extends further to the bronchi (if there is also bronchomalacia), it is termed tracheobronchomalacia. The same condition can also affect the larynx, which is called laryngomalacia.