Tracheal dilatation and lengthening occurs during inspiration, narrowing and shortening during expiration. Accentuation of this cyclic process may cause excessive narrowing of tracheal lumen thus deforming the entire length or a localized segment. In general, abnormal collapsibility denotes a loss of structural rigidity, i.e. softening, better expressed as abnormally increased compliance. Any disease process affecting the integrity of the tracheal wall is apt to cause a change in tracheal compliance. The anatomic defect may be trivial or even may escape detection, the functional interference with ventilation may cause expiratory flow obstruction and interfere with clearance of secretions.
Functional impairment is proportional to the length of involved segment and degree of stenosis.
Furthermore, kinking may occur at the transitionbetween normal tracheal wall and indurated segment as well as in malacic segment. In diffuse tracheal disease or extensive peritracheal adhesions, the trachea usually distends unevenly during inspiration and collapses during expiration, thus interfering with the tracheal function. Expiratory stridor may worsen with supine position, crying and respiratory infections. Feeding difficulties sometimes reported. Hoarseness, aphonia and breathing may also be reported.