Airway stents. Coloured chest X-ray of a woman in her early 40s whose collapsing airways are being held open by metal stents (black, upper centre). The trachea and bronchi have become softened due to tracheobronchial malacia. The lungs are pale orange/yellow. Tracheobronchial malacia is caused by weakness or a lack of supporting cartilage in the airways. Coughing can lead to the total collapse of the airways.