Airway stents. Coloured chest X-ray of a woman in her early 40s whose weakened airways are being held open by metal stents (dark green, upper centre). Her trachea and bronchi have become softened due to tracheobronchial malacia. The lungs are light green. 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.