This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
After suffering a respiratory tract infection, a 64-year-old female biochemist develops chronic lung disease requiring intubation in the ICU for an 8-week period. Tracheal stenosis is noted. What is the most likely cause of tracheal stenosis? 
Select and explain. 
A. Prolonged intubation, B. Tuberculosis, C. Scleroderma, D. Riedel struma (fibrous thyroiditis)
A: Prolonged intubation
Answer: A: Prolonged intubation 
Explanation: Any object that compromises the blood supply to the tracheal mucosa or cartilage can cause stenosis. When the mean intramural pressure exceeds 20-30 mm Hg, damage may be anticipated. Riedel struma is a rare fibrosing thyroid condition, which must be differentiated from carcinoma and may cause severe tracheal stenosis. Achalasia is a neuromuscular defect at the lower end of the esophagus causing dysphagia, because of nonmechanical esophageal obstruction.