This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Local and Regional Anesthesia, Subject name: Anaesthesia
ETT is not useful for: 
Select and explain. 
A. Pneumothorax, B. Pulmonary toilet, C. Obstruction, D. Decreased level of consciousness
A: Pneumothorax
Answer: A: Pneumothorax 
Explanation: Ans. (a) PneumothoraxRef: Miller's Anaesthesia 7h ed. / 288ETT is Endotracheal Tube Toilet* It involves clearance of airway secretions, and is a normal process needed for the preservation of airway patency and the prevention of respiratory tract infection.* Impaired clearance of airway secretions like in patients with depressed level of consciousness can result in atelectasis and pneumonia, and may contribute to respiratory failure.* The primary indications for tracheal suctioning is to remove secretions in order to enhance oxygenation or to obtain samples of lower respiratory tract secretions for diagnostic tests. In the end, perform tracheal suctioning after endotracheal intubation to clear the airway of aspirated material or secretions or to enhance oxygenation in a tracheostomy patient with respiratory insufficiency.* Perform bronchopulmonary toilet when secretions are visible in the endotracheal tube or at the orifice of the tracheostomy tube. Perform tracheal suctioning when the patient has coarse rales, rhonchi, or tubular breath sounds; acute or worsening dyspnea; or arterial oxygen desaturation.