This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
[{'content': 'Standard method to differentiate between endotracheal and esophageal intubation is- \nSelect and explain. \nA. End tidal CO2, B. Chest X-rays, C. Auscultation, D. Paial pressure of 02', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Auscultation is the most commonly used method to detect endobronchial intubation. But it may be misleading, as breath sounds can be transmitted to opposite side of the chest. Chest x-ray is reliable but time consuming and expensive. The radio opaque marker at the patient end shoilube in the middle third of trachea. End tidal CO2 is the most reliable and standard method to detect endobronchial intubation.', 'role': 'assistant'}]