This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
[{'content': '55 year old female a known case of thryotoxicosis in control posted for abdomino perineal resection during surgery there was sudden drop in B.P., and end tidal CO2 decreased from 40 to 10 mmHg. On auscultation there was a mill wheel murmur, what is the diagnosis – \nSelect and explain. \nA. Thyroid storm, B. Bleeding, C. Hypoxia, D. Air embolism', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Presence of Mill wheel murmur and decrease in End tidal CO2 during surgery suggests Air embolism:-\n"If air enters the vein in sufficient amount, it will go to the right heart and lung causing an air-lock obstruction in\xa0the pulmonary artery. This may result in a loud continuous precordial murmur, the so called "Mill wheel murmur".', 'role': 'assistant'}]