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': '5 year old child going to sitting craniotomy while positioning in O.T. developed end tidal CO2 0mm HgPO2 80 mm Hg implies – \nSelect and explain. \nA. Endotracheal tube in oesophagus, B. E.T. blocked with secretion, C. Venous air Embolism, D. Left lung collapse', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Information in this question : -\n\n\nChild is under going sitting craniotomy\nRapid fall of ETCO2 (while in position, child develops ETCO20)\n\n\nThis indicates venous air embolism due to sitting craniotomy.\nIn esophageal intubation, ETCO2 will be zero from the start only (unlike venous air embolism in which initially there is detection followed by rapid fall).', 'role': 'assistant'}]