<prompt> 5 year old child going to sitting craniotomy while positioning in O.T. developed end tidal CO2 0mm HgPO2 80 mm Hg impliesEndotracheal tube in oesophagusE.T. blocked with secretionVenous air EmbolismLeft lung collapse  <response>: Information in this question : -Child is under going sitting craniotomyRapid fall of ETCO2 while in position, child develops ETCO20This indicates venous air embolism due to sitting craniotomy.In esophageal intubation, ETCO2 will be zero from the start only unlike venous air embolism in which initially there is detection followed by rapid fall. 