<prompt> 5 yr old child going to sitting craniotomy while positioning in O.T. developed End Tidal CO2 0mm Hg P02 80 mm Hg impliesEndotracheal tube in oesophagusE.T. blocked with secretionVenous air EmbolismLeft lung collapse  <response>: C i.e. Venous Air embolism A patient undergoing laprothoraco-scopyQ or procedure eg craniotomy in sitting, head upQ, park-bench, knee-chest positions that place the operative site above the right atrium carry an increased risk of VAE. Sudden decrease in end-tidal CO2 concentration ETCO?, sudden hypotensioncirculatory arrest and Mill wheel murmur indicate the diagnosisQ. 