5 year old child going to sitting craniotomy while positioning in O.T. developed end tidal CO2 0mm HgPO2 80 mm Hg implies –
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Child is under going sitting craniotomy
Rapid fall of ETCO2 (while in position, child develops ETCO20)


This 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).
Endotracheal tube in oesophagus
E.T. blocked with secretion
Venous air Embolism
Left lung collapse