. Difficult airway society suggests that when critically ill patients are intubated, preoxygenation should be performed until an End tidal oxygen level of greater than or equal to 85% is attained.

Effectiveness of preoxygenation can be assessed by values of oxygen saturation on pulse oximeter (SpO₂ ) and End tidal oxygen [ETO₂]. Although SpO₂ is gold standard for assessing adequacy of preoxygenation as it is inexpensive and easily accessible. However it is an indirect measure of preoxygenation.

In earlier times ETO2 was not included for standard monitoring as it was expensive and not easily available. Therefore there was paucity of literature for assessing efficacy of preoxygenation using ETO₂. With advancement of technology, availability of modern equipment, end tidal oxygen monitoring is feasible and should be considered as a monitoring standard for adequacy of preoxygenation . There is paucity of literature supporting the use of ETO2 as a guide for preoxygenation particularly in Indian hospital set up

Patient will be taken as per inclusion criteria. Preanesthetic evaluation of the patient. Written informed consent taken from patient. Patient taken to operation theatre, monitoring established, baseline vitals noted, monitoring of SpO₂ and ETO₂ concentration at the start of preoxygenation

Preoxygenation for 3 minutes with 100% oxygen

Monitoring of SpO₂ and ETO₂ concentration at the end of preoxygenation

Induction with Fentanyl, thiopentone or etomidate followed by suxamethonium 

Apnoeic oxygenation 100% oxygen for 45 seconds

Monitoring of SpO₂ and ETO₂ concentration at the end of intubation / beginning of capnographic waveform

n=70

Confirmation  of achieving effective ventilation