Several techniques such as positive airway pressure and head-up tilt during preoxygenation have shown to prolong non-hypoxic apnea period compared to conventional technique. However, uniform recommendations have not yet been made. Therefore, in the present study the investigators attempted to find out the effect of combination of 5 cmH2O CPAP and 25° head up position during preoxygenation.

In this study 60 non-obese healthy adult patients were divided into three groups; Group C receiving preoxygenation in conventional technique, Group S receiving preoxygenation with 5 cmH2O CPAP and Group H receiving preoxygenation in 25° head-up position with 5 cmH2O CPAP. After 3 min of preoxygenation, anesthesia was induced and trachea intubated. After confirming the tracheal intubation by direct visualization, all patients were left apneic in supine position with the tracheal tube exposed to atmosphere till the SpO2 dropped to 92%. The primary outcome compared between the groups was the non-hypoxic apnoeic period (time to fall SpO2 to 92%).

Inclusion Criteria:

• adult patients of ASA physical status I and II undergoing surgery under general anaesthesia

Exclusion Criteria:

• anticipated difficult mask ventilation/ intubation
• individuals with significant cardiorespiratory or cerebrovascular disease
• pregnant ladies
• patient with history of epilepsy
• body mass index >25 kg/m2
• hemoglobin <8 gm/dL
• patients who were non-ambulant for >24 h, having SpO2 < 97% while breathing in room air
• phobia to facemask.