BACKGROUND Pre-oxygenation with 100% oxygen is performed routinely before induction of anaesthesia. The purpose of pre-oxygenation is to increase the body oxygen stores and to replace nitrogen in the lungs by an equivalent volume of oxygen, thus delaying the onset of oxygen desaturation and hypoxemia during the apnoeic period following induction of anaesthesia. The objectives of this study were to compare the effects of varying periods of preoxygenation on intraoperative oxygen saturation and its hemodynamic effect. MATERIALS AND METHODS Sixty adults ASA I and II patients scheduled for surgery under general anaesthesia were divided into three groups according to method of pre-oxygenation. In Group 1 (n=20) patients were preoxygenated for 60 seconds, Group 2 (n=20) patients were pre-oxygenated for 120 seconds and Group 3 (n=20) patients were preoxygenated for three minutes of tidal volume breathing using oxygen flow of 6 Lmin-1. Following preoxygenation, face mask oxygenation was continued until the patient got relaxed and then trachea was intubated. Intraoperative saturation was measured using pulse oximetry after every 5 minutes along with other hemodynamic parameters. RESULTS The mean values of intraoperative oxygen saturation at 5 min, 10 min, 15 min and 20 min among three groups did not fall significantly and were statistically non-significant between the three groups (p value of > 0.05). Likewise, at different intervals of intraoperative stage like after 30 min, 45 min, 60 min, 75 min, 90 min, 105 minutes, the values remain same and statistically non-significant (p value> 0.05). Regarding vital parameters (heart rate, blood pressure, respiratory rate, oxygen saturation), there was non-significant difference between the three study groups (p value >0.05). CONCLUSION Rapid preoxygenation by one-minute and two-minutes, normal tidal volume breathing technique is equally efficient to three minutes of preoxygenation in healthy patients.

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