A study of role and comparison of tidal volume and deep breathing techniques of preoxygenation

Background: This study was envisaged to emphasize the importance and necessity of preoxygenation in all cases before induction. The commonly used 3 minute tidal volume breathing (TV) and 4 deep breaths (DB) in 30 seconds techniques were compared using pulseoximetry. The effect of preoxygenationon vital haemodynamicparameters with these techniques and also the effects, if preoxygenation is not done, were also evaluated. Material and Methods: This randomized clinical study was done in a tertiary care medical college hospital. Ninety adult patients(18-45 years) of both genders, ASA grade I-II, undergoing elective surgery were included and studied in three groups with 30 patients randomly allocated to each group. Group I-Received no preoxygenation, but ventilation was done during apnoea using AMBU with oxygen 2 liters/minute with 4 maximal chest inflations. Group II-Received preoxygenation with 100% oxygen in the form of 4 vital capacity breaths in 30 seconds and ventilation was done during apnoea with 4 maximal chest inflations of 100% oxygen. Group III- Received preoxygenation with 100% oxygen, for 3 minutes in the form of tidal volume breathing and ventilation was done during apnea with4 maximal chest inflations of 100% oxygen. The pulse, blood pressure and oxygen saturation were recorded before induction, after premedication, after preoxygenation, after induction and intubation. The values were compared statistically using paired and unpaired t-test and one-way analysis of variance test as applicable. A p-value of less than 0.05 was considered as statistically significant at 95% confidence interval. Results: During induction there was a fall in saturation in patients of Group I with a meanSpO2 after intubation of 94.71% ±3. 61 and the lowest value recorded being 88%. In the Groups II and III, the SpO2 was maintained at a level of 100% throughout induction. There was a rise in pulse and blood pressure after intubation in all the groups as a result of intubation response. The rise in blood pressure in Group I (mean SBP=144.6±16.8, mean DBP=95. 46±11.49) was higher though not significant, as compared to the other two groups. (Mean SBP in Group II=142.63±13.03, mean DBP in Group II=92. 33±23.72, mean SBP in Group III=136.73±8.1, mean DBP in Group III=93. 4±10.16). (p>0.05).The vitals started approaching the baseline values and blood pressure reached baseline values significantly faster in preoxygenated groups as compared to Group I (p<0.05). Conclusions: Preoxygenation is a must before induction in all patients. Both 3 minute tidal volume and 4 deep breaths in 30 seconds techniques are equally effective in uncomplicated inductions. Ventilation during apnoea provides added oxygen reserve. Besides protection from hypoxia, preoxygenation contributes to hemodynamic stability.