Pre-oxygenation in obese patients: facemask versus facemask with nasal prong

Introduction: Anatomical and physiological changes of the respiratory system in obese patients predispose them to rapid oxygen desaturation during apnoea. Adequate pre-oxygenation before anaesthesia induction allows a period of safe apnoea. The efficacy of pre-oxygenation with facemask versus facemask with nasal prong was compared. The time taken for expired end-tidal oxygen (FEO2) to reach 0.8 (T0.8) from commencement of pre-oxygenation (T0), and time to oxygen desaturation to 95% (T95%), following apnea (TA) was studied. Methods: This prospective, randomised study recruited 36 surgical patients of body mass index (BMI) ≥ 30 kg/m2 requiring general anaesthesia with endotracheal intubation. They were randomised to receive pre-oxygenation with oxygen facemask at 12 L/min, or concurrent pre-oxygenation with facemask at 7 L/min and nasal prong at 5 L/min. Oxygen saturation (SpO2) and FEO2 were recorded at T0, T0.8, and at TA following completion of rocuronium administration. Oxygen was then discontinued, and the patient left apnoeic with no ventilation. Intubation was performed 60 seconds after TA, and the patient left apnoeic with the endotracheal tube exposed to room air. Duration from TA until the patient’s SpO2 reached 95% (T95%) was documented. Results: Pre-oxygenation with facemask and nasal prong resulted in a shorter T0.8 compared to facemask alone (48.61 s ± 23.3 versus 77.72 s ± 26.15), p = 0.001. There was no difference in T95% between the groups. Conclusion: Pre-oxygenation with facemask plus nasal prong resulted in a shorter time taken to reach FEO2 0.8, but with comparable time to oxygen desaturation between both groups.