Low-positive pressure ventilation improves non-hypoxaemic apnoea tolerance during ear, nose and throat pan-endoscopy A randomised controlled trial

Abstract : BACKGROUND It has been suggested that oxygenation using pressure support ventilation (PSV) before general anaesthesia can reduce the duration of non-hypoxaemic apnoea. OBJECTIVE The objective was to determine whether or not pre-oxygenation with PSV increases the duration of non-hypoxaemic apnoea in non-obese patients during pan-endoscopy. DESIGN A randomised, controlled trial. SETTING Amiens University Hospital, France. PATIENTS Fifty patients scheduled for ENT pan-endoscopy with a BMI lower than 35 kg m(-2). INTERVENTION Patients scheduled for pan-endoscopy were enrolled to receive either 100% oxygen at neutral pressure (the control group) or 100% oxygen with positive-pressure ventilation (a positive inspiratory pressure of 4 cmH(2)O and a positive end-expiratory pressure of 4 cmH(2)O; the PSV group) during spontaneous ventilation with a face mask. The goal of pre-oxygenation was to obtain an end-tidal oxygen concentration of more than 90% prior to induction of anaesthesia. MAIN OUTCOME MEASURES The primary efficacy criterion was the duration of non-hypoxaemic apnoea (i.e. before the peripheral capillary oxygen saturation fell to 90%). Secondary outcomes were duration of pre-oxygenation, pre-oxygenation failure and tolerance. RESULTS The mean (interquartile range) duration of non-hypoxaemic apnoea was longer in the PSV group [598 (447 to 717) s] than in the control group [310 (217 to 451) s] (P < 0.001). Oxygenation time was shorter in the PSV group [190 (159 to 225) s] than in the control group [245 (151 to 435) s] (P = 0.037). Pre-oxygenation was unsuccessful (i.e. end-tidal oxygen concentration was < 90%) in 20% of the patients in the control group but none in the PSV group. The intergroup difference in the duration of pan-endoscopy was not significant. Tolerance was good or very good in all patients. CONCLUSION Our results show that pre-oxygenation with PSV is associated with a longer duration of non-hypoxaemic apnoea and a lower frequency of manual reventilation during ENT pan-endoscopy. CLINICALTRIALS.GOV REGISTRATION NUMBER NCT02167334.