PurposeThere is an elevated incidence of hypoxemia during the airway management of the morbidly obese. We aimed to assess whether optimizing body position and ventilation during pre-oxygenation allow a longer safe non-hypoxic apnea period (SNHAP).MethodsFifty morbidly obese patients were recruited and randomized for this study. Patients were positioned and preoxygenated for three minutes in the ramp position associated with spontaneous breathing without additional CPAP or PEEP (RP/ZEEP group) or in the reverse Trendelenburg position associated with pressure support ventilation mode with pressure support of 8 cmH2O and an additional 10 cmH2O of PEEP while breathing spontaneously (RT/PPV group) according to randomization.ResultsThe SNHAP was significantly longer in the RT/PPV group (258.2 (55.1) vs. 216.7 (42.3) seconds,p= 0.005). The RT/PPV group was also associated to a shorter time to obtain a fractional end-tidal oxygen concentration (FEtO2) of 0.90 (85.1(47.8) vs 145.3(40.8) seconds,p< 0.0001), a higher proportion of patients that reached the satisfactory FEtO2of 0.90 (21/24, 88% vs. 13/24, 54%,p= 0.024), a higher FEtO2during preoxygenation (0.91(0.05) vs. 0.89(0.01),p= 0.003) and a faster return to 97% oxygen saturation after ventilation resumption (69.8 (24.2) vs. 91.4 (39.2) seconds,p= 0.038).ConclusionIn the morbidly obese population, RT/PPV, compared to RP/ZEEP, lengthens the SNHAP, decreases the time to obtain optimal preoxygenation conditions, and allows a faster resuming of secure oxygen saturation. The former combination allows a more significant margin of time for endotracheal intubation and minimizes the risk of hypoxemia in this highly vulnerable population.Trial registrationNCT02590406, 29/10/2015.