End-Tidal Oxygen Saturation with Nasal Cannula During Noninvasive Positive Pressure Ventilation: A Randomized Crossover Trial.

BACKGROUND: Simultaneous use of nasal cannula (NC) with noninvasive positive pressure ventilation (NIPPV) may help streamline the transition from preoxygenation to intubation with apneic oxygenation in patients with deteriorating respiratory status, but may also compromise preoxygenation by impairing NIPPV mask seal.

OBJECTIVES: To demonstrate that end-tidal oxygen (EtO2 ) after NIPPV with NC is noninferior to that of NIPPV without NC.

METHODS: We conducted a randomized cross-over noninferiority study using healthy volunteers. All subjects underwent a 3-min trial of NIPPV with or without high-flow NC at 15 L/min of oxygen, followed by a 5-min washout period, and then a second 3-min trial of the opposite intervention. We randomized subjects to order of interventions. The primary outcome was postintervention EtO2 as measured by immediate exhalation into an oxygen analyzer after the 3-min ventilation period. We compared this outcome between the two study arms using an absolute 5% noninferiority margin.

RESULTS: We enrolled 37 subjects, each of whom underwent both interventions of NIPPV alone and NIPPV with 15 L/min NC. The paired mean difference in EtO2 between NIPPV with NC measurements vs. NC alone measurements was 0.5% (95% confidence interval -∞ to 2.7%). Analyses stratified by order of intervention yielded similar results.

CONCLUSIONS: The mean difference confidence interval did not include the noninferiority margin. Hence, NIPPV with NC seems noninferior to NIPPV alone with regard to EtO2 . These results indicate that concomitant use of NC with NIPPV may be an appropriate preoxygenation strategy in anticipation of the potential need for transition to intubation.