Preoxygenation is important to prevent oxygen desaturation during emergency airway management. The purpose of this study is to describe the use of end tidal oxygen (eto₂) during rapid sequence intubation in the emergency department.

This study was carried out in 2 academic centers in Sydney, Australia, and New York City. We included patients undergoing rapid sequence intubation in the emergency department. A standard gas analyzer was used to measure eto₂. Preoxygenation methods included nonrebreather mask and bag-valve-mask ventilation. We measured eto₂ before preoxygenation and at administration of rapid sequence intubation medications. We also characterized peri-intubation SpO₂, identifying instances of SpO₂ less than 90%.

We included 100 patients during a 6-month period. Median eto₂ level before and after preoxygenation was 53% (interquartile range [IQR] 43% to 65%) and 78% (IQR 64% to 86%), respectively. One fourth of patients achieved an eto₂ level greater than 85%. Median eto₂ level achieved varied with preoxygenation method, ranging from 80% (IQR 60% to 87%) for the nonrebreather mask group to 77% (IQR 65% to 86%) for the bag-valve-mask group. The method with the highest median eto₂ level was nonrebreather mask at flush rate (86%; IQR 80% to 90%) and the lowest median eto₂ level was nonrebreather mask at 15 L/min (57%; IQR 53% to 60%). Eighteen patients (18%) experienced oxygen desaturation (SpO₂ <90%); of these, 14 (78%) did not reach an eto₂ level greater than 85% at induction.

ETO₂ varied with different preoxygenation techniques employed in the emergency department. Most patients undergoing rapid sequence intubation did not achieve maximal preoxygenation. Measuring ETO₂ in the emergency department may be a valuable adjunct for optimizing preoxygenation during emergency airway management.