End-tidal Oxygen Can Reliably Predict the Arterial Partial Pressure of Oxygen Among Emergency Department Patients

Rapid Sequence Intubation (RSI) is the preferred and most commonly-used method of definitive airway management among critically ill emergency department (ED) patients requiring intubation. Adequate preoxygenation is intended to prolong the safe apnoeic period. Optimal preoxygenation for ED patient undergoing RSI is best described as a two-part process of denitrogenation of the functional residual capacity (FRC) and the formation of an oxygen reservoir within the alveoli. End-tidal O2 (EtO2) has been shown to be a reliable surrogate marker for denitrogenation. Most of the literature supporting EtO2 as an adequate maker of adequate preoxygenation has been conducted in the operating room setting. This population varies significantly from the population requiring endotracheal intubation in the ED. Our study aim was to show that the use of a gas analyzer measuring the fraction of inspired oxygen (FiO2) and EtO2 during the preoxygenation phase of ED RSI can reliably predict the minimal PaO2 at the end of the ED preoxygenation period.