Critical Care, Clinical, Critical Care Alert

Critical Care ALERT! Apneic Oxygenation in RSI

A 57-year-old male presents to the emergency department for shortness of breath. He became more hypoxic despite applying NIPPV. You decided to proceed with rapid sequence intubation. Do you routinely use apneic oxygenation?

Caputo N, Azan B, Domingues R, et al. Emergency Department Use of Apneic Oxygenation Versus Usual Care During Rapid Sequence Intubation: A Randomized Controlled Trial (The ENDAO Trial). Acad Emerg Med. 2017;24(11):1387-1394.

Apneic oxygenation (AO) was developed to prevent oxygen desaturation during the apnea period during rapid sequence intubation. The purpose of the study was to determine if the application of AO increases the average lowest oxygen saturation during RSI when compared to the usual care (UC) in the emergency setting.

Using the concept of “aventilatory mass flow,” apneic oxygenation has been theorized to be effective in preventing the occurrence of desaturation during the apneic period. Apneic oxygenation is performed by delivering various rates of oxygen flow through the nasopharynx during the apneic period of laryngoscopy. Though methods using specialized high flow cannula (eg, THRIVE or high flow systems capable of up to 70 liters per minute of flow) have been studied, recent work has explored the utility of standard nasal cannula for AO at “flush flow” rates, which achieve  ³ 15 LPM. Though variation exists, many emergency department oxygen valves are capable of delivering flow rates exceeding the 15 LPM labeled on the outlet by turning the valve to maximal capacity past the 15 LPM gradation.

The primary outcome of this investigation was to determine if the use of AO via flush flow rates increases the average lowest oxygen saturation during RSI when compared to usual care. Caputo and colleagues also sought to determine if the use of AO increased first pass success rates and decreased the rates of desaturation, time to desaturation, and mortality.

Randomized controlled trial, single-center urban, academic, Level I trauma center in New York City.
Inclusion criteria: Any adult patient (age >18 years old) requiring intubation
Exclusion criteria: Non-preoxygenated patient to the standard RSI protocol of a goal of 3 minutes with 100% FiO2 by means of BVM, BPAP, and/or NRB, a cardiac/traumatic arrest, or intubated without an apneic period.

Study Protocol
All adult patients undergoing endotracheal intubation the ED were randomized to receive supplemental O2 via NC and NC EtCO2 both at flush flow rates  ‰¥15 LPM during laryngoscopy (AO group) or no supplemental oxygen (UC group).

Data collection during intubation was performed by independent observers who were not directly involved in the performance of the procedure.

Apnea time was defined as time from first look (defined as insertion of the laryngoscope blade into the patient's mouth) to confirmation of endotracheal tube placement by waveform capnography (EtCO2). Intubation attempts were counted for each patient.

Measured Outcomes
Primary: The average lowest oxygen saturation during apneic period or the following 2 minutes after intubation
Secondary: First pass success, desaturation below SpO2 90%, and desaturation below SpO2 80%.

Key Results
Enrollment of 200 patients (100 in each category) provided an 80% statistical power to detect a moderate difference between groups for the primary outcome.
Enrolled n=209; Included n=200
More than 70% of patients were successfully intubated by 60 seconds, 80% by 80 seconds, 90% by 100 seconds, and 100% by 195 seconds.
Patients with prolonged apnea times (>130 secs) did not desaturate to an average SpO2 <90% (n=22). There was no difference in O2 saturation between the groups at any of the time intervals during the periprocedural period; also, there was no difference in rates of desaturation below 90% or 80% between groups.

This study demonstrated that in patients who are properly preoxygenated during RSI in the ED, the application of apneic oxygenation via flush flow rates on standard nasal cannula did not show any differences in lowest mean SpO2 nor in rates of moderate or severe desaturation. It is important to consider the study was performed at a single-center, academic ED with a residency training program. Furthermore, the intubations were performed promptly and the results may not be generalizable across all populations.