Emergency Department use of Apneic Oxygenation Versus Usual Care During Rapid Sequence Intubation: A Randomized Controlled Trial (The ENDAO Trial)

Academic Emergency Medicine 2017. Doi:10.1111/acem.13274 (epub ahead of print)

Presented by: Dr S. Young             


  • Desaturation leading to hypoxaemia may occur during rapid sequence intubation (RSI)
  • Preoxygenation is an important part of RSI n order to increase the amount of oxygen present in the functional residual capacity of the patients lungs to prolong the maintenance of acceptable oxygen saturation during the apnoeic period of endotracheal intubation
  • Apnoeic oxygenation was developed with the aim to prevent the occurrence of oxygen desaturation during the apnoea period.
  • It involves leaving the nasal cannulae in place with oxygen flowing during laryngoscopy and intubation.
  • It is being used more and more commonly in emergency and critical care departments.

Design & Setting

A randomised controlled trial based in the emergency department looking at whether apnoeic oxygenation during RSI reduces patient desaturations versus usual care.


  • 206 Emergency department patients presenting requiring emergency rapid sequence intubation with preoxygenation for any reason apart from cardiac or traumatic arrest.
  • Based in a level 1 trauma centre in New York.


  • Use of high flow oxygen via nasal cannula during the apnoeic period vs no nasal cannula.


  1. Primary: Oxygen saturations were measured by pulse oximetry during and for 2 minutes after the apnoeic period during the RSI. The lowest recorded saturations were taken and the means were compared between the two groups.
  2. Secondary: Desaturations below 90%, 80% and 1st pass success.


  • There was no difference in means of lowest recorded saturations detected between the study groups both 92%.
  • There was also no difference in secondary outcomes.


  • The application of apnoeic oxygenation did not change desaturation in the study population.
  • Its use compared with usual care did not prevent desaturation or reduce the chances of it.


  • Well designed study
  • Randomised Controlled Trial
  • Good patient selection and randomisation
  • Relevant study population
  • Good recording of data (trained uninvolved assessors)
  • 100% follow up
  • Real life setting


  • The trial was not powered highly enough to detect clinically important differences in patient outcome.
  • The primary outcome measured, mean lowest saturations, did not give a patient orientated outcome such as mortality or morbidity.
  • There were very short apnoea times and high first pass success; as such there was very little time for the patients to desaturate.


The implication is that although this is a negative study it may not have been large enough to detect the patients where apnoeic oxygenation is beneficial.

Even if there had been a statistically significant difference in lowest mean saturations it would have been difficult to read this as a clinically important patient orientated outcome. The trial looked into mortality as a secondary outcome and there was no difference but it was not highly powered enough for this.

Potential for impact

This trial adds to the evidence that there is very little to be gained in most patients with apnoeic oxygenation. It does not however prove that the technique is not useful in some patients.

The paper reviewed earlier this year (see: Journal Club 1st August) suggested that apnoeic oxygenation is a relatively simple and safe intervention with few complications which seemed to be of benefit.

What the ENDAO trial does do is offer evidence that apnoeic oxygenation is not the magic solution to maintaining saturations during RSIs in Emergency department patients. The evidence surrounding apnoeic oxygenation is still not certain and large randomised controlled trials are needed to study this further.

At present we can therefore remain justified in not using this method in our patients.