Subject tolerance of higher-flow nasal cannula in Annals

Looks like the Sharp End managed to get something into Annals

http://www.annemergmed.com/home

http://www.annemergmed.com/article/S0196-0644(14)01410-3/abstract

A Randomized Trial on Subject Tolerance and the Adverse Effects Associated With Higher- vs Lower-Flow Oxygen Through a Standard Nasal Cannula

Andrew Brainard, MD, MPH, Danny Chuang, MBChB, Irene Zeng, MS, G. Luke Larkin, MD, MSPH

Study objective

Experts advocate the use of a standard nasal cannula to provide oxygen at flow rates of up to 15 L/minute during emergency intubation. However, because of concerns about potential patient discomfort, some providers avoid providing nasal cannula oxygen at flow rates greater than 6 L/minute. This trial is designed to determine the participants’ ability to tolerate 10 minutes of nasal cannula oxygen at higher flow rates.

Methods

This was a prospective, randomized, crossover trial of healthy volunteers at an emergency department in New Zealand. Participants were randomized to first receive either higher-flow (15 L/minute) or lower-flow (6 L/minute) nasal cannula oxygen for 10 minutes. After a 1-hour washout period, they received the alternate flow rate for 10 minutes. The primary outcome was the ability to tolerate 10 minutes of the nasal cannula oxygen at each flow rate. The secondary outcome was the difference in discomfort between the flow rates as measured on a 100-mm visual analog scale.

Results

All 77 of the participants (100%) were able to tolerate 10 minutes at both flow rates. Participants rated the higher-flow nasal cannula oxygen as a mean of 25 mm (SD 20 mm) more uncomfortable than the lower-flow nasal cannula oxygen. One minute after the oxygen was discontinued, the mean difference in discomfort between the flow rates was a clinically insignificant 9.8 mm (SD 17 mm) more uncomfortable. There were no adverse events.

Conclusion

Participants were able to tolerate higher-flow nasal cannula oxygen for 10 minutes without difficulty. Higher-flow nasal cannula oxygen at 15 L/minute was associated with some discomfort, but the discomfort quickly dissipated and caused no adverse events.


Editor’s Capsule Summary

What is already known on this topic
Nasal cannula during preoxygenation and after the onset of muscle relaxation prolongs safe apnea during intubation.
 

What question this study addressed
This prospective, randomized, crossover trial of 77 healthy volunteers compared the pain scores of 10 minutes of standard nasal cannula oxygenation at 6 and 15 L/minute.
 

What this study adds to our knowledge
Pain scores were somewhat higher in the high-flow group but 15 L/minute was tolerated by all participants, and pain scores obtained 1 minute after stopping oxygenation were similar.
 

How this is relevant to clinical practice
Patient discomfort should not preclude using nasal cannulas at flow rates up to 15 L/minute during the brief period of peri-intubation.