Assessment of Preoxygenation Strategies in the Prehospital Environment

Prospective randomised interventional study.

Healthy volunteers will be positioned supine and undergo preoxygenation by tidal volume breathing for 3 minutes using each technique in turn. The sequence of techniques for each volunteer will be randomised in advance. Investigators will be instructed to ensure a good mask seal throughout the testing period. At the end of a 3 minute preoxygenation period, after a brief breath hold, the volunteer will exhale into reservoir tubing, allowing the fractional expired oxygen concentration (FeO2) to be determined (primary outcome) using a calibrated gas analyser.

The techniques being assessed have been chosen from methods of preoxygenation commonly available to clinicians in the prehospital environment:

1. Continuous Positive Airway Pressure mode with fractional inspired oxygen concentration (FiO2) 100% using a portable ventilator.
2. Bag-valve-mask device (BVM) with 15 l/min oxygen flow.
3. Non-rebreather mask (NRM) device with 15 l/min oxygen flow.

Volunteers will also be asked to indicate the subjective ease of breathing for each technique (secondary outcome) using a visual analogue scale (VAS).