The effect of supplemental nasal prong oxygen during standard pre-oxygenation techniques in healthy volunteers.

INTERVENTION: Randomised crossover trial The five preoxygenation techniques include: 1. “Non rebreather” mask Non‐rebreather mask involves wearing a mask over the mouth and nose, held by an elastic round the back of the head. The mask is attached to a reservoir bag which re‐fills with oxygen from a tank as the participant inhale. The oxygen flow rate is 15L/minute. 2. “Non rebreather” mask at maximum flow rate. The flow rate is unmeasured but approximately 30‐40L/min. 3. ”Non rebreather” mask at 15l/min + Nasal Oxygen 10l/min Nasal Oxygen involves wearing nasal prongs in the nose with oxygen delivered at 10L/minute 4. Bag valve / mask Bag valve /mask involves wearing a tightly held mask over the mouth and nose. The mask is attached a oxygen source at 15L/min. 5. Bag valve / mask 15l/min+ Nasal Oxygen 10l/min 100% Oxygen was used for all run at the flow rates listed above Each participant will do each of the above techniques (1‐5) in a random order. Each technique will consist of a run with 16 deep breaths over 2 minutes, followed by a washout period of 3 minutes then a run with 3 minutes tidal breathing for each technique. After each technique (that is, both 16 deep breaths and 3 minutes tidal breathing runs) there will be a 3 minute wash out period before the next technique End tidal oxygen fraction will be measure by capnography on the anaesthesia machine Results will be logged CONDITION: Preoxygenation PRIMARY OUTCOME: End tidal O2 measure by capnography SECONDARY OUTCOME: Tolerance ‐ assessed with a visual analogue scale by participant INCLUSION CRITERIA: 1. Fit and healthy 2. Age > 18 3. English speaking