Airway oxygen concentration during administration of oxygen from the inside of the cheek under general anaesthesia

Aims and Justification The induction of anaesthesia can be associated with a drop in oxygen saturation particularly when there is difficulty in intubation (the placement of a flexible plastic tube into the trachea (windpipe) to maintain an open airway). We have recently published a study which showed that buccal (attached to the inside of the cheek) oxygen administration was highly effective at prolonging the time to oxygen desaturation in obese patients, at induction of anaesthesia. Nevertheless, a third of patients desaturated earlier than expected. This may have been due to the development of pulmonary shunt (collapse of the small airways) or a failure of the device to maintain a high oxygen concentration at the open glottis (start of the windpipe). The device may also be limited by accumulation of carbon dioxide during breaks in breathing (apnoea), and the degree of positive pressure generation at the glottis. This follow up study will repeat the methodology of the original project, whilst assessing glottic oxygen concentration and pressure, as well as carbon dioxide accumulation. The objective is to ascertain the reliability of this technique at maintaining glottic oxygen concentration >0.7 over 10 min apnoea. This will help us to further evaluate and refine this technique for oxygenation during apnoea. Project Design and Participant Groups This will be an open label, randomised, controlled trial in healthy, non-obese patients due for elective surgery. Methods The protocol is based on our previous study with two study groups: (a) 10 l/min oxygen via a buccal RAE tube attached to the inside of the cheek as the intervention group, compared to: (b) Standard care. Measurements of glottic oxygen concentration (FO2), glottic airway pressure and transcutaneous carbon dioxide (CO2) concentration will be taken during 10 min of apnoea from induction of anaesthesia. The primary outcome will be the maintenance of glottic oxygen concentration >0.7 after 10 min apnoea. We hypothesise that >80% patients will maintain a glottic FO2> 0.7 at 10 min apnoea using buccal oxygen in comparison to the <10% of control patients. Our secondary aim is to find out the pressure at the glottis and rate of rise of CO2 during this technique. This secondary information will delineate the possible length of its clinical use and further evaluate this technique.