Assessing the Potential Use of Optiflow as a Preoxygenation Method Prior to Anaesthesia.

The Optiflow device is used to deliver high flow humidified oxygen/air via nasal cannulae to patients who have respiratory problems. More recently it has been used in patients having surgery on their larynx who are intentionally paralysed under anaesthesia where the surgeon does not want any tubes in the airway. This makes access for surgery easier/possible. Perhaps surprisingly, these patients can be left apnoeic for 30 minutes without falls in blood oxygen levels. The lungs are oxygenated despite there being no in and out breathing/ventilation.

We propose that applying Optiflow at the start of an emergency anaesthetic may be beneficial when an anaesthetist finds that tracheal intubation is impossible - a "failed intubation" scenario. Optiflow might maintain oxygenation during further attempts at intubation or until more skilled anaesthetists arrive.

Another alternative technique presently in common use is for the patient to breathe 100% oxygen via a facemask and conventional anaesthetic circuit for 3 minutes before anaesthesia starts (preoxygenation). This fills the functional residual capacity of the lungs to about 90% oxygen giving an oxygen reserve when the breathing stops until the anaesthetist breathes for them after intubating the trachea. This can result in the maintenance of normal blood oxygen saturation for several minutes longer than would be the case if the lungs had only been exposed to air before anaesthesia.

The research question that we ask is whether we can just use Optiflow instead of the conventional mask/circuit to preoxygenate patients to a similar extent and as quickly as using a facemask so that, in emergency surgery, Optiflow could be used to preoxygenate and then already be in place in case there is a failed intubation. This would enable Optiflow to be used for both purposes seamlessly without the need to switch between the two methods of oxygenation.

Research to date has not yet identified how long Optiflow needs to be in place before anaesthesia for it to be able to produce adequate preoxygenation of the lungs before the patient stops breathing. The 3 minute timing for preoxygenation is important in emergency cases e.g. when there is an emergency caesarean section to be done and every minute before the baby is delivered matters. If it were not possible to preoxygenate a patient's lungs within 3 minutes using Optiflow we would suggest that it is inappropriate to replace conventional mask pre-oxygenation and that its value in emergency anaesthesia might be reduced (although it may still have potential for less urgent anaesthesia when it could be applied for a longer duration before anaesthesia).