Randomised Controlled Trial of Intubation, Comparing Pentax AWS Against Macintosh Laryngoscope.

General anaesthesia often requires that the trachea be protected by intubation. This involves placement of a cuffed endotracheal tube into the trachea, after the onset of unconsciousness and muscle relaxation. Usually this requires the anaesthetist to obtain a direct view of the patient's vocal cords via the mouth, using a laryngoscope such as the Macintosh laryngoscope. The endotracheal tube is then guided through the vocal cords into the trachea.

Difficult or failed intubation, is a potentially serious and occasionally life threatening complication. This is the unexpected inability to place the endotracheal tube in the correct place. The commonest cause is a failure to achieve an adequate view of the vocal cords at laryngoscopy.

Failed or difficult intubation significantly delays establishment of a secure airway and therefore can lead to major morbidity from hypoxia and/or aspiration of gastric contents. Other morbidity can also ensue from delay to the procedure in emergency situations or airway trauma due the various devices used or the force required to secure intubation. Whilst all anaesthetists and their assistants are trained to deal with difficult or failed intubations, disasters do occur. For example, in obstetrics, the previous Confidential Enquiry into Maternal Deaths reported five of the six deaths directly due to anaesthesia were related to intubation difficulties.

The Pentax Airway Scope AWS-S100 (Pentax AWS), Rigid Video Laryngoscope for Intubation is a new self-contained video laryngoscope with an integral colour-viewing screen mounted on the handle. A camera at the tip transmits an indirect image, which obviates the need to obtain a direct view of the vocal cords. It requires no prior set-up of equipment and is intuitive to use for anyone already competent in traditional direct laryngoscopy. Previously conducted evaluations of the scope have been presented and show that intubation can be secured within a clinically normal time span by various grades of anaesthetists in various clinical situations. Authors are currently suggesting it has a role as a back-up device for difficult intubations and for training. One has been obtained for the Foresterhill site for these purposes.

RATIONALE The simplicity of use and intuitive function of the Pentax AWS suggests it may have a wider role than as a back-up and could possibly be the first-line laryngoscope for situations where difficulty with intubation is more likely or more hazardous.

The incidence of difficult or failed intubation for an individual anaesthetist is related to their experience, decreasing as experience increases.

The purpose of this trial is to evaluate the Pentax AWS when used by relatively inexperienced anaesthetists. Inexperienced anaesthetists are those most likely to encounter difficulties and thus their practice carries the highest risk. Therefore, this is a setting in which there would be a particular benefit to patient safety in having the most effective tool for successful and timely completion of tracheal intubation.

METHODS The study will compare intubation using the Pentax AWS vs. the usual Macintosh laryngoscope in a sample of patients where 1st and 2nd year specialist trainees in anaesthesia (ST's) perform the intubation. There will be no other change in routine practice for the purposes of the trial. Specifically, the trial will recruit only from the population of patients that the ST's are routinely scheduled to intubate anyway. They will be working under the direct supervision of a consultant or senior specialist registrar (SpR), at all times.

Initially, data relating to routine intubations with the Macintosh laryngoscope will be collected. We will conduct training in the method of use of the Pentax AWS with the ST's, to a pre-determined level (see below) and collect and compare learning data, during routine clinical work with this laryngoscope. Following on from this, we will determine the effectiveness of the Pentax AWS in patients undergoing routine tracheal intubation.

4 ST's will perform the intubations within the trial. They fulfil the experience criteria required of the study, they began anaesthetic training between August 2010 and August 2011, have reached the required Royal College of Anaesthetists' level of competency in the practice of intubation and are approved to anaesthetise with indirect supervision.

Prior to commencement of recruitment into this study, it will be necessary for these ST anaesthetists to demonstrate a safe level of ability with the Pentax AWS. This is in order not to compromise safety in those patients randomized to undergo intubation with the Pentax AWS. They will be trained in the use of the Pentax AWS by the principle investigator (PI), initially using an airway training manikin and then in normal clinical practice. After gaining basic skill with the Pentax AWS, intubation with this scope will be timed. Supervised training with the Pentax AWS will continue until the ST anaesthetist is able to intubate in a clinically safe timeframe and then ST anaesthetists will be required to perform this successfully without trainer input in ten consecutive procedures. Once assessed as competent with the Pentax AWS by the PI they will be eligible to intubate patients entering the trial.