Comparison of Glottic Views and Intubation Times in the Supine and 25 Degree Back-up Positions

Completed

Brief Summary: Our hypothesis is that the view of the glottis may be improved by putting all patients requiring intubation in the ramped or back up position while maintaining the classic sniffing position.

Detailed Description: The sniffing position has traditionally been considered the optimal head position for direct laryngoscopy and is the usual patient position preferred by most anaesthetists. In theory, neck flexion aligns the pharyngeal and laryngeal axes, and head extension at the atlanto-occipital joint aligns the oral axis with these two axes allowing the line of sight to fall on the glottis. It is recognized as the starting head position for direct laryngoscopy because it provides the best chance of adequate exposure.

However the sniffing position does not guarantee adequate exposure in all patients because many other anatomical factors control the final degree of visualization.

To achieve a proper sniffing position in obese patients, the "ramped" (or the back-up) position has been used as this produces better neck flexion and head extension in these patients when compared to the horizontal supine position. Also the forces required to elevate and move the tongue and other tissues out of the line of sight are less when the patients are ramped.

Our hypothesis is that the view of the glottis may be improved by putting all (ie not only obese) patients requiring intubation in the ramped or back up position while maintaining the classic sniffing position.

Recruitment & Eligibility

Inclusion Criteria

Adult surgical patients who required intubation as part of their routine anaesthesia

Exclusion Criteria

Patients less than 18 years old,
Patients recognised to have difficult airways where an alternative method of intubation (e.g. fibre optic) was the method of choice,
Patients undergoing emergency surgery where patient positioning and data collection might cause delay (e.g. exsanguinating patients) or where the supine position is not optimal (e.g. brisk bleeding into the upper airway),
Patients requiring rapid sequence induction of anaesthesia

Arm && Interventions

Group	Intervention	Description
Back-up	25 degree back-up position	A subsequent group of similar the patients who had their anaesthesia induced and tracheas intubated in a 25 degree back-up position achieved by flexion of the operating table at the hips

Primary Outcome Measures

Name	Time	Method
The Best Glottic View Obtained During Laryngoscopy	The view of the glottis was measured once while the patient was being intubated	The best glottic view obtained during laryngoscopy was assessed using the Cormack and Lehane classification by the anaesthetist performing the laryngoscopy. The Cormack and Lehane classifies glottic views as follows: Grade 1: Most of the glottis is visible, Grade 2: At best almost half of the glottis is seen, at worst only the posterior tip of the arytenoids is seen., Grade 3: Only the epiglottis is visible, Grade 4: No laryngeal structures are visible.

Secondary Outcome Measures

Name	Time	Method
The Number of Attempts at Both Laryngoscopy and Tracheal Intubation	Once at intubation	The number of attempts at both laryngoscopy and tracheal intubation were recorded
The Use of Ancillary Equipment	Once at intubation	The use of ancillary equipment (e.g. bougie, alternative laryngoscope blades) and manoeuvres (e.g. laryngeal manipulation) were recorded but applied at the intubating anaesthetist's discretion
The Time Between the Beginning of Laryngoscopy and Detection of Carbon Dioxide on the End-tidal Carbon Dioxide Monitor	Once at intubation	The time between the beginning of laryngoscopy and detection of carbon dioxide on the end-tidal carbon dioxide monitor after the successful placement of the tracheal tube was recorded