Optimal Head and Neck Position for Videolaryngoscopy

The introduction of videolaryngoscopy constituted a revolution in airway management since it could provide better laryngeal exposure (indirect) in situations of difficult or impossible visualization by direct laryngoscopy. The use of Videolaryngoscopes, however, does not always guarantee adequate exposure or end up always in successful tracheal intubation. Failed tracheal intubation with videolaryngoscopy has been reported. We hypothesized that may be the failure was due to omitting some preparatory steps, including optimal head positioning, leading to a less than expected exposure and/or difficult or impossible intubation. There are no recommendations currently from the scientific organizations regarding the optimal head position when using a GlideScope and it is unknown currently whether head position can affect visualization or tracheal intubation attempts when using this device.

* Multicentric,randomized, prospective and controlled study.
* After Institutional Review Board approval, signed written informed consents will be obtained from 165 adult patients with American Society of Anesthesiologists physical status 1-3 who are scheduled for elective surgery requiring endotracheal intubation.
* The following parameters will assessed and documented during the preoperative airway evaluation: BMI, mouth opening, thyromental distance, range of neck movement, and modified Mallampati classification. An 8cm non-compressible pillow.
* Patients will be randomized following coin toss into two groups depending on intubation position; Group Sniffing position(S) for obverse side and group flat position(F) for reverse side
* After premedication, American Society of Anesthesiologists' standard monitors will be applied, and preoxygenation for 3 to 5 minutes will be performed. After anesthesia induction and complete muscle relaxation as evidenced by loss of all evoked adductor pollicis responses to train of four stimulation of the ulnar nerve:
* Group sniffing (S): investigator will start by performing first videolaryngoscopy to find best view in flat position then the anesthesiologist will remove the Glidescope and the patient will be positioned in sniffing position using the pillow and another videolaryngoscopy will be attempted in sniffing position to find best view in this position and the patient will be intubated in this position.
* Group flat (F): same procedure will be done but starting from sniffing position and the patient will be intubated in flat position.
* The laryngoscopist will be asked not to use external laryngeal manipulation and to use the same lifting force throughout the study period. If these maneuvers deemed necessary for tracheal intubation (no visualization of vocal cords from full inflation to full deflation or the reverse, the laryngoscopist will be asked grade the view before applying the maneuver then use the required maneuver and record which intervention was needed and utilized.
* The estimated time to review theses different head elevation degrees is around 45 seconds.
* After preoxygenation technique we have a margin of 6 to 8 minutes of apnea without significant desaturation. Investigator will exclude also patients with high risk of desaturation (obesity and initial low saturation).
* The indirect laryngoscopic views will be graded using the same grading method used for direct laryngoscopy i.e. modified Cormack and Lehane. POGO score (percent of glottis opening viewed) will be also used to subcategorize subjects whose views lie between grade 1 and 3 C\&L.

Analysis of the recorded videolaryngoscopic attempts will be performed later by a blinded researcher who was not involved with airway management.

Eligibility Criteria:
Inclusion Criteria:

* Adult patients with American Society of Anesthesiologists physical status 1-3 who are scheduled for elective surgery requiring endotracheal intubation.

Exclusion Criteria:

* history of difficult intubation, poor dentition, gastroesophageal reflux disease ,initial low oxygen saturation, severe/morbid obesity (body mass index \[BMI\] greater than 35 kg/m2),neck deformities, atlano-axial subluxation or at risk of aspiration.