In the preoperative holding area, the primary investigator that is the anaesthesiology post graduate will examine the upper airway by transcutaneous Ultrasound and predict difficulty in laryngoscopy and intubation based on the following parameters 1.Tongue thickness at the level of hyoid bone, Anterior neck soft tissue thickness at the level of the hyoid bone measured from the skin on the short axis. 2. Tongue thickness at the level of thyrohyoid membrane Anterior neck soft tissue thickness at the level of thyrohyoid membrane 3. Transverse tracheal air shadow diameter in the subglottic area of the front of the neck 4. Soft tissue depth from the skin to the anterior part of the trachea, determined at three levels: 1) vocal cords 2) thyroid isthmus 3) suprasternal notch
5. The distance from the epiglottis to the midpoint of the distance between the vocal folds (E-VC) . 6. The depth of the pre-epiglottic space. 7. Depth of skin to epiglottis 8.Submandibular ultrasound Hyomental distance measured in neutral Hyomental distance measured in hyperextended position of the neck And their ratio . 9.Tongue volume 10.The shortest distance from the skin to the anterior commissure. 11.Tongue thickness, Thyromental distance and their ratio.
The secondary investigator that is the anaesthesiology consultant who will be blinded to the ultrasound measurements and its interpretation will intubate the patient under general anaesthesia and establish the Cormack- Lehane grading. Preoperatively he would have access to non ultrasound predictors of difficult airway. Data from ultrasound parameters and Cormack- Lehane ( CL) grading will be correlated to check for accuracy in identifying difficult airway by ultrasound predictors of difficult airway. |