All patients posted for elective surgical procedures under general anaesthesia requiring endotracheal intubation, who satisfy the inclusion criteria and give a written informed consent will be recruited to the study. In the preoperative period, pre-anaesthetic assessment will be done by the primary investigator. Height (cm), weight (kg), age (in years), body mass index (BMI) and ASA physical status will be noted for all patients. If they satisfy the inclusion criteria, patients will be instructed about the study procedure and a written informed consent will be obtained. Preoperative airway assessment will be done which will include recording the modified Mallampati classification (MMP) [ Class I -visualisation of the hard palate, soft palate, fauces, uvula and pillars; Class II- visualisation of the hard palate, soft palate, fauces, and uvula; Class III- visualisation of the hard palate, soft palate, and base of uvula; Class IV- visualisation of only the hard palate.], inter- incisor gap (distance between upper and lower incisor) in cm, thyromental distance (in cm), sternomental distance (in cm), and neck circumference (in cm) at mid neck just below the laryngeal prominence with the subject sitting and facing forward with shoulder relaxed. All measurements will be done using a standard measuring tape by the primary investigator who will not be involved in performing laryngoscopy and intubation. On the day of surgery, ultrasound measurements of the airway will be done by the primary investigator in the preoperative room, using a linear high frequency probe (8- 13Hz), with the patient lying in supine position with head and neck in neutral position. Anterior soft tissue thickness of the neck will be measured at three levels, the hyoid, thyroid hyoid membrane and anterior commissure of the vocal cord. The same measurements will then be repeated with the patient in sniffing position. In the operating room, ASA standard monitors will be attached, baseline vital parameters will be recorded, the patient will be preoxygenated and induction of anaesthesia will proceed as per standard uniform protocol. After adequate muscle relaxation(TOF=0), direct laryngoscopy will be performed by an experienced
anaesthesiologist (> 3 years) who is independent of the study and the difficulty of laryngoscopy will be scored using the modified Cormack Lehane grading with and without BURP ( backward upward rightward pressure). A note will also be made of the number of attempts at intubation, change in position or technique, and failed intubation. If there are 3 failed attempts, alternate methods of securing the airway will be pursued and the patient will no longer be included in the study. Anaesthesia will proceed as per routine protocol and the patient will be continuously monitored throughout the procedure. The measured parameters will be subjected to statistical analysis to find any correlation between them. |