Correlation between neck circumference and ultrasound guided measurement of anterior neck soft tissue thickness in predicting difficult laryngoscopy in obese patients.

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.