Pre-operative USG Based Measurement of Airway Parameters For Predicting Difficult Airway- Cross Sectional Study

The aim of my study is

A. To Ultrasonographic assessment of anterior neck preoperatively based on 2 parameters

The 2 parameters chosen will be –

1. Thickness of anterior neck soft tissue in transverse view at level of hyoid bone - Minimal distance from hyoid bone to the skin (DSHB)

2. Thickness of anterior neck soft tissue in transverse view at level of thyrohyoid membrane –Distance from skin to epiglottis midway between hyoid bone and thyroid cartilage (DSEM)

B. To find out if the above two USG parameters can predict difficult airway in adults by correlating with Cormack and Lehane grading.

A Cross sectional study will be conducted in the department of anaesthesiology at Navodaya medical college hospital and research centre in Raichur district of Karnataka from March 2024 to September 2025. As  approval from institutional ethical committee was obtained written and informed consent will be taken from the patients coming for surgery under general anesthesia are satisfying the inclusion criteria.

Patient detailed history taking, physical examination and necessary investigations like complete blood count, blood urea, serum creatinine, chest x ray, ECG, HIV, HBsAg etc.

All patients will undergo pre anaesthetic evaluation, Assessment of airway using USG was conducted preoperatively, Procedure was explained. Written and informed consent was obtained. The patient was made to lie down in supine position with head in neutral position, chin lift, looking straight with mouth closed. Ultrasound machine with linear frequency probe 3-5 MHz frequency. The linear frequency probe was placed in submandibular area in midline. The thickness of anterior soft tissue (transverse view) was obtained at 2 levels –DSHB and DSEM

Tab Alprazolam 0.5mg and Cap Pantoprazole 40mg are given orally at night on the day before surgery. All the patients are kept nil per oral as per standard guidelines.

Preoperatively before intubation Modified Mallampatti Grading and ultrasound parameters will be recorded

The 2 ultrasound  parameters chosen will be –

1. Thickness of anterior neck soft tissue in transverse view at level of hyoid bone - Minimal distance from hyoid bone to the skin (DSHB)

2. Thickness of anterior neck soft tissue in transverse view at level of thyrohyoid membrane –Distance from skin to epiglottis midway between hyoid bone and thyroid cartilage (DSEM)

·DSEM >2.03cm -predicted to be difficult airway

·DSEM <2.03cm - predicted to be easy airway

·DSHB >0.66cm -predicted to be difficult airway

·DSHB <0.66cm -predicted to be easy airway

During intubation Cormeck Lehane grading will be noted

On arrival in the operating room IV line was secured and base line parameters was monitored, patient was pre-medicated with Injection Glycopyrrolate 0.004mg/kg and Injection Fentanyl 2mcg/kg, pre-oxygenated for 3 minutes with 100% oxygen. Induction was done with Injection Propofol 2mg/kg and neuromuscular blockade was achieved with Injection Succinyl choline 2mg/kg IV. Direct laryngoscopy was done by anaesthesiologist using an appropriate size curved Macintosh blade and Cormack Lehane grade noted. The intubating anaesthesiologist of not less than 3 years of experience, was not involved in the preoperative sonographic and clinical airway assessment .CL grade I and II was considered to be easy laryngoscopy. After laryngoscopy, patient was intubated with appropriate sized endotracheal tube and allowed to start with surgery and patient was monitored throughout the surgery.