It is common during elective surgeries to face an unanticipated difficult airway despite clinical criteria on preoperative airway examination which indicate otherwise. This leads to delay in securing the airway, multiple laryngoscopic attempts, airway trauma and the need to mobilise expensive equipment on an emergent basis. This process is time consuming, interferes with the smooth flow of patient care and might contribute to increased morbidity in the patient population as well as physician stress.

Clinical examination criteria are not applicable in the emergency setting and in the critical care environment as patients are confused and uncooperative. This further limits their safe use as a means of assessing and preparing for a difficult airway.

There are several studies that have attempted to assess the effectiveness of a preoperative ultrasound screening of the airway for the assessment of difficult intubation. There have been pilot studies to compare the effectiveness of clinical assessment over the use of ultrasound examination but we lack any large scale study of Indian patients in our hospital environment moreover - most studies have been restricted to specific groups of patients. This study aims to fill this void.

Following approval by the Institutional Ethics Committee, the study is planned for completion over a period of 18 months. This study plans to include adults aged 18 years and above of either sex, undergoing elective surgery requiring general anesthesia with nasotracheal intubation. A preoperative ultrasound screening would be performed to assess for anterior neck soft tissue depth at the level of the hyoid bone and the thyrohyoid membrane. This measurement would be assessed for correlation with the Clinical assessment of the airway and the CL grading upon intubation.

It is always wise to plan for a difficult airway - although the history and the physical examination of a patient prior to surgery is thorough, preoperative anticipation of a difficult airway occurs in only 50% of the patients subsequently found to have a difficult airway (Baker 2015).

Current bedside tests have limited and inconsistent capacity to discriminate between patients with difficult and easy airways.(Vannucci and Cavallone 2016) In view of this finding it becomes imperative to search for better methodologies for the assessment and evaluation of the airway.

Why is this study necessary?

1. The one indian study I discovered utilised ONLY the Mallampati grading and the anterior neck soft tissue thickness to assess for difficult laryngoscopy. I would like to use a larger number of clinical tests to look for difficult airway - a single Mallampati test is not adequate to look at airway difficulty. In addition the study tries to identify the combined utility of clinical screening tests and the ultrasound - I aim to find out if Ultrasound can replace existing clinical tests.

2. The large Observational study from Italy (Falcetta et al, 2018) does not address the problem of applicability to the indian population. It is largely applicable to a European population. I aim to produce a study that aims to make it feasible to apply ultrasound assessment in the Indian population.