Airway examination is the most important component of anaesthesiologist’s pre- operative assessment and is a prerequisite for successful airway management. Repeated attempts to perform laryngoscopy or intubation can lead to lack of adequate oxygen delivery to brain and other vital organs, which can threaten patient life1 and it is the most important cause of anaesthesia related morbidity and mortality.  

The most important factor in successful management of the difficult airway is thorough evaluation and identification of any possible problem. Various clinical parameters determining difficult airway are body mass index, atlanto-occipital extension, temporomandibular joint mobility, hyomental distance, neck mobility, mouth opening and the anatomical location of larynx etc.

The incidence of difficult laryngoscopy and tracheal intubation still ranges between 1.5%-13%.The inability to predict difficult airways is probably due to high inter observer variability and low predictability of commonly used airway assessment screening tests like modified Mallampati test (MMT), thyromental distance (TMD), hyomental distance (HMD) etc.

Hyomental distance is calculated in neutral head position (HMDn) and in extreme of head extension (HMDe). It is taken from anterior most bony landmark palpable on mentum to skin just above the hyoid bone. Hyomental distance ratio (HMDR) is taken as ratio of hyomentaldistance in extreme of head extension (HMDe) to hyomental distance in neutral head position (HMDn). Hyomental distance tell us about the submandibular space and hyomental distance ratio gives us an idea about the capacity to 

extent atlanto-occipital joint, which is required to align oro-pharyngeal and laryngeal axis during direct laryngoscopy.

Tongue thickness (TT)assessed by ultrasound gives us an internal characteristics of patients upper airway and helps us in predicting difficult laryngoscopy

Condylar mobility assessed by ultrasound tells about the adequate mouth opening of the patient which is required for direct laryngoscopy

However ,studies are still insufficient to say that combined ultrasound measurement of hyomental distance ratio,tongue thickness and condylar mobility are the best predictors for difficult laryngoscopy

Ultrasound (USG) being a non- irradiating, non-invasive and simple to use technique is being seen as the best modality for airway evaluation in future. 

Thus ,we planned a study for the prediction of difficult laryngoscopy by ultrasound measurement of combination of airway parameters .