As securing airway through front of neck is essential measure in cannot intubate cannot ventilate situation and thus cricothyroid membrane(CTM) localisation is crucial step.The preferred position for standard airway management and for surgical Cricothyrotomy are different.

So skin marking for cricothyroid membrane in head and neck in neutral position might not be same when head and neck is in extension position. And also during extension of head and neck the height of cricothyroid membrane might increase. So localisation of cricothyroid membrane as precautionary measure is important.

The study aims to assess the effect of change in head and neck position on ultrasonographic localisation of cricothyroid membrane.

The primary objective of the study is to investigate whether a skin mark placed directly over the center of the cricothyroid membrane (CTM), while the head and neck are in a neutral position, shifted beyond the CTM boundaries during head and neck extension. The secondary objective is  to ascertain if the distance between the upper and lower boundaries (height) of the CTM altered when the head and neck transitioned from a neutral to an extended position. Every patient will lie supine on an operating theatre trolley, with their head rested on a pillow to attain a neutral position of the head and neck.The upper and lower borders of the CTM using a linear ultrasound probe will be identified and marked.The height of membrane will be measured and centre of Cricothyroid membrane will be marked. After that  patient will be asked to extend head and neck and again same measurements will be recorded.