This is a non-randomised observational pilot study. The results of the study will be used to determine the size of the sample required for a planned randomised controlled trial in the future. All the volunteers will be asked to lie on a trolley with the head in neutral position- Defined as alignment of external auditory meatus (outer ear canal) to the sternal angle (prominent portion of breast bone) is horizontal. A radiologist trained in ultrasound of the neck will identify the position of upper and lower border of the cricothyroid membrane using ultrasound and then mark these borders and the centre point with a black surgical marker pen. Then the volunteer will be asked to extend the neck and the same steps will be repeated using a red surgical marker pen. The distance between the two centre points will then be measured using a calliper/ measuring scale.