Study Assessing the Position of Cricothyroid Membrane in Relation to Movement of Neck From Neutral to Extended Position

Overview

Ability to provide oxygen to patients undergoing general anaesthesia is crucial. This is traditionally provided using face mask, supraglottic airway (breathing tube above voice box) or endotracheal tube (breathing tube in wind pipe). However in some patients it may be impossible to provide oxygen through any of these above means which can be life threatening and lead to permanent brain damage/death. One of the ideal ways of managing this emergency situation is to pass a breathing tube through a membrane in the front of the neck called cricothyroid membrane with the neck in extension position where permitted. Many studies have recommended identifying the cricothyroid membrane before general anaesthesia in high risk patients but with their head in neutral position. This study will be a pilot study to check if the cricothyroid membrane remains in the same place in neutral and extended positions.

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.