Ultrasound or landmark for identification of the cricothyroid membrane.

A small number of patients who are brought to the emergency department need a general anaesthetic. This lets us help them by keeping their airway open and breathing for them, and allows us to perform tests and provide further treatment. In very rare cases, the breathing tube cannot be passed through the mouth. This is a life threatening emergency, and an emergency procedure called a cricothyroidotomy then has to be performed. This involves making a cut in the front of the neck, directly into the windpipe, so that the breathing tube can be put directly into the airway. This is similar to a tracheostomy. The area of the neck where the cut is made is called the cricothyroid membrane, and it is usually identified by feeling the front of the neck with a finger. Recently, it has become clear that ultrasound scans can be used to locate the membrane, but it is not clear if this is more or less accurate than locating it by feel, and whether using an ultrasound takes more or less time. The study aims to compare two groups of patients. One group will have their cricothyroid membrane identified by touch, and the other group will have it identified by ultrasound. The participants in the study, will be randomly assigned (like tossing a coin) into one of these two groups. Immediately before having a CT scan, a doctor will try and locate the patients’ cricothyroid membrane using either touch or ultrasound (depending on the group they are randomised to), and then place a marker (a small metal cross) on the neck, which will be held in place with adhesive tape. After the CT scan, an x-ray specialist will then be able to see whether or not the marker has been placed accurately. We will then compare whether one method is more accurate than the other, as well as how long it took to place the marker. With the exception of (1) the attempt of cricothyroid membrane localisation, via ultrasound or landmark palpation and (2) placing a marker on their neck, the rest of the participants’ care will be carried out as normal.