The Geniohyoid Muscle in Critical Illness

Many patients lose muscle due to being unwell in an intensive care unit. This muscle loss can lead to weakness of the arms and legs when they leave the unit, and when they go home. For many years investigators have measured the size of these arm and leg muscles using an ultrasound machine, to take a picture of the muscles.

It is also known that patients who are on a ventilator (or "breathing machine") often have problems swallowing when the breathing tube is removed from their mouth. This may be because the muscles of swallowing may also shrink. One of these muscles sits under the jaw and can be measured with ultrasound - the method has been shown to be accurate and reliable in awake volunteers, but these volunteers are usually sat upright in a chair with their mouth closed.

Before it can be assed whether these muscles get smaller, it is needed to assess whether the chosen method is suitable in patients on a ventilator; these patients are lying in bed, and their mouths are open slightly due to the breathing tube.

Proposed Method

This investigation will measure the size of a muscle under the jaw (called the geniohyoid muscle) in patients who are sedated and have a breathing tube in their mouth connected to a ventilator.

Using a normal hospital ultrasound machine, one researcher will place the ultrasound probe under the patient's jaw. When the researcher is happy the probe is in the right place, they will take a picture of the muscle and measure its size and thickness. After a short break, the researcher will repeat this process. After a second short break, another researcher who did not watch the first researcher will also place the probe under the jaw and take a picture of the muscle.

These measurements can be used to to answer the following questions:

1. How many patients scanned produced images that could be measured? 2. How consistent are the measurements if one person measures the same muscle twice? 3. If two people measure the same muscle, do their measurements agree with each other?

The patients will be under sedation when they take part in the study. Because of this, they cannot consent to take part in the study. The patient's next of kin or carer would advise on whether the patient would want to take part. When the patient is awake and has the breathing tube removed, the research team would ask them to sign a consent form to use their data.