Skip to 0 minutes and 6 seconds Assessing the anatomy of the neck, there are two bedside techniques that you can use. You can use manual palpation, and you can use the ultrasound. So I’m just going to run through how you would palpate the neck to find the cricothyroid membrane. You use the laryngeal handshake. You put your hand on the patient’s neck, and the larynx should be sitting underneath your hand. And then, you should be able to palpate structures in the neck. You can feel the trachea is central and the tracheal rings through the skin. The cricoid cartilage and the thyroid cartilage and between them is the cricothyroid membrane.
Skip to 0 minutes and 46 seconds First using the ultrasound, you would position the patient in the position that you would want to do a surgical cricothyroidotomy. So you have a pillow behind the shoulders and the neck fully extended. You ask the patient to lift their chin up to the ceiling, thank you. To do the ultrasound, we keep the patient in the same position. This is going to be a little bit cold on your neck. You put some jelly on the patient’s neck. I always start with the probe and horizontal position. So start up underneath the chin, and you’re looking up at the tongue base, so you can see the tongue there. As you come down, the thyroid cartilage.
Skip to 1 minute and 28 seconds You can identify the thyroid cartilage because it’s a nice triangular shaped cartilage. And within the thyroid cartilage, you can see the false cords and the true cords. So if you ask the patients who speak at that point– so can you count to three? One, two, three. You can just see the vocal cords there, moving, coming together as she speaks. Then, as you’ve come further down the neck, you’ll see a very bright echoic structure, and that is the cricothyroid membrane.
Skip to 2 minutes and 14 seconds So that’s the cricothyroid membrane, bright white shadow just below the larynx. And it’s the air interface that you’ll see in the white line. Then as you go further down, you can see a large, round cartilage coming into view as a black shadow there. And that’s the cricoid cartilage. And as you go below the cricoid cartilage, the cartilage, as you can see, becomes smaller and closer together. So you can see that that’s the trachea. And either side, you’ll now see the thyroid gland coming into place. The other way you can find the anatomy is to put the probe in a vertical direction, and then you would start low down in the neck. What you’re looking for is the pearl necklace appearance.
Skip to 3 minutes and 11 seconds You need to be directly over the front of the trachea to get the best image, and what we’ll see is little black dots, which are meant to be the pearls of the pearl necklace, and a white line. And that white line is that air-tissue interface on the anterior wall of the trachea. As you come higher up, you’ll be able to see a bigger cartilage, which is the cricoid cartilage. As you go further up, you can see the cricothyroid membrane and the thyroid cartilage.
Point of Care Ultrasonography (POCUS) has become widely available in recent years, and anaesthetists have become increasingly familiar with its use. Over the next two steps we are going to explore the role of US in airway assessment: firstly with a video demonstration of Airway Ultrasound with Dr Catriona Ferguson, Consultant Anaesthetist at the Royal National Throat, Nose and Ear Hospital, part of University College London Hospitals.
You may want to review some anatomy knowledge presented in Week 1.
Airway ultrasound helps to locate the cricothyroid membrane and trachea, the location of the thyroid gland and overlying blood vessels.
Ultrasound can also be helpful to perform nerve blocks for awake intubation, and facilitate localisation of tracheal rings for tracheostomy. Ultrasonography is an excellent diagnostic tool in intraoperative and emergency diagnosis of pneumothorax. You can find more information on the topic in the resources below.
In the next step we will learn about gastric ultrasound. Both techniques can add useful information to devise an airway management strategy.
Have you got access to ultrasound scanning in your practice? Is it used for airway assessment?