YOU CAN’T FIND THE CRICOID

So, you know how to do a cricothyrotomy. But can you find the right place to make the incision? It turns out, many times, you can’t. Especially if the patient is female and obese.

This observational study in Anesthesia and Analgesia on female patients shows that with palpation, none of the attempts to identify the cricoid membrane through the skin were successful in the obese patients lying supine in a neutral position. With the neck extended, one doc was able to identify one cricoid membrane through the fatty tissue. Luck?

And even in the non-obese patients, there were significant deviations from the level of the actual cricoid membrane in most of the attempts. The physicians in question were fairly experienced anaesthetist and gyn/obs trainees.

Depressing. It also touches on the discussion of horizontal vs vertical incision. If you can’t be sure about the level of the cricoid, you might be better off with a vertical incision? I’m not sure. But apart from that, after reading the study, I have two points to make.

Under the skin, your finger can see
Even if you can’t positively locate the criocoid membrane from the outside, you might have more luck finding it once you’re on the inside. From my own experience (n=1), I believe it should be easier to find the cricoid after the initial incision. With your finger in the incision, under the skin, and through some of the fatty tissue, it should be easy to move around in there, and much easier to palpate the laryngeal structures. Your finger can see.

Ultrasound finds the cricoid
And another positive opening: In this study, the actual position of the cricoid membrane was determined by ultrasound. It was always successful. Maybe not the best choice in an emergency situation if it’s not right there next to you, turned on and ready to go – but if you have an ultrasound machine with the patient in the OR for line placement or nerve blocks, it could be a good habit to palpate, mark the spot, then check the neck with ultrasound to see if you got the cricoid right.

Brief report: accuracy of identification of the cricothyroid membrane in female subjects using palpation: an observational study, Anesth Analg, 2012, April.

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7 Responses to YOU CAN’T FIND THE CRICOID

  1. All good points. I remember Paul Baker of ANZCA difficult-airway fame presenting some data on the (in)accuracy of cricotyhroid membrane localisation on one of his airway courses. Sobering, and makes me more likely to mark the spot with a marker and ultrasound on any anticipated difficult airway ‘just in case’. Takes under a minute and even doing on an elective list (yesterdays BMI 45 female ramped for RSI gynae op) was good practice for having to do with a trauma patient.

    My n is now up to 5 (gulp!) but agree the finger is great…otherwise its scalpel-bougie/finger-ETT each time now. The Paix/Griggs series would support this.

    So, bottomline – it can be hard to find, USS can be useful if you’ve time in advance of anticipated difficulty (but not, I reckon, when they are turning blue)…and be prepared for blood and a finger scrabble.

    • K says:

      Thanks for the input Tim.

      As for the incision. I like my incisions vertical(n=0). I thought vertical incisions resulted in less bleeding as it results in cutting less vessels?

  2. Yep, also easier to move up/down if you are off target.

    • Thomas D says:

      I’ve gotten interested in this lately, as my n=2 and several tries on pigs and cadavers, I find that you have quite a bit of leeway up/down even with a horizontal cut, as the skin on the neck is very loosely connected to the underlying structures.

      My thinking lately have therefore been to go with a horizontal cut (easier in my simple mind to keep the knife in the same direction for both the skin/tissue cut and CTM cut). Then, if I’m really off and can’t get to the CTM, to expand the horizontal cut with a vertical one (to get a cross-shaped cut). Any thoughts on that?

      [CTM=cricothyroid membrane]

  3. Simon b says:

    Hi, as a junior registrar in Ed, often in charge on nights, this situation is something that puts the shivers through me. I’ve read so much about emergency crics and have simmed in my head, I know what I want to do and the processes I will undertake if the moment arises. I know there will be blood. The question I have may sound silly, but here we go. What does the cricothyroid membrane feel like? I’m on the lookout for animal specimens, what type of animal is best representative? I do hope this situation never arises but you do never know what will roll in the door. Thanks

    • Thomas D says:

      Thanks for your comment! We all have those shivers, and the best way to battle them is to be prepared. I believe that when you know what to do, that lessens the fear substantially.

      For animals models, I’ve only practiced on pigs, and their supposed to be good representatives. You can probably get specimens at a butcher.

      About your question. Seriously, there are no silly questions. Often, the ‘silly’ questions teaches both the learner and teacher. As I outlined in my Code Brown: Emergency Surgical Airway Revisited (http://www.scancrit.com/2014/03/01/code-brown-emergency-surgical-airway-revisited/), one of the problems with my fist cric was that I hadn’t asked all the questions because I didn’t know what to ask. And the teachers can often forget to teach everything, as for experts some things are taken for granted along the way, but for the novice these things stay in the dark if not explained explicitly.

      It’s not so much about the cricothyroid membrane, as it is about the larynx and cricoid cartilages. Knowing the larynx and cricoid structures is key, inside the incision, your finger will ‘paint a picture’ that fits with your image of these structures.

      So, I don’t think I’ve ever ‘felt’ the membrane, but I feel for the larynx and cricoid structures, and know the membrane is in-between them. And if your finger meets resistance, it’s still there. If your finger goes through, or you can feel a hole, you’ve punctured the membrane.

      I hope that answered your question. It certainly made me change my thinking/teaching slightly, when explaining the cric from now on – thanks!

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