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.
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.
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?