I feel the sands keep shifting in this Mac 3/4 debate, so here’s my final rant on the topic…
Firstly, obviously I’m not disputing that airway management is primarily about alveolar oxygen delivery (Vortex Approach anyone?) but this discussion is about how to have an optimal attempt at laryngoscopy in as few tries as possible. When talking about best attempts at intubation, it is all about “getting the tube in”.
Secondly I’m not dismissing the importance of technique – but I’m assuming the operator is going to be equivalently trained and use the appropriate technique with either the 3 or the 4 blade – so technique shouldn’t be a factor in this discussion. There’s no technique I’m aware of that can be used with the 4 but not the 3 (lifting the epiglottis directly with the laryngoscope blade if desired is usually equally possible with the 3 blade and is part of choosing a blade that’s “long enough” – see below).
Thirdly it’s fine to talk about “the right tool for the right job” but you have to be able to specify how you’re going to make this choice in a particular patient. My whole point is that if you make the judgement that the 3 is long enough (which in my experience it is 95% of the time) it is the better blade – because as well as sufficient length it will provide added strength to lift (as demonstrated in the video). Clearly I’m not disputing that the 4 is better if the 3 is too short, no competition there. We are only discussing the situation in which the Mac 3 is considered long enough (which is pretty easy to judge prospectively by measuring the distance from the lips to the thyroid cartilage). So again, inadequate length of the Mac 3 shouldn’t be a factor in this discussion.
Fourthly the point has been made that force isn’t the major factor in optimal laryngoscopy. This may be true but there’s no doubt that sometimes in a difficult intubation, an extra bit of lift may be what gets you the glimpse of the arytenoids that makes the difference. This is particularly true when there may have been more than one previous attempt at laryngsocopy. The decrement in arm strength with multiple laryngoscopies is pretty marked and is one reason that getting another operator to have a try in a difficult intubation is so useful – as once other factors have been optimised between attempts, a return to “full power” using the “new arm” can be the difference between yielding the benefit of these optimisations and getting a view or not (otherwise these optimisations may be counterbalanced by a decrease in laryngoscopy strength with successive tries and the view may not improve). Clearly force of laryngoscopy can be an issue, and for many clinicians (esp. in a pre-hospital setting) having another clinician attempt laryngoscopy when they fatigue may not be an option, so why not maximise your own ability to lift the tissues at the tip of the blade by choosing the shorter blade (where that is going to be long enough!!). I’m not talking about unnecessarily using brute force – you don’t HAVE to pull as hard as you can, of course be gentle, but the ability to invoke use of that strength if required is there with the Mac 3. You might not need that extra strength on your first attempt (but then again you might!) but making optimal use of your residual strength may be critical on your second attempt. The suggestion has been made that this strength could be provided by alternative mechanisms (2 hands or an assistant). If you want to talk about losing the nuances of good technique, surely this would be when that would happen!
Finally I agree that it’s ultimately about personal preference and what “works for you” – but I get the impression that many staff I teach have chosen the Mac 4 from the outset on the logic of having been told by their seniors that a Mac 4 blade “is a 3 & a 4 combined”, without appreciating the mechanical disadvantage the Mac 4 brings with it. You can’t talk about personal preference if you haven’t given the alternative a decent try. You can’t say the Mac 3 doesn’t work for you if you’ve only used it once or twice as clearly it will feel awkward if it’s not your usual blade. Equally many clinicians have told me they’ve always felt they’ve been able to get a better view with the Mac 3 but couldn’t explain why. Hence the challenge to do 20 intubations using the Mac 3 before deciding.
In summary: when the Mac 3 is long enough and used with the appropriate technique and the minimum force required to get a view – why wouldn’t you want that added mechanical advantage up your sleeve in case you need it? You’re losing nothing. At the end of the day it doesn’t matter which blade you choose, provided you choose it for the right reasons – because if you don’t you will be less successful at intubating. If you have used the Mac 3 repeatedly over many months/years, and found you consistently get a better view with the Mac 4, even when the Mac 3 was long enough, then absolutely you should use the Mac 4 as your primary “go to” blade. Do what works. #MakeYourFirstTryYourBestTry