There is a smart anesthesiologist out there called Nicholas Chrimes. He along with his mate Peter Fritz invented the Vortex Approach to Airway Management. He also runs a blog called Clinical CrEd.
He did a post advocating the Mapleson B Circuit as the Ultimate Preox Device
What is the Mapleson B? The Mapleson circuits were used for anesthetics in the good old days. At least in the US, we have move to bigger, and arguably better designs for our operative patients. Many would have thought this device would have been consigned to the trash heap, but seemingly not.
My Recommended Approaches
I recommend two approaches to preox: standard and shunt physiology strategies. I outlines these strategies in the paper Rich Levitan and I wrote.
Standard: NRB @ >=15 lpm and NC >= 15 lpm for 3 minutes (or NRB alone at flush rate (>50 lpm))
Shunt Physio: Choose 1
- BVM with PEEP Valve & NC @ 10-15 lpm
- NIPPV Ventilator with NIPPV Mask or BVM Mask & NC @ 10-15 lpm
Nick makes a number of arguments as to the superiority of the Mapleson circuit over these standard techniques. His points are excellent, but I disagree with pretty much all of them–I think it becomes a question of perspective.
Automatic Checking
Yes, using the same device for reox and preox makes sure the reox device is there and hooked up, but this for me is an inadequate argument to dispense with NRB/NC set-up.
Multiple BVM Masks
We don't have these readily available in any ED or ICU I've worked in. We have neonate, peds, and adult. Our masks also are not inflatable.
PEEP
PEEP is good, Mapleson may or may not be a good way to provide this for the reasons I've mentioned in the wee, but a BVM with a PEEP valve or a vent are at least as good. Plus with the Mapleson circuits, the PEEP is not quantified [https://www.sciencedirect.com/science/article/pii/S0964339721001750]
ApOx
Mapleson may provide this better than BVM, but not as well as a NC, which should be on during any intubation.
ETCO2
No advantage of Mapleson
Low resistance
Maybe this matters, as soon as you put on the PEEP, I can't imagine this difference persisting
Room Air Entrainment
Release your seal for even one breath and you have blown denitrogenation. Always, always use a strapped system if possible=NRB/NC, NIV mask, or BVM mask with OR straps.
Troubleshooting Leaks
This is the real area in which Nick and I differ. Nick makes the point that a good seal in preox guarantees a good seal in reox–this may be true, but it is unimportant. What I care about is does a bad, one-handed seal in preox mean I won't be able to reox with the BVM–this is entirely untrue. If I did to an awake patient what I will do to them when asleep and desaturating, they would, quite rightfully, punch me in the face.
Anesthesiologists should use Mapleson B/C; ED/ICU should only use BVM +/- PEEP Valve with two hands and oral airway and a rocking triple maneuver (that no pt should experience if they are conscious) otherwise they should be NIV mask with straps or (BVM mask with straps).
This is the same reason I tell my residents to just train with Macintosh blades.
Primary and secondary leaks are the main thrust of Nick's love for the old-timey circuits. But all of us have appreciated this easily by squeezing the bag-valve-mask: Easy-squeezy or Hard Squeezy
ETCO2 with a monitor you can see
Is he holding or squeezing?
I can feel compliance with a BVM if I squeezed it, but I don't unless the pt needs it during reox. But are they squeezing the Mapleson? If they are, they may be doing damage. This study (Anesthesiology 2014;120:326) talks about the myths of Gentle Facemask Ventilation:
>15 cmH20 may be entraining gas into the stomach via the LES (in some patients, even 10 cmH20 may be a problem)
UES will withstand at least 20 cmH20 until NMB at which point again 15 seems to be the number (The latter is why we don't bag during apnea unless we have to)
Two hands ALWAYS on the mask
Recently, I spent 2 weeks intubating 10-15 patients per day. One hand mask skills got better and better–all for naught.
Train how you want to Fight
Hands free
BVM with a PEEP valve solves equipment issues entirely
ventilator or oxylator
Better BVMS
Lower possible Vt and restriction of Inspiratory Flow Time (Maybe a peds bag is the answer–thanks, Peter. Anaesthesia. 2011 Jul;66(7):563-7 and Resuscitation 1999;43(1):31) and Vt of 500 seems the way to go (Crit Care Med. 1998 Feb;26(2):364-8.)
or Use Ventilator or Use an Oxylator
Now on to the wee…
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Professor
Nassau University Medical Center
No conflicts of interest (coi).
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thanks for doing this Scott. saves me a lot of arguing with the Chrimestar
somehow I doubt it will save you : )
Scott your plan has worked! I don’t have time for my usual manifesto – but you’ll pay for it with a protracted verbal rant at smaac! As you know from our face-to-face discussions, our areas of agreement actually far outweigh our areas of disagreement. I will say this though. Whilst I agree 100% re 2 handed face mask technique (and the use of the “thumb grip” rather than the “classical grip”), I disagree that the benefits of the collapsible bag on the Mapleson are negated by using two hands. I also think that it’s worth delineating the issues with FMV… Read more »
can’t wait! i won’t rile you up by responding–I’ll wait to hoist a beer in person, my friend.
he keeps getting back up..
Hi Nick,
Having reasonable familiarity with both self-inflating ventilators and the Mapleson circuit I certainly can appreciate the greater tactile and visual feedback you get with the latter that I (or the patient is) achieving adequate ventilation via the mask. But from a practical viewpoint how would you alter your strategy if you felt prior to induction that you were likely to enter a can’t ‘ventilate’ scenario. Would you more likely to ‘vortex’ to LMA rather than trying a mask seal if you had trouble intubating?
best off going to Nick’s original post and commenting there, not sure if he is reading the comments here
Hey Scott, I debated a bit with Nic and Minh about this a while back, frankly I’m still somewhat on the fence. I found you kind of jumped all over the place in the wee, comparing Mapleson to BVM, NRB mask, NC and ventilators as it suited you. If you take nasal prongs and 2 hand mask seal as a given in both scenarios, the comparison between BVM and Mapleson is simpler: -Mapleson does PEEP like a vent, better than a PEEP valve. That’s why we use flow inflating bags in grunting, indrawing newborns, they just need a bit of… Read more »
Sean, I refuse to have to pick just BVM vs. NRB/NC for the simple reason that I don’t use just one. The debate Nick set up is use of mapleson B for everything vs. Rich’s and my strategy of NRB/NC unless shunt and then a PEEP-capable device. You’ve got to accept the bundle b/c that is how it is done on pts. Mapleson doesn’t do PEEP like a vent the BVM with a PEEP valve does (low-flow CPAP), in some ways the Mapleson does it better than a vent (high-flow CPAP). However, if the NC cannula is there, then all… Read more »
Don’t bring one to a code either.
1. I’ve already started preoxygenating before anesthesia gets arrives.
2. The middle of a code is not the time to introduce new equipment to the team.
I also want a peep valve on every single bm that I use you never know when that patient is going to need to peep.
Hi Scott, You know I love your podcast and look forward to hearing it. I agree with most of what you say, except on airway issues where I often disagree considerably. Case in point: your friend is correct here. The Mapleson D set-up is vastly superior to BVM and there are only two reasons not to use it for initial airway management: you don’t have one or you don’t know how to use it. I suspect in the ED the issue is both, in which case one can use a BVM with PEEP valve, although it should be of the… Read more »
Hi Scott, Being an Intensivist of anaesthetic background and having worked and trained in the UK, I enjoyed your podcast greatly. The Mapleson C and not B as suggested here is used extensively in UK in anaesthetic practice. The difference between the Mapleson C and Mapleson B is that the Mapleson C is devoid of the long tubing between the valve and the bag and therefore easier to handle than the Mapleson B. The big advantage with these is that you can see the bag move and therefore have a rough idea of the increasing tidal volume and rate. This… Read more »
fantastic comment. you will however see the BVM bag moving with spont resps, just as you do with the Mapleson–for both of them of course, this is reliant on a tight mask seal
Hi Nick,
Having reasonable familiarity with both self-inflating ventilators and the Mapleson circuit I certainly can appreciate the greater tactile and visual feedback you get with the latter that I (or the patient is) achieving adequate ventilation via the mask. But from a practical viewpoint how would you alter your strategy if you felt prior to induction that you were likely to enter a can’t ‘ventilate’ scenario. Would you more likely to ‘vortex’ to LMA rather than trying a mask seal if you had trouble intubating?
Great post Just a note – the animation above depicts a Mapleson A not Mapleson B (where the FGF should enter after the corrugated tubing near the patient.) – I usually anaesthetise in theatre and will therefore use either the ventilator (plus or minus cpap/pressure support + CPAP if required) or a variant on mapleson A the parallel lack system (http://www.frca.co.uk/images_main/resources/Intersurgical/lack.jpg), why this doesnt exist with simple one way inspiratory / expiratory flutter valve down each limb I dont know as this would massively reduce the required FGF to prevent rebreathing of dead space gas for SV or IPPV. As… Read more »
thought all of these were specifically designed for rebreathing to save on volatile gas costs, is this not the case?
I am in support of a BVM with NC + Peep Valve….i work in ED..but when i was in Anaesthetics, using a mapleson with a relaxed time controlled environment was excellent and trains you to understand lung compliance and improves use hand masking…However, i cannot even remember the last time i was in ed, with a crashing patient who i had the luxury of time with. Usually on night shifts, I’m intubating and running the resus as well so the chances of me being able to perfectly face mask bag my patients is prob not very high.id like all the… Read more »