What follows are links to [access to this video and all the outstanding resources of Open Pediatrics requires free registration]:
Non-Rebreather Mask and Manual Ventilation Bag [Video], Robert Pascucci, MD
Clinicians might think, well, I already know all this stuff but as the coach used to say “fundamentals win games.”
The anesthesia bag has many advantages but it does require some practice and the novice can benefit from practice under the supervision of an experienced mentor.
And there is an outstanding demonstration of Mapleson/Magill Circuit or Anesthesia Bag (Chapter 3). Chapter 3 is 6:40 long, and well discusses the advantages of the anesthesia bag in resuscitation. And it well demonstrates its use. I have included the transcript from this chapter below (and be sure and review the article, Using Anesthesia Bags (1), link in Resources):
Mapleson/Magill Circuit or Anesthesia Bag
If you have a patient that is breathing spontaneously, you can probably assist them better with theMapleson circuit, Magill circuit, anesthesia bag, whatever you want to call this thing.
Now, this is a completely different design than the bag we’ve been using up until now. This is really more like a T-piece: There’s a fresh gas flow, there’s a baby down here, and there’s an expiratory limb.
We’ll talk about the design a little bit more in a minute. The big disadvantage of this is that you have to have a fresh gas source. If you don’t have a fresh gas source, you really can’t do much, and you really can’t ventilate the patient. So if you’re in a situation where you can’t have a reliable source of fresh gas that can run at a decent liter flow, you probably are not going to be able to use this bag.
If you do have a fresh gas source, however, the nice thing is that you can let the patient breathe spontaneously. So, if this were attached to the patient, and he were breathing on his own, you’d be able to get a good mask seal, or potentially with an endotracheal tube, use the same system, and then just watch the baby breathe, and if you look at the bag going up and down, you can see that the baby is breathing spontaneously from this bag. So I’ve been able to get a good mask seal and I’ve been able to give a high oxygen concentration and been able to monitor the baby’s breathing all by switching to this particular system.
Now, suppose the baby needs a little bit more assistance, for example, someone that you’re sedating for a procedure, and you give a little bit of midazolam, or a little bit of fentanyl, or some sort of sedation, and the baby starts to get a little bit obstructed, well, in that case I can just increase the amount of pressure I’m giving the baby, turn up the Continuous Positive Airway Pressure (CPAP), and I’ll show you how to do that in a second, and now the baby can still breathe spontaneously, but I’ve got five centimeters or eight centimeters or ten centimeters of CPAP, sort of splinting the airway open and helping the baby breathe.
If I give even more sedation and the baby becomes apneic, then I can just start mechanically ventilating the patient with the same system, and I can adjust the pressures again by adjusting the pop-off valve, and so I can go full mechanical ventilation, and then when the baby starts to breath spontaneously, I can back off a bit, let the baby breathe spontaneously again, and it’s a seamless transition from spontaneous ventilation to full mechanical support, back and forth, back and forth, and you really can’t do that with a self inflating bag, you can really only do that with the Mapleson system.
So for me, that’s the big advantage of this system: being able to follow the patient a little bit more effectively, allow them to breathe on their own if they can, support their own spontaneous ventilation, and you really can’t do that with the self inflating bag.
Now, a few more details about this; again, how does it work? It is a T-piece system, so that there’s fresh gas coming in here, I can adjust the fresh gas to keep the bag full, and that’s typically what one would do. You do need to have a fresh gas source and you can’t operate without one.
What about CO2? Well, there are no valves in the system. There have been valves in everything we’ve used up until now, but there really are no one-way valves in this system so it is possible for the patient to rebreathe CO2.
For example, if the flow rate is too low coming into the bag – let me just demonstrate this on myself – the bag will keep going up and down, but really it’s just me breathing back and forth into the bag, and I am rebreathing CO2 because there’s no way for it to get out. So even though it looks like I’m being ventilated,I’m really not because the CO2 is just bouncing back and forth.
The key to getting rid of CO2 is to have a fast enough fresh gas flow that at the end of every breath, the fresh gas flow pushes the CO2 through the tubing, through the bag, and out the hole, wherever the hole turns out to be in the valve. So if I turn the fresh gas flow up, now if I breathe, at the end of every breath the CO2 is getting pushed out of the system, and I am not rebreathing CO2 simply because of the faster fresh gas flow.
So the key to getting rid of CO2 in a system like this is to have a fresh gas flow that’s fast enough to flush the system in between breaths, and typically you want about two-and-a-half to three times the patient’s normal minute volume as a reference for how much fresh gas flow you need to go into the bag. Typically, for a baby, it’ll be around 3-4 liters per minute, for an older child it may be 6 or 7 liters per minute, and for an adolescent it may be 10 or 15 liters per minute, enough to make sure the bag fills up very easily in between breaths, and that, in fact, you are flushing the system and getting rid of the CO2.
Now, the last thing – I keep talking about valves, and this particular system doesn’t really have a valve in it; the valve in this particular case is the hole at the end of the bag, and I’m just squeezing that with my fingers to generate the effect of a valve and PEEP and CPAP and that sort of thing.
Many designs will have a valve built into the system, and it will either be located here, here, or somewhere else in the system, and you can adjust that valve ahead of time to generate a certain amount of PEEP or CPAP, or you can set it to five or six or eight, or whatever you seem to want. And the advantage of that is that it’s a lot easier to control the pressures that you’re giving the baby and know that you’re generating the CPAP at the end of the breath that you want.
The disadvantage of the valve, and the reason we tend not to use them here, is because it’s potentially possible that they will stick, and then be a potential risk to the patient because this system is a closed system and if the valve isn’t working, then all that pressure is going to get transmitted to the baby. So for various reasons, we don’t use valves here at Children’s Hospital; we tend to use our fingers and a cutoff tip, and that functionally is the same thing, it’s just a little bit trickier to learn how to use.
Now, on the baby, again, I will tend to choose a smaller mask. Come around, get a good mask seal; I have to have my fingers on the valve, but once I do that, then if the baby is breathing spontaneously, I can let them go ahead and do that; and you can see the bag going up and down. If they’re having a little difficulty doing that, then I can generate some positivepressure and generate some CPAP,and then, if the baby really isn’t breathing adequately and I want to take over, I can fully ventilate the patient just using this system. And again, it’s a seamless transition back and forth between spontaneous ventilation and mechanic ventilation, which you really can’t do very well with the self-inflating bag.