Understanding Pneumomediastinum: When Air Escapes into Potential Spaces

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Okay, invictus people.
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First some updates.
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Then we're going to talk about Pneumo Media, steinman and Pneumo Pericardium.
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First of all, Invictus has been put together now lots of lectures have been put together.
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We're adding emphasis, getting transcripts done, making lots of multiple choice questions.
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Matt Delaney's come on board.
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He's helping us putting it all together.
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This thing is really going to be quite spectacular and I really believe that's going to be something that every resident in every country is going to want to have through their entire residency, and some of the smarter ones are going to want to use it for the rest of their career.
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There is so much to know on Immune Smiths and I've always believed that what you should be doing is basically a form of continuous board review.
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Yes, mrap is fantastic, of course.
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It's fantastic, and EMA to keep you up to date with the latest, greatest stuff.
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But I always found that by the time I'd sort of gone through learning all of them and I'd started to forget some stuff.
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So continuous board review, I think, should be part of your life.
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All right, that is my opinion.
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So let's talk about pneumomediastinum and pneumopericardium, and I'm not afraid to say that for a long time I didn't really understand this, but it's actually quite simple.
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So here's your heart and imagine these two balloons I tried to find balloons but I couldn't find them, so we'll draw on this thing that are squished around this heart like this, and so if those balloons start to leak, then you can get air that comes around the heart, into the mediastinum and that air can track up into the neck, into the subcutaneous tissues.
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So if you have blunt force trauma or penetrating trauma that pops a hole in one of these balloons, these lungs, one of the places that the air can leak out is into a pneumothorax, obviously.
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But if it goes more centrally into a same potential space and produces pneumomediastinum, okay, and now these can get quite tense and there are cases where you can get tension pneumomediastinum with so much air coming out it's dissecting and they're turning into a balloon.
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And you may have noticed this on the Pit, actually, if you watch the show where we did one of these radical procedures where cutting above the clavicles to try and let some of that air out of the subcutaneous tissues.
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That's the extreme, incredibly rare form.
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But another thing that can happen and this is where I was a little confused is that air under pressure there can actually dissect into the pericardium, which is surrounding the heart.
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We think of this as a firm, fibrous thing around the heart which is hard to get through except with a knife.
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But air can actually dissect into the pericardium and parts of the pericardium where there's some reflections and it's a lot weaker.
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So that air that's coming from the lungs or from the giant esophagus that comes behind here is in that same potential space.
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So you've got Borchov syndrome and you're vomiting, you've got a tear in your esophagus and air is getting in and food is getting in.
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So that air from either the lungs or that air from the esophagus or that air from the broken trachea low down can be under pressure and can dissect also into the pericardium, giving you pneumopericardium.
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So here's an example of that.
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So that's where it's very discreet, it's around around the heart, it's in the pericardium and you can obviously get parts of both of those and, yes, you can get a tamponade from pneumopericardium.
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There's a lot of case reports of that, often actually, when you and I did it, where there was fluid around their heart and we put a needle in and we did it wrong and some of that air got entrained into the pericardium.
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You took the fluid out and you replaced it with air.
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Not a great thing to do.
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So again, think of these two big balloons squishing this heart.
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There can be a hole in that balloon or in that esophagus and that air gets into this pneumometastinum or into the mediastine, causing a pneumometastine.
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That air that can then track up into the neck and you see it and you can feel the crackles up here.
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And it can also dissect into the pericardium much less likely but can dissect into the pericardium.
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Or you get a stab wound that goes through and there's a little hole in the pericardium and can go in that way.
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Or you put a needle in and you can get a pneumomeric pericardium.
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That way Most pneumomediastinums don't need any treatment.
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You just sit on them, you watch them, you don't do anything.
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Like I said, in rare, rare circumstances they can be under tension and you might have to do a radical procedure, or they might even have to go to the OR.
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And if they've got air in the pericardium, if it's small, if they're not hemodynamically unstable again, it'll absorb over time.
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If there's a continued leak there and it's under pressure, you might have to drain it, just like you would have to drain any other sort of collection in the pericardial itself.
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So pericardiosynthesis, but don't add more air when you do your pericardiosynthesis.
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So does that make sense?
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Just basically two big balloons that are squishing around the heart, producing a potential space around the heart with the big esophagus in the back.
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That's your mediastinum.
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Air can get in there, pneumomediastinum, or it can get into the pericardial sac, pneumopericardium.
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Oh, oh, oh, oh, oh.
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And I should say let's now have Chris Riley and Misa Ho go through some examples of pneumomediastone, because it can be a little hard to pick up on plain chest x-ray and this is part of our radiology x-ray fundamental series.
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It is fantastic, there's a full series on MRAP, so go check it out.
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Link in the show notes.
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But here it is, chris Riley going over a number of x-rays.
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These might come up on the boards and after blunt trauma, repetitive training, trauma, and you're going to have to make the diagnosis and again the treatment.
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Most of the time there's nothing else going on.
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Just wait and see and watch and it'll usually get better by itself.
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All right, chris Riley.
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All right, mies, we're going to go through some more examples here.
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We have three examples right off the bat of pneumomediastinum.
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All are varying in how severe they are and the least severe.
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If you're looking at this film right here, the error is really tough to see along that pericardial border and also going up through that mediastinum, tracing out the azagus vein and these areas.
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It's a little bit more subtle but you can see that subcutaneous emphysema that we feel on exam.
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All right, I like this because I'm not looking at the azygous vein normally when I'm looking at my chest x-rays.
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But to your point, if I have this systematic approach, I can see there's a lucency there that shouldn't be there something abnormal.
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So it's good, exactly, all right.
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Show me another example.
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This next example is a little bit more obvious.
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You can see that the pericardium is a little bit more pulled away from the rest of the heart, again going completely up, but not as much subcutaneous emphysema in this one.
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All right, this last case is a disaster.
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Yeah, this is not subtle.
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This is esophageal perforation.
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Okay, not great.
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There is air everywhere.
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Yeah, I'm sure they felt like Crunchy cues, crunchy Qs, crunchy Qs Exactly.
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So that's Pneumomediastinum.