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Hi, this is Marc Gosselin.

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We're going to now keep going with the

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Cardiopulmonary Imaging Master Series.

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This session is going to be on aspiration

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and aspiration is a very common thing

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that we see, especially in ICU patients.

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Um, the objective is to understand how

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common it is and that it is most likely,

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the cause of low-grade

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fever in these ICU patients.

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And as in our previous episode or

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previous sessions, atelectasis is not.

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Atelectasis is not a cause for fever.

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That is a myth.

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And if you still teach it, you need to stop.

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Recognize the common imaging

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findings of aspiration.

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We'll go over them and we'll briefly just kind

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of review again, compare and contrast the CT

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enhancement of atelectasis versus consolidation.

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So, this is an ICU patient, endotracheal tube,

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central line, and what we have here is bilateral

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lower lobe areas of ill-defined opacity.

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We see some of the vessels of ground glass,

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other areas we don't, consistent with consolidation.

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What you notice, though, is that margins

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are a little ill-defined, and the

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patient does have a low-grade fever.

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Well, rather than saying, well, it's the atelectasis

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No, this is more consistent with aspiration.

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Now, another term that is commonly

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used, and you feel free to use it,

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is the term retained secretions.

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People who just can't cough

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up their bronchial secretions.

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And that can sometimes have

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an overlap in appearance.

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So, you know, if it's clearly a big

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consolidation, you know, call it aspiration.

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If you're not sure, you know,

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aspiration/retained secretions.

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And then again, this is most likely

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the cause of low-grade fevers.

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What does it look like?

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Well, it looks different

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than atelectasis in most cases.

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You might see the poorly defined three

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to four-millimeter clustered nodules.

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That's really key.

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It spares the subpleural area.

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So if it looks like it's touching the pleura,

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that's probably more of a consolidation.

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This is the so-called budding tree.

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Right?

2:00

Appearance, and that's what it looks like in a

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radiograph, three to four-millimeter nodularity.

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There'll be airway thickening, mucous

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plugging, and the other thing you might notice

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is you'll just gestalt the radiograph, and

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it just looks busy, and if it looks busy,

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and you see that kind of clustered three

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to four-millimeter nodularity, probably

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some aspiration/retained secretions.

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It's gravity-based and that's the key thing.

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It just kind of goes down to the lowest

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point of the terminal bronchioles.

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If you're lying on your side, that's usually

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part of the lung that overlies the axilla.

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If you're upright, it's going to

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be middle lobe and lower lobes.

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Um, That's the key, it's gravity-based.

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Just a quick, um, statement about this so

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called dense hilum or B6 side, anybody who's

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intubated or been extubated on a supine, the

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the hilum will look big and ill-defined and dense.

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The hilum is not changed.

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That is simply atelectasis or aspiration

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slash retained secretions in the superior

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segments of the lower lobes overlapping.

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And this is what it looks like.

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Look at the hilum.

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Endotracheal tube removed.

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Now look at the hilum.

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The hilum really are exactly the same.

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The pulmonary arteries haven't changed,

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but this ill-defined nodular kind of

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consolidated process and increased density,

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it's more white, represents the aspirated

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secretions that are in the superior segment.

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This is often misdiagnosed as

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pulmonary congestion and edema.

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It is not.

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It is a normal variant.

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Another patient.

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What do you see?

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Well, it's busy.

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You see a lot of three to

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four-millimeter nodularity.

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It spares the subpleural.

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It's in the dependent portions of both lower

3:44

lobes, posterior segment of the upper lobe.

3:46

This is an aspiration.

3:49

You can see aspiration is airway nodular.

3:52

Related.

3:53

And you can see the dependent

3:55

portion, some of it's coalescing.

3:57

This is characteristic for aspiration pneumonitis.

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If this were a trauma patient,

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this is aspiration, not contusion.

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Why?

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Because contusion doesn't bleed

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just in the airways, right?

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So this is aspiration.

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Low-grade fever.

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Now, just to compare again with our

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previous session, this is atelectasis.

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Notice it's got sharp margins

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and radiates from the hilum.

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That's what atelectasis is.

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It doesn't cause fever.

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This is different.

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Look at this.

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Slightly busy here.

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Witness aspiration.

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You see these little three to four-millimeter

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branching clustered nodules, sparing the

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subpleural dependent portion of the lung.

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This is aspiration pneumonitis/retained secretions.

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This is a few days later.

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This induces a low-grade chemical pneumonitis

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and is a likely cause for low-grade fever.

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Think about it.

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When a patient is aspirating, they're usually

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kind of on their PCA pump of morphine.

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They're aspirating small amounts.

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When you wake them up, have them use the

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incentive spirometer, they cough it up.

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Clear it, and the fever goes away.

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That has been mistaught in our, by, um, by

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the many generations of physicians as saying,

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see, that's why atelectasis causes fever.

5:16

No, it was.

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It was aspiration all along, uh, patient with a

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feeding tube going in the wrong direction, feeding

5:23

up the esophagus and then down into the lung.

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Large amount of aspiration.

5:28

You should be aware of the endotracheal

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tube does not protect you from aspiration.

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It can still occur.

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In fact, does almost 24 seven in

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this case, that aspiration is more

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than just an aspiration pneumonitis.

5:41

That's a full-on consolidation

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and likely high-grade fevers.

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Aspiration pneumonia.

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Another patient with high-grade fevers.

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Remember, aspiration pneumonitis,

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it'll give you low-grade fevers.

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Atelectasis gives you no fever.

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161 00:05:58,855 --> 00:06:00,764 Aspiration-based infectious

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pneumonia, high-grade fevers.

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And that can be a useful way to

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help differentiate the three, okay?

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That's a big consolidated

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aspiration-based pneumonia.

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Word of wise, Aspiration pneumonia is

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almost always gram-negative bacteria.

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The so-called anaerobic, that was from

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the 50s with the skid row, bad dentition.

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So we don't see that as much anymore.

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Aspiration pneumonia should equal gram-

6:27

negative bacteria like Pseudomonas.

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Just as a review, If you have a contrast-

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enhanced CT scan, pneumonia or consolidation

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enhances less than atelectasis.

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Atelectasis, all the vessels are together.

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It fills with the contrast and is very bright.

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Consolidation, the vessels are separated.

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It does not enhance to the same degree.

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It should enhance the same as the

6:55

paraspinal muscles, and it does.

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Atelectasis enhances much more.

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So if you're someone who says it could

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be atelectasis or pneumonia and a

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CT that's contrast-enhanced, you can

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favor one very strongly over another.

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So with that, Uh, let's review,

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atelectasis is not a cause for fever,

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please don't propagate that myth.

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It's most likely aspiration,

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which will be gravitational.

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Look for the busy clustered nodularity,

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um, and remember that atelectasis and

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consolidation enhance differently.

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Thank you very much.