Pediatric Airway Assessment, by Dr. Tonya Miller.
Hi there.
I'm Tonya Miller, one of the anesthesiologists here on staff at Children's Hospital Boston,
and I'm going to speak about airway management, or approach to the airway management of pediatrics,
which can sometimes be somewhat challenging.
The goal of this talk is to give you an idea of how to approach the airway of a patient
from the perspective of an anesthesiologist.
We're going to go over assessment, and then some special circumstances that you might
want to keep in mind when you're approaching a pediatric airway.
Airway Exam.
For assessment of the patient, always look to the ABCs: the airway, breathing, and circulation.
As far as the specific airway exam, you're assessing the ability to intubate.
Alignment of the oral axis and the tracheal axis is one thing that you need to keep in
mind.
Are you going to be able to align these axes in this patient or not, or how difficult will
be?
Are you going to have any visualization obstacles, such as do they have limited mouth opening?
What is their tongue to box ratio, and we'll go over that in a minute, and how much range
of motion do they have with their neck?
As far as mouth opening, we frequently will talk about classification of an airway with
the Mallampati Classification.
When a patient fully opens their mouth, if you can see the uvula, and space, and the
tongue, and the posterior pharynx behind it, that's a class one.
And in this picture, you'll see that there are four classifications all the way to a
class four, which would be where you can only see, really, the hard palate when they open
their mouth.
As far as anterior mandibular space is concerned, frequently you're taught to measure the thyromental
distance from underneath the chin with your fingers.
This works fine in adults because you can standardize saying three finger breadths,
but in small patients, everybody has different finger sizes, and so this becomes much less
useful.
However, as you get accustomed to looking at the children and their faces and their
neck structures, you can see if they have an adequate amount of anterior mandibular
space.
And what that is, is how much space they have to house the tongue that is inside.
The tongue size is also something that you'll want to look at.
Do they have an extremely large tongue?
Is it protuberant out of their mouth?
Do they not have space inside their mouth to house that tongue?
This is what I'm talking about when I talk to a tongue to box ratio.
If you think of the tongue as a structure that's normally contained inside of a box,
does that box have any more space inside of it than just the area that is needed for the
tongue to take up?
Or, is the tongue so large that it is taking up the entire space inside the box of the
mouth, and even protruding out?
Most patients are somewhere in between the two.
As far as oropharyngeal shape, you'll look at the palate, the tonsils, and think about
the choanae of the nose, because infants, as you know, are obligate nasal breathers.
So becoming difficult to mask ventilate if you can't get an airway in through the mouth
and have to rely on the nose, and yet, if they have choanal atresia or some other issues
with formation of the nose, that might be also a very difficult situation to even ventilate.
So to give you an example of the pharyngeal shape, this picture shows a patient that has
a cleft lip and palate.
You see that the palate actually is open on the inside, and these palates typically have
a smaller lateral to lateral side distance, but they're very open so the shape of the
box in which the tongue is housed is going to be completely different.
When it comes to intubating these patients, you may find that your laryngoscope may get
caught up inside the cleft that is there, as opposed to being able to intubate normally
through a patient who has an intact palate.
When we talk of range of motion of the neck, we're talking about head extension and head
flexion, but we're also talking about how much the mandible is mobile.
The TMJ joint, is it able to be subluxed?
Can you pull it forward?
Can you open your mouth all the way, completely?
Or do you have limitation for some reason, whether you have joint disease, some sort
of trauma, or some other sort of dysplasia, or extra small mandibular bone size issue.
The neck itself-- is it long enough to be able to extend and flex, or is it very short,
is it contractured, does the patient have a syndrome that their neck is not a normal
size for them?
Lastly, in assessing the alignment and visualization in preparation for instrumenting the airway,
you want to look at the neck structure and the neck structures inside, such as the thyroid.
Does the patient have a big thyroid?
Are there any other masses that would alter the normal anatomy that you would expect when
you're going to be encountering the larynx and the sublaryngeal area.
Pediatric Considerations.
So in terms of pediatric airway development, the head and the occiput of their head has
a different relationship to the rest of the size of their body.
This diagram shows a situation of a patient laying supine in where you may or may not
want to be bolstering a patient in order to get an optimal visual alignment of the oral
and then the laryngeal axes.
You see, in the newborn or very young child, it's less likely that you're going to want
a pillow under the head because they already have a large occiput and putting a pillow
under their head would malalign these axes of the oral pharynx and the larynx versus
in a kid who is 10, 15, or an adult, where you frequently will put a pillow behind the
head to bolster in order to bring up their oral access to meet their laryngeal access.
Also, their tongue is very large compared to an adult.
So again, going to the box-to-tongue ratio, they already start off with a larger tongue
to the box of their mouth ratio than an adult.
The larynx location tends to be more cephalad and more anterior than in an adult.
And therefore, the tracheal opening will be more difficult to align when you are looking
through the oral pharynx down towards the tracheal axis because you will note it's more
anterior than you would expect.
Again, this is why we don't put a head pillow underneath an infant automatically.
The cricoid cartilage is a circumferential ring, and in pediatrics, this becomes the
smallest part or the narrowest part of the pediatric airway.
Versus in an adult, as the patient grows and all their structures grow, actually, the inlet
to the larynx is smaller than the cricoid cartilage.
Critical Update: Recent radiologic studies have demonstrated that the subglottic region,
not the cricoid, is the narrowest part of the pediatric airway.
However, there is concern that these findings may be the result of artifact related to which
phase of respiration was captured in the images.
Autopsy specimen still confirm that the cricoid outlet is the narrowest level of the pediatric
airway.
The epithelium of a pediatric airway is very delicate, moreso than in the adult.
And airway diameter being extra small in a pediatric patient, the epithelium, if it gets
irritated, inflamed, or incurs any sort of swelling in the airway management process,
more swelling in a small airway will lead to a much greater effect on airway flow dynamics
than would the same amount of airway swelling in an airway that starts out at a much larger
diameter to begin with.
The epiglottis is something to make comment on.
The adult epiglottis tends to be longer, broader, more easily manipulated with a laryngoscope
blade than does a neonate glottis.
Here are two pictures-- one showing the adult glottis, which is much larger, and one showing
the neonate glottis, which you can tell is very short and quite narrow-- almost omega-shaped
we would call it.
This is much more difficult to put behind a blade or to manipulate because it's very
stiff and will flop everywhere you don't want it to go.
As far as the laryngeal opening, this picture denotes that the laryngeal opening is more
conical almost-- like a funnel-- where the thyroid cartilage down to the cricoid cartilage
narrows quite a bit.
By the time children become adults, this becomes much more cylindrical as opposed to a funnel
shape.
Again, just emphasizing that the cricoid ring may be your smallest area in your pediatric
patient's airway.
These two x-rays, if we compare them, the one on the right is an adult airway.
And you can see that the epiglottis and the posterior laryngeal airway, the glottic area,
and then the trachea all almost line up naturally in a very vertical line.
Compare that to the pediatric airway where the epiglottis and the glottic opening is
on an angle coming from the posterior pharynx and then makes a turn as the trachea then
dives back posteriorly from the glottic opening.
Abnormal Anatomical Relationships.
Continuing on as to some abnormal anatomical relationships that you may encounter in a
pediatric patient.
You may, from a multitude of reasons, have an abnormal situation of an otherwise normal
bit of anatomy for the pediatric patient.
For example, if they've had surgery or radiation or some sort of disease process that lends
to scarring, you may find that their face looks very different, as this teen pictured
here appears very different after he's had surgery and radiation for a cancer that was
found in and around his neck.
Or you may see a pediatric patient with a very common disease process, such as a retropharyngeal
abscess, in which there is some sort of inflammatory mass that creates a distortion of normal airway
anatomy.
This is a CT scan showing such an abscess and how its displaced the airway to be off
center and a little bit smaller than otherwise expected.
There are other issues that you may have, such as bone or spine issues.
A patient with severe scoliosis or some sort of disease process that lends their spine
to have an abnormal curvature.
Or if they have any kind of inflammation or joint disease, they may have limited mobility
of their neck, but also can lead to distortions of anatomical relationships.
Childhood obesity is another issue with airway management in terms of getting a proper positioning
for alignment of your axes.
Here, we see a teenager who is quite obese.
And in order to align all the different areas or axes-- the LA, being the Laryngeal Airway,
the OA, being the Oral Airway, and the PA, being the Pharyngeal Airway.
In order to align these as closely as possible to one another for the optimal airway intervention,
you see here we have a big ramp made out of blankets and pillows in order to get her in
the proper position.
Likewise, if you have some sort of trauma coming in and, for example, a pneumothorax,
as shown in this slide, you could have distortion of the airway anatomy distal to the supraglottic
structures that may make the placement of a breathing tube more difficult.
Other abnormal and anatomical relationships can come in pediatrics from simply having
congenital abnormalities.
Here are a few different examples of this.
The first is laryngomalacia, where the structures of the larynx are extra floppy.
It may be more difficult to get the breathing tube into a patient who has laryngomalacia
because the epiglottis may be even more compacted on itself.
It may be difficult to visualize the cords.
And, also, your patient's breathing status, respiratory status, at the time of airway
intervention may require some unique manipulations or pharmacological choices in order to preserve
the respiratory function as much as possible while intubating these patients.
A patient Pierre-Robin syndrome is another classical example of an abnormal airway, where
they have mandibular hypoplasia.
They have a very short neck, and they have a large tongue.
Very difficult to intubate these patients from the standpoint of alignment of all the
axes and being able to see the glottis, which is very anterior and very cephalad in these
patients.
Trisomy 21 children.
This is a typical face of a child with Down Syndrome.
As you recall, the tongue is very, very large.
They tend to have very short necks.
They may have atlanto-axial instability of their C1 spine.
Thus, making it maybe more dangerous to manipulate their head into an optimal position.
And, then, the Kippel-Feil patient, who has a very, very short neck and some bony abnormalities
that inhibit the extension of the spine.
Again, all these patients may require different techniques in order to align their axes for
visualization, or they may be impossible to visualize and intubate directly, and may need
to have other sorts of intubating techniques.
And, lastly, as far as abnormalities of anatomical relationship, if you have abnormal masses
that just normally aren't there.
They're not congenital, or they may be, but they are acquired or otherwise.
Whether it's a mediastinal mass, a foreign body in the airway, or vascular malformations
that can grow over time.
These can make your airway management very difficult.
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