Now let's talk about the
respiratory disorder, croup.
What is croup?
Croup is a symptom
characterized by infection
and inflammation of the upper airway,
which is the trachea and larynx.
Here, on the left, you'll
see the normal larynx.
There's a normal tracheal opening and
the vocal chords are not swollen.
Over on the right, you'll
see an inflamed larynx.
In the setting of croup, the vocal chords
and the surrounding structures
cause a narrowing of the trachea,
and this causes the symptoms
we see in croup.
Some children are more prone than
others to develop croup symptoms
when they get a viral upper
and most outgrow croup by the age of
5 when their airway becomes bigger.
Croup is more prevalent in the
autumn, winter, and spring,
and typically lasts about 1 week.
The most common cause of croup are viruses.
The parainfluenza viruses types 1 and 3
are responsible for about 80% of cases.
Influenza A and B can also cause croup,
along with the respiratory
syncytial virus, or RSV.
The adenovirus and rhinovirus
can also cause croup symptoms.
Rarely, croup is caused by a bacterial
infection, including <i>staph aureus</i>,
<i>strep pyogenes, strep pneumoniae,</i>
<i>haemophilus influenzae,</i> and <i>M. catarrhalis</i>.
First, the infection, which is usually
viral, will infect the laryngeal mucosa.
Then inflammation, hyperemia,
edema, and epithelial necrosis
and shedding begin due to the
irritation from the virus,
and this is going to start the
narrowing of the subglottic region.
The child will then begin
to breathe more rapidly
and deeper to compensate
for the narrowed airway.
The respiratory rate and
effort increase in this stage
as the patient tries to move the same
amount of air through a much smaller space.
Next, the patient will develop
stridor, which is turbulent air flow.
Imagine you're sitting in a cabin in the
woods and suddenly, a blizzard develops.
Near the fireplace, you'll
hear a whistling of the air
as that turbulent air flow goes down.
Well, that's the same thing that happens
in the airway, and that's stridor.
You can hear it on the other side
of the room without a stethoscope.
The patient's chest wall
will start retracting
to try to help the lungs move in more air.
Next, the patient will develop asynchronous
chest and abdominal movements,
and the overuse of these muscles
will cause the child to fatigue.
This is a very important stage to recognize
and intervene before the
child fatigues too much.
Lastly, hypoxia and hypercapnea will develop,
and this can progress to
respiratory failure and arrest.