What is Tracheobronchomalacia, by Dr. Wendy Jo Svetanoff.
Hello.
My name is Dr. Wendy Jo Svetanoff,
and I work with the esophageal and airway treatment team
at Boston Children's Hospital.
This is the first in a series of videos
describing tracheobronchomalacia and potential interventions.
In utero, the trachea begins formation
during the fourth week of life, forming multiple rings
that connect the back of the throat down
to the distal airways.
The anterior rings are made of hyaline cartilage,
while the posterior membrane consists of smooth muscle.
The trachea can be separated into three areas,
with T1 located in the cervical area
and extending to the clavicles.
T2 can be found in the upper thoracic area,
from the clavicles to the aortic arch,
while T3 is located from the aortic arch to the carina.
The normal trachea takes on the form of a C shape
with a short, stiff posterior membrane
that prevents collapse.
An example of this is seen in the bronchoscopy picture
on the right.
In this bronchoscopy, you can see the nice C shape
of the tracheal cartilages.
The posterior membrane is short and firm, preventing collapse.
Tracheobronchomalacia is a condition
where the rings of the trachea and bronchus
take on an abnormal shape, leading to laxity and collapse
during breathing and/or coughing.
The estimated incidence is about 1 in 1500 to 2000 cases.
However, the true incidence is unknown.
Multiple factors can contribute to the development
of tracheobronchomalacia, including genetic factors,
collagen disorders, associated anomalies,
such as esophageal atresia, vascular malformations causing
compression of the trachea, as well as chronic inflammation
or complications from prolonged mechanical ventilation.
When diagnosing tracheobronchomalacia
on bronchoscopic exam, a patient has
to demonstrate greater than 50% intrusion or collapse
of the airway when coughing.
With normal tracheal anatomy, the length ratio
of the anterior cartilage to posterior muscle ratio
is 4 to 5 to 1.
In tracheomalacia, this ratio can be as great as 2 to 1,
with the loss of the C shape of the hyaline cartilages.
This diagram illustrates the deformities
that occur leading to tracheomalacia.
Anterior compression is most often caused
by a vascular malformation putting pressure
on the trachea.
Posterior intrusion is more dynamic,
consisting of a longer, weaker posterior
membrane that easily protrudes into the tracheal lumen
with coughing.
This can occur in one area of the larger airway,
but can also be found in multiple areas
of both the trachea and bilateral main stem bronchus.
As the posterior membrane becomes larger,
the cartilage lose their C shape, first
forming a U shape that is nicely illustrated
in both the picture and the bronchoscopic photographs.
This bronchoscopy shows U-shaped anterior cartilages
attached to a longer posterior membrane, leading
to greater laxity and mobility.
In severe cases, the cartilage takes on the shape of a bow,
with the even longer posterior membrane
being the string of the bow.
With this anatomy, the trachea can easily
collapse during forced expiration or coughing.
Both the pictures and the video show the decreased
tracheal lumen that is seen in patients
with bow-shaped cartilage.
Patients with tracheomalacia can present
with a wide range of signs and symptoms,
which could make the diagnosis challenging in some cases.
Symptoms can include chronic cough, noisy breathing,
recurrent respiratory infections,
failure to thrive as a young infant or child, inability
to wean from mechanical ventilation,
multiple BRUE episodes, which are Brief Resolved Unexplained
Events that can lead to cyanosis, absent breathing,
or altered level of consciousness,
and limited exercise reserve.
To best determine the therapeutic options
for patients that are referred, we
have followed the following algorithm.
As noted, patients should be experiencing symptoms
during the exhalation phase of breathing
and have notable symptoms present,
such as recurrent infections, persistent oxygen requirements,
exercise limitations, and/or episodes of cyanosis
with altered levels of consciousness.
If these are present, the patient
will be scheduled for two tests--
a bronchoscopy to evaluate tracheal anatomy
with static and dynamic visualization of the airway,
and a CT scan of the chest where specific focus
is paid to the anatomy of the aortic arch, the great vessels,
and the artery of Adamkiewicz, looking for any malformations
or compression on the trachea.
This specially designed airway CT
may show collapse of the trachea due to anatomic anomalies.
We have found that the 3D reconstruction
of both the airway and the great vessels
can give us a better roadmap to the areas that
are most affected.
To end this presentation, these 2 bronchoscopies
show, in real time, the significant collapse
of the tracheal lumen and the wide bow-shaped cartilages
that are identified in patients with tracheobronchomalacia.
Thank you.