Third Street Veterinary Hospital, PC
McMinnville, Oregon 97128
Office phone: (503) 472-9418
The
trachea, also known as the windpipe, is an important structure that connects
the throat to the lungs. It serves the
purpose of directing air into the respiratory tract.
The
normal trachea is tubular. It maintains
its shape because of a series of rings made of cartilage. These rings do not completely encircle the
trachea. Instead, they go from the 2
o'clock to 10 o'clock positions. The
remainder of the trachea composed of a flexible membrane that joins the ends of
the cartilage rings.
When
the cartilage rings are flattened from the top to the bottom, the trachea is
said to be collapsed. Rapid inhalation
of air can cause the trachea to flatten and make it difficult for air to enter
the lungs.
Cause
We
do not completely understand how this condition develops. However, we know that these dogs have an
abnormality in the chemical makeup of their tracheal rings. The rings loose their stiffness so they are
not able to retain their circular shape.
We also know that it occurs in certain breeds of dogs, notably Chihuahuas,
Pomeranians, Shih Tzus, Lhasa Apsos, Toy Poodles, and Yorkshire Terriers. Because of that, we suspect that there is a
genetic factor involved.
Clinical Signs
The
most common clinical sign is a chronic cough.
It is often described as dry and harsh and can become quite
pronounced. The term "goose
honk" is often used to describe it.
Coughing is often worse in the daytime and much less at night. The cough may also begin due to excitement,
pressure on the trachea (from a leash), or from drinking water or eating.
Diagnosis
A
dog of the breeds listed above with a chronic cough, especially a “goose honk,”
should be suspected as having collapsed trachea. Many times, very light pressure placed on the trachea during the
physical examination can raise a suspicion of collapsed trachea in a small dog
with a persistent dry cough. While the
information gained from the physical examination is helpful, other tests are
needed to confirm this condition.
Radiographs
(x-rays) of the chest can identify the trachea and its shape. However, a collapsed trachea changes its
diameter during the respiratory cycle.
It is usually collapsed during inhalation and normal during exhalation. Therefore, we attempt to make radiographs
during both phases of respiration. This
is easy in some dogs and rather difficult in others since dogs are not likely
to understand the command, “Take a deep breath and hold it.”
Endoscopy
is another way to visualize the trachea.
An endoscope is a tube that is small enough to insert into the trachea;
the operator can see through it and visualize the inside of the trachea. By watching the trachea during inspiration
and expiration, abnormal collapsing can be seen. Unfortunately, tracheal endoscopes are expensive and not
available at every veterinary hospital.
Coughing and Heart Failure
Coughing
is a common sign of heart failure, and many dogs with collapsed trachea will
also have heart disease. Testing that
occurs when diagnosing this disease should include chest radiographs (x-rays)
so the heart can be evaluated.
Treatment for heart disease is not indicated unless it can be
demonstrated with some form of testing.
Treatment
Collapsed
trachea can be treated medically or surgically. Some dogs respond well to brochodilators and various types of
anti-inflammatory drugs. The trachea of
these dogs is easily infected, so antibiotics are usually part of the
treatment. If obesity is present,
weight loss is often beneficial.
Excitement and vigorous exercise are likely to cause a relapse, so they
should be avoided as much as possible.
Some
dogs respond well to the medical approach, and others do not. Because medical therapy only treats the
symptoms and does not correct the problem, these dogs are always subject to
recurrences of coughing and breathing difficulty.
If
medical therapy is not successful, the dog should be evaluated for possible
surgery. Radiographs and endoscopy are
used to determine how much of the trachea is collapsed. If the only abnormal part is that segment
between the throat and the point where the trachea enters the chest (the
thoracic inlet), surgery may be curative.
However, if the segment of the trachea that is within the chest cavity
is abnormal, surgery is not likely to be helpful because that part is not
accessible to the surgeon.
There
are several surgical approaches that have been used. Each approach implants an artificial support device that is
secured around or within the trachea.
The purpose of the support device is to hold the tracheal rings in their
normal, open position. Although some
dogs have excellent results and are truly cured of the disease, the outcome is
not uniformly successful.