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Collapsing Trachea 

The trachea, or windpipe, is the tube that connects the nose, mouth, and throat to the lungs. The trachea is meant to be a fairly rigid tube. It consists of muscle connecting a group of cartilaginous rings. The rings are actually not complete circles: They form a C with the open end of the C facing towards the animal's back. There is a muscle covering the open end of the C which is called the tracheal membrane.

When the diaphragm (the flat muscle separating the abdomen from the chest cavity) flattens and the intercostal muscles (the muscles between the ribs) move, air is sucked into the lungs. The muscles move in the opposite direction and the air is pushed out of the lungs. The trachea serves as a pipeline bringing air into the chest.  The trachea has two parts: The part of the trachea in the throat is called the extrathoracic portion, the other part of the trachea extends into the chest is called the intrathoracic portion.

Why Would a Trachea Collapse?

Tracheas collapse because the cartilage which makes up the rings becomes weak. Dogs can inherit a tendency for this to happen. When the C loses its curvature, the tracheal membrane that bridges the C  gets loose and floppy. Instead of being a tight muscle covering, the membrane moves as air passes through the trachea. When air rushes into the chest, the membrane of the intrathoracic trachea balloons outward and when air rushes out, the membrane of the intrathoracic trachea droops down into the C cartilage causing an occlusion. The tickling sensation of the membrane touching the tracheal lining generates coughing and if the obstruction interrupts breathing, the patient may become distressed. If the collapse is in the extrathoracic (also called the cervical) trachea, the opposite occurs; the collapse occurs during inhalation and the ballooning during exhalation. Panting or rapid breathing for any reason makes the collapse and anxiety worse, which unfortunately tends to generate more rapid breathing and a vicious cycle of distress.

Tracheal collapse creates increased secretion and inflammation thus promoting yet more coughing which creates yet more inflammation. Ultimately the tissue of the trachea changes and loses its normal characteristics and the condition gets worse and worse.  Some animals will get so much inflammation that a secondary infection results.

The trachea may be collapsed along its entire length, only in the intrathoracic section, or only in the extrathoracic section. Most commonly the collapse is at its worse right where the trachea enters the chest.

Which breeds of dogs tend to be affected?

The victim of tracheal collapse is almost always a toy breed dog, especially Miniature Poodles, Yorkshire Terriers, and Pomeranians. The disease usually becomes problematic in middle age but can occur at any age. The cartilage defect that leads to the flattened C rings seems to be hereditary.

Many dogs with collapsed tracheas do not ever show signs until a second problem complicates things. Factors that can exacerbate collapsing trachea include:

• Obesity
• Anesthesia involving the placement of an endotracheal tube
• Development of kennel cough or other respiratory infection
• Increased respiratory irritants in the air (cigarette smoke, dust, etc.)
• Heart enlargement (the heart can get so big that it presses on the trachea)

If a secondary factor such as one of those listed above should occur and make a previously incidental collapsed trachea a problem, often removal of the secondary factor (weight loss program, getting an air filter, etc.) may alleviate the symptoms of the collapsing trachea.

Treatment:

The following steps are often helpful in long-term management of the tracheal collapse patient:

• The most important step in managing this disease if the affected individual is OBESE, is to work very hard to get the excess weight off of the patient.  We may place your pet on a special prescription diet in order to do this successfully. 
• The affected individual should have comprehensive blood work and if heart disease is suspected an x-ray and cardiac ultrasound to ensure that there are no additional problems which could make the tracheal collapse worse or be the result of the tracheal collapse.  An enlarged heart due to heart disease can exacerbate this condition.
• Dogs with collapsed tracheas become unable to efficiently clear infectious organisms from their lower respiratory tracts. Antibiotics may be needed to clear up an infection if one is present.
• Cough suppressants such as hydrocodone or torbutrol may be helpful.
• Corticosteroids such as prednisone and related hormones cut secretion of mucus effectively, but are best used on a short term basis due to the potential of dangerous side effects. Long-term use may promote infection and weaken cartilage further.
• Airway dilators such as theophylline or terbutaline are controversial as they may dilate lower airways, but not the actual trachea. By dilating lower airways, the pressure in the chest during inhalation is not as great and the trachea may not collapse as much as without treatment.

In a recent retrospective study of 100 dogs with collapsing trachea, 71% responded to medication and management of secondary factors (obesity, irritants in the air, etc.), 7% had disease so severe that they died within one month of diagnosis, 6% had severe additional disease problems, and the other 16% were felt to be candidates for surgical treatment.

Emergency Care:

The patient's distress can reach a level so severe that the normally pink mucous membranes become bluish and fainting can result. When this occurs, tranquilization is helpful to relieve the anxiety that perpetuates the heavy breathing and coughing. Oxygen therapy and cough suppressants also help. If your dog reaches the point where distress seems extreme or if fainting results, seek emergency veterinary care.

Can tracheal collapse be treated surgically?

If medical management does not produce satisfactory results, it is possible that surgery may be of benefit. Basically, a rigid prosthesis is placed and bonded around the trachea effectively creating a non-collapsible tube. This is largely effective as long as the portion of trachea that is collapsed is external to the chest. Should the intrathoracic trachea be involved, the surgery becomes far less successful, more expensive, and the prosthesis must be ordered according to the specific patient’s measurements.

In all surgery cases, the younger the patient, the more successful the surgery is likely to be with success dropping off in patients over age 6 years. Severity of the collapse prior to surgery is not a tremendous factor in obtaining a successful outcome; improvement is reported in 75% to 85% of patients.

A new technique is being explored using a self-expanding stainless steel prosthesis.  A study reporting results of 24 dogs receiving this treatment was published in January 2004.  Of these dogs, 96% showed improvement after surgery. Two dogs died within the first week due to stent placement complications.  One dog experienced some bleeding.  After this 30% were reported to be completely free of symptoms, 61% showed marked improvement, and 4% continued to have symptoms. This appears to be a promising technique but has still only been used in a small number of patients.

Surgical therapy of tracheal collapse requires a board certified specialist.  We are happy to help arrange a consultation with one of our board certified surgeons to discuss your pet’s tracheal collapse.

Adapted from the Pet Healthcare Library

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