Tracheal Collapse

Many of our brachycephalic dog breeds, majority of them small dog breeds, are prone to tracheal collapse which usually progresses with age.

Tracheal collapse is an acquired condition, that most commonly occur in middle-aged to aged dogs, but it has also been described in young dogs as a congenital lesion.  It is most commonly seen in toy and miniature breeds, especially Toy Poodles, Yorkshire Terriers, Pomeranians, Chihuahuas, Pugs, Shih Tzus and Lhasa Apsos.

1. Dorsoventral form (flattening from the back to the belly surface)

2. Lateral form (flattening from the one side to the other side)

The lateral form is unusual.  Dorsoventral flattening (narrowing of the trachea) is caused by an abnormal weakness of the tracheal cartilage which is further complicated by a redundant and flaccid membrane that prolapses into the tracheal lumen (the cavity or channel within the trachea).  The tracheal rings of the middle third of the trachea are usually most severely affected.  Increasing respiratory work further leads to dynamic collapse of the dorsal tracheal membrane into the tracheal lumen, which further irritates and inflames the mucous membranes, disrupts the mucociliary apparatus and increases the risk of associated small airway problems and signs.

Tracheal collapse produces a respiratory distress syndrome which becomes progressively worse and eventually results in severe exercise intolerance, a dry honking cough and severe dyspnoea (laboured or difficulty breathing).  The disease often has a history of chronic coughing, with the cough being harsh and dry and sometimes described by owners as a "goose honk" sound.  The coughing initially occurs during the day and occasionally in the evening hours.  The characteristic cough is elicited by excitement, tracheal pressure, and drinking of water or eating of food.  Tracheal pressure is commonly induced by pulling on a leash, or by picking the pet us which places excessive pressure on the thoracic inlet.

The most significant finding during clinical examination would be the elicitation of a "goose honk" cough when the trachea is palpated in the region of the thoracic inlet.  Radiographs are indicated, but a considerable percentage of false negative diagnoses occur because of the dynamic nature of the condition.

In all cases, medical treatment is first attempted as the majority of cases can be successfully treated symptomatically.  Medical treatment includes:

• Weight loss in obese patients by means of high-fiber, low fat diets because exercise modification is unlikely.  Weight loss alone can be curative with regards to the symptoms of the disease.
• Bronchodilators (medicines that help open the bronchial tubes (airways) of the lungs, allowing more air to flow through them.)  These drugs therefore do not have a direct effect on the trachea, but they decrease the negative intrathoracic pressure by dilating the lower airways and this in turn reduces the pressures within the chest that causes tracheal collapse.
• Cough suppressants to decrease the tracheal inflammation secondary to coughing.
• Corticosteroids may also be used short term to decrease tracheal inflammation.
• Collars are to be replaced by harnesses.

Other measures include exercise restriction and a reduction of excitement and stress.

When medical treatment fails to alleviate symptoms, then surgical intervention is indicated.

For other articles on Congential Defects:

Defects of the vertebral column in dogs - Congenital conditions

Deafness in Dogs

Canine Leukocyte Adhesion Deficiency

Congenital Portosystemic - Shunts in dogs

Defects of the Nervous System of Dogs

Defects of the vertebral column in dogs

Dog Hernias

A chart of many inherited dog health conditions  - Dog health conditions

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Veterinary articles supplied by Dr S Strydom and published with kind permission of DIA Publishing - publishers of KUSA Dogs in Africa Magazine.

Dr Sunelle Strydom qualified as a veterinarian in 2004 at the Faculty of Veterinary Science, University of Pretoria.  She has a passion for writing and the sharing of knowledge to promote animal health and welfare. She has written several articles for KUSA Dogs in Africa as well as for Vra vir Faffa on the Landbouweekblad website at www.landbou.com

References

• Ettinger S J and Feldman E C. 2000.  Textbook of Veterinary Internal Medicine 5th Edition. W.B. Saunders Company, USA
• The Merck Veterinary Manual (website). Available from http://www.merckvetmanual.com/ as accessed on 20 March 2010.
• The Free Dictionary by Farlex (website). Available from http://medical-dictionary.thefreedictionary.com as accessed on 20 March 2010.
• BVSc class notes.

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