Diseases of the Trachea
and Upper Airways
Noninfectious Tracheitis
• Tracheitis refers to an inflammation of the epithelial lining of the trachea.
• This inflammatory response may be infectious or noninfectious;
primary or secondary.
• The noninfectious causes of chronic tracheitis are probably more common and are discussed as a group.
• Noninfectious tracheitis is usually a secondary problem to prolonged
barking, collapsing trachea, chronic cardiac disease, and disease of
the oropharynx.
• Most patients with tracheitis are asymptomatic except for a cough, which is characterized as resonant, harsh, paroxysmal, and often terminated by nonproductive or slightly productive gagging.
• The physical examination is often normal and no fever is present. Firm palpation of the trachea near the thoracic inlet elicits the typical tracheal cough.
• If a cardiac murmur or arrhythmia exists, cardiac disease must be eliminated as the primary cause for the coughing or as the cause of chronic tracheitis.
• Tracheitis as a primary disease often has no specific radio- graphic features. ]n acute tracheitis edema of the mucosal lining may result in a reduction of the lumen diameter.
• Care must be taken not to confuse this for a fixed, hypoplastic trachea. The radiographic features that occur when tracheitis is secondary to other diseases are included in the discussions of those conditions.
• Therapy should be directed at the primary underlying disease process, and these treatments are discussed in their appropriate sections.
• The cough associated with secondary tracheitis may act as a continued source of irritation, which perpetuates the tracheitis, and a vicious cycle ensues. Treatment of the underlying disease process may not always be adequate to relieve the cough because of this cycle of "cough-induced tracheitis:' which perpetuates the cough and the tracheitis.
Infectious canine tracheobronchitis
• Infectious canine tracheobronchitis, also known as canine respimtol}' disease complex and kennel Cough,is not a single disease, but rather a clinical disease
syndrome. Included in this mu!tietiology syndrome are infectious agents such as viruses, bacteria, mycoplasma, fungi, and parasites. The most frequently isolated organisms responsible are H. bnmcltiseptica with canine parainfluenza or canine adenovirus (CAV; CAD-2).
• Infectious canine tracheobronchitis is highly contagious and most commonly occurs where groups of dogs of different ages and susceptibility are congregated.
• There is almost always a history of exposure to other animals, as in a
kennel, hospital, or dog show
• Diagnosis is made most often on the basis of circumstantial evidence. History of exposure with a dry hacking cough is usually sufficient.
• Thoracic auscultation, thoracic radiographs, and hemograms are usually unremarkable. Tracheal cytology may reveal increased numbers of neutrophils and bacteria. Bacterial or Mycoplasma spp. isolation, as well as virus isola- tion and serologic evaluation, can be performed but are usually unnecessary.
• Uncomplicated cases of tracheobronchitis probably do not require antimicrobials.
Even though antibiotics have not been shown to reach significant concentrations in tracheobronchial secretions or to shorten the course of infection, prophylactic therapy has been recommended by some.
• Antibiotic treatment is indicated if there is deeper respiratory involvement or if the animal is showing signs of systemic illness. Drugs chosen should be based on results of bacterial culture and sensitivity testing. In the absence of culture results, choices of oral anti- biotics include azithromycin chloramphenicol, fluoroquino- lones, or cephalosporins. Fluoroquinolones, as with most antimicrobials, poorly penetrate tracheal and bronchial secretions.~
Lungworm (Oslerus osler;; Filaroides osleri)
• Filaaroides asoleri, renamed Oslerus asleri, is a worldwide parasitic disease in dogs younger than 2 years of age. It can be seen in individual situations but is more often a kennel- related problem (especially in Greyhounds).
• Although most often described in young dogs, the infestation does persist in older animals, often without significant pathophysiologic effects.
• Dogs usually present with chronic, mild to severe inspiratory wheezing sounds, dyspnea, coughing, and/or debilitation. Usually panting is not prominent except in advanced cases.
• The severity of the clinical signs may be overplayed in the literature. Most dogs experience definite but mild, often non- progressive respiratory signs. Exercise intolerance does occa- sionally occur and coughing is typically characterized as a harsh tracheobronchial sound associated with attempts at terminal retching.
• Many drugs have been reported to be effective in treating lungworms, such as thiacetarsemide sodium, diethylcarbam- azine, levamisole, fenbendazole, and albendazole.
• We have treated several dogs with oral ivermectin at 1000 I1g/lb once weekly for 2 months. The nodules were reduced in size but did not resolve entirely. All of these dogs became asymptomatic and continued to thrive.
• Thiabendazole was administered at 35 mg/kg twice daily for 5 days and then at 70 mg/kg twice daily for 21 days. Along with thiabendazole, prednisone at 0.5 mg/kg was given twice daily every other day
Tracheal and Bronchial Travma
• Laceration of the tracheal wall causes subcutaneous and/or mediastinal emphysema. Blunt trauma to the trachea, although unusual, may cause a tear.
• Bite wounds to the neck incurred during a dog or cat fight, transtracheal wash procedure, and inadvertent laceration of the trachea during jugular venous puncture, severe coughing episodes, and overinflation of an endotracheal cuff in cats intubated for anesthetic rrocedures may all be responsible for tracheal tearing
• A ventrolateral tear of the annular ligament may rroduce secondary subcutaneous emrhysema over the entire body.
• This latter condition develors frequently in dogs or cats involved in fights during which a tooth punctures or lacerates the tracheal wall. Air escares from the tracheal orening and enters the subcutaneous tissue of the neck
• The subcutaneous emphysema may involve only the reri- tracheal region or be more extensive and involve the entire subcutaneous area of the hody. Such tears may also be resron- sible for the development of pneumomediastinum in both the dog and the cat
• If the subcutaneous air collection is regressing and there are no signs of pulmonary distress, it is usually recommended that the patient be mildly sedated and be cage rested, which allows the emphysema to regress by slow ahsorrtion, and occasion- ally hy aspiration through a large-bore needle and wrapping the body with elastic handages, being careful not to mechanically restrict resriration.
• Surgical repair of a torn tracheal ligament may be required. Most tears have been found dorsolaterally on the trachea at or near the thoracic inlet.'
CANINE CHRONIC BRONCHITIS
• An inflammatory process of the upper airways and specifically the hronchi, chronic hronchitis results in daily coughing for a period of greater than 2 months. It is less often diagnosed in the cat and then is part of the reline Bronchial Disease syndrome
• Chronic bronchitis is associated with neutrophilic an
• d/or eosinophilic intiltration of the mucosa, thickening of the smooth muscle layer, tibrosis, and scarring of the lamina propria with increased goblet and glandular cell size and numbers.
• Clinicopathologic abnormalities are not commonly noted with chronic bronchitis unless there is an infection present.
• The most significant signs (and diagnostic as well) are noted with thoracic radiography. Although films of the thorax can establish the suspicion of chronic bronchitis, normal chest radiographs do not rule out chronic airway disease.
• The bronchial pattern observed radiographically includes increased nonvascular linear markings, cross-sectional end-on bronchi (doughnuts), and longitudinal section (tram lines) airway walls thickened by inflammation.
• Peribronchial wall infiltra- tion (peribronchial cuffing), bronchial wall calcification, and puffy alveolar infiltrates are additional diagnostic features observed more commonly in dogs with bron- chitis than in age- and breed-matched controls.
• Computed tomography enhances the smaller and finer bronchial structures and is likely to identify cases not visualized on routine flat plate radiography.
