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194 Collapsing Trachea

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BASIC INFORMATION
generally not associated with clinical
signs requires assessment of the trachea with radio-
graphs, fluoroscopy, or bronchoscopy.
Definition ○ II: 50% reduction in airway lumen, tra-
Progressive weakening of the tracheal cartilages cheal rings elongated and mildly flattened Differential Diagnosis
with dorsoventral flattening of tracheal rings ○ III: 75% reduction in airway lumen, • Cough (pp. 217 and 1209)
and prolapse of the tracheal membrane (TM) tracheal rings markedly flattened • Other causes of syncope (p. 953) or collapse
into the lumen resulting in cough and airflow ○ IV: >90% reduction in airway lumen, (p. 1206)
limitation severely flattened tracheal rings, possibly
with dorsal deviation of ventral tracheal Initial Database
Synonyms surface; often associated with severe clini- • CBC/serum biochemical profile/urinalysis:
Collapsing trachea, tracheal collapse (TC), cal signs unremarkable or increased liver enzymes
tracheomalacia • Heartworm antigen: rule out heartworm
HISTORY, CHIEF COMPLAINT disease
Epidemiology • Chronic paroxysms of a loud, honking cough • Radiographs: inspiratory (cervical collapse)
SPECIES, AGE, SEX (goose honking) ± terminal gag/retch and expiratory (thoracic collapse) views
• Small- and toy-breed dogs; rarely reported ○ Signs may worsen with excitement, heat, are necessary. Both false-positive and false-
in large-breed dogs and cats eating/drinking, or exercise negative interpretations occur.
• Considered a disease of middle-aged dogs, • Clinical signs are often progressive. ○ Minimum of three thoracic views to assess
although 25% of affected dogs show clinical • Cyanosis, respiratory distress, or syncope in for comorbid conditions (e.g., pneumonia)
signs by 6 months of age severely affected animals ○ May underestimate degree of collapse or
• No sex predisposition miss dynamic collapse
PHYSICAL EXAM FINDINGS
GENETICS, BREED PREDISPOSITION • Cough elicited with tracheal palpation Advanced or Confirmatory Testing
• Yorkshire terriers: one-third to two-thirds ○ Nonspecific: dogs with other respiratory • Fluoroscopy: noninvasive and helpful in
of reported cases disorders, (e.g., pulmonary edema), and identifying dynamic collapse in real time;
• Toy and miniature poodles, Maltese, Chi- clinically normal dogs may have elicitable an elicited cough may improve detection
huahua, and Pomeranian cough and can help grade collapse severity
• Congenital disorder suspected ○ Occasionally, tracheal shape abnormalities • Bronchoscopy: assesses location and severity
palpable of collapse and allows collection of airway
RISK FACTORS • Extrathoracic TC: wheezes may be ausculted wash samples to rule out concurrent
Conditions leading to exacerbations of clinical over the cervical trachea. infectious/inflammatory conditions
signs ○ ± Increased effort on inspiration ○ Requires anesthesia and intubation that
• Inhalation of airway irritants • Intrathoracic TC: tracheal snap may be can precipitate respiratory decompensation
• Obesity ausculted due to dynamic opening and in severely affected patients.
• Respiratory tract infection collapse of large airways (sound due to airway
• Tracheal intubation opening during inspiration). TREATMENT
• Stress/excitement ○ ± Increased effort on expiration
• Increased environmental temperatures/ • Although not related to TC directly, many Treatment Overview
humidity affected dogs are obese, demonstrate systolic Medical management includes antitussives,
mitral murmurs, and/or have palpable weight management, environmental modifica-
ASSOCIATED DISORDERS hepatomegaly. tion, and treatment of comorbid conditions.
• Laryngeal paralysis (p. 574) Other therapies (e.g., antiinflammatories,
• Chronic bronchitis (p. 136) Etiology and Pathophysiology antibiotics, +/− bronchodilators) can be added
• Bronchomalacia (45%-83% of dogs with The cause is unknown and likely multifactorial. if initial response is inadequate or during exac-
tracheal collapse) Suggested mechanisms: erbation in signs. In severe cases nonresponsive
• Pneumonia secondary to impaired tracheo- • Congenital to medical management, tracheal stents can be
bronchial clearing mechanisms ○ Failure of chondrogenesis placed to alleviate airway obstruction.
• Hyperthermia • Acquired
• Respiratory distress (p. 879) ○ Secondary to chronic small airway Acute General Treatment
• Syncope disease • Oxygen support (p. 1146), sedation, external
• Hepatomegaly (significance unclear) ○ Cartilage degeneration cooling, and cough suppressants may be
• Pharyngeal collapse ○ Trauma necessary in an acute crisis (pp. 879 and 574).
• Mitral valve endocardiosis ○ Loss of innervation of the trachealis ○ Antitussive: butorphanol 0.02-0.1 mg/kg
dorsalis muscle SQ q 4-6h
Clinical Presentation • Disease is exacerbated/perpetuated by a cycle ○ Low-dose acepromazine 0.05-0.1 mg/kg
DISEASE FORMS/SUBTYPES of chronic inflammation worsened by chronic IM, maximum of 3 mg/DOG for sedation
• Can involve the extrathoracic and/or intratho- cough. in cases of severe TC-related coughing.
racic trachea. Common at the thoracic inlet, Some authors have reported excessive seda-
TC often occurs in more than one location. DIAGNOSIS tion at this dose, preferring 0.01-0.03 mg/
Collapse of the large bronchi also common kg IM or IV.
• Grades of TC Diagnostic Overview • Intubation may be required for dogs in
○ I: minor protrusion of TM into airway TC is suspected in at-risk breeds with charac- respiratory distress, ideally followed by
lumen, < 25% reduction in diameter; teristic history and exam findings; confirmation immediate stent placement.

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