Contributors: Vetstream Ltd

 Species: Feline   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Cause: congenital anatomical defects present in brachycephalic breeds.
  • Signs: mouth breathing, stertorous breathing, collapse when playing, cyanosis.
  • Diagnosis: breed, signs, radiography and advanced imaging, endoscopic examination.
  • Treatment: surgical correction of underlying defects.
  • Prognosis: good in mild-moderate cases with surgery.
Print off the owner factsheet on Brachycephalic upper airway obstruction syndrome (BUAOS) Brachycephalic upper airway obstruction syndrome (BUAOS) to give to your client.

Presenting Signs

  • Exercise intolerance.
  • Stertor, stridor.
  • Cyanosis.

Acute Presentation

  • Respiratory distress or sudden collapse (particularly in hot weather).
  • May have almost total airway obstruction, can develop non-cardiogenic pulmonary edema Lung: pulmonary edema, and can die rapidly without treatment.

Age Predisposition

  • Clinical signs in severely affected cases manifest at a young age.
  • Many will present at 2-4 years of age.

Breed Predisposition

Cost Considerations

  • Moderately expensive surgery required in cases with clinical signs.



  • Syndrome comprising one or more of the following defects:
    • Elongated soft palate.
    • Everted larngeal saccules Larynx disease.
    • Collapsed larynx.
    • Stenotic nares.
    • Hypoplastic trachea.
    • There may also be a contribution from intranasal stenosis due to abnormal conchae and from nasopharyngeal turbinates.

Predisposing Factors


  • Obesity.
  • Hot weather.
  • Exercise.
  • Excitement.


  • Airflow through airways is impeded due to abnormal anatomy   →   noisy breathing and inadequate oxygen intake to meet increased demands.
  • Restricted airflow   →   increased inspiratory effort   →   increased negative pressure within airway and eversion of laryngeal saccules, in severe cases laryngeal collapse. Both changes exacerbate the problem.
  • Increased respiratory effort may   →   upper airway edema   →   further obstruction to airflow and vicious cycle is set in motion.


  • Weeks to months.


Presenting Problems

  • Stertor.

Client History

  • Mouth breathing.
  • Noisy breathing.
  • Collapse after playing.
  • Signs may be exacerbated by exercise, excitement or hot weather.
  • Gagging/retching cough.
  • Vomiting.

Clinical Signs

  • Stertorous respiration with increased laryngeal noise on auscultation.
  • Turbulent airflow in airways.
  • Cyanosis.
  • Narrow nares.

Diagnostic Investigation

Investigations that require sedation or general anesthetic are dangerous for cats with upper respiratory disease Viral-induced upper respiratory tract disease, particularly during the recovery. It is recommended that these investigations are only performed when there is the ability to proceed to correction of the suspected defect under the same anesthetic.


  • Direct examination of the airways with a laryngoscope Laryngoscopy under heavy sedation or light anesthesia permits assessment of:
    • Function/collapse of larynx.
    • Eversion of laryngeal saccules.
    • Soft palate length.


  • See thoracic radiography Radiography: thorax.
  • The trachea can be examined in the thorax and cervical region to assess for hypoplasia.

CT scans

Biochemistry and hematology

  • Blood gas analysis Arterial blood gas sampling may show reduced arterial blood oxygen saturation in severe cases.
  • Chronic hypoxia can lead to polycythemia.


  • See ECG overview  ECG: overview.
  • May have marked sinus arrhythmia.

Gross Autopsy Findings

  • Signs related to syndrome, ie elongated soft palate. 

Differential Diagnosis


Initial Symptomatic Treatment

Standard Treatment

  • Weight loss.
  • Surgical correction of anatomical defect:
    • Soft palate resection.
    • Laryngeal saccule resection.
    • Correction of stenotic nares.
  • Neutering at the time of corrective surgery is recommended.



  • Patients with clinical signs require surgical intervention as continued increased inspiratory effort will exacerbate severity of underlying pathology.
  • Prognosis depends on the severity of underlying anomalies and the ability of the surgeon to correct them.
  • With appropriate surgical correction the prognosis can be good.
  • Laryngeal collapse carries a very poor prognosis and cannot be surgically corrected, would require permanent tracheostomy.

Expected Response to Treatment

  • Reduced respiratory noise.
  • Reduced respiratory rate.
  • Improved exercise tolerance.
  • Improved oxygen saturation of blood.

Reasons for Treatment Failure

  • Failure to diagnosis and manage all elements of airway obstructive syndrome.
  • Cats appear to be difficult to manage surgically.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Corgozinho K B, Pereira A N, Cunha S C et al (2012) Recurrent pulmonary edema secondary to elongated soft palate in a cat. J Feline Med Surg 14 (6), 417-419 PubMed.
  • Hammond G, Geary M, Coleman E et al (2011) Radiographic measurements of the trachea in domestic shorthair and Persian cats. J Feline Med Surg 13 (12), 881-884 PubMed.
  • Mercurio A (2011) Complications of upper airway surgery in companion animals. Vet Clin North Am Small Anim Pract 41 (5), 969-980 PubMed.
  • Engberg (2010) Brachycephalic cats - is it too late for the Persian? J Feline Med Surg 12 (1), 55 PubMed.
  • Keyes M (2010) Brachycephalic cats - is it too late for the Persian? J Feline Med Surg 12 (1), 55 PubMed.
  • Ginn J A, Kumar M S A, McKiernan B C et al (2008) Nasopharyngeal turbinates in brachycephalic dogs and cats. J Am Anim Hosp Assoc 44 (5), 243-249 PubMed.
  • Aron D N, Crowe D T (1985) Upper airway obstruction. General principles and selected conditions in the dog and cat. Vet Clin North Am Small Anim Pract 15 (5), 891-917 PubMed.

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