Abnormal respiratory sounds often provide valuable diagnostic clues in veterinary practice. For veterinary technicians preparing for the VTNE®, it is very important to be able to distinguish between stertor and stridor.
Both sounds indicate upper airway compromise but they originate from different parts of the upper respiratory tract and suggest different underlying causes. Learning to distinguish these sounds helps technicians assist veterinarians with clinical localization and rapid patient assessment for best treatment outcomes.
What Is Stertor?
Stertor is a low-pitched respiratory noise often described as snoring, often audible during both inspiration and expiration.
This occurs when airflow passes by abnormal/narrowed soft tissues in the upper airway (particularly obstruction of the nasal passages, soft palate, or pharynx) causing vibration of the tissues.
Common Causes of Stertor
Several conditions can produce stertor in veterinary patients.
One common cause is nasopharyngeal polyps in cats. These inflammatory growths develop from the mucosal lining of the tympanum, pharynx, or auditory tube and partially obstruct airflow if they extend into the nasopharynx.
Stertor also occurs frequently in brachycephalic dog breeds, such as bulldogs (American or French) and pugs. These breeds classically have anatomical abnormalities collectively known as “brachycephalic airway syndrome.”
Common features of brachycephalic airway syndrome include:
- Elongated soft palate
- Narrow nostrils (stenotic nares)
- Everted laryngeal saccules
- Hypoplastic trachea
What is Stridor?
Stridor is a high-pitched, harsh respiratory sound caused by a narrowing of a large, rigid airway structure such as the larynx or trachea.
The sound often resembles a whistle or squeal and often is louder during inspiration when airflow increases.
Common Causes of Stridor
Several diseases can produce stridor in dogs and cats.
One of the most recognized causes is laryngeal paralysis, a condition in which the nerves responsible for opening the larynx during inspiration fail. Instead of actively retracting during inspiration, the arytenoid cartilages remain flaccid and the negative pressure of inspiration further pulls the tissues inward. This causes airflow restriction and a characteristic high-pitched sound.
Another important cause is tracheal collapse, which commonly affects small breed dogs such as Yorkshire terriers and Pomeranians. The cartilage rings that normally support the trachea weaken and flatten, narrowing the airway during inspiration and producing a distinctive wheezing or honking sound.
Other potential causes of stridor include airway tumors, foreign bodies, or severe inflammation.
A Core Triage Skill for Veterinary Technicians
Veterinary technicians are often the first members of the veterinary team to observe abnormal respiratory sounds during their initial patient assessment.
Recognizing the difference between stertor and stridor can help technicians:
- Localize respiratory disease within the airway
- Identify potentially life-threatening obstructions
- Communicate critical findings to the veterinarian
- Prioritize triage and stabilization
In patients with severe respiratory distress, rapid recognition of airway obstruction can be essential in initiating appropriate therapy.
The Veterinary Technician’s Role in Identifying Airway Obstruction
Stertor and stridor both indicate airway obstruction, but they arise from different regions of the respiratory tract and suggest different underlying diseases.
By learning to recognize these sounds and understanding their clinical significance, veterinary technicians improve diagnostic accuracy, better assist with emergency triage, and strengthen their VTNE® exam preparation.
More from Zuku Review:
- Shop the VTNE® Test Prep Summer Sale
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