Stertor and stridor are abnormally loud sounds as air passes through a narrowed airway during breathing. Both result from vibration of tissue protruding into the airway.
Stertor is snoring or a low-pitched sound that arises from air passing over loose tissue projecting into the airway. It occurs during inhalation.
Stridor is a high-pitched sound, like wind, that results from air passing over more rigidly anchored tissue.
The origin of abnormally narrowed air passegeway may be the back of the throat (nasopharynx), the throat (pharynx), the voice box (larynx), or the windpipe (trachea).
In most situations, stertor arises from pharyngeal airway obstructions, while stridor is commonly the result of nasal or laryngeal obstructions.
Noisy breathing is a common condition in short-nosed, flat-faced (brachycephalic) dog breeds. Inherited paralysis of the voice box, known as laryngeal paralysis, has been identified in Bouviers des Flandres, Siberian huskies, bulldogs, and Dalmatians. It mostly occurs in the first year of the dog,
Acquired paralysis of the voice box (laryngeal paralysis) is more common in certain giant-breed dogs, such as St. Bernards and Newfoundlands, and in large-breed dogs, such as Irish setters, Labrador retrievers, and golden retrievers, than other breeds. Acquired paralysis of the voice box typically occurs in older dogs.
Common symptoms associated with noisy breathing include:
Change or loss of voice – inability to bark
Partial blockage of the upper airways produces an increase in airway sounds before producing an obvious change in breathing pattern
Unusually loud breathing sounds may have existed for as long as several years
Breathing sounds can be heard from a distance without the use of a stethoscope
Nature of the sounds range from abnormally loud to obvious fluttering to high-pitched squeaking, depending on the degree of airway narrowing
May note increased breathing effort; breathing often accompanied by obvious body changes (such as extended head and neck and open-mouth breathing)