Page 43 - Problem-Based Feline Medicine

4 – THE CAT WITH STRIDOR OR STERTOR 35

INTRODUCTION DISEASES CAUSING NASAL STRIDOR

MECHANISM? SECONDARY BACTERIAL RHINITIS***
Airflow through a narrowed upper airway has increased
Classical signs
resistance and becomes more turbulent. This resistance
is a function of the diminished luminal diameter of the ● Chronic sneezing and snuffling.
tube, the resistance increasing to the fourth power of ● Chronic mucopurulent nasal discharge.
the radius. ● Stertorous respiration or stridor.
● Occasionally, nasal distortion.
With dynamic obstructions, dyspnea occurs during
inspiration, because the negative intraluminal airway
See main reference on page 21 for details (The Cat
pressure creates a vacuum, pulling the walls inwardly.
With Signs of Chronic Nasal Disease).
Any weakened area of the airway wall will tend to
move into the lumen, decrease the luminal diameter,
Clinical signs
and create an obstruction.
Chronic secondary bacterial rhinitis occurs in some
Fixed obstructions cause both inspiratory or expira-
cats following viral upper respiratory tract disease.
tory stridor, although inspiratory noises are more
prominent. Typically there is a history of chronic sneezing and snuf-
fling following acute upper respiratory tract signs.
Stertor are snoring sounds. Stridor is a harsh,
high-pitched whistling respiratory sound created Chronic mucopurulent nasal discharge.
by upper airway obstructive diseases, such as the
Stertorous respiration (snoring) or stridor (high pitched
inspiratory sound of acute laryngeal obstruction.
whistling respiration).
Occasionally, nasal distortion.
WHERE?
Diagnosis
Stridor or stertor arise from luminal narrowing in the
upper airways, generally involving the pharynx, soft Diagnosis is based on a history of chronic signs of long
palate, laryngeal structures and the upper trachea. duration (>6 months), especially if the history includes
Nasal stridor or stertor may also be encountered. acute upper respiratory tract signs preceding the
chronic problem. Diagnosis is based on exclusion of
neoplasia and cryptococcosis.
WHAT?
With dynamic obstructions, the airflow limitation STENOSIS OF THE EXTERNAL NARES**
occurs mainly during inspiration. Dynamic obstruc-
tions include laryngeal paralysis, tracheal collapse Classical signs
and epiglottic entrapment.
● Chronic snuffling and stertorous
Fixed obstructions, such as foreign objects and mass respiration or stridor.
lesions, affect airflow during both inspiration and expi- ● Dyspnea or mouth breathing.
ration, although inspiratory noises are generally more ● Narrow external nares.
prominent.