Page 303 - Small Animal Internal Medicine, 6th Edition

CHAPTER 17 Diagnostic Tests for the Larynx and Pharynx 275

region. A tongue depressor for elevating the soft palate and dogs required intubation when increased breathing efforts
a head lamp or well-positioned surgical lamp facilitate the resulted in significant obstruction to airflow at the larynx.
VetBooks.ir examination. arytenoid cartilages should be continued as long as possible
If no laryngeal motion is observed, examination of the
The motion of the arytenoid cartilages is evaluated while
the patient takes several deep breaths. An assistant is needed
thesia and shallow breathing are the most common causes
to verbally report the onset of each inspiration by observing while the animal recovers from anesthesia. Effects of anes-
chest wall movements. Normally the arytenoid cartilages of an erroneous diagnosis of laryngeal paralysis.
abduct symmetrically and widely with each inspiration and After evaluation of laryngeal function, the plane of anes-
close on expiration (Fig. 17.4). Laryngeal paralysis resulting thesia is deepened and the caudal pharynx and larynx are
in signs of upper airway obstruction is usually bilateral. The
cartilages are not abducted during inspiration. In fact, they
may be passively forced outward during expiration and/or
sucked inward during inspiration, resulting in paradoxical
motion.
If the patient fails to take deep breaths, doxapram hydro-
chloride (1.1-2.2 mg/kg, administered intravenously) can SP
be given to stimulate breathing. In a study by Tobias et al.
(2004), none of the potential systemic side effects of the
drug were noted following the 1.1 mg/kg dosage, but some

*

A E

SP

A

*

E

B

FIG 17.5
The laryngeal anatomy from a healthy dog (A) is contrasted
with that of a dog with laryngeal collapse (B). In the
B collapsed larynx, the cuneiform process (*) of the arytenoid
process has folded medially and obstructs most of the
FIG 17.4 airway. Also labeled are the soft palate (SP) and the
Canine larynx. (A) During inspiration, arytenoid cartilages epiglottis (E). In the photograph from the healthy dog, the
and vocal folds are abducted, resulting in wide symmetric soft palate is being held dorsally by a retractor (reflective,
opening to the trachea. (B) During expiration, cartilages silver), and the tip of the epiglottis is not in view. (Courtesy
and vocal folds nearly close the glottis. Elizabeth M. Hardie.)