Proceedings of a Workshop on - The Havemeyer Foundation

Havemeyer Foundation Monograph Series No. 11
itself difficult. This creates a small risk <strong>of</strong> injury to
the horse or the people involved with the
procedure. Sedation is usually not an option. Thus,
experienced handlers become very important.
To address the above concerns, some vendors
will allow only a few experienced veterinarians to
examine endoscopically certain yearlings. They
may ask other veterinarians wanting to examine
the UA to contact the few veterinarians who did
examine the horse, for their opinion. However, in
general, most vendors allow as many UA
examinations as requested. There is a direct
relationship between the number <strong>of</strong> veterinary
examinations <strong>of</strong> the UA and the number <strong>of</strong>
potential buyers.
INTERPRETING UPPER AIRWAY FINDINGS
Accurate interpretation <strong>of</strong> the findings from UA
examination is not difficult for most horses as they
are well within normal limits. However, for some
horses this can be challenging. A veterinarian is
expected to determine suitability <strong>of</strong> the UA for
racing during a brief single examination. The
pharynx/larynx is observed at rest, after
swallowing, and usually during nasal occlusion.
In most immature horses the arytenoids are
well abducted throughout much <strong>of</strong> the UA
examination, or easily maximally abduct following
swallowing, or when the UA is stressed during
nasal occlusion. Rarely is complete paralysis <strong>of</strong> an
arytenoid found in a yearling. In the experience <strong>of</strong>
the author’s practice this occurs in less than 0.2%
<strong>of</strong> the general population <strong>of</strong> thoroughbred
yearlings examined during the first three-quarters
<strong>of</strong> their yearling year. The arytenoid function <strong>of</strong>
yearlings that fall between complete paralysis and
relatively easily achieved maximal abduction can
be difficult to interpret and requires good judgment
to determine suitability for purchase.
It is recognised that many normally functioning
arytenoids that are neither perfectly symmetrical
nor synchronous, do not become dysfunctional. It is
also generally believed that complete arytenoid
paralysis is usually preceded by progressive,
deterioration <strong>of</strong> arytenoid function <strong>of</strong> variable
duration. Thus, when evaluating the UA <strong>of</strong> a sales
yearling the arytenoids that do not function in an
ideal fashion do raise the level <strong>of</strong> concern.
It has been noted that arytenoid movement in
some yearlings can change mildly over a few to
several months, over a few days, or even from
morning to afternoon. This may change the
opinion <strong>of</strong> the examining veterinarian <strong>of</strong> whether
the UA is acceptable. Some yearlings are
uncooperative and cannot be induced to fully
abduct the left and right arytenoids even with nasal
occlusion. The author considers this within normal
limits for this age if they are relatively
symmetrical and synchronous. In some yearlings
one arytenoid (usually the left) does not fully
abduct, even with nasal occlusion. The author
considers this normal if the arytenoid abducts to at
least 95% <strong>of</strong> what would be considered maximal
abduction.
Is a yearling within normal limits if an
arytenoid can fully abduct briefly after swallowing
and fully abduct briefly with nasal occlusion, but
not maintain abduction? This becomes a judgment
call on whether the abduction was maintained long
enough to be considered acceptable by the
examining veterinarian.
RECORDING FINDINGS (GRADING
SYSTEMS)
Being able to record endoscopic findings in a
consistent manner is important. This allows
subsequent review <strong>of</strong> notes to determine
accurately the status <strong>of</strong> the UA during that
examination. The veterinarian can then explain to
a client or another veterinarian what was seen at
that time. This also provides a comparative
reference for a subsequent examination <strong>of</strong> the
same horse and for UA findings <strong>of</strong> other horses.
Different grading systems for arytenoid
movement have been used. This can make
communication between veterinarians difficult
unless the actual description <strong>of</strong> the arytenoid
movement is used. Some <strong>of</strong> the grading systems
proposed and used have had from 4 to 10 different
categories for arytenoid movement. Some
veterinarians have abandoned these grading
systems and just describe what was seen. Some
veterinarians combine all the findings <strong>of</strong> the UA
endoscopic examination and give the entire
pharynx/larynx a letter grade.
A relatively simple grading scale that is easy
to use and widely accepted is needed. The problem
with having too few categories is the broad range
<strong>of</strong> arytenoid movements that fit in a single
category. A system with too many categories
becomes too complicated to use easily.
Regardless <strong>of</strong> the grading system used, some
arytenoids will not fit precisely into a specific
category. However, a widely accepted grading
43