Page 616 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Respir atory system: 3.1 Introduction 591

VetBooks.ir 3.2

Fig. 3.2 Auscultation of the lung
field at rest often fails to reveal
significant abnormalities because
the horse has a large respiratory
reserve.

being exercised (Fig. 3.2). Its sensitivity can be Less marked airway constriction generates
improved by auscultation during and immediately bronchial sounds that are harsher and more
after re- breathing. Abnormal sounds can be accen- audible than normal, rather than wheezes.
tuated by: • Crackles are short, harsh sounds that sound
like bubble wrap packaging and are generated
• Use a large-volume plastic bin liner and fold the by collapsed small airways or alveoli (because
free edges over to give better control. of surface tension effects of discharge) snapping
• Introduce the bag over the horse’s muzzle, open at the end of inspiration and during
gather the free bag to form a good seal between expiration. Fluid or bubbling sounds are very
the bag and the muzzle, and hold the bag in unusual in horses. Note that, in contrast
position under the nose band of the head collar. to humans, crackles are usually not due to
• As the horse re-breathes the air from the bag, emphysema; this is a rare pathology even in
its breathing rate and effort increase as carbon horses with severe pulmonary disease.
dioxide concentration increases. • Friction rubs are high-pitched, squeaky
• Keep the bag in place for as long as the horse will sounds generated by inflamed pleural surfaces
tolerate it (the length of time the bag is tolerated is rubbing together, indicating pleuritis or
not an indicator of abnormality); auscultation can pleuropneumonia.
be done with the bag in place if desired.
• The horse will continue to take deep rapid Lung field percussion
breaths for a minute or two after the bag is Percussion is often omitted from the clinical exami-
removed, accentuating abnormal sounds. nation, but this is a mistake as valuable information
• This method is more informative than occluding about the presence of pleural effusion and, possibly,
the nostrils and is usually better tolerated. the extent of the inflated lung field can be obtained.
Percussion can be carried out either by placing the
There is a surprisingly small range of abnormal first two fingers of one hand over an intercostal
sounds heard in horse lungs: space and tapping these fingers firmly with the tips
of the first two fingers of the other hand or, more
• Wheezes are musical, sighing sounds generated effectively, by using a plexor and pleximeter.
by air moving through airways narrowed Working from cranial to caudal, each intercostal
by bronchoconstriction and/or discharges. space is percussed from dorsal to ventral to identify