Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 7
Elastic band
Plastic rectal
glove
Figure 7.7 Rebreathing bag can be used to increase the respiratory rate and to aid auscultation of the lung sounds.
cise, excitement) or due to pathological states (e.g.
pyrexia, pneumonia with lung consolidation). Louder
or abnormal sounds are produced by increased
air velocity through narrowed airways. Sound is
transmitted more efficiently by denser material, and
louder breath sounds can be caused by an increase
in the density of the tissue through which the
sound is being transmitted. Pneumonia with lung
consolidation and atelectasis are examples.
Abnormal inspiratory sounds These indicate
upper airways abnormalities. In conditions which
cause narrowing of the upper airways, such as a
retropharyngeal abscess or laryngeal calf diphtheria,
abnormal respiratory sounds such as stridor may
be heard on inspiration. This noise may radiate
throughout the trachea and the lung fields. It is produced
by an increase in the airflow velocity through
the narrowed upper airway. Narrowing of the airway
is most pronounced on inspiration because of
the lower pressure in the trachea at this stage of the
respiratory cycle. During expiration there is a higher
positive pressure in the airway which tends to open
it up.
Abnormal expiratory sounds These indicate lower
airway abnormalities. In conditions which cause
narrowing of the lower airways within the thorax,
such as bronchopneumonia, the breath sounds are
louder during expiration and quieter during inspiration.
During inspiration, the diameter of lower airways
within the thorax is increased by the outward
movement of the chest wall and decreased during
expiration by compression of the chest. The airflow
velocity is therefore greatest during expiration.
In cattle with tachypnoea and hyperpnoea there is
an increase in the airflow velocity on both inspiration
and expiration, with an increase in the loudness of
both sounds.
Decreased loudness of breath sounds The reasons
may be physiological (e.g. a very fat animal) or
pathological (e.g. pleural effusion, pneumothorax,
space-occupying lesions). These conditions insulate
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