Page 27 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery

Auscultation congestive heart failure. Crackles occurring during
both inspiration and expiration are a feature of chronic
The essential goal of auscultation is to answer three
VetBooks.ir questions: to movement of secretions in the large upper airways
bronchitis or bronchiectasis. Coarse crackles are due
and can be heard at the patient’s mouth.
• Are breath sounds present over the left and right lung
fields?
• Are the breath sounds the same over the left and right External examination and palpation
lung fields? Examination should be thorough but as stress-free as
• If the breath sounds are not the same over the left and
possible. Careful palpation of the external nasal cavity,
right lung fields, how are they different (e.g. diminished, pharynx, larynx, neck and ribs should be performed and
bronchial, presence of adventitious sounds)?
chest wall movement with respiration should be noted if
this has not already been done. Mucous membranes and
Because of variation in patient size and conformation, capillary refill should also be assessed. Cyanosis is always
the easiest approach is to divide the thoracic wall into grid a late sign in respiratory disease and may not be evident in
squares and auscultate each in turn. A good stethoscope patients with severe anaemia or poor perfusion.
(preferably with a paediatric chestpiece) and a quiet envi-
ronment are essential for accurate and meaningful auscul-
tation. Sounds on one side should be compared with those Radiography
heard on the contralateral side, during both inspiration and A detailed discussion of cervical and thoracic radiography
expiration. The patient’s hair can be moistened to limit mis- is outside the scope of this chapter. Although cervical and
interpretation of hair sounds as adventitious lung sounds.
thoracic radiography is undoubtedly an invaluable tool for
Normal lung sounds can be defined as follows:
the assessment of respiratory disease, the necessary
chemical or physical restraint required to produce an image
• Bronchial sounds are heard directly over the trachea of diagnostic quality may be counterproductive or even life-
and major bronchi during inspiration and expiration. threatening. Sufficient information to allow the patient to be
They are loud and high pitched, with a pause between stabilized can usually be gained from the history, physical
inspiration and expiration. The duration of the examination and initial laboratory investigations. If pleural
inspiratory sound is slightly shorter than that of the
space disease is suspected, thoracocentesis may prove
expiratory sound therapeutic as well as being diagnostic.
• Bronchovesicular sounds are heard over the major
bronchi and are softer and lower pitched than bronchial
sounds. They are heard equally during inspiration and Ultrasonography
expiration
Ultrasound examination in the investigation of non-cardiac
• Vesicular sounds are heard over all areas of the chest thoracic disease is now a well-established tool. A detailed
distal to the central airways. They have a softer
discussion is beyond the scope of this chapter, but the
intensity and are heard throughout all of inspiration and concept of TFAST (thoracic focused assessment with
only the first third of expiration. sonography in trauma, triage and tracking) examinations in
patients with respiratory distress is well described.
Absence or reduction of lung and/or heart sounds on Examination is rapid, safe, non-invasive and allows prompt
auscultation is indicative of pleural space disease, with air,
detection and monitoring of pneumothorax, pleural effu-
fluid or (in the case of diaphragmatic rupture) abdominal sion, chest wall injury and pulmonary contusions or other
viscera separating the heart and lungs from the chest wall.
pathology (Lisciandro, 2014).
Careful bilateral auscultation is important to determine any
asymmetry in distribution, and diagnostic thoracocentesis
is usually indicated. Pulse oximetry
Abnormal lung sounds can be most easily classified as Saturation of arterial haemoglobin with oxygen can be
wheezes or crackles. more accurately monitored by pulse oximetry. This is an
extremely useful non-invasive method for assessing and
• Wheezing results from airway narrowing and monitoring dyspnoeic patients. However, it has a number
subsequent increases in airflow through the segment. of limitations that must be understood if the information
A high-pitched wheeze is usually associated with provided by the pulse oximeter is not to be misinterpreted.
tighter obstruction, whereas a low-pitched wheeze Pulse oximetry works by comparing the absorption by
usually indicates less obstruction. Wheezes are haemoglobin of two different wavelengths of light passed
generated in large bronchi and are musical sounds with through an extremity. The degree of absorption changes
a constant pitch, more often heard during expiration. with the percentage of haemoglobin that is saturated with
They are commonly associated with small airway oxygen. A value of S aO 2 (arterial haemoglobin oxygen satu-
disease, bronchitis and feline asthma. A wheeze on ration) is determined from the ratio of the absorption of the
inspiration usually comes from the extrathoracic energy at the two wavelengths. Pulse oximeters generally
airways; the sound heard when there is severe display pulse rate and S aO 2. A beep may sound to indicate
narrowing is known as stridor. pulse rate, with the pitch varying with changes in S aO 2. A
• Crackles are intermittent crackling or bubbling sounds good estimation of the oxygen saturation of haemoglobin
of short duration, heard most commonly during is provided. However, it should be realized, from the sig-
inspiration. They are associated with both restrictive moid shape of the oxyhaemoglobin dissociation curve,
and obstructive disease. Early inspiratory crackles are that although S aO 2 varies in a fairly linear way with P aO 2 at
a common feature of small airway disease, whereas low partial pressures, the slope flattens at higher partial
late or end-inspiratory crackles can occur with pressures. Therefore, S aO 2 will be reasonably high (>90%)
atelectasis, pneumonia, pulmonary fibrosis or unless P aO 2 is as low as about 60 mmHg. When using a

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