Page 313 - Small Animal Internal Medicine, 6th Edition

CHAPTER 19 Clinical Manifestations of Lower Respiratory Tract Disorders 285

were described in the previous sections. A complete physical
examination, including a fundic examination, is warranted
VetBooks.ir to identify signs of disease that may be concurrently or sec-
ondarily affecting the lungs (e.g., systemic mycoses, meta-
static neoplasia, megaesophagus).
The cardiovascular system should be carefully evaluated. 4 1
Mitral insufficiency murmurs are frequently auscultated in 3
older small-breed dogs brought to the clinician with the 2
primary complaint of cough. Mitral insufficiency is often
an incidental finding, but the clinician must consider both
cardiac and respiratory tract diseases as differential diagno-
ses in these animals. Mitral insufficiency can lead to con-
gestive heart failure with pulmonary edema, and left atrial
enlargement itself may contribute to cough. Cough associ-
ated with mitral insufficiency has been presumed to be a
result of airway compression by an enlarged left atrium, but
collapse of the left bronchus appears to be independent of FIG 19.2
Auscultation of the respiratory tract begins with the
atrial size (Singh et al., 2012). Other factors, such as vibra- stethoscope positioned over the trachea (stethoscope
tion from a mitral jet or concurrent bronchial inflammation, position 1). After upper airway sounds are assessed, the
may be involved. Congestive heart failure most often results stethoscope is positioned to evaluate the cranioventral,
in tachypnea or dyspnea, rather than cough (Ferasin et al., central, and dorsal lung fields on both sides of the chest
2013), and tachycardia. Other signs of heart disease include (stethoscope positions 2, 3, and 4). Note that the lung fields
prolonged capillary refill time, weak or irregular pulses, extend from the thoracic inlet to approximately the seventh
abnormal jugular pulses, ascites or subcutaneous edema, rib along the sternum and to approximately the eleventh
intercostal space along the spine (thin red line). Common
gallop rhythms, and pulse deficits. Thoracic radiographs mistakes are to neglect the cranioventral lung fields,
and occasionally echocardiography may be needed before reached by placing the stethoscope between the forelimb
cardiac problems can be comfortably ruled out as a cause of and the chest, and to position the stethoscope too far
lower respiratory tract signs. caudally, beyond the lung fields and over the liver. (Thick
Thoracic auscultation black line indicates position of the thirteenth rib.)
Careful auscultation of the upper airways and lungs is a
critical component of the physical examination in dogs and
cats with respiratory tract signs. Auscultation should be per- The lungs are auscultated next. Normally, the lungs
formed in a quiet location with the animal calm. Panting and extend cranially to the thoracic inlet and caudally to about
purring do not result in deep inspiration, precluding evalu- the seventh rib ventrally along the sternum and to approxi-
ation of lung sounds. The heart and upper airways should be mately the eleventh intercostal space dorsally along the spine
auscultated first. The clinician can then mentally subtract the (see Fig. 19.2). The cranioventral, central, and dorsal lung
contribution of these sounds from the sounds auscultated fields on both the left and right sides are auscultated system-
over the lung fields. atically. Any asymmetry in the sounds between the left and
Initially, the stethoscope is placed over the trachea near right sides is abnormal.
the larynx (Fig. 19.2). Discontinuous snoring or snorting Normal lung sounds have been described historically as
sounds can be referred from the nasal cavity and pharynx a mixture of “bronchial or tracheal” and “vesicular” sounds,
as a result of obstructions stemming from structural abnor- although all sounds originate from the large airways rather
malities, such as an elongated soft palate or mass lesions, than the alveoli (vesicles). The terms “breath sounds” or “lung
and excessive mucus or exudate. Collapse of the extratho- sounds” are now preferred. Tracheal and bronchial sounds
racic trachea can also cause coarse sounds. Wheezes, which are louder, harsher, tubular sounds heard over the trachea
are continuous high-pitched sounds, occur in animals with and, less prominently, in the central regions of the lungs.
obstructive laryngeal conditions, such as laryngeal paraly- Over the majority of the lung field, sounds are normally soft
sis, neoplasia, inflammation, and foreign bodies. Discon- and have been likened to a breeze blowing through leaves.
tinuous snoring sounds and wheezes are known as stertor Decreased lung sounds over one or both sides of the
and stridor, respectively, when they can be heard without thorax occur in dogs and cats with pleural effusion, pneu-
a stethoscope. The entire cervical trachea is then auscul- mothorax, diaphragmatic hernia, or mass lesions. It is sur-
tated for areas of high-pitched sounds caused by localized prising to note that consolidated lung lobes and mass lesions
airway narrowing. Several breaths are auscultated with the can result in enhanced lung sounds because of improved
stethoscope in each position, and the phase of respiration in transmission of airway sounds from adjacent lobes.
which abnormal sounds occur is noted. Abnormal sounds Abnormal lungs sounds are described as increased breath
resulting from extrathoracic disease are generally loudest sounds (alternatively, harsh lung sounds), crackles, or
during inspiration. wheezes. Increased breath sounds are a nonspecific finding