Page 407 - Small Animal Internal Medicine, 6th Edition

CHAPTER 25
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Emergency Management

of Respiratory Distress

GENERAL CONSIDERATIONS respiratory disease. Normal breath sounds may be increased
in dogs and cats without respiratory disease, but crackles or
Respiratory distress, or dyspnea, refers to an abnormally wheezes are not expected.
increased effort in breathing. Some authors prefer to use A physical examination should be performed rapidly,
terms such as hyperpnea and increased respiratory effort in with particular attention paid to the breathing pattern, aus-
reference to this abnormality because dyspnea and distress cultatory abnormalities of the thorax and trachea, pulses,
imply feelings that cannot be determined with certainty in and mucous membrane color and perfusion. Attempts at
animals. Breathing difficulties are extremely stressful for stabilizing the animal’s condition should be made before
people and are likely so for dogs and cats as well. Dyspnea further diagnostic testing is initiated.
is also physically exhausting to the animal as a whole and to Dogs and cats in shock should be treated appropriately
the respiratory musculature specifically. Animals in respira- (see Chapter 28). Most animals in severe respiratory dis-
tory distress at rest should be managed aggressively, and tress benefit from decreased stress and activity, placement
their clinical status should be frequently assessed. in a cool environment, and oxygen supplementation. Cage
A dog or cat in respiratory distress may show orthopnea, rest is extremely important, and the least stressful method
which is difficulty breathing in certain positions. Animals of oxygen supplementation should be used initially. An
with orthopnea will assume a sitting or standing position oxygen cage achieves both of these goals, with the dis-
with their elbows abducted and neck extended. Movement advantage that the animal is inaccessible. Sedation of the
of the abdominal muscles that assist ventilation may be exag- animal may be beneficial (Table 25.1). More specific therapy
gerated. Cats normally have minimal visible respiratory depends on the location and cause of the respiratory dis-
effort. Cats that show noticeable chest excursions or open- tress (Table 25.2). Ventilatory support is needed for patients
mouth breathing are severely compromised. Cyanosis, in that are not adequately oxygenating despite appropriate
which normally pink mucous membranes are bluish, is a sign treatment or who have ventilatory failure. Oxygen supple-
of severe hypoxemia and indicates that the increased respira- mentation and ventilator support are discussed later in
tory effort is not sufficiently compensating for the degree of this chapter.
respiratory dysfunction. Pallor of the mucous membranes is
a more common sign of acute hypoxemia resulting from
respiratory disease than is cyanosis. EMERGENCY MANAGEMENT BASED
Respiratory distress caused by respiratory tract disease ON LOCALIZATION
most commonly develops as a result of large airway obstruc-
tion, severe pulmonary parenchymal or vascular disease (i.e., LARGE AIRWAY DISEASE
pulmonary thromboembolism), pleural effusion, or pneu- Diseases of the large airways result in respiratory distress by
mothorax. Respiratory distress can also occur as a result of obstructing the flow of air into the lungs. For the purposes
primary cardiac disease causing decreased perfusion, pul- of these discussions, extrathoracic large airways (otherwise
monary edema, or pleural effusion (see Chapter 1). In addi- known as upper airways) include the pharynx, larynx, and
tion, noncardiopulmonary causes of hyperpnea must be trachea proximal to the thoracic inlet; intrathoracic large
considered in animals with apparent distress, including airways include the trachea distal to the thoracic inlet and
severe anemia, hypovolemia, acidosis, hyperthermia, and bronchi. Animals presenting in respiratory distress caused
neurologic disease. Pain and steroid administration can by large airway obstruction typically have a markedly
cause tachypnea and should be considered among the dif- increased respiratory effort with a minimally increased
ferential diagnoses in patients without other evidence of respiratory rate (see Table 25.2). Excursions of the chest may

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