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Lower respiratory disease in cats (Proceedings)

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Nov 01, 2010

Approach to the Cat with Lower Respiratory Tract Disease

If the cat is presented for labored breathing questions should be directed to assist in differentiating upper from lower respiratory disease as some owners perceive stertorous breathing in a cat with upper respiratory disease as a form of labored breathing. This could be misleading to a clinician. Does the cat have a history of coughing? Cats with airway diseases such as asthma or bronchitis often times will have historical coughing versus cats with respiratory distress from congestive heart failure which commonly do not cough. Character of the cough should be discerned: is the cough dry or does it appear productive which can be quite difficult to evaluate in a cat. The clinician should discuss with the owner whether the cat's chest wall is moving more than normal (faster or larger chest excursions) and if the patient is tiring more than usual. Many of our feline patients are indoor only and are not required to perform much physical activity and many outdoor cats are not supervised thus making an assessment of exercise intolerance somewhat difficult. Additionally information regarding timing, frequency, onset, and duration of clinical signs should be acquired from the owner. The owner should be questioned as to the cats overall health. Has the cat shown other signs of systemic illness such as lethargy, inappetence, vomiting. Cats with pneumonia or pyothorax may show signs of systemic illness. The animal's environment, access to the outdoors (possibility of trauma), access to other cats (potential for cat-fighting) and any change in environment in respect to onset of clinical signs should be obtained. The cat's vaccination status and retroviral status are important as well as travel history.

Even before approaching the cat an attempt should be made to observe the animal paying close attention to its respiratory pattern. A normal cat breathing at rest shows minimal movement of the chest wall. When breathing becomes labored the ribs are pulled caudally and laterally by the diaphragm and the chest wall muscles and the abdomen moves slightly outward. Flaring of the nostrils, open-mouth breathing or contraction of abdominal muscles indicates severe labored breathing.

Certain breathing patterns can be associated with disease at a specific location in the respiratory tract. Short and shallow respirations with small tidal volumes are indicative of stiff non-compliant lungs or restricted expansion of the lungs from pleural or thoracic wall disease. Prolonged deep inspirations may be more associated with laryngeal, pharyngeal, or cervical tracheal disease. Prolonged expirations and inspirations are more compatible with a fixed obstruction. Narrowing of small airways has a more profound effect on expiration than inspiration and clinically appears as an expiratory or abdominal push. Animal in severe distress may assume an orthopneic position.

After observing the animal a complete physical examination may be performed. The animal's overall body condition should be noted. Mucous membranes should be checked for pallor, cyanosis indicating the immediate need for oxygen therapy. Assessment of the upper airway should be made and tracheal and thoracic cavity palpation performed. Normal breath sounds include soft low-pitched airway sound most often appreciated on inspiration; in cats it may be difficult to appreciate normal sounds. Lungs should be ausculted for increased sound, crackles and wheezes. Wheezes are primarily classified according to pitch (high vs low) and timing (inspiratory vs expiratory); they are generated by airway narrowing, stenosis, or obstruction. Crackles are typically produced by a delayed opening of small airways attributable to an abnormal fluid-air interface (pneumonia, pulmonary edema, bronchitis). Muffled lung sounds and heart sounds may be indicative of pleural effusive disease (pyothorax, chylothorax), pneumothorax, hernia, or mass. (Miller, CJ, Vet Clin Small Anim, 2007, 861-878)