Page 340 - Clinical Small Animal Internal Medicine

308 Section 4 Respiratory Disease

Possible environmental causes should be identified
VetBooks.ir and eliminated. Owners should be advised not to smoke
indoors, or in closed environments with affected pets.
Any air‐borne irritants should be eliminated such as per-
fumes, incense, scented detergents, and aerosolized
cleaners. Owners should also be encouraged to remove
as much dust from the environment as possible. Cloth
furniture should be cleaned or removed, carpets cleaned
or removed, and frequent vacuuming/dusting should be
encouraged. If extensive remodeling is planned that is
likely to produce potentially noxious fumes or a large
amount of aerosolized particles then plans should be
made for CCB patients to stay with friends or family.
Exposure to potentially sick puppies should be avoided
as well as trips to dog parks, grooming parlors, and
boarding facilities. If a patient is obese, an appropriate
Figure 31.3 Photomicroscopy from a patient diagnosed with
chronic bronchitis showing a typical cytologic representation weight loss program should be established. Activities
with abundant mucus and neutrophils, and prominent that incite excess barking or strenuous exercise should
“Curschmann spirals.” Source: Image courtesy of Eric J. Fish, be curtailed. The importance of replacing neck collars
DVM, DiplACVP. with harnesses should be emphasized.
Antiinflammatory medications are typically employed
defects associated with chronic bronchitis. Although to assist with reducing inflammation in the airway,
tidal breathing flow‐volume loops have been described in and glucocorticoids are still the mainstay of treatment.
veterinary medicine, they are not widely used due to lack Reducing inflammation can limit cough and assist in
of patient cooperation. Forms of pulmonary function reducing the positive feedback cycle that perpetuates
testing that are more practical and may be used in dogs CCB. Glucocorticoids may be administered orally or via
include the collection of arterial blood gas samples, the inhalation. Prednisone is the most commonly used glu-
measurement of oxygen saturation with pulse oximetry, cocorticoid. Initial dosing of prednisone is 1–2 mg/kg/
and use of the six‐minute walk test (6MWT). Arterial day though it should be tapered to the lowest effective
blood gas analysis may document hypoxemia (PaO 2 dose that controls clinical signs. Inhaled glucocorticoids
<80 mmHg) or an increased alveolar‐arterial (A‐a) gradi- have been widely used in people, and there is growing
ent (>15), although due to difficulty with technique and a frequency of their use in veterinary medicine. Inhaled
lack of necessary equipment, this is not commonly per- steroids are delivered via a spacer chamber and face-
formed in the clinical setting. Pulse oximetry is widely mask designed specifically for dogs (e.g., AeroDawg,
available in practice, and may be used to estimate arterial wwww.trudellmed.com). Inhaled glucocorticoids are
saturation with a value of >97% considered normal. Pulse more expensive than oral steroids, but the benefits
oximetry may also be assessed after a short walk, as desat- include a directed therapy approach that limits systemic
uration may be more commonly observed after exercise absorption and subsequent steroid side‐effects. One
in patients with more mild compromise to their airway study demonstrated benefits of therapy with fluticasone
function. The 6MWT formally measures the distance at 125 μg q12h.
that a dog can walk over six minutes; distances less than Bronchodilators are commonly prescribed for dogs with
400 meters are supportive of significant lung disease. The CCB and evidence supports an improvement in clinical
6MWT may also be combined with pre‐ and post‐walk signs in approximately half of treated dogs. Theophylline
pulse oximetry to evaluate for exercise‐induced oxygen (extended release, 10 mg/kg PO q12h) has been shown to
desaturation. have nonspecific effects that may benefit patients with
CCB. These include decreasing diaphragmatic fatigue,
increasing mucociliary clearance, and enhancing the effi-
Treatment cacy of glucocorticoid activity. Beta‐2‐agonists, such as
terbutaline, may be less effective due to the lack of revers-
Due to the lack of a definitive treatable etiology for CCB, ible bronchoconstriction in some patients. The use of
the treatment options are limited to therapy to amelio- theophylline versus beta‐2‐agonists is still a clinical pref-
rate known clinical signs and co‐morbid conditions. erence. It should be noted that beta‐2‐agonists might
Primary treatment focuses on limiting inflammation, cause some anxiety and restlessness when initiated
limiting cough, and improving exercise stamina. although these signs often resolve within a few day.