Recurrent Airway Obstruction (RAO)

Question 1

What is characteristic of recurrent airway obstruction in horses?

Answer 1

increased expiratory effort caused by bronchoconstriction and accumulation of mucus and neutrophils within the airways

Question 2

What is thought to be the etiology of recurrent airway obstruction in horses? What is the pathogenesis?

Answer 2

hypersensitivity to environmental antigens such as dust, molds, or fungi within the environment

upon exposure to these antigens, bronchoconstriction of the small airways occurs as well as accumulation of neutrophils within the airways, resulting in compromise of oxygen exchange

Question 3

What horses are most commonly affected by recurrent airway obstruction? When is this most commonly seen?

Answer 3

older horses (>7-8 y/o)

when horses are stalled in a barn during the winter months and fed hay

Question 4

What is a characteristic acute and chronic clinical sign associated with recurrent airway obstruction in horses? What are some other signs?

Answer 4

ACUTE = increased respiratory effort characterized by exaggerated end-expiratory effort

CHRONIC = hypertrophy of the external abdominal oblique muscles (heave line)

• cough
• exercise intolerance
• production of mucopurulent nasal discharge
• weight loss
• wheezes and crackles head on thoracic auscultation

Question 5

What is an important supportive diagnostic used for recurrent airway obstruction in horses?

Answer 5

bronchoalveolar lavage - increased number of neutrophils and Curshmann’s spirals (inspissated mucus plugs)

• healthy horses will have mostly macrophages

Question 6

What are 2 aspects to treating recurrent airway obstruction in horses?

Answer 6

1. environmental control
2. medications that control inflammation and bronchoconstriction

Question 7

What are 4 ways to control the environment in horses with recurrent airway obstruction?

Answer 7

1. discontinue stabling the horse in a stall to allow exposure to fresh air and decreased exposure to antigens
2. do not bed horses with shavings or straw while in the stall –> wet down bedding lightly, do not store hay above the stall
3. wet down/soak hay
4. change to a pelleted diet or alfalfa cubes

Question 8

What 2 types of medications are recommended for horses with recurrent airway obstruction?

Answer 8

1. corticosteroids (Dexamethasone, Prednisolone) - used in acute episodes to decrease inflammation
2. bronchodilators (Clenbuterol, Albuterol) - helps reverse bronchoconstriction

Question 9

What is prognosis like for horses with recurrent airway obstruction?

Answer 9

typically horses cannot be cured, but can be managed through environmental changes +/- medication

• prognosis while treating is good, but the owner must be willing to monitor and treat routinely