Changes

Mildly affected horses generally present with a history of occasional coughing and exercise intolerance. Signs become more obvious as the disease progresses. Tachypnoea is often seen, and there may be a mucopurulent nasal discharge. Severely affected animals show signs of respiratory distress at rest. These can include flared nostrils, wheezing, paroxysmal bouts of coughing and a laboured abdominal component to expiration. Chronically, marked dyspnoea increases energy expenditure and the animal may lose condition, as well as developing a "heave line" due to hypertrophy of the external abdominal oblique muscle^{allen, merck, ivis}. Fever does not normally develop unless there are secondary bacterial complications.

Mildly affected horses generally present with a history of occasional coughing and exercise intolerance. Signs become more obvious as the disease progresses. Tachypnoea is often seen, and there may be a mucopurulent nasal discharge. Severely affected animals show signs of respiratory distress at rest. These can include flared nostrils, wheezing, paroxysmal bouts of coughing and a laboured abdominal component to expiration. Chronically, marked dyspnoea increases energy expenditure and the animal may lose condition, as well as developing a "heave line" due to hypertrophy of the external abdominal oblique muscle^{allen, merck, ivis}. Fever does not normally develop unless there are secondary bacterial complications.

On physical examination, thoracic auscultation typically reveals a prolonged expiratory phase of respiration and adventitious respiratory noises. Wheezes are most pronounced during expiration, and crackles are associated with the excessive mucus production^merck.

On physical examination, thoracic auscultation typically reveals a prolonged expiratory phase of respiration and adventitious respiratory noises. Wheezes are most pronounced during expiration, and crackles are associated with the excessive mucus production^merck. In some severely affected animals, the lungs can be quite silent despite very strong inspiratory and expiratory efforts. This is because the airways are so obstructed that there is insufficient air movement to generate audible breath sounds. There may be an increased sensitivity of the cough reflex on compression of the cranial trachea¹.

 

Abnormal lung sounds are heard to varying degrees depending on the severity of airway obstruction. In some severely affected animals, the lungs can be quite silent despite very strong inspiratory and expiratory efforts. This is because the airways are so obstructed that there is insufficient air movement to generate audible breath sounds. Usually however, breath sounds are increased at all levels of the airways but particularly over the peripheral lung fields. Wheezing is heard quite commonly but it is wise to listen for several breaths at many points over the lung because wheezing can be intermittent. Wheezes referred from deeper in the lung may be heard over the trachea and sometimes simply by listening at the nostrils. In horses that are less severely affected, ventilation may have to be increased by use of a rebreathing bag or exercise in order to hear abnormal lung sounds. Percussion will reveal increased size of the lung field in severely affected animals.

===Diagnostis Imaging===

===Diagnostis Imaging===