Recurrent airway obstruction, also known as broken wind, heaves, wind-broke horse, or sometimes by the term usually reserved for humans, chronic obstructive pulmonary disease or disorder (COPD) – it is a respiratory disease or chronic condition of horses involving an allergic bronchitis characterised by wheezing, coughing and laboured breathing.
In some cases (secondarily), the horse may present with acute severe dyspnea, such that it really struggles to inspire sufficient air.
The veterinarian will usually auscultate (listen to the horse's chest with a stethoscope) to attempt to detect adventitious lung sounds.
In some cases, a bronchoalveolar lavage may be carried out - an endoscope is used to look down the trachea, and mucus and cells are washed out of the lower airways for analysis.
Typically, a BAL recovers an abnormally high percentage of neutrophils from an RAO horse - up to 50 or 70% in severe cases.
[1][2] An allergic reaction to certain otherwise innocuous substances - allergens, typically dust and mold spores (e.g. Aspergillus spp.).
In contrast to human asthma (which it otherwise resembles), RAO is associated primarily with neutrophil mediated inflammation, and IgE and mast cells are much less important in the pathophysiology.
[6] In animals maintained in stable during several hours of the day, other causes, like inhalation of ammonia (mainly from urine), a gas that is potentially damaging to the lungs, should also be considered.
If a horse is severely dyspnoeic (that is, struggling to breathe), the most important measure to take is to remove it from the stable or barn into fresh air.
The length of time to soak hay for the maximum benefit is debated; however, approximately 30 minutes appears to be the current consensus.
[20] Other bronchodilators that may be used include aminophylline, although this may lead to excitation, and is only effective in 50% of cases,[21] or ipratropium (which is relatively short acting at 4–6 hours duration).
Stored hay contains dust and fungal spores that can cause irritation and inflammation, that can lead to COPD, airway and digestive conditions.