RAO One of the most troublesome conditions that affect respiration is recurrent airway obstruction, or heaves, formerly known as chronic obstructive pulmonary disease (COPD). Basically, RAO is inflammation of the small bronchioles in the lungs. When RAO strikes, the lower airway system is unable to function effectively. The inflammation serves to develop obstructions within the delicate airways and air is unable to flow freely. As the condition worsens, more and more physical effort is involved when the horse inspires air.