The abdominal muscles in a horse with heaves can form a “heave line”. A British study has shown no differences in mucus between healthy horses and those with recurrent airway obstruction ...

The horse’s chest heaves in and out to pull in oxygen. ... soft cough and sometimes a ‘heave line’ where intercostal muscles around the rib cage have overdeveloped to assist expiration.

Imagine horses with recurrent airway obstruction (RAO, or more commonly heaves) wearing Darth Vader-like masks and breathing in corticosteroids every day sun, rain, or snow.