Here's something new that I learned today: horses can benefit from using nasal strips!
From the website of Flair Equine Nasal Strips:
FLAIR Strips support the nasal passages during exercise and improve the horse’s airflow when it needs oxygen most. Unlike humans, horses can only breathe through their nose. During exercise when horses begin to breathe hard the soft tissues overlying the nasal passages are sucked in, reducing the airway diameter. This reduction in diameter causes greater resistance to airflow into the lungs. FLAIR Strips are proven to reduce airway resistance during exercise.
Link (Photo: Lucy Mathews)