What designates the raising of the horse's flanks whose breathing is obstructed by emphysema?

The raising of a horse's flanks, known as "abdominal breathing," occurs when the horse is experiencing respiratory distress, such as from emphysema. This is a compensatory mechanism where the horse relies more on its abdominal muscles to assist with breathing due to the obstruction of airflow in the lungs. The increased effort is visible as the flanks rise and fall more prominently, indicating the horse's struggle to obtain adequate oxygen. This symptom highlights the severity of the condition and the need for veterinary attention.