How come cluster headache sufferers get short on breath?

Unclear reason: Shortness of breath is not often listed as a symptom traditionally associated with cluster headaches. However, my patients who have cluster headaches often mention that the pain is excruciating to the point that they feel out of breath. They also tend to pace and are extremely anxious. The anxiety may contribute to the shortness of breath too. Inhaling oxygen dramatically relieves the symptoms.