Cephalalgia. 2012 Jul 6.
The history of oxygen inhalation as a treatment for cluster headache.
Haane DY, Dirkx TH, Koehler PJ.
SourceAtrium Medical Centre, The Netherlands.

Abstract
Overview: Oxygen has been a generally accepted treatment method for cluster headache attacks ever since Kudrow (1981) conducted a controlled trial showing that oxygen was equally or even more effective than ergotamine injections.Purpose: The aim of the present study was to provide a historical perspective of oxygen treatment in cluster headache and to find the origin of this treatment. Oxygen for cluster headache was first described by Horton in 1952 and for migraine patients in 1940 by Alvarez. At the time, neither of the authors provided any reason why they chose for this treatment method.

THE VASOCONSTRICTIVE EFFECT OF OXYGEN WAS NOT DESCRIBED BY HORTON UNTIL 1961.CONCLUSION: WE SUGGEST THAT THESE AUTHORS ORIGINALLY ADHERED TO THE VASOCONSTRICTIVE THEORY OF VASCULAR HEADACHE THAT WAS PREVALENT IN THE EARLY 20TH CENTURY UNTIL WOLFF DEMONSTRATED THE CONTRARY IN THE LATE 1930S. THE EARLY LITERATURE DESCRIBES AN ANALOGY BETWEEN ANGINA PECTORIS AND MIGRAINE, AS BOTH BEING DUE TO VASOCONSTRICTION.

As oxygen was described as a treatment for angina pectoris, this may be the reason why oxygen was tried for migraine and cluster headache at a time when they were not recognized as separate entities. Later it turned out to be more effective for cluster headache.

PMID:22773467[PubMed]

So in trying oxygen for clusters, we kind of got lucky.



Quote:

EARLY LITERATURE DESCRIBES AN ANALOGY BETWEEN ANGINA PECTORIS AND MIGRAINE, AS BOTH BEING DUE TO VASOCONSTRICTION. As oxygen was described as a treatment for angina pectoris, this may be the reason why oxygen was tried for migraine and cluster headache at a time when they were not recognized as separate entities.

But if the analogy for treatment was carried further, nitoglycerin I believe is a BIG trigger for clusters.  Glad no one throught of it as a clinical trial.   ;)


[from a treatment page]

Angina pectoris, commonly known as angina, is chest pain due to ischemia (a lack of blood, thus a lack of oxygen supply and waste removal) of the heart muscle, generally due to obstruction or spasm of the coronary arteries (the heart's blood vessels).

The most specific medicine to treat angina is nitroglycerin. It is a potent vasodilator that makes more oxygen available to the heart muscle. Beta-blockers and calcium channel blockers act to decrease the heart's workload, and thus its requirement for oxygen.