Perhaps I may be able to provide enough evidence on the efficacy of oxygen therapy as a CH abortive to convince some of the doubting neurologists who are hesitant to prescribe it to their CH patients.
I've spent the last 10 years studying different methods of oxygen therapy at flow rates that support hyperventilation (25-40 liters/minute). I've also conducted a study with seven CH'ers using oxygen regulators capable of delivering 100% oxygen at flow rates of 0-60 liters/minute and with oxygen demand valves with flow rates up to 120 liters/minute (average flow rate of 40 liters/minute) to abort their CH...
For starters, any CH'er having difficulty obtaining an Rx for oxygen therapy from their neurologist needs to print out the following link and take it to their neurologist.
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

This is the Guideline recommended treatments for Cluster Headache and other Trigemino-autonomic Cephalgias developed by a task force from the European Federation of Neurological Societies (EFNS).
This task force was comprised of some of the brightest minds in the field of neurology and recognized internationally as experts in the treatment of cluster headache and other trigemino-autonomic cephalgias. This task force included some very familiar names if you've read any cluster headache studies... It includes Evers S, Afra J, Frese A, Goadsby PJ, Linde M, May A, and Sandor PS.
I had the opportunity to meet with Dr. Arne May and spent two days with him at his facilities at the University of Hamburg. I've also met with Dr. Peter Sandor at the 2009 International Headache Society Annual meeting in Philadelphia, PA, and I've met with Dr. Peter Goadsby at two OUCH conferences where he was our guest speaker.
Closer to home, I've spent the last 8 years working with Dr. Todd Rozen on more effective methods of oxygen therapy as an abortive for CH. This work started initially at the Michigan Headache & Neurological Institute (MHNI), AnnArbor, MI, and more recently at the Geisinger Health System’s Neuroscience Institute, Headache Center in Wilkes Bare, PA.
All of of these experts prescribe oxygen therapy as the first abortive of choice and this is reflected in the EFNS recommended treatments in the link above illustrated in the following chart.
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

The following chart from the 2008 study I conducted using oxygen therapy at flow rates that support hyperventilation illustrates the benefits of hyperventilation during oxygen therapy as a rapid and reliable CH abortive.
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

During this study the seven participants, six chronic and one episodic, six men, one woman, collected data on every abort with high flow oxygen therapy for 8 weeks each. This resulted in abort time and pain level data on 366 aborts.
The overall efficacy was 99% in affecting an abort within 20 minutes, and an average abort time of 7 minutes across pain levels 3 through 9.
As you can see, oxygen therapy at flow rates that support hyperventilation results in abort times four times faster than at a flow rate of 15 liters/minute.
This study also revealed for the first time that the higher the cluster headache pain at the start of oxygen therapy, the longer it took to abort that cluster headache. This should be reason enough to start oxygen therapy at the first sign of an approaching CH... Waiting is only going to prolong the time to abort.
You can improve the above average abort time or eliminate the need for oxygen therapy completely by starting the anti-inflammatory regimen with 10,000 IU/day vitamin D3 plus the vitamin D3 cofactors and Omega-3 fish oil. See the following link for details:
Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

Hope this helps.
Take care,
V/R, Batch