I couldn't find anything recent here about this. The controversy over EPO got me wondering if this would help cluster sufferers. Below is a link to an interesting article. I would stress not using the illegal drug, but the article suggests there are ways to increase our natural EPO. Also, has anyone ever been tested to see if Cluster Sufferers have low red blood cell count or low EPO?
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I know my red cell count is fine...
As far as I know, with CH it is not about lack of O2 or our ability to uptake it. it helps in heavy concentrations to abort more because of the physiological changes hyperventilating pure O2 produces (ie vasoconstriction).

After further consideration...
I would not be surprised if the % of those not helped by O2 might more closely correlate to the % of people in the general population with red blood cell or EPO problems (or something completely different like not clearing CO2 well enough). This might be a topic of consideration for them.
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Headache. 1990 Oct;30(10):656-9.
Cluster headache: the effect of low oxygen saturation.
Zhao JM, Schaanning J, Sjaastad O.

Department of Neurology, University Hospital, Trondheim, Norway.

The present study concerns the possible relationship between hypoxia and the generation of cluster headache attacks. Fifteen controls and 25 cluster headache patients were studied. The patients were allocated into two groups according to cluster headache stage, i.e. cluster or remission period. During the tests, all the subjects were asked to inhale 12% oxygen (88% N2) for 30 min, and the decreasing oxygen saturation (SaO2%) was monitored. Patients in the remission period showed nearly the same decrement of SaO2% as controls. At the end of the test, patients in the bout showed significantly less reduction of SaO2% than the controls. In 5 patients, the test was carried out both in and outside the cluster periods. The tendency to less decrement in oxygen saturation in the cluster phase was as marked with this comparison, but the difference between the groups was not significant, probably partly due to the low number of tests carried out. Only one patient got a typical attack. It seems that hypoxia of this magnitude per se is not the cause of attacks. The different pattern with respect to SaO2% following 12% O2 inhalation in cluster headache may be due to an abnormality in central regulation and/or chemoreceptor sensitivity.

PMID: 2272817
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If I am reading this correctly, it would seem to indicate that if anything, CHer's are naturally adjusting to be more efficient with their oxygenation. Might explain the quick dramatic effects of pure O2 on those of us for whom it works.
Food for thought.

Interesting discussion on EPO...  However, if the RBC count is low or there's an EPO hormone imbalance where one or both were affecting blood oxygenation, I would think there would also be physiological indications of renal and or cardiovascular insufficiencies over and above cluster headaches...

From the reading and studies I've done with saliva pH, the more likely culprit affecting the frequency and severity of our CH is a low arterial pH...  too much acid.

I've found it only takes a slight downward shift in serum pH (more acid) to trigger a higher frequency and severity of my CH... 

I've also found that alkalizing my system with a half teaspoon of baking soda in a half glass of water four to five times a day results in a marked decrease in the frequency and severity of my CH...

Oxygen therapy at flow rates that support hyperventilation is the fastest way blow off CO2 faster than it's produced through normal metabolism to elevate arterial pH and push the cardiovascular system into respiratory akalosis.

Not only does an elevated arterial pH trigger vasoconstriction, the Bohr Effect also comes into play as an elevated arterial pH gives hemoglobin a greater affinity for oxygen...

The net effect is rapid vasoconstriction triggered by the elevated arterial pH and a super-oxygenated blood supply to the brain.

Of course the cluster headache intervention I prefer most is the anti-inflammatory regimen with at least 10,000 IU/day vitamin D3 to prevent my CH... 

It keeps me PF as long as I stay on schedule...  At last count...  76% of the 250 CH'ers here at CH.com who have tried this regimen have also had a favorable response.

Take care,

V/R, Batch

Great information. Thanks for the replies. I know someone who has gone chronic. I will remind him to check in here to find out more about the anti-inflamatory regeiment. The baking soda and pH issue is new to me as well. Glad to see there are some additional plausible causes and/or solutions on the horizon. The "broken hypothalamus" statements never did much for me. Wishing all PFDAN and praying for you as well.