Hoeboe,

Sorry to be so slow in responding...  I should have caught this last night. 

A 15 LPM O2 flow rate is not high enough to support hyperventilation or to abort high Kip-level attacks effectively if at all during high cycles.  I use a minimum of 25 LPM...  and higher.  If started at the first indication an attack is about to start, 15 LPM will work effectively under normal conditions for low Kip-level attacks measured during therapy where the max is at Kip-4 to kip-5.  Above Kip-5 during a high cycle, the wheels start coming off... a Kip-6 could take 20+ minutes, and a Kip-7 up to 30 minutes or more.  At Kip-8 you're looking at 30+ minutes to an hour if it works at all.   Above that...  All bets are off...  You can't get there from here under high cycle conditions with a 15 LPM flow rate.

I'll send you a PM with a suggested link for higher flow O2 regulators, but in the mean time, here are a few things I do when I go into a high cycle.

I suspect you may be having a mild case of acidosis (low pH) for some reason...  and this condition is kicking you into a high cycle.  This is arterial pH not your tummy.  There must be a reason why your oxygen therapy is not working when it used to work so effectively.  A low pH (too much acid) is usually the culprit in my case.

I've been charting my saliva pH for the last three months and found that when my saliva pH starts to drop below normal levels, I go into a high cycle where the attacks are more frequent and intense.  When my pH is above the normal range...  I'm nearly PF and all I use is oxygen...  no other CH meds.

When my pH drops, I do two things: I change my diet and start taking mineral supplements.  I lay off the red meat and cheese in favor of more green veggies with small portions of chicken or fish, and I chew almonds for snacks.  The following link has a chart of foods to eat and foods to avoid when pH is low:

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I also start taking mineral supplement tablets containing Calcium and Magnesium with Zinc.  You can get them at Sam's or Costco.  Most food stores carry them as well. 

I use the Nature Made brand, but the other brands will work just as well.  I take them as directed on the label (one tablet 3 times a day) until I'm out of the high cycle.  In a pinch, I chew up some Tums...  Tums are also a good inexpensive source of calcium and chewing them gets the calcium into your system faster than the horse pill tablets.

The change in diet and mineral supplements will help elevate a low pH condition back up to a range where oxygen therapy will become effective again.  It usually takes up to a full day or two for this to happen, but you might see an improvement in as little as few hours...  It all depends on how low a pH you have.

Once I've started taking the mineral supplements and changed my diet, there's one more thing I would try:

If I was limited to 15 LPM, I would take one of the old Satler Labs disposable NRB oxygen masks, remove both of the exhaust check valves (silicone disks) located on both sides of the mask, crank the flow rate up to 15 LPM on the O2 regulator, and start breathing as fast as I can.  The physiology and blood chemistry behind this gets a bit lengthy to explain. Essentially, in addition to upping the oxygen concentration to achieve an abort, we also need to get rid of excess CO2.  Ventilating the lungs at a higher respiration rate and tidal volume than normal is the fastest way to accomplish this..

I stay seated because if done right, this is hyperventilating and I get dizzy.  That's good. 

Just like Oxygen is our friend... CO2 is our enemy.  A low pH compounds a high CO2 level in the blood stream and both conditions are powerful vasodilators. As such they will combine to diminish or completely negate the effectiveness of the oxygen (a vasoconstrictor) to the point where it will no longer abort our cluster headache attacks.

This method is not as effective as hyperventilating on 100% oxygen at a flow rate of 25 LPM or higher, but it's more effective than a constrained respiration rate caused by using the NRB O2 mask at 15 LPM that allows CO2 levels to build above normal.

The above should help...  Please let me know either way. 

Ernie,  Check your PM too.

Take care,

V/R, Batch