Slacker,

If possible, try to find another home oxygen provider that carries the cast iron M-size oxygen cylinders or the aluminum M or smaller M60.  If you're having an average of 3 CH a day/24 hours, you really need to have 3 of the M-size oxygen cylinders on hand for a one month's supply.  The E-size oxygen cylinders are great for local travel and work but as they're only good for three aborts, you'll need a lot of them as you've probably already figured out. 

At an average cost of $20 before insurance for an E-size oxygen cylinder (708 liters), the cost/abort is $6.67  An M-size oxygen cylinder that holds 3995 liters and costs around $30 before insurance, but you'll get 25 to 30 aborts so your cost/abort is $1.00 - $1.20.

The Flotec InGage™ regulator is the only medical oxygen regulator I've found that delivers at greater flow rates than 25 liters/minute.  Mine has higher flow rate settings for 15, 25, 40 and 60 liters/minute.  If you go this route, order the InGage™ regulator with a DISS fitting just in case you want to use a demand valve at a later date.

You can always use the less expensive welder's oxygen regulator but they're rated in psi and not in liters/minute so you'll need to figure out what psi delivers oxygen at a high enough flow rate for a fast aborts.  This is usually a high enough flow rate to hyperventilate all the way to the abort without getting too pooped out... Then remember the psi setting.

The other thing you need to do is use a breathing technique called breathing at forced vital capacity tidal volumes...  If used properly, a flow rate of 25 liters/minute should work effectively...  and by working effectively, I mean you'll experience the symptoms of paresthesia and your abort will be much faster.

The most effective breathing technique to use in order to hyperventilate effectively when using oxygen therapy as an abortive for cluster headache involves breathing as deeply as possible at forced vital capacity tidal volumes. 

Tidal volume is the lung volume representing the normal volume of air or oxygen displaced between normal inspiration and expiration when extra effort is not applied...

I'll explain...  The critical part of the respiration cycle using this method of oxygen therapy is exhalation.  You need to stand to give your diaphragm a full range of motion and lean against a wall (you will get dizzy and if you feel too dizzy, sit erect in an upright chair). Open your mouth and drop your jaw like saying the word "Haw" and exhale forcibly until it feels like there's no breath left to exhale...  there is... 

At that point do an abdominal crunch like doing sit-ups and hold the chest and abdominal squeeze until your exhaled breath makes a wheezing sound for a couple seconds.  The crunch will squeeze out another half to a full liter of breath. 

Then without delay, inhale rapidly until it feels like your lungs can't hold any more... then repeat the forced exhalation with a crunch.   Repeat this sequence without hesitating between inhalation and exhalation and keep repeating it until the pain is completely gone.

Three things will happen when you use this breathing technique.  The first thing is you'll start coughing...  this is normal and the coughing will clear in 5 to 10 seconds.  This is why you can take your time with the first 3 to 4 breaths using this procedure and breathing technique.  When the coughing clears, you can start increase the respiration rate.

The second thing that will happen is you'll start to experience the symptoms of paresthesia after three to five respiration cycles using this breathing technique.  The symptoms of paresthesia include a very slight tingling or prickling of the fingertips, lips, or back of the neck with no apparent long-term physical effect.  You'll also experience a slight dizziness.

Strange as it may sound, the symptoms of paresthesia are your friend and they are the best indication you're breathing correctly for the fastest abort of your CH as possible.  As you are using this breathing technique to voluntarily hyperventilate, the symptoms of paresthesia will clear in 10 to 15 seconds after you return to a normal respiration rate.

The third thing that will happen is you'll get tired.  If you're executing this breathing technique properly, it's hard work...  but well worth the effort.

The reason for using this breathing technique is simple.  It's the most effective way to push your system into respiratory alkalosis as fast as possible.  As the last volume of exhaled breath exhaled (the end tidal flow), contains the highest concentration of CO2, using this breathing technique will pump CO2 from your lungs through exhaled breath faster than your body generates it through normal metabolism.

Lowering CO2 levels with this breathing technique elevates your arterial pH making it more alkaline, hence the name respiratory alkalosis.  This condition stimulates vasoconstriction of the arteries and capillaries in an around the trigeminal ganglion to start the abort process.   

This is an important bio-mechanical step in the process of aborting a cluster headache as narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels counteracts the vasodilation associated with the cluster headache syndrome that's causing all the pain. 

If you think about it, sumatriptan succinate (imitrex, imigran) or any of the other family of triptans do the same thing... only they carry some onerous side effects and costs a lot more per abort than oxygen...

If you're still having trouble aborting your CH using this technique with an oxygen flow rate of 25 liters/minute, you might want to consider trying the anti-inflammatory regimen.  It can help reduce abort times and if you stay on this regimen long enough, like two to three weeks, it can also prevent most if not all of your cluster headaches. 

To date, based on reports back from CH'ers who have started this regimen, it's proving to be 75% effective with a ±15% margin of uncertainty in preventing cluster headaches.

Hope this helps.

Take care,

V/R, Batch