Hey Guido,

Understand your problem of not being able to hyperventilate with a low oxygen flow rate even with an OPTIMASK™... 

There's a simple solution if all you can afford is an oxygen regulator capable of 15 liters/minute. 

For starters, an oxygen flow rate of 15 liters/minute is more than sufficient to oxygenate blood hemoglobin to 100% saturation. 

What these low oxygen flow rates can't do, even with an O2PTIMASK™, is ventilate the lungs with a sufficient volume to cast off excess CO2 faster than the body generates it from normal metabolism.

Again, the solution is simple...  Hyperventilate with room air then breathe the 100% oxygen.  In short, take two very full breaths of room air and while you're doing this, the 3-liter reservoir bag on the O2PTMASK™ will fill with oxygen.  It helps if you block the exhaust port on the green "T" manifold with the palm of your hand and use the mouthpiece with the open end pressed against your lower lip to prevent the oxygen from leaking out while you're breathing air. 

When the reservoir bag is full, inhale fully from the mouthpiece.  Keep repeating this sequence, two breaths of air to one breath of oxygen until you reach the abort of your CH.

The breathing technique here is very important. I've found it's best to do the following while standing and lean against a wall with mouth open and jaw dropped like saying the word "Haw."  Doing this will give your diaphragm full range of motion to better ventilate the lungs.

Start by exhaling forcibly and when it feels like your lungs are empty, (they're not), do an abdominal crunch like doing sit-ups and hold the chest squeeze until your exhaled breath makes a wheezing sound for a couple seconds...  This will squeeze out another half to full liter of breath...  Then inhale rapidly until your lungs can't hold any more and repeat the forced exhalation with the abdominal crunch.

Use the same breathing technique when you inhale the oxygen.

You'll experience coughing for the first few breaths using this breathing technique...  this is normal and the coughing will clear after 30 seconds or so... 

If you use this breathing technique properly, you'll also experience the symptoms of paresthesia - a very slight tingling or prickling of the fingertips, lips or back of the neck...  you'll also get a little dizzy...  That's why you lean against a wall...  If you feel too dizzy, sit erect in a chair but don't bend over in a fetal position as this will limit lung ventilation.

Strange as it my sound, paresthesia and dizziness are your friends and a good sign you've hyperventiated sufficiently and long enough to cast off CO2 faster than your body generates it.  This overall procedure will push your body into a temporary condition called respiratory alkalosis...  the best indication you're hyperventilated your lungs long enough to pump out enough CO2 elevate your arterial pH and make it more alkaline.

Why you do this is important...  You take sumatriptan...  one of the most pronounced mechanisms that makes the triptans effective as a CH abortive is vasoconstriction...

Guess what, a higher than normal arterial oxygen concentration (hyperoxia), and respiratory alkalosis, also trigger vasoconstriction...  only their effects are short lasting and there are no side effects like you'll experience with the triptans...

Take care,

V/R, Batch