Hey Scott,

Welcome back aboard.  We all know getting nailed by the beast at night is a bummer.  The pain gets a head start before you wake up enough to realize what's happening and you end up in a tail chase that at best, results in a second place finish in most cases.  Traditional oxygen therapy prescribed by most PCPs and neurologists at 7 to 9 liters/minute is useless above a kip-4 or Kip-5 at start of therapy under these conditions.  Even a flow rate of 15 liters/minute prescribed by forward thinking neurologists will be largely ineffective in aborting cluster headache attacks and stopping the pain at Kip-7 or above at start of oxygen therapy.  

This information is based on over a year's worth of data collected on hundreds of aborts to determine the effectiveness of oxygen therapy as an abortive.  For example, the pain of an average cluster headache attack increases in intensity by at least one Kip-Level after start of oxygen therapy and prior to the abort at flow rates of 15 liters/minute and above.  At lower flow rates it can easily increase by two Kip-levels.  

There's also a direct correlation between the Kip-Level of pain and time to abort.  In short, the higher the Kip-Level during the oxygen therapy, the longer it will take for this therapy to effectively abort the cluster headache attack.  What's even more interesting is there's an equal but opposite correlation between flow rate and time to abort, meaning the higher the oxygen flow rate, the shorter the time to abort.

Much of the ineffectiveness of oxygen therapy is due to a reduced respiration rate and the higher effectiveness is due to an increased respiration rate.  I know this might sound confusing, but when you use a non-rebreather oxygen mask, your respiration rate is restricted to the flow rate of the oxygen regulator.  For example, at a flow rate of 7 to 9 liters/minute, your respiration rate will be 10 to 15 at best depending on the tidal volume of oxygen inhaled with each breath.  That makes oxygen therapy at lower flow rates only effective for attacks at Kip-4 to Kip-5 during the therapy, and even then, the time to abort will be lengthy.  

This is due to a build up of CO2 caused by the restricted lung ventilation. As the pain increases so does the level of our physical activity.  At Kip-7 to Kip-8, most of us are dancing the Tarantella or Cha Cha, and above that we're running into walls or banging our heads on the floor.  This level of physical activity generates even more CO2, but the restricted ventilation of the lungs makes expelling this excess CO2 impossible so CO2 levels rise even more.

The bad news is an elevated CO2 level in the arterial bloodstream above normal (hypercapnia) serves as a powerful vasodilator.  As cluster headache attacks are associated with a rapid dilation of the arteries in and around the trigeminal nerve, that actually makes the cluster headache attack worse as it can completely negate the beneficial effects of vasoconstriction provided by elevated levels of oxygen (hyperoxia).

The good news is that higher oxygen flow rates at 25 liters/minute and above support progressively higher respiration rates and the higher rates reduce excess levels of CO2 in the arterial bloodstream below normal. In simple terms, this is called hyperventilation and it results in a temporary condition called respiratory alkalosis/hypocapnia that serves as a powerful vasoconstrictor.

If you've followed me so far, you've figured like I and others have, that a good non-rebreather mask and an oxygen regulator capable at least 25 liters/minute makes aborting cluster headache attacks a lot easier and far more effective than flow rates of 15 liters/minute or lower.

Take care, and please shoot me a PM if you have any questions.

V/R, Batch