I'm In...  But only to clarify a few of the facts about breathing oxygen and to quell any worries about the safety of using oxygen therapy as an abortive for cluster headaches. 

The use of oxygen therapy as an abortive for cluster headaches is very safe...  Much more so than taking any of the far more invasive triptans as oxygen therapy has no lasting side effects if used properly.

Oxygen therapy is also a heck of a lot cheaper than triptans.  If used properly at a high enough flow rate, you own your own mask and regulator, with oxygen coming from an M-size oxygen cylinder, the cost per abort before insurance is $1.20 to $1.50.  It’s as low as 20 cents/abort with insurance co-pay.   On the other hand, 25mg to 50mg sumatriptan tablets run $7 to $9 each, a 5mg sumatriptan nasal spray applicator costs $32 and a sumatriptan SC Stat Pen injector costs $89 per shot.  Do the math...

Oxygen toxicity at normobaric (Sea Level) pressure is not really a problem for cluster headache sufferers who use oxygen therapy either.  An otherwise healthy adult would need to breathe 100% oxygen continuously at normobaric pressure (sea level) without any breaks breathing normal air for 10 to 12 hours to encounter the symptoms of oxygen toxicity. 

At a flow rate of 7 liters/minute, that would require an oxygen cylinder with over 5,000 liters of oxygen.

And, as the symptoms of oxygen toxicity are very similar to pneumonia where it becomes very painful to inhale, most of us would stop breathing the 100% oxygen at the first sign of breathing difficulties and switch to normal air long before incurring any lasting lung damage.

I'm an old Naval aviator and fighter pilot with over 3000 hours in jet fighters.  All of that flight time was spent breathing 100% oxygen from engine start and takeoff/cat shot to an arrested landing/trap aboard ship or field landing.  The average mission length was two hours and I have flown several extended missions that lasted 7 hours. I also routinely flew two and three of these two hour missions a day/night. 

I can also say that during actual and training air combat maneuvering where G-forces routinely get up to and exceed 6 Gs (six times the force of gravity), the work load is such that we inhale that 100% oxygen at flow rates greater than 50 liters/minute for several minutes at a time.

I accrued these flight hours over a 15 year period and passed my annual flight physicals with chest X-Rays for the entire 24 years I served as a Naval Officer...  I was also required to attend annual Aviation Physiology training that included an altitude chamber run every 4 years with a stop at 26,000 feet where we would take off our oxygen masks to intentionally experience hypoxia and then zoom up to a cabin pressure equal to 35,000 to 43,000 feet to experience pressure breathing where the oxygen regulator forced oxygen into our lungs to keep us conscious.

I've also used oxygen therapy at flow rates that support hyperventilation since 2004 and I'm still here at age 66.

All of my experiences breathing 100% oxygen can easily be considered anecdotal information.  The following isn't.

I've checked with Flight Surgeons and Aviation Physiologists at the Naval Safety Center, the Naval Aerospace Medical Institute, the Naval Air Systems Command, and NASA. None of them were able to cite any medical problems experienced by Naval Aviators or Astronauts associated with repeated exposures to breathing 100% oxygen. 

My contact at NAVAIRSYSCOM also indicated that there have been over 125,000 designated Naval Aviators with fighter and attack aviation warfare specialties since the early 1940s. All these pilots and aircrew also had to pass annual flight physicals just to stay flying.

Given the average Naval Aviator flies between 1500 and 3000 hours during his or her career in the Navy or Marine Corps, you could easily say this is the single largest ongoing retrospective study on the effects of repeated exposure to breathing 100% oxygen in history. 

What’s even more impressive is the fact that they have yet to find any long-term medical problems associated with repeated exposure to breathing 100% oxygen. 

Good people of Clusterville…  That is hardly anecdotal.

OPNAV Instruction 3710.7T states in section 8.2.4.3 Tactical Jet and Tactical Jet Training Aircraft.  “Oxygen shall be used by all occupants from takeoff to landing.”

You might want to ask yourself why the Navy would require these pilots and aircrew to breathe oxygen while flying fighter and attack aircraft costing more than $40 Million dollars each plus an additional Million dollars to train a Naval Aviator if oxygen represented a potential health hazard.

The only exception to the OPNAV 3710 mandatory requirement is the Blue Angels who have a waver for air shows where they don’t wear and oxygen mask as all of their shows are conducted well below 10,000 feet, but even they must wear an oxygen mask during cross-country flights above 10,000 feet to and from show sites.

The oxygen masks and mini-regulators we've used over the years and the versions that are in use today function very similar to the oxygen demand valves some of us use for cluster headaches.  The only difference is when you connect the oxygen hose to the aircraft oxygen supply and turn it on you also get a constant flow of 100% oxygen at around 15 liters/minute.  If the workload requires additional lung ventilation to expel excess CO2, the mini-regulator functions just like the demand valve delivering the additional oxygen on demand.  These regulators can also support peak flow rates up to 200 liters/minute.

Around 2004, the Navy started converting its fleet of F/A-18 aircraft from the 5 liter liquid oxygen (LOX) dewar flasks that delivered gaseous 100% oxygen through a LOX converter to the air crews over to an onboard oxygen generating system (OBOGS).  An OBOGS is like an oxygen concentrator on steroids.  It uses 17th stage bleed air from the jet engine compressor section to produce oxygen at high volume at an average of 93% purity by passing it through a molecular sieve pressure swing adsorption (PSA) system.  If you’re interested, the remaining 7% is Argon, an inert noble gas.

So…  I’ll say it again…  Breathing 100% oxygen as an abortive for cluster headaches is very safe.

Take care,

V/R, Batch