I'm posting the link below just to show that medical concentrators are a viable, clever (and ridiculously expensive) method of maintaining O2 saturation when flying high. I'm
not posting it because I think it's a good idea to buy a unit from this particular source. This industrious seller simply takes the standard medical unit and glues the brand "Aviator" on it and magically it's now an aviation component instead of a medical unit.
http://www.inogenaviator.com/products.html
There are several - many in fact - manufacturers of medical oxygen concentrators. The field narrows when it comes to light, portable, 12-volt models, but there's still quite a few companies to choose from. Based upon a quick look around, Inogen seems to still be the market leader in sales and innovation. Their G1 is less than three pounds and is seven inches by six by three or so wide and is good to 15K based upon reviews I've read several years ago. Their G4 (larger, but still small compared to standard-sized medical oxygen concentrators) is claimed to be good to 18K. I don't recall flow rates at those altitudes but I do recall the claims are that they'll keep saturation above 95%.
Downsides are cost and having only a single lumen. My plane is single-place so for those with a single-seater a single lumen is plenty. Cost can be gotten around by keeping a sharp eye out on Craigslist and other venues. Paid for originally by insurance, survivors often have no idea how much these things cost so with some luck one can find one of these treasures amidst all the other medical leftovers that survivors dump once the principal has passed.
I just came across an old posting by Dr. Bruce on the subject of these things and his report was that the one he was trying out (he didn't say which one it was) worked well at 12 but was useless at 15. Performance does vary a lot among the different models. The trend however is towards lighter, smaller and ever more capable machines. As we baby-boomers slide downhill, competition is fierce among the circling carrion feeders.
An Inogen G1 (unless there's something new out there I don't know about yet) would be absolutely wonderful to have in the plane, wired into the ship's power and controlled with a simple off/on switch on the panel. However . . . my current set-up works exceedingly well so unless I actually do stumble across one on CL for $150 I'll stick with my aluminum E tank (24 cu.ft.) with Devilbiss PD-1000
(
https://goo.gl/6M9tB6)
and Osysaver cannula (its a single line and works fine with the pulse-demand regulator even though theory says it shouldn't because of it's reservoir). The demand regulator is absolutely what makes it possible to turn on the O2 before takeoff, cross the country and return to California without turning it off (except overnighting of course) . . . and still have O2 left in the tank when I get home. Several companies besides Devilbiss make these demand regulators for medical use. And for about twenty times as much money, they can be had from Mountain High, Precise Flight & other aviation sources. Tank re-fills are at dive shops for about $30. Tank needs re-certification every three years (or is it five?). The dive shop I use has the certification to do the tank certs so it all works exceedingly well. However . . . if I came across a G1 for $150 or anywhere near that number . . . I wouldn't hesitate for a second. Its just too elegant to never have to get the tank filled anymore.
