I agree with Marc, it is probably a blood/oxygen saturation test, which is totally bogus for our application.  BUT, it is a good excuse for your insurance company to decline covering it.

HOWEVER, all is not lost!  Many times the insurance company denies coverage, with the hope that you will just go away.  DON'T do it!  Become the squeaky wheel!  Squeak so loud and often, that they will oil that wheel, JUST to shut you up!

Get your doctor and oxygen supplier to work with you.  Bombard the insurance company with phone calls, and information.

My insurance company (Blue Cross & Blue Shield - BC&BS) refused to pay for a LONG time!  But they just recently started to pay the bills.  In the past month, my insurance company paid out over two thousand dollars for my oxygen!  And there are still more bills to be paid!  My supplier found the way to get them to pay.  They said that they had to give BC&BS the right code, in order to pay.  I am not sure what that code is, but if you need it, I can get it for you.

You said that you suspect that your cycle may be ending.  That is GREAT!  I hope it is!  BUT, do not drop this fight, just because your cycle has ended!  Fight it NOW, and get some oxygen in the house, so that when you come back in cycle, you will have it right there.

Here's another trick, regarding your cycle ending.  I am not sure if you have a prescription for Imitrex, or not, but if you DO have one, do NOT stop filling it, just because you are out of cycle!  Stock pile it, so that you have plenty on hand, for the next cycle.  

As long as it is stored in a cool dark place, you can use it well after the expiration date on it.  I have used Imitrex injections that are three years past their expiration date.  The only problem, that I have heard of, for out of date Imitrex, is that it MAY loose some of its strength.  It does NOT become dangerous to take, from what I have heard, read, and experienced!

Good luck, and keep us informed!
Chuck