Travel Technology - Using a CPAP w/Empower port

I hope to use a CPAP machine on a UA flight with Empower outlets. The CPAP runs on variable voltage. On the CPAP, the wall plug cord connects to the machine in a round female outlet labeled 13V - 1.5A. The other end of the wall plug cord is a standard US 2-prong plug, and I have a plug adapter for Euro plugs.

Any suggestions on how to hook up the machine? A colleague does have an iGo
Everywhere (15W) system that I can use, if that helps.

You'll need something the Xantrax inverter, which has an Empower plug that goes into the seat socket and allows you to plug a two-prong US power plug into it. It's discussed in this thread:
http://www.flyertalk.com/forum/showthread.php?t=534424
But note that it didn't fit the seat socket the first time I tried it, and I had to grind it down a bit.