I don't think they made up diseases, but as far as being physically possible, they took a lot of dramatic license. This clip is a good example.I never watched it, but wasn't it a big point of the show that the medical stuff was, however unlikely, at least physically possible? The sudden loss of consciousness is unlikely, but the the other symptoms are not unreasonable. And the suggested treatment of administering O2 and lowering the ambient pressure is exactly what you'd expect.
... I decided to do a quick search to see if my understanding about the show was correct. It looks like it was - with the big caveats of House doing everything by himself (as noted by DDM) and also his apparently constant unethical or illegal behavior. But more to the point, I found a now defunct website created by a physician who reviewed every episode as they came out for story and medical accuracy. It looks like the clip is from "Airborne" (season 3, episode 18). Here's his summary:
"Both of tonight’s medical mystery were good and deserve an A. The solutions fit the cases and earn another A. The medicine was a mixed bag, a B- for the hospital plot, and an A for airplane plot, so I’ll give it a B+ overall. The soap opera aspect was decent — not terribly exciting, but not bad either — and earns a B."
The full review is at: Polite Dissent » House – Episode 18 (Season Three): “Airborne”
Best regards,
DDM