The basics of HBO Treatment:
I went once a day, five days a week.
When I arrived I went to a bathroom that had small lockers for our personal belongings and I changed into a hospital gown.
No makeup, NO jewelry, NOTHING is allowed in the cylinder with you. If you are doing treatments in a room with others I believe you are able to keep some reading material, although I'm not sure.

I would get onto a gurney that was put directly into the cylinder.
A black bracelet is put on you, called a "ground".
You are given a bottle of water, sometimes in childs sippy.
You are given an oxygen mask for your "oxygen breaks".
They wheel you in and start taking you down. Not that you go anywhere, but they start decompressing the cylinder, if that is the correct terminology.
The first time it's a little scary because you expect all this pain in your ears but I didn't suffer that at all. I eventually was able to go "down" without even a drink and could control popping my ears by swallowing.
I was able to watch TV and could even choose a movie to watch, which I didn't often do as I usually didn't get to see the end of it.
They will check your ears at each treatment to watch for any problems.
Ask for extra blankets, I always found it cold in the cylinder. I didn't have claustrophobic issues with this treatment, the cylinders are quite roomy.
You will have changes in your eyesight. If you wear glassed your eyes will reach near perfect vision for an extended period of time, for me it was over a month. I would have to take my glasses off a good part of the day. Eventually your eyesight will return to it's original state.
Minnie