For the majority of the past 4 months I've spent 2.5 hours a day inside a hyperbaric oxygen chamber. It's basically a human-sized test tube that simulates the pressure of being 40' under water only the chamber uses 100% pure oxygen. You can't bring anything inside with you other than some water to drink and sheets/blankets/pillow. There's a tv outside the chamber to watch/stream and sound is piped in. The nurse has to change the dvd when the show ends because you can't take the remote in, either.
I'm laying there facing the tv, and just to the side is the monitor showing heart and breath rates, staring straight at me. Depending on the weather it can get really hot inside the chamber because the oxygen tanks have to be stored outside the building (hospital). There's no room to maneuver. At most you can lift your knees or flip onto your side. Also about 45 minutes in, nausea starts to set in. In the beginning I had a a couple panic attacks...watching the hr monitor go up only increases the anxiety and heart rate. Scared the fuck out of me and I felt sheepish knocking on the glass to get a nurses attention. They can pull a person out of the chamber but if they have to do it too quickly due to something serious, it risks popping an eardrum. Fortunately I've become used to the whole routine but it took awhile. It's really the only claustrophobia I've experienced.