I am a good friend of Rhett's as well. I was actually dm'ing some of his earlier classes. All I know at this point is it was on the oriskany. He is doing much better. He's off the ventilator, talking and responding and starting to get feelings in his extremities. He still needs our prayers.
I've asked around, and all of my people said that this is the first they've heard of it. I'm assuming he was on a private boat? The charter community in Pensacola is pretty close, and I'd be surprised if this was a charter, and I still didn't have details.
I am curious to know if he was a technical diver, and/or if this was a technical dive.
Please tell your friend that we are all thinking about him and pulling for him. I hope he feels better soon.
+1
Does anyone have a provisional diagnosis to explain the paralysis? The Oriskany is fairly deep. Was he severely bent?
** This is an attempt to answer your question, and by no means is a comment on what may, or may not have happened to Mr. Barnes. **
Depending on where you are on the ship, it's 206 to 220ft to the sand. 145 to 150ish on the Flight Deck, and the floor of the Hangar Deck is 170 to 174ish. You can get yourself in serious trouble at any of these depths, and, of course, much shallower.
What I see most is recreational divers going into decompression, and not doing their required stops. On the better boats, the DM's try to catch it before, or while the diver is getting out of the water, and find a way to get the guy back in asap, and breathing with enough gas to work off his obligation, sometimes bringing additional bottles down. I've seen this WAY too many times, and the DM's warn folks about this 100 times before the boat gets tied in. People don't watch their gas, don't know how to read their computers, or draw a blank when their comp tells them they have a required stop.
Now, to get back on track, and answer your question more directly (remember, I'm a layman. I'm not an instructor, physician, or expert in anything). When you're underwater breathing compresses gas, inert gasses (nitrogen, helium) begin to work their way into your tissues. The amount of loading is related to what you're breathing (the percentage of Nitrogen or Helium in your mix), time, and depth. So time, mix, and depth govern your uptake. In recreational diving, your stay is short, and shallow, so you can ascend directly to the surface (at a safe rate) without any required pauses at any particular depth.
Where humans run into trouble, is when we start back up. If we move up faster than those gases can work their way out of our tissues, then the tissues are damaged. On helium dives, you have to be very careful, because it moves into, and out of the tissues very quickly. Nitrogen is more forgiving, but it will take you longer to offgas, because it's slower into and out of your tissues.
As we ascend, the atmospheric pressure falls, this allows the inert gasses to leave the tissues, where the blood, and respiration (exhalation) evacuate them from the body. Move too fast, and the gasses outrun the body's ability to manage those gasses. One of the failure points is the nervous system, another is the joints. Nerve tissue and joints don't do well vs. expanding gasses. Sometimes the bubbles themselves cause the damage, and sometimes the bubbles interfere with your blood, keeping much-needed oxygen away from critical components (brain, spine, heart). Oxygen therapy, and recompression combined with oxygen therapy, can sometime reverse, or partially reverse the damage.
There are other mechanisms that can promote, or trigger decompression sickness, but the injuries themselves, are a result of what I have described above.
-h
