Today I think i survived a CNS hit at depth

[OzGriffo]

I think today that I survived a ox-tox at depth, and owe my life to my instructor and DM. I'll be happy to hear dissenting opinions on what exactly happened to me, however no matter what, i certainly was in a situation where I was rescued and had to be assisted to the surface. At this stage I think I am still a little in post drama shock, so I may come back to clarify things tomorrow. Next step after posting this will be to ring DAN to discuss, however I thought posting now this may help me clarify my thoughts.

Background:

I am in Koh Tao Thailand for a 3 week dive holiday. I am around half way through my stay, and have been diving pretty much every day. Mostly on Nitrox. My last rest day was 3 days ago on the 18th. While here I have been doing a number of courses (rec) to do the SSI Master Diver rating. The last course I completed on the 17th was Stress and Rescue. I have tried my best to stay hydrated, however have not been sleeping well (body clock will just not adjust for some reason) and have had the occasional night out. The night before I had 3 beers but also a lot of water that night, and 1L of electrolyte formula in the morning as a safeguard.

On the 19th I completed 2 dives
a) Entry: 10.36am, Max Depth 19.2m, Avg Depth 11.0, 50 min, 29C, 50 min 32% Nitrox
On this dive I had regulator issues, this was not a comfortable dive
b) Entry 12.28pm, Max Depth 11.4m, Avg 8.7, 54min, 30C, 54min 32% Nitrox
On this dive I had regulator issues, this was not a comfortable dive

On the 20th I completed 2 dives
a) Entry: 8.13am, Max Depth 28.7m, Avg Depth 17.8, 50 min, 28C, 39 min 32% Nitrox
Nice Comfortable dive
b) Entry 9.54am, Max Depth 24.3m, Avg 18.3, 54min, 30C, 54min 32% Nitrox
Nice Comfortable dive

Today:

Todays dive was planned as a deep dive to around 36m to do my deep cert. A mix of 28% Nitrox was decided upon for the dive. I analyzed the tank to be 27.2% with the shops Analox tester. The tank was re-analysed afterwards and showed 27.5%.

The dive plan was to drop to the main part of the dive site at around 25m, then swim outwards to a max depth of around 36m. On this dive would be me, a DM, and the instructor.
Entry was at 1.33pm, and the start was uneventful and a nice calm dive.
At the edge of the site near 23m, we passed through a thermocline, and the temperature dropped markedly (maybe 4-5C), and vis reduced to around 1-2m.

We continued down to our max depth at 36m. This was at around the 7min mark. I then completed the narcosis test (fine),checked our NDL's (mine said 8) and we turned around and started to swim back in the direction from which we had come. At this stage we were swimming into the current, in very low visibility. I had dropped to the back of the 3 person team. At around 1min elapsed time, I started to feel.. wrong. We were around 31m at this stage I believe. I struggle to describe it, but I just felt really really weird. I have experienced vertigo before, this was not vertigo. My vision started to go weird too. It was like when you look through a thermocline, it's just a bit warped, and it started to narrow.

I instinctively knew something was wrong, kicked one or two kicks to get to the DM, and grabbed him. I signaled a problem, pointed to my head, and thumbed the dive. He signaled OK and took off to grab the Instructor, who was only 2-3m away but was already disappearing into the haze. I reached for my inflator, and tried to ascend a couple of meters. I don't think I was successful (certainly I see nothing on the computer to indicate that I was). I was remarkably calm, my SAC rate was fine, but I was feeling like I was going to pass out. Then I started to shake. I could feel my arms and legs shaking. I managed to grab the reg and hold it in my mouth, but could not work the inflator button. My hands simply wouldn't do as commanded. Around now the DM re-arrived with the Instructor, not 100% before seeing me understanding the gravity of the situation (I believe). I let go of the inflator, grabbed the DM's arm, and held on for dear life. I consciously then ceded control to them (not that they didn't take over anyway), and became a passenger.

The ascent from 31m to 20m is a bit of a blur. I didn't pass out, but I certainly was "out of it", and don't recall much of it. The shakes subsided on the way up, and by the time we got to around 20m, I felt almost normal. We spent a few minutes swimming around with them checking on me constantly, then ascended up. I think I came up with 120bar left.

So at this stage, I need to go have a drink, and re-asses my diving plans. I certainly would never ever want to do a deep dive again with anyone who is not Rescue trained.

And I need to go buy my DM and Instructor a large number of drinks.

[tracydr]

Do you have any history of migraines or seizures?

[OzGriffo]

No I don't.


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[Quero]

Oh wow. Glad you're back on dry land. Do post about what you learn from DAN. If you need any help from Phuket side, give me a call.

[ianr33]

What was your maximum pO2 and for how long? (Sorry,can't cope withe meters before coffee ! )

[Quero]

What was your maximum pO2 and for how long? (Sorry,can't cope withe meters before coffee ! )

pO2 would have been less than 1.3 ata.

[ianr33]

pO2 would have been less than 1.3 ata.

Thanks. I find it hard to believe that level of O2 could be a problem for that length of time.
My first guess is a contaminated tank. Will see if I can find a post from the Decostop that sounds somewhat similar

Edit: Here it is http://thedecostop.com/forums/showth...ght=compressor

[pickens_46929]

I would say that or a combination of that plus Narcosis.

If this was the first dive of the day, you were out of the water for just shy of 24 hours. You weren't doing particularly high O2 Nitrox mixes the previous days nor were you doing 4 or 5 dives back-to-back to back.

Also the symptoms of a CNS hit, while they do vary, aren't like this typically. Most common is seizure like convulsive behaviors or twitches. Rarely do you hear someone explain it with tunnel vision, visual disturbances, etc. Those symptoms are more closely related with Narcosis.

Had you ever been that deep before?

The reason I ask, is that I never really experienced narcosis until one particular dive that really rang my bell. Funny thing was, now that I really knew what it was like, I started to recognize some of the symptoms are other dives going forward when previously I hadn't.

Glad you are ok. Not sure you have to really re-evaluate diving as much as you think. Just make sure you get back on the horse and have some fun.

Thanks. I find it hard to believe that level of O2 could be a problem for that length of time.
My first guess is a contaminated tank. Will see if I can find a post from the Decostop that sounds somewhat similar

Edit: Here it is The Deco Stop

[Quero]

pickens, what you are describing is CNS O2 toxicity. There are other sorts of toxins that can affect the CNS with differing symptoms. The link that ian posted from TDS discusses oil vapor-induced CNS narcosis. In other words, what OzGriffo experienced may have been due to bad gas.

[Jim Lapenta]

Conventid. Convulsions, visual disturbances, ears - auditory disturbances, nervousness, tingling, irritability, and dizziness are all symptoms of a cns hit. 1.3 is definitely enough to cause it. Like dcs it is not an exact science. We had a diver from this area tox in a cave at 1.3 a few years back. As a result many of us who knew him mix for 1.3 working and 1.5 on deco just as an added safety margin. You may have gotten very lucky. Jeff knew his hit was coming on and signaled his buddy. He tried to get to the ceiling of the cave to ward it off but it was too late. His buddy held him as he drowned. Could not get the reg back in. Your buddies being able to get you shallower may be the only reason you are alive.

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