Dive safe! A short story from a chamber operator

[melanie.]

I'd love to be able to video record the experience, especially from an attendant point of view. When transferring in or out, you sit in a very tiny lockout chamber, and the first time I did that, I felt a tinge of claustrophobia. Also one thing that surprised me, is how much different equalizing your ears is in the chamber. I have very good ears for diving, but during decent in the chamber, I find that I have to equalize almost every foot, which is way more often than when I'm diving.

Did you have a chance to experience what the chamber was like before going in with a patient for the first time? I could only imagine how unsettling the changes are

 

[ChuckP]

I don’t fully agree with the guy above me .

While diving conservatively is likely not an issue, 4-5 long and deep dives/day for multiple days could get you into trouble.

After 4 Nitrox dives in 1 day in GC last Feb (2 tank AM + 2 tank PM), I was at ~28% CNS - so I would imagine that keeping that schedule with a 5th /night dive thrown in for a week could ratchet up CNS - certainly worth watching/monitoring, imho.

Just to put you worries at rest, plans were run on Multi Deco

7 consecutive dives using 36% to 80 foot for 40 minutes, one hour surface intervals between every dive - that's a pretty dang aggressive day of diving on your body as that's a square profile. After your first dive your CNS is 20.4%, after your sixth it's 51.6% and your seventh dive it's 52.9%.

The eighth dive after a 12 hour surface interval, your CNS% is right back at 20.4%.

I understand or remember the half life for CNS as being 90 minutes, not longer and it sort of shows in the dive plans, your CNS% jumps up there your first few dives then gradually rises - it's definetly not linear.

CNS comes into play after long exposures to high PO2 levels, something rebreather divers and tech divers face, not very likely, while anything may be possible just not likely in recreational diving.

I was taught in tech diving to plan a dive keeping the CNS% below 40% for the dive in case of an emergency long deco, it just doesn't ever get that high even with multiple dives per day. The OTU's MAY cause some irritation in your lungs but I've never heard of it, and was taught more to manage CNS and OTU will follow.....

Great story on the chamber by the way - I dive out of a place right across from one of the local chambers and have seen ambulances drop off, taxis drop off - I look at that building every day and remind myself why I don't want to go there.

 

[KathyV]

Deleted, I was going to tell a "clueless diver that I once met" story but that is not the purpose of this thread.

Please do tell, or even start a thread with that heading. I might “get a clue” from hearing other people’s stories, as that is part of “NOT learning the hard way.”

Okay, but I am sure that you are already much more informed and proficient than these folks!

Many years ago we went to a Club Med Resort for a dive vacation. I understand that the dive ops have changed a lot at Club Meds since then but we've never been tempted to do another CM trip to find out if they have improved. The dive boats were cattle boats that were full of inexperienced divers proudly carrying Club Med C-Cards. Once upon a time they had done some minimal training and a check-out dive at a Club Med and now they enjoyed traveling to CM resorts to dive, bragging about how they "never had to do any expensive and difficult dive training" and they could still dive at CM resorts all over the world.

After our last dive I mentioned to a Club Med C-Card diver (who told me she was a Doctor) that it was our last dive because we would be flying home soon. She looked at me in surprise and said "What has flying home have to do with it being your last dive?!" I answered that "we have to wait 18 to 24 hours before flying to give our bodies time to eliminate the excess nitrogen." She just looked at me blankly and said "Nitrogen, what nitrogen?" So I just told her "If you plan to keep diving, do yourself a favor and take a real training course and get certified, you might live longer!" I wonder if she ever took my advice.

On another trip in the Bahamas I overheard a guy that was signed up to go on the same boat talking on the phone and making air reservations to fly home that same afternoon. He was trying to figure out how much time he would have after the 2-tank morning dive to pack, grab his stuff, and get to the airport. I admit that I was a snitch and told the dive shop manager about it. He talked to the guy and confirmed that he was indeed planning to fly back to the US that very afternoon. The diver was stunned when the manager told him that he wouldn't be able to dive after all. He became furious and stormed out of the place yelling and I'm betting that he went directly to another dive shop, signed up to dive and kept quiet about his flight plans.

I also once met a divemaster in Egypt that had gotten a ceiling alarm on his computer but he was running low on air, so he left his computer sitting on a rock at depth to finish his safety stop for him. Then he geared up with a fresh tank and went back down later to retrieve his computer. He said that he "didn't want to get locked out of his computer" and that his "computer was over-sensitive and he knew that he would be okay." Maybe he was right, but I don't think that he was setting a good example for others.

And then there was the couple that we met in Cozumel (I think) that didn't want to spend money on 2 computers so they just dived with one and figured it would be okay as long as they stayed fairly close to each other during the dive.

But my all-time favorite, that I've mentioned on SB before, was the ditzy woman in Cayman that went to 150 feet on Nitrox and couldn't figure out why her computer was screaming at her. The dive master caught her and stayed with her and got her back safe. She was livid when the divemaster told her that her diving was over for the rest of the trip. She grabbed her gear and stormed away in a huff and I'm betting that he didn't even get a tip after all his efforts.

We are just recreational vacation divers, and I have made some dumb mistakes in the past myself and will probably make some more in the future. Some of our equipment is old (but well-maintained) but I'll bet that some younger divers laugh at us a little, so I don't mean to sound all superior or sanctimonious. We're not "hotshot divers" at all, but these folks really surprised (and scared) me with their cluelessness!

I should also add that I have met many, many more good divers than clueless divers, but we have been diving for a long time so we have come across a few "memorable gems" along the way.

 

[JohnN]

I know people who actually dive Nitrox without setting their Nitrox enabled computer for Nitrox. Multiple day trips with 4-5 dives a day for at least 3-4 days. They admitted they don’t keep track of their O2 exposure, when I specifically asked them. That’s why I posted this question.

For recreational depths (<130 ft) and no deco profiles, it is not possible to exceed the O2 clock

 

[JohnN]

Just to put you worries at rest, plans were run on Multi Deco

7 consecutive dives using 36% to 80 foot for 40 minutes, one hour surface intervals between every dive - that's a pretty dang aggressive day of diving on your body as that's a square profile. After your first dive your CNS is 20.4%, after your sixth it's 51.6% and your seventh dive it's 52.9%.

The eighth dive after a 12 hour surface interval, your CNS% is right back at 20.4%.

I understand or remember the half life for CNS as being 90 minutes, not longer and it sort of shows in the dive plans, your CNS% jumps up there your first few dives then gradually rises - it's definetly not linear.

CNS comes into play after long exposures to high PO2 levels, something rebreather divers and tech divers face, not very likely, while anything may be possible just not likely in recreational diving.

I was taught in tech diving to plan a dive keeping the CNS% below 40% for the dive in case of an emergency long deco, it just doesn't ever get that high even with multiple dives per day. The OTU's MAY cause some irritation in your lungs but I've never heard of it, and was taught more to manage CNS and OTU will follow.....

Great story on the chamber by the way - I dive out of a place right across from one of the local chambers and have seen ambulances drop off, taxis drop off - I look at that building every day and remind myself why I don't want to go there.

NOAA (Bless their Ludite hearts) still insist the O2 clock "magically" resets at 24 hours. Laws of Physics, we don't need no stinking laws)

 

[Joneill]

Just to put you worries at rest, plans were run on Multi Deco

7 consecutive dives using 36% to 80 foot for 40 minutes, one hour surface intervals between every dive - that's a pretty dang aggressive day of diving on your body as that's a square profile. After your first dive your CNS is 20.4%, after your sixth it's 51.6% and your seventh dive it's 52.9%.

The eighth dive after a 12 hour surface interval, your CNS% is right back at 20.4%.

I understand or remember the half life for CNS as being 90 minutes, not longer and it sort of shows in the dive plans, your CNS% jumps up there your first few dives then gradually rises - it's definetly not linear.

CNS comes into play after long exposures to high PO2 levels, something rebreather divers and tech divers face, not very likely, while anything may be possible just not likely in recreational diving.

I was taught in tech diving to plan a dive keeping the CNS% below 40% for the dive in case of an emergency long deco, it just doesn't ever get that high even with multiple dives per day. The OTU's MAY cause some irritation in your lungs but I've never heard of it, and was taught more to manage CNS and OTU will follow.....

Great story on the chamber by the way - I dive out of a place right across from one of the local chambers and have seen ambulances drop off, taxis drop off - I look at that building every day and remind myself why I don't want to go there.

Thanks - good analysis and explanation for us rec divers!

 

[CandiveOz]

Some computers have a safety factor that can be varied to shorten NDL times for the same O2 mix (air or nitrox), while still keeping track of MOD and total O2 exposure accurately.

For what its worth, with my Galileo Sol I can use the computer's Microbubble levels (MB) to offset the increased NDL due to the nitrox mix. For example for 32% I would set it at MB 3 and for 36% MB 4. These are not exact offsets but close enough.

 

[Divetech Cayman]

Did you have a chance to experience what the chamber was like before going in with a patient for the first time? I could only imagine how unsettling the changes are

Yes the training is pretty thorough. You begin with many classroom sessions. 6 weeks of evening sessions twice per week. You take an exam, then you get an orientation session inside, and you have to learn what everything is and how to use it. Then you do a training session inside to practice the decent/ascent and the lockout techniques. Once this is complete, you then have to have 4 sessions operating the chamber under the supervisor of a training operator, and 4 sessions as an attendant with a training attendant. Once then, they evaluate you to see if you are ready to go solo as an operator or attendant.

 

[miked]

To the OP: thanks for posting all the nitty-gritty details Involved in going on a "chamber ride". They expressed the detail far better than I could have, and I did experience six U.S. Navy table 6 "rides" after an incident in Grand Cayman in 2004. Also thank you for pointing out the dedication of the Cayman hyperbaric team. They were great in so many ways.

 

[ReadyDiverOne]

@miked did you dive again? What precautions did you take/what did you do differently?