DCS due to reading computer wrong (I think)

[vladimir]

Thanks everyone. I take on board the criticism, which is no more than what I deserve, probably less. My wife gave me a real jawing out when I told her!

I was on a single tank, as were everyone else. Without stirring up some hornet's nest, it looks like on board the Truk Odyssey they allow everyone to do the SFM dive as a recreational one on the last day and with very few exceptions, on a single tank. Of the 16 divers and 4 divemasters doing the dive, only one had twins.

Regarding poor pre-dive plan, I accept full responsibility. The pre-dive briefing was long and detailed and the captain assured everyone that they did this dive on every trip and seldom had problems. That reassurance and my own excitement at this dive made me rather careless and there is no excuse for it. It will NEVER happen again. But in the Captain's defence, he did warn us to follow our computers closely and adjust times accordingly.

I am a keen student of WW2 and had read up a lot on Operation Hailstone and the wreck dives. I was concentrating too much on the object of the dive - the wreck itself - rather than the dive profile. As I said, no excuse. (IMO, that is one main difference between a reef/wall dive and a popular wreck dive. In the latter, one knows what to expect and concentrates on looking for it)

As to exactly what happened in my own dive, my guess is that flots am is very close to the truth. Although I thought that I was not narked, I probably was slightly so - at least enough to upset my concentration, which is usually very good during dives. That might be why I read the computer wrong and failed to check it during the stops except for the time countdown.

As you guys said, I was lucky.

As an aside, I corresponded and spoke with Klaus Lindemann some years back, on a few occasions, before he died. As you probably know, he is the author of Hailstorm Over Truk Lagoon, the bible for divers in Truk. He was generous with his time and seemed to appreciate my interest in his work.

 

[DandyDon]

Thanks for sharing. Glad you're ok, or think so at least. Yeah, think you were a lot more narced that you realize, like most DUI drivers who are arrested. There are skills tests that can be ran at depth to demonstrate such. I have never felt narced, and I've been deep, deeper than you once by mistake. I just remind myself that I must be and try to allow for it.

I do not know your computer at all, but you need to know it well - a lot better than you did. Mine shows my nitrogen loading into green, yellow, and red zones as well as how many minutes of deco I need to clear red - and I can understand that regardless of how narced I may be and not realize it.

Keep learning...

 

[clownfishsydney]

I do not want to seem critical, but you asked for comments.

I have dived the San Francisco Maru 7 times. I have looked back through my Smart Trak software (for Uwatec computers) and found that for a 15 minute bottom time on air (but diving deeper than you did - 61.6 m to steamroller), I required 1 min at 9 metres, 4 mins at 6 metres and 11 mins at 3 metres (total of 16 mins). Even doing with 24% using my current computer and its settings, it comes out similar.

Since when are deco stops (or safety stops as you call them) done at 15, 10 and 5 metres? Since when are they all the same time time of 5 mins?

In addition, on the 6 trips I have done to Chuuk, I have always made sure that once deco is cleared, we stayed a minimum of 10 mins further as a safety stop.

I am also amazed that the operator did not insist you went to the chamber considering your symptoms.

My view - you did the deco stops way too deep, blew off considerable deco and did not do an additional safety stop as a precaution. Didn't your computer beep at you or at least show that you did not complete the required decompression?

 

[chillyinCanada]

Another thing that surprises me, is that OP experienced such intense DCS symptoms but was recovered enough to fly within 24 hours to no further ill effect.

 

[halocline]

Lots of red flags here, but I have to say I'm a little surprised that a professional dive operator would ever take clients to 52 meters on a single tank, presumably without evidence of decompression training. And then, when one of their clients exhibited these symptoms, did not insist that he seek treatment, and then, after not seeking treatment, allowed him to fly the next day.

If this is really the way things happened, that seems pretty irresponsible dive guiding to me. Maybe I'm missing something. The big thing is to send recreational divers down to technical depths without the training or the equipment, thinking that's somehow okay by telling them to "follow their computers closely." What a crock...every dive computer that I've ever seen comes with several warnings to NOT go into deco deliberately without the proper training and equipment. So, in this case, "following the computer" means don't do this dive.

But, I'm glad the OP is safe and sound, I think he's pretty lucky.

 

[JamesK]

Wow. This tread brings to light just how many people ride their computer and think that is deco. A dive operator that "seldom" has problems and allows people to dive that deep without any training just a "pay attention to your computer" briefing pretty much scares the hell out of me.

I understand that they do this all the time, and thousands have done it without I'll effect, but de those thousands even realize why they had no ill effect?

I am a big fan of computers. Guilty. However, any dive where I am either planning deco, or know that any unforeseen circumstance can put me in deco, the table get cut an put in my wet notes. The gas planning I done to ensure that I have enough gas to get myself, and my buddy back to the surface.

This single tank computer ride of an air dive is just stupid. And yet, thousands of people do it.

 

[openmindOW]

My wife gave me a real jawing out when I told her!

Thank you for sharing your story, Hintermann. By posting your account here, you are helping other divers to dive safely.

I am glad that you are okay. I suspect that your wife probably won't let you forget about this for a while.

Please discount some of the impolite criticism that might get posted to this page over the next few weeks. Some of my fellow SB'ers can be rude.

 

[TSandM]

The OP got significantly bent from not doing all of his deco. What is really scary is to contemplate what kind of shape he would have been in had a hose blown, or a reg freeflowed. Without any redundancy at all, and with no one in his party carrying enough gas to help him to the surface, he would simply have had to "blow and go", and he might not have survived to write a report of it.

The deeper you dive, the higher the stakes are, and once you begin incurring significant deco obligations on a single tank, you are really rolling the dice and counting on NOTHING going wrong during the dive. You don't have enough gas to lose any, and no one you are with has any to share. A large part of tech diving training is learning to calculate the amount of gas needed for a dive, and what reserves you need for contingencies. Recreational divers generally are not only not taught to do this, but they aren't even taught the mindset. As I've heard said before, you can survive bent, but you can't survive drowned.

In addition to Mark Powell's book, I would highly recommend the OP read NW Grateful Diver's article on gas management. Then sit down and run the numbers for that dive, and see what you think.

 

[MSDT476614]

Not going to ad nauseum.

Here's something else you can maybe take away. A final redundancy if your hose does blow is to shut down your air, get on your buddy's AAS. When your bud's tank is drained, swop regs to your tank (which hopefully has some left). But this too takes training in a controlled condition till its second nature.

A wet swop is perfectly ok in an emergency but is never taught (I always wonder why). Just remember to give it a good purge before you inhale! Just get your reg serviced after the trip and rent another for the duration if you're still diving?

Old habits and old hoses die hard. Hoses used to get 'pregnant' every now and then. These days the quality is much better. Then along came miflex (and its copies) with its teething problems which got everyone out buying 8x the number of hoses and regs they really needed to be safe!

Dive safe and dive sensible. I'd point you to other threads relating to diver training.

 

[Doubler]

Having dove the Odyssea last year as I recall the theme of the week by JJ was "run your computer into Deco so you see how it operates and you will be ready for the San Fransisco Maru" it was your call on doing the dive, I planned it as a no decompression and dove that very short plan for several reasons. I did no deco dives all week because there is basically no chamber available so why push the envelope. I was diving an 80 and didn't have enough back gas for stops and any emergent situation that might occur. I asked "if someone in the first group grabs the bailout bottle at 90ft is it replaced" answer "No"
I also didn't do the dive following this one. JJ also stated that they see DCS often, I believe him.