DCS due to reading computer wrong (I think)

[RJP]

If this is really the way things happened, that seems pretty irresponsible dive guiding to me. Maybe I'm missing something.

The Odyssey, unlike many/most liveaboards, treats every diver like an adult. They give very thorough briefings on each site, including depths to all areas of the wreck in question. They do not, however, plan your dive for you. Planning the dive - including depth, mix, bottom time, and stops - is up to the individual diver. Part of that plan should involve a solid "should I even be doing this dive?" reflection. To me, if you only have an aluminum 80 as your gas supply... the answer should be "no."

Anyone who dives a wreck like the SFM should know what their deco time and gas plan is prior to hitting the water. I won't pile on with what has been said above, but I would ask the OP how many PSI they had left when they got back on the boat? Did you even have enough gas on hand to do the required stop per your computer? Suppose you had stayed on the bottom another 5min? How much more deco time would have been required? Do you know the answer to that question? Did you have enough gas to do that much deco?

Also note that it is entirely possible that your computer did tell you that you had 14min of deco obligation when you began your ascent from 51meters. However, given how deep you were, you were still racking up more and more deco time even as you ascended. I don't have dive planning software handy, but I would guess you didn't start offgassing until you got to about 50ft or so. So at a "slow ascent rate" of .5ft/min you would have spent another ~3min or so ADDING to your deco obligation as you ascended.

"Ride your computer" is not a plan, especially if you don't understand deco diving/theory.

 

[Boiler_81]

While aluminum 80s are listed as available on the Odyssey website, I believe steel 108s were used by everyone on the trip I was on other than two divers who used double 80s. I did the SFM on my trip but just did a quick trip to the deck gun then over to the tanks and back up. My computer indicated a couple of few minutes of deco but was nearly cleared by the time we got back to the stop. We did a short deco and a long safety stop to make sure. Yes, this dive was outside my training and there was known risk. Given the once in a lifetime nature of the dive and the precautions put in place by the crew, my buddy and I were willing to take the risk of a short dive. There were two divers who did not feel comfortable doing the dive and were taken to an alternative site while the rest of us did the SFM. As stated above, the Odyssey treats you like an adult. I appreciated that in this "everyone is your nanny" world we now live in. Given the same circumstances, I would do it again.

The Odyssey, unlike many/most liveaboards, treats every diver like an adult. They give very thorough briefings on each site, including depths to all areas of the wreck in question. They do not, however, plan your dive for you. Planning the dive - including depth, mix, bottom time, and stops - is up to the individual diver. Part of that plan should involve a solid "should I even be doing this dive?" reflection. To me, if you only have an aluminum 80 as your gas supply... the answer should be "no."

 

[vladimir]

While aluminum 80s are listed as available on the Odyssey website, I believe steel 108s were used by everyone on the trip I was on other than two divers who used double 80s. I did the SFM on my trip but just did a quick trip to the deck gun then over to the tanks and back up. My computer indicated a couple of few minutes of deco but was nearly cleared by the time we got back to the stop. We did a short deco and a long safety stop to make sure. Yes, this dive was outside my training and there was known risk. Given the once in a lifetime nature of the dive and the precautions put in place by the crew, my buddy and I were willing to take the risk of a short dive. There were two divers who did not feel comfortable doing the dive and were taken to an alternative site while the rest of us did the SFM. As stated above, the Odyssey treats you like an adult. I appreciated that in this "everyone is your nanny" world we now live in. Given the same circumstances, I would do it again.

I am not being critical—I did much the same thing when I was in Truk. But maybe we should be reasoning, "Given the once-in-a-lifetime nature of the trip, I should get some tech training before I go."

 

[Boiler_81]

That is a valid view for some people. For me, I knew what I was getting into and understood the risks. I was OK with it. The risk reward for a one time event was frankly not worth it to me. Others will come to a completely different conclusion. Once again being treated like an adult and allowed to make decisions for ME was great.

I am not being critical—I did much the same thing when I was in Truk. But maybe we should be reasoning, "Given the once-in-a-lifetime nature of the trip, I should get some tech training before I go."

 

[Griffo]

Glad the OP is ok, but 50m on a single? That's the definition of a trust dive. On an air share you'd be sucking down, what, 400+PSI per minute at that depth?

 

[AfterDark]

You're joking, right...?!

About what?

 

[DandyDon]

You're joking, right...?!

About what?

You said "I'd take a little DCS to dive TRUK!"

 

[bamafan]

You are definitely lucky. I ran this on V-planner with a zero conservative factor and you didn't do nearly enough deco especially on the shallow stops. Below is copy of what V-planner showed.

Decompression model: VPM - B
DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0m
Conservatism = Nominal
Dec to 52m (3) Nitrox 24 15m/min descent.
Level 52m 11:32 (15) Nitrox 24 1.48 ppO2, 50m ead
Asc to 21m (18) Nitrox 24 -9m/min ascent.
Stop at 21m 0:33 (19) Nitrox 24 0.74 ppO2, 20m ead
Stop at 18m 1:00 (20) Nitrox 24 0.67 ppO2, 17m ead
Stop at 15m 2:00 (22) Nitrox 24 0.60 ppO2, 14m ead
Stop at 12m 3:00 (25) Nitrox 24 0.53 ppO2, 11m ead
Stop at 9m 3:00 (28) Nitrox 24 0.45 ppO2, 8m ead
Stop at 6m 17:00 (45) Nitrox 24 0.38 ppO2, 5m ead
Surface (45) Nitrox 24 -9m/min ascent.
Off gassing starts at 31.2m

I dove Truk in December on the Odyssey and I did this dive with 2 sidemount 108's with air and 2 each aluminum 80's with 30% for deco. I know when we did the dive the recreational groups had a divemaster with them who had an extra 80 for bailout. They also had another dive master around 60 feet or so with another bailout bottle and there was the always present bailout bottle on the safety stop hang bar. This dive is definitely a tech dive but they have a pretty good safety record on board the Odyssey and like has been stated before they let you dive like a grown up and don't hand hold. Below is a copy of my dive profile from this same dive.

View attachment SanFrancisco Maru Dive.pdf

 

[JohnN]

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.



---------- Post added February 16th, 2013 at 10:01 PM ----------

YIKES!!! with EAN25 and 172 fsw, I get a ppO2 of 1.55.

Have you taken a Nitrox class, or do you just do what the DM says ?

Sorry to bust your chops, but DCS would have the lesser of my worries

V-planner gives me 101 cu ft of gas (with proper deco) (SAC=0.7). Is your SAC really that good?

 

[Quero]

I got better during the day and was fine to fly late that night.

Hintermann, from what I recall about you on other online communities where you contribute, you're a medical doctor, correct? So maybe you believe you are in a position to self-diagnose. Have you done any specific study to gain an in-depth understanding of decompression sickness? Have you noted while doing so that a common feature of those afflicted is their denial at the severity of their hit?

"I am not excatly sure what I was looking at but in my excitement of the dive I failed to read it properly somehow."—that's surprising, given that you had no narcosis.

It's also difficult to read @167' when you're narced.

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.

Those who point out that while you didn't believe you were narked, you most definitely were are correct, and I suspect you were much more than just 'slightly so' given that you made very fundamental newbie mistakes like not knowing how to interpret what you were seeing on the computer display. You were very lucky indeed. I hope this is a wake up call to you that mere frequency of diving with your 14 liveaboards cannot replace proper training for 'big' dives, and that the complacency that your many exotic dive trips have fostered in you is a dangerous attitude. You may be very accomplished in your professional role, but being intelligent as well as capable in one complex realm of your life doesn't make up for ignorance in other areas. To redress that ignorance, please get the requisite training and put it into practice before engaging in any other 'big' dives.