DCS due to reading computer wrong (I think)

[vladimir]

Thanks, John, for correcting that.

 

[Duke Dive Medicine]

JJ did say "you guys will have some narcosis" and that "we have had quite a few cases of DCS" at various times.

If this is an accurate statement, there's something very wrong here. What you're saying is that the dive operator is aware of the high incidence of DCI on this particular dive yet makes a conscious choice not to intervene. There are ways to reduce the probability of DCI, most of which have been discussed here. The operator should know this, and should also be well aware of the "once-in-a-lifetime dive" mentality that they must see on a regular basis. I would argue that they have a responsibility to ensure that dives are carried out within accepted parameters, as Halocline pointed out earlier in the thread. "Treating us like adults" and "helping ensure our safety in this environment" can coexist.

 

[Edward3c]

On a recent trip to Truk Lagoon, I had my first and hopefully only experience of DCS. Fortunately, it was not severe and I did not need to go into a decompression chamber. I believe it was a diver error, most likely because I did not read my computer right.

It was on the penutimate dive of the week long cruise on board the MV Truk Odyssey. Like others on board, I had a great time diving the Operation Hailstone wrecks and apart from a problem with my camera housing, all had gone well till that dive.

The dive was over the wreck of San Francisco Maru, the so-called "Million Dollar Wreck". It was a deep dive just beyond the 50m mark and since we were all diving on single tank 24% nitrox, the dive plan was very carefully discussed. For a start, we were required to miss the night dive the previous evening to increase the surface interval. The divers would go down in 2 groups of 8 divers each and each group was supervised by 2 divemasters who hovered just above the top deck where they could keep all their charges in sight. The visibility was good to the point of eeriness as we descended down the line to the top deck at 52m. Although we were warned about the possibility of narcosis, I did not experience any. Bottom time was strictly limited to 15 minutes and since the wreck lies dead upright with the cargo holds wide open and all the interesting bits clearly visible on or just inside the deck, exploration involved little more than swimming up and down the ship looking at things. My own maximum depth was 51.4 metres and at exactly 15 minutes I began a slow ascent. At that point I checked my Aladin Tec 2G computer and thought it indicated a safety stop of 14 minutes. I am not excatly sure what I was looking at but in my excitement of the dive I failed to read it properly somehow. Later check by the DM revealed that it should have been 22 minutes.

I did 5 minute stops at 15, 10 and 5 meteres, totalling 15 minutes and ascended to the surface. Feeling fine, I stripped off, had a cold shower and wrote-up the log. I then went to the lounge and was sipping a lemonade when I felt pain in my lower ribs. It quickly spread to the entire rib cage, both arms and shoulders and I felt weak and dizzy. I alerted a nearby divemaster who immediately made me lie down and administered 100% oxygen. After about an hour of that the pain gradually went away but the dizziness persisted for 4 to 5 hours. But the worst part of the ordeal was unbelivable weakness that lasted for almost 24 hours. I was only able to lie on my bunk for most of that time and was barely fit to disembark next morning. But I got better during the day and was fine to fly late that night.

First thing I did after reading this post was check the BSAC Nitrox Tables.

The planned dive was off the tables. We use 1.4 ppo (which is becoming the accepted limit, not 1.6).

On air most divers start to get narked from 15m, but the individual doesn't notice the effect much before 30m. (The error when recording marine species starts at 15m.) so when diving to the ppo limit with a weak mix the effects of narcosis (24%) will happen.

At the depth of this dive I would have thought trimix would be a better gas, see here for BSAC courses so you can get trained for your next trip.

Kind regards

 

[Boiler_81]

When I did the dive I don't remember JJ saying in the breifing that they had seen a lot of DCS on the site. What he did say is in his experience the risk of DCS is higher than the risk of O2 tox with the light Nitrox used on the dive.

As boulderjohn stated, the dive is commonly done on a single which is overfilled. I will have to look at my log to see what my starting pressure was.

I am still curious where the OP dive buddy was during his accent and decompression. This dive should have been a buddy dive and both computers should have cleared before getting back on the boat.

If this is an accurate statement, there's something very wrong here. What you're saying is that the dive operator is aware of the high incidence of DCI on this particular dive yet makes a conscious choice not to intervene. There are ways to reduce the probability of DCI, most of which have been discussed here. The operator should know this, and should also be well aware of the "once-in-a-lifetime dive" mentality that they must see on a regular basis. I would argue that they have a responsibility to ensure that dives are carried out within accepted parameters, as Halocline pointed out earlier in the thread. "Treating us like adults" and "helping ensure our safety in this environment" can coexist.

 

[openmindOW]

As you can all see on their website, Twin tanks are offered only on request on board Truk Odyssey and they have only 3 sets on board. They have 16 divers on board and are usually full. On my trip, there were 16 divers and all but 2 dived the SFM. Only one person was on twins - from the start.

Hintermann has repeatedly acknowledged that he made a mistake. He has repeatedly accepted responsibility for what happened.

Frankly, he did the dive community a favor by openly posting his account here on SB.

Could we please treat our fellow diver with respect. Please.

I wonder if the Divemasters were wearing doubles or had pony bottles.

---------- Post added February 19th, 2013 at 11:20 AM ----------

If it makes you feel better, fine, but I would not assume it adds any significant safety on it's own.

Halocline, my friend, I see your point. I suppose we could quibble about the words "any significant."

My view is that a Pony on a deep recreational dive is something. You're absolutely right that it won't help with narcossis, navigation issues or entanglements. But a pony bottle is better than nothing.

The size of the pony does matters. I suspect that a cubic 19 foot bottle won't don't you much good at 50 metres.

 

[RJP]

Hintermann has repeatedly acknowledged that he made a mistake. He has repeatedly accepted responsibility for what happened.

Frankly, he did the dive community a favor by openly posting his account here on SB.

I wonder if the Divemasters were wearing doubles or had pony bottles.

Yes, he has done divers a service by posting his story. However, the real cautionary tale here - and I don't say this to pile on - is that the mistake he's acknowledging having made... is not the mistake he actually made. The critical mistake he made happened before the dive, not at depth.

I know some guys that died several years ago on a wreck dive, due to a critical error they made. Sadly, they made that error sitting around at a kitchen table 1,500mi from the wreck site. It just took a few weeks for the impact of their error to cost them their lives.

PS - Having done that dive from the Odyssey on more than one occasion I can tell you that the guides more than likely did the dives on single tanks. They probably also used the gas they had left after the dive for another two dives later in the day.

:d

When I was there at least one, if not both of the guides, carried extra 80's in case any of the paying customers ran into trouble. So I guess you could say they were also carrying their own redundancy.

---------- Post added February 19th, 2013 at 07:19 PM ----------

I'd like to watch you and your buddy air share from 50 meters. I'd shoot video but I wouldn't want to ascend nearly that fast. I'll keep lugging my frady-cat bottle...

Not a problem at all. Nor would the ascent be any faster than than normal, because - with the proper gear, training, and gas planning - there would be no need to ascend any faster than normal. In fact, other than an unlikely failure such as TWO simultaneous blown burst disks PLUS lost deco gas, there'd probably be no reason to air share from 50M to the surface anyway.

 

[halocline]

Yes, he has done divers a service by posting his story. However, the real cautionary tale here - and I don't say this to pile on - is that the mistake he's acknowledging having made... is not the mistake he actually made. The critical mistake he made happened before the dive, not at depth.

My thoughts exactly. This thread might better be titled "DCS due to diving to 52 meters without the correct training, planning, or equipment".

 

[Hintermann]

I understand that you are writing in response to my comments. Let me say yet again that I intend no insult, but I also don't believe that this serious incident merits coddling your sensibilities. Here is a definition of complacent:
You are a very experienced diver who has had the means and opportunity to dive in the world's premier dive destinations. I would expect anyone who has done as much diving in varied locales as you have to be a confident diver. I believe that any of us, in your situation, would be 'pleased' with ourselves, our accomplishments, and our good fortune (in the terms of the definition above)! However, when it comes to technical diving conditions like your 52 meter dive to the SFM, you simply didn't have the first clue what you were getting yourself into. In other words (and again in terms of the definition) you were 'without awareness of some potential danger or deficit'. In reality, my post only offered an analysis of events based on the facts you yourself have provided. There is simply no way to sugar coat reality: you attempted a technical dive (danger) that you were unprepared to do (deficit) in spite of of your extensive experience with other sorts of dives.


The objective of this forum is to provide 'case studies' that might help other divers avoid making the same mistakes as those who have experienced incidents in which they were in mortal danger. You, Hintermann, were in mortal danger, and not because you were suffering from narcosis, or because you weren't 'careful', but because you quite simply did not know how to plan and execute a dive of this type. 'You don't know what you don't know' is a common theme running through the Accdidents and Incidents forums. Fortunately, ignorance is easily remedied by getting training, particularly for someone with the resources and intelligence you appear to possess. Here is my 'constructive criticism' exactly as I phrased it in the first post I made to this thread. I still don't see how this can be construed as an insult--your belief that it is lends credence to my belief that you're in denial. In other words, merely being 'more careful in the future' isn't enough. You need additional training before you can attempt another dive like the one you injured yourself on. I'm sorry that your feelings are hurt, I'm glad you've learned something from the event, and I hope that others can learn through it to avoid the same mistakes, but most of all, I'm glad that you have lived to recount your experience.

OK, Quero thanks for that. I take back what I said about you. And I agree that my preparation for the SFM dive was inadequate and I was lucky not to have been more seriously injured.

But based on what you guys have said (which I fully accept), why then do they allow us to dive the SFM on single tanks? I mean why is there that arrangement at all? Of the 13 other divers on the SFM dive, at least 7 (including me) did not have tech diving experience - I know because we talked about our experiences during the course of the week. All except one were on single tanks - I do not have twin tank experience anyway. From what was said by JJ during the week, I understood that this was quite common. I tried to find an old e-mail from them where it simply said " a few of our dives are a lot deeper than 40m" and copy it here as proof but I must have deleted it.

Also, Alex at BL Dive shop said that alot of divers arriving a few days before the cruise, request diving the Amagisan Maru because it is not covered on the liveaboard. As you know, that is almost as deep as the SFM.

 

[bamafan]

My opinion is the boat captain is just a bus driver. They owe it to you to get you safely to and from the wreck. As a certified diver you are responsible for your own self. I am pretty sure they could not do these dives in the U.S. since we are such a nanny state with lawyers run amuck. The SFM is probably the most famous wreck in Truk. There is a large demand for this wreck. They give a thorough briefing and don't force anyone to do the dive. They have divemasters in the water with bailout gallore. I think they make a basic tech dive reasonably safe for all but the worst divers who I have seen them talk them out of doing the dive. So in my opinion the answer to your question about why they let single tank divers do the dive is market demand ($$$$) and as I stated earlier I think people today lack personal responsibility. Any dive training covers the limits of that training so when pne exceeds that training they are assuming the risk. I do not see how the bus driver is at fault. I think they go above and beyond.

 

[boulderjohn]

If I could get back to the original question, someone asked a good question that was never answered. I would like to bring it up again.

You originally said your computer appeared to you to indicate a "safety stop" of 14 minutes. I am going to assume you meant it told you to do a single decompression stop of 14 minutes at normal safety stop depth. I am not familiar with that computer and its algorithm, but that would not be surprising if that were the case.

Instead of doing that, though, as I understand your post, you did 3 stops at 15, 10, and 5 meters, totaling 15 minutes. (I don't know how the time was divided.) It may seem as if you were following the computer's directions, but you were not. You overruled it by imposing a different approach to decompression than the one in its algorithm. During the 15 meter and 10 meter stops it should have been adding time to your final stop because you were not ascending as it thought you would. I would guess that it would have wanted quite a bit more than those original 14 minutes by the time you reached that final stop.