DCS due to reading computer wrong (I think)

[Hintermann]

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.

 

[eelnoraa]

15 minutes at 51m (167ft) is really a technical dive. You should have the deco procedure (stop depth, time) planned out before you even hit the water. To rely on only the computer to give your deco information on the fly is dangerous. According a quick run with v-planner, yeah, you didn't have enough deco.

What tank are you using for this dive? single or double?

 

[g1138]

Some constructive criticism. At your dive count, and given your occupation, mis-reading mistakes shouldn't happen. Better brush up on your computer manual.

Personally, any dive past 15m (50ft), I would plan out my entire dive profile, stops, air management, and the such before hitting the water.
I'm in agreement that this dive should be considered a technical dive. Have you consulted a medical opinion to see if you need hyperbaric treatment as a precaution?

How were your safety stops by the way? Were you pretty static or yo-yo-ing by a few feet? Were you kicking to hold your stops or hovering motionless in place?

 

[vladimir]

No narcosis at 50 meters—good for you!

"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.

I am also surprised that you did not consult your computer again at your decompression stop, as your account seems to indicate.

I know that the chamber in Truk is less than convenient, but I would have made the trip with the symptoms you describe.

15 minutes at 51m (167ft) is really a technical dive. You should have the deco procedure (stop depth, time) planned out before you even hit the water. To rely on only the computer to give your deco information on the fly is dangerous. According a quick run with v-planner, yeah, you didn't have enough deco.

What tank are you using for this dive? single or double?

Were you not paying attention? He used an Aladin Tec 2G.

 

[superspeed]

Thanks for sharing, good to hear your ok. As it has been stated that dive should not have been done without a lot more planning. Quick crunch on v-planner says about 31min of deco. Learn from this lesson and consider taking an intro to tech class, and a tech class. It will really open your eyes to dive planning and why so many people who are going to be posting are going to freak out about this thread.

 

[JamesK]

The dive you did should have been a planned decompression dive. A 14 minute stop is not a "safety stop" it is a decompression stop.

 

[theduckguru]

To OP, its easy to misread a computer if you don't have readers in the mask at our age.

 

[flots am]

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.

Just a couple of notes, narcosis isn't always noticeable from the inside, however your inability to figure out your computer should have been a big red flag.

Also, according to my dive planning software you blew off over a half hour of deco. You're lucky you're OK now. I would have called DAN and let them use some of my insurance money.

FWIW, while I like computers as much as anybody, I never ride one on a deco dive. If you had printed a plan before the dive and stuck it on a wrist slate before you splashed, you would know beforehand how much time and gas you needed and where the stops would be and for how long. When riding the computer on a deco dive, it's entirely possible for the computer to tell you that you need 30 minutes of deco and have 5 minutes of air left, which would really suck.

> Fortunately, it was not severe and I did not need to go into a decompression chamber

Even my doctor tries to avoid self-diagnosis. How did you determine this?

> 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.

You should buy lottery tickets. You're incredibly lucky and apparently quite sturdy.

flots.

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

To OP, its easy to misread a computer if you don't have readers in the mask at our age.

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

 

[TSandM]

Wow -- given your symptoms, and knowing what you must know about DCS as a physician, I'm really surprised you were okay with not going to the chamber.

As everybody else has said, this was a technical dive. If you did it on a single tank, there is no way you had enough gas to bring another diver up to the surface, if a hose had blown or a reg had freeflowed.

When you dive to this depth, you have lost the surface as an option. This means that the dive really requires a lot more planning, in terms of gas volumes, in terms of ascent strategies, in terms of buddy behavior and responsibilities. There is a REASON that technical diving requires a whole mess of training. It's not as simple as extending a safety stop, and the price to be paid for mistakes is pretty high.

I'm glad you are okay. If I were you, I'd get a copy of Mark Powell's excellent book, Deco for Divers, and think long and hard about what you committed your body to do.

 

[Hintermann]

flots am;6644986]Just a couple of notes, narcosis isn't always noticeable from the inside, however your inability to figure out your computer should have been a big red flag. It's also difficult to read @167' when you're narked.

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 ----------