Mike's DCS And Some Lessons Learned

[Insta-Gator]

As we all wish to avoid a similar situation for ourselves or family/friends, here is a web site I found that my be helpful in planning your next dive vacation. I can't swear to the accuracy of the information, but it gives you a place to start. Also, you can always contact the resort you are interested in and inquire about the availability of medical assistance and chamber.

Worldwide Hyperbaric Chamber Locator, Contact London Recompression & Hyperbaric facilities - The London Diving Chamber

 

[ofg-1]

I am sorry to hear about your friend, and I wish him the best. With that said, we have all become more reliant on computers for our decompression profiles. As a old guy, I have often wondered the wisdom of this. I clearly remember when the idea of multi-level decompression, or depth averaging, was first floated. It was not well received.

If you look at the rules associated with the U S Navy tables for air diving, this dive would have been considered at a depth of 90 feet, for 50 minutes. you never round down. Even at 90 feet for 40 minutes, you are above the NDL according to these tables as well as the NOAA air tables. The Navy tables would have required a 14 minute stop at 20 feet on air, 7 minutes on 50/50. The physiology of this person, on this day, under these conditions obviously would have been somewhere between what his computer told him, and the tables.

My point is, I believe it is prudent to have a set of table available during dive planning. If your computer tells you something really different than the tables, I recommend doing something other than trusting the computer. When you are diving away from treatment facilities, my sincere suggestion would be to spend the 14 minutes at 20 feet.

 

[Wookie]

Is is possible that when he was twisted between the bench and the side of the boat his circulation was disrupted--kind of like when you sit on a leg and it goes to sleep. Is there any research to suggest this type of action could affect how nitrogen is eliminated?

Given that he had bubbles in the spinal cord, I doubt the position in the panga made any difference.

Anecdotally, I've seen a liveaboard captain (not me this time) catch a bubble in his shoulder (type I, pain only) because of being in a compromising position. His arm was twisted around his back, something about there not being enough room in the bunk for 2 comfortably, which is another story....

 

[herbdb]

Thank you for sharing this story. It has opened my eyes to the need for rapid access to emergency treatment - something I had never considered.

As an older diver with scar tissue from several surgeries, I have taken to conservative profiles and use Nitrox where available. Now I will ensure that I can get treatment for any "undeserved" hit.

Best wishes for a complete recovery.

 

[RedSeaDreamer]

I am sorry to hear about your friend, and I wish him the best. With that said, we have all become more reliant on computers for our decompression profiles. As a old guy, I have often wondered the wisdom of this. I clearly remember when the idea of multi-level decompression, or depth averaging, was first floated. It was not well received.

If you look at the rules associated with the U S Navy tables for air diving, this dive would have been considered at a depth of 90 feet, for 50 minutes. you never round down. Even at 90 feet for 40 minutes, you are above the NDL according to these tables as well as the NOAA air tables. The Navy tables would have required a 14 minute stop at 20 feet on air, 7 minutes on 50/50. The physiology of this person, on this day, under these conditions obviously would have been somewhere between what his computer told him, and the tables.

My point is, I believe it is prudent to have a set of table available during dive planning. If your computer tells you something really different than the tables, I recommend doing something other than trusting the computer. When you are diving away from treatment facilities, my sincere suggestion would be to spend the 14 minutes at 20 feet.

OK guys, what am I missing? I'm showing on the Navy Tables that the NDL on a 90 foot dive would be 30 minutes? Dusting off the Wheel shows the NDL at 25 minutes.

 

[victorzamora]

Here's a chart of the dive. Just thought a visual would help.

 

[Insta-Gator]

Tables assume max depth is primarily where the majority of the dive occurs. Table really don't have a convenient way of showing multi-level dives. That's why most of us use computers today. They do the math we can't/won't do on the fly based on changing ATA.

 

[ofg-1]

OK guys, what am I missing? I'm showing on the Navy Tables that the NDL on a 90 foot dive would be 30 minutes? Dusting off the Wheel shows the NDL at 25 minutes.

See page 9-72

http://www.usu.edu/scuba/navy_manual6.pdf

This is the 2008 edition, it may have been changed again. I haven't used The Wheel in years.

The NOAA table is about the same, harder to read.

http://www.ndc.noaa.gov/pdfs/NoDecoAirTable.pdf

 

[Akimbo]

Given that he had bubbles in the spinal cord, I doubt the position in the panga made any difference.

Anecdotally, I've seen a liveaboard captain (not me this time) catch a bubble in his shoulder (type I, pain only) because of being in a compromising position. His arm was twisted around his back, something about there not being enough room in the bunk for 2 comfortably, which is another story....

Although I concur with TSandM in this case, I have seen a lot of evidence of bad limb position causing DCS during decompression (explained in the next paragraph). Since the body continues to decompress by “venting” dissolved gasses after decompression procedures, Wookie’s hypothesis is probable. Granted, he may have been on the edge of getting a hit anyway… but aren’t we all?

Surface Decompression using Oxygen (Sur-D-O2) is a common procedure in commercial surface supplied diving. Basically the diver is yanked from his last water stop, stripped out if their gear, pressurized in a deck chamber (usually 60'), and put on pure O2 to complete scheduled decompression. Total decompression is much shorter and safer because they are warm, relaxed, and on very high O2. It also makes concurrent diving operations practical. See http://www.scubaboard.com/forums/diving-medicine/440726-oxygen-toxicity-limits-symptoms.html for more info.

Diving supervisors are pretty good about reminding divers in the chambers to keep their limbs more or less straight. There was one guy who consistently ignored the advice and sat on a leg folded under him. Sure enough, after a few dives he took a hit in the knee. That still didn’t cure his bad habit and he took a couple of more hits, increasingly closer together. It got to the point where he got hit in the same knee even on no-D dives. He had to change careers.

The same is true for saturation divers where decompression lasts for days. Standard procedure is to stop decompression during sleeping periods. It isn’t practical to wake everyone in the chamber when somebody is sleeping on a folded arm. See http://www.scubaboard.com/forums/commercial-divers/467739-what-saturation-diving.html

 

[Mike Boswell]

Here's a chart of the dive. Just thought a visual would help.

View attachment 173691

Thanks, Victor. Hey, how'd you do that? I couldn't get my Excel graph to post properly.

As you can see, we left the bottom and began our slow ascent at about the 28-minute mark, riding the current over the reef. The stop at 32 minutes/50 ft. was in mid-water and was intentional, as a "deep stop" to off-gas a bit.

None of us felt we had "pushed the envelope". That's why it was hard to grasp that Mike's initial symptoms were DCS.

As to your earlier questions: We took some pains to avoid being tired or dehydrated. We all had a good night's sleep - 8 hours or more. We each had two beers at dinner and also had some bottled water during the van ride the previous evening: We were well aware of, and talked about, the need to stay hydrated and not drink too much alcohol. So - we may have been a little tired and dehydrated, but not for lack of trying.