Bent. I guess it really can happen to me.

[ajduplessis]

I would really be nice to see the dive profiles/data logs for the day in question.

 

[TechDeep]

What is your depth at this specific time? I can't tell from the photo.

Yea the reason you can't see the depth is the refresh rate of the computer is not in sync with the frame rate of the GoPro, so there is always a moving band of black traveling down the computer display in the video. Depth at that time was 49 ft.

 

[TechDeep]

I would really be nice to see the dive profiles/data logs for the day in question.

I posted these earlier in the thread, but it has become a huge thread, so I'll post here....

 

[flots am]

I posted these earlier in the thread, but it has become a huge thread, so I'll post here....

I've never used that computer or software. Is the dive supposed to start at 30'?

flots.

 

[beaverdivers]

Yea the reason you can't see the depth is the refresh rate of the computer is not in sync with the frame rate of the GoPro, so there is always a moving band of black traveling down the computer display in the video. Depth at that time was 49 ft.

Thanks.

What was your lowest No Stop time?

It may be at the deepest point of your dive. You should be able to figure the lowest number by scrolling through your dive.

 

[bada3003]

Glad to hear you're ok and thanks for sharing your experience.

Two thoughts: One, you need to have a ballpark sense of what NDL numbers are in repetitive dives. Blindly relying on a dive computer is a bad idea. On my iPhone I have a free app for 2-dives (air) called iScuba Plan Lite. For different depths and SIs, it gives a clear sense of what I need to do. Then I use my dive computer, but I keep the ballpark figures in mind. Even on safety stops I use manual numbers (e.g., 3 mins at 60 ft and 3-5 mins at 15 ft), not relying on my dive computer. For ascend rate, again I use bubbles as the main reference point.

Two, it's surprising that you did many dives with such an incorrect dive profile. Based on your numbers, the second dive's NDL is around 30 mins. Since NDLs are derived from physiology models, you may never experience DCI symptoms with your stated profiles but, then again, you might and that appears to have happened. The actions you took to contact DAN and find a compression chamber was super smart. Please be careful to understand what you are doing and use tools, including dive computers, as tools.

This past Saturday I did a two tank dive as I have done hundreds of times before, on a wreck which I have many logged dives. I relied on my computer as I always do, and it did not indicate any sign of a decompression obligation. I have several other dives downloaded to my dive log from my computer with practically this same profile with no issues. If you go by the computer, it was undeserved. If you go by the tables, witch of course do not give you credit for the shallower parts of the dive and require you to round up your depth, it would be considered deserved.


The profile - Dive 1-55.5 ft. 42:49. Surface interval 43:55 Dive 2-55.5 ft. 44:21. Ascent rate was less than 30ft./min. on both dives, much slower on first dive. I'm getting all of this information as it was uploaded from my dive computer to my PC. I think the slow rate on the first dive was due to seeing a bunch of barracuda, and having plenty of air. Like I said, this is a profile that has not caused any issues in the past. Plenty of air remained on both dives, nothing unusual as far as the dives went. I was not cold, and did not over exert myself. I dive solo with a redundant air source in the form of a 13cf pony bottle, which was unused.

Full 3 min. safety stops on both dives.

What happened - There was a delay as we waited for some divemasters to run lines out to some APCs that had been dumped at the site. I used this time to break down and pack up my gear. I had no indication of an issue until probably about 30 minutes after the last dive. We were already under way back to the dock. I started getting numbness in my left hand and arm. I gave it the usual amount of attention, and would not have suspected dci had it stopped there. Problem was, it got worse, quickly. I mentioned it to one of the instructors on board, and he didn't see how it could have been dci given my profile, so we agreed to keep an eye on it. Within another few minutes, I started losing the use of my arm and hand. At that point the instructor did more evaluations. He pinched my hand several times as hard as he could, and I had no feeling. The paralysis in my hand got progressively worse very quickly. A stroke was a stronger suspicion than dci given my dive profile and symptoms.

I was put on 100% Oxygen via a demand regulator, and an ambulance was called to meet us at the dock. By the time we got back to the dock (I am guessing the time on O2 was around 30 min.) My symptoms were completely gone. There was the temptation to send the ambulance guys home and call it a day, but the fact that the oxygen relieved my symptoms made me suspect very strongly that I had suffered a level 2 dci hit, so I went to the ER in the ambulance, and asked the ER doctor and nurse to contact DAN.

Needless to say, the DAN medical professionals strongly recommended recompression, even though my symptoms never returned. I was given a CAT scan to rule out stroke, and then I was taken by ambulance to the closest chamber that could take me right away. I went for a Navy table 6 ride in said chamber. I'm very grateful to be fine now, but no diving for 30 days, and I need to figure out as close to the actual facts as possible, what happened.

I'm posting this so that we all may benefit from whatever there is to learn here, and because I know there are experts on this board that could provide some of the best information available anywhere. And of course I feel like a genius for having DAN insurance, on top of my regular policy. I was sure I would never need it, but really glad I have it, and strongly recommend it.

 

[Tigerman]

...
Two, it's surprising that you did many dives with such an incorrect dive profile. Based on your numbers, the second dive's NDL is around 30 mins. Since NDLs are derived from physiology models, you may never experience DCI symptoms with your stated profiles but, then again, you might and that appears to have happened. The actions you took to contact DAN and find a compression chamber was super smart. Please be careful to understand what you are doing and use tools, including dive computers, as tools.

As we have pointed out both with tables, vplanner and the fact that people do thousands of profiles just like those every day, the profiles is not "such an incorrect dive profile". Infact I have personally witnessed thousands of dive profiles that goes WAY beyond what the OP did over the course of a day. Ill easilly do two 1-hour 30m(100ft) dives before lunch and another 18m(60ft) dive after lunch and then maybe a 18m night dive to top it off and I know loads of people who will do the same. Ive done it both on nitrox and on air, the only difference is how long I can stay at the deepest part of the dive.

 

[mmadiver]

Every single case of DCS in a healthy diver, without exception, has been caused by the diver not doing enough decompression!

Great writeup by John Chatterton on "Unearned Hits" and using computers for managing deco: The Unearned Bullhit | Shadow Diver | John Chatterton

Apologies if its a double-tap...

 

[drrich2]

mmadiver:

Chatterton's article you linked to was quite interesting, though I contest the idea that you 'earned' the hit if you get DCS, because you 'came up too soon,' made in the style of a blanket statement (I'm not using a direct quote, but reading the article, I believe I've summarized the sentiment).

Because people don't have any way to know for sure just how much decompression to do on the dive. Turning to greater conservatism to reduce DCS is an issue of diminishing returns. You could just stay on the boat. Or you could dive, but use tables and do your multi-level dive as though the whole dive was done at the deepest depth. Or dive a Suunto on the grounds it's said to be more conservative than some competitors, or an Oceanic on its more conservative setting. Or dive nitrox on an air dive profile. Then there are the arguments about how long to wait before flying.

My point is, it's not precisely known at what point diminishing conservatism becomes recklessness, and cause to 'blame' somebody or say he/she 'earned' the hit. Taken to an extreme, if you chose to get in the water, you asked for it, eh?

A small excerpt from Chatterton's article:

When we look at the information from our computer or table, it is only numeric data for a baseline dive based on time and depth. Then…….. and I know this is hard to believe, but the diver needs to get personally involved, and interpret this data as it applies to himself/herself on that particular day, and that particular dive. You may need to buffer the calculated hang, safety stop, or ascent. Just because the computer, and/or tables say it is okay to surface, does not mean that it is absolutely safe to do so.

Yes, that's all true. But how do you modify anything based on your interpretation? For example, let's say you plan to do a pair of 1 tank boat dives on air, on a charter boat. I'm not going to drag out tables, but let's stay for sake of argument they will be square profile wreck dives, fairly deep, with large tanks that can push NDLs, and these dives come out to:

Dive 1 - NDL 40 minutes.

Dive 2 (1 hour later) NDL - 20 minutes.

So, how much NDL time do you knock off, or how much do you add to your 15' safety stop, for account for any one of these factors:

1.) You're fat - 150% ideal body weight.

2.) You're old - 55.

3.) You're 'out of shape' - not terribly so, but an office worker who doesn't do any fitness regimen, mid. 40's, in decent health but you get winded a little easily.

4.) Water's cold - 45 degrees. You're in a 7 mm wet suit.

5.) There's modest current and so you'll exert moderately swimming against it part of the dive.

6.) Low viz. muck dive & keeping up with your buddy is mentally stressful.

7.) You stayed up late and didn't get much sleep.

8.) You're a little jet-lagged from yesterday's flight.

9.) You might be a little dehydrated because you don't want to pee in your wet suit on the boat trip.

So, what do you do? Halve your NDL? Add a pressure group, or reduce your depth to move up one? Knock 25% off your NDL? A 5 min. safety stop instead of a 3? Do a deep stop? Stay on the boat if you can't run a mile in 10 minutes (inside joke from another thread)?

What's 'good enough' conservatism?

Richard.

 

[pocky21]

Yes, that's all true. But how do you modify anything based on your interpretation?

This is exactly what I asked in an off-topic thread. Seems there's little consensus.

I've since amended my philosophy on conservatism based on an outside source:

[video=youtube;Jj4nJ1YEAp4]http://www.youtube.com/watch?v=Jj4nJ1YEAp4[/video]