Bent. I guess it really can happen to me.

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TechDeep

Contributor
Scuba Instructor
Divemaster
Messages
333
Reaction score
132
Location
Virginia Beach, Virginia, United States
# of dives
500 - 999
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.
 
What were you using for an algorithm and settings on your computer?
 
The profile - Dive 1-55.5 ft. 42:49. Surface interval 43:55 Dive 2-55.5 ft. 44:21.
...
Those numbers alone is WAY more conservative than my normal THREE dive day, repetetive days. What was the average depths? Where the profiles square?

A normal 3-dive day for me would look something like 1: 30m 60min, 1hr si 2: 30m 60 min, 1,5-2hr si and 3: 18m 60 minutes. All on 32% EAN. The average depth might vary a bit more though, depending on wethere theres anything of interest down at depth or I just go furthere up the reef looking for tinies..
 
Yikes! Based on what you've told us do far, other than the short interval, we should all be bent many times over. As others have asked what were you breathing? (Though you've referred to "air" numerous times in your post please confirm) Also do you recall the depth at which you stopped to look at the barracuda and duration thereof?

Glad that your symptoms abated and have not recurred but yes, this must be figured out.
 
What was your back up plan? IS your computer set to take into account your body type, whether or not you were dehydrated, your age, your general physical health, or your level of fitness? If not why would you blindly rely on it?

As long as it doesn't indicate deco it's ok? Not a good way to conduct dives.

There's a reason why we say to plan your dives. I'll use this as a prime example of why I do not teach computers in the OW class and insist students plan their dives on tables and try to do that whenever possible. And use a computer as a back up.

Let's see on the SEI tables we have

42:49 rounded up to 45:00 @ 60 ft gives pressure group H

SI 43:55 takes you to pressure group H (well whaddaya know)

RNT of 46 minutes

Next dive

44:21 rounded up to 45:00 @ 60 ft

Add in your RNT and your TBT is 91:00 minutes! At a depth with an NDL of 51 minutes. But hey what's 40 minutes? You got lucky the last time (or times) you did this.

91 minutes @ 60 ft puts you well into deco. On our tables you end up in fact with a 1:20 ascent to 20 feet where you then get to spend 57:00 minutes if decoing on air.

Had you planned this dive out on tables would you have done it? I

I'd throw that damn computer in a box until until I'd developed the discipline and good sense to plan my dives as square profiles beforehand and then MAYBE allow a little extra for the computers sampling rate.

Yeah I'd call that a deserved hit.

And another huge reason DM's should be required to take an actual tech course before starting DM. Even if it's an intro to tech. A good one will put the proper amount of fear in you and go a long way towards reinforcing planning over all.
 
OK that said, OP, how long were you actually at depth?
 
Doesn't seem fair to call something a deserved hit if you don't know the full profile. Taking max depth and assuming square doesn't seem right to me.

Regarding the "short" 40+ minute surface interval, what's wrong with that? Even assuming a square profile that doesn't put you into the W, X, Y, Z groups that PADI RDP requires a 1 hour SI for. I know the boats I go on < 1 hr SI is normal. 1/2 hour to get to first site, 1 hours in the water, 1 hour to get to the next site, 1 hour in the water and 1/2 hour to get back = 4 hour charter. It doesn't always go that smooth so 45 minutes is likely.
 
<lots of assumptions that have nothing to do with the dives actually conducted>

Yeah I'd call that a deserved hit.

Lapenta's suggested approach makes no more sense than insisting that everyone use tables to plan a dive that's twice as long and/or deep than you actually will go, and dive according to that plan, because conservative. I'll agree that knowing the square profile in advance is a good idea, since your dive could look like that.

However, if you know you're not diving square profiles, and then go out and dive not a square profile that's within the computer's algo... calling it a "deserved hit" because of some table citing with no basis in the reality of the dive actually conducted is, for lack of a more polite term, :censored:ing stupid. That said, I'm assuming the OP understood how his computer works and set it realistically. If not...well, you rolls your dice and you takes your chances.
 
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