DCS incident analysis requested

[Charlie99]

A dive profile that requires deco is risky if the diver is on a single tank, solo, deep, with no deco training.

He had passed DIR-F on 1st try and was wearing a BP/W, though

Seriously, I was trying to get you, and others, to separate out the decompression aspects of the dive (air vs nitrox; depth profile including SI times, exercise/hydration/PFO/alcohol/obesity etc.) from other things such as who planned the profile, whether it was on single tank or double, solo or insta-buddy, or known good buddy, or what sort of gear he was wearing.

A good test of whether you are looking at the information objectively is to imagine that you did NOT know that he had skin bends after dive #2. If you did NOT know that this dive sequence caused problems, what would you have noted as remarkable, unusual, or dangerous from a DCS point of view?

The things that caught my attention was the statement about completing 5 minutes of obligated deco, but then staying shallower than 30'. If this was a case of going up to 10', doing the deco, then back down to 30', that's not a good profile. A possibility, but not clear. If he cleared the deco obligation while puttering around in the 25-30' range, then that would have been a good thing.

There was also that bit about surge causing an abort of dive 2. Surge often causing up and down yo-yo action. Again, not good, but in a later post Spoon seems to say that didn't really happen.

Another thing that caught my attention was his reply to your post recommending 1-1-1 deco, in which he stated that he used the deco method he learned in DIR-F of 1 @ 30', 1 @ 20', 1 @ 10' on these dives while others in his group did 3@ 20'.

At this point, I don't have much comment other than to agree with the general advice of Lamont:

i really think that another thing you need to focus on is your deco. if you're doing air you need to be doing 1-1-3-3s or 1-3-5 or 1-3-7 or something like that, 2-2-2 at a minimum. anything shorter than that should be reserved for emergencies. and don't let your DMs short change you on your deco because they just want to clear their computer and come up. and keep in mind if you're doing repetetive diving that the free phase gas in your system from your last ascent is going to get compressed and then expanded by boyle's law and that you need to deco that junk as well.

 

[pilot fish]

Hi, pilotfish thanks for referencing the link, very interesting read. But I am still having trouble how it relates to predive exercise. Maybe you can help me.

Here's the entire paragraph that you quoted in your other text (the bold here is the one you omitted):

Divers need to obtain a physical fitness that allows maximum oxygen consumption. This is the ability to do work, such as swimming a reasonable distance with diving gear without getting too short of breath, and be able to help a partner who has been injured or requires assistance to return to the boat. One way of adjusting to the fitness needs of diving is to carefully plan your dives, avoiding situations requiring excess physical exertion above and beyond your physical capacities. This works well for the elderly diver or the diver who has physical incapacities. The best way is to exercise regularly.

So when Dr. Campbell says to avoid situations requiring excess physical exertion above and beyond your physical capacities I took it that he was referring to the dive itself (not predive exercise). I see how predive exercise may cause you to fatigue quicker. But by just capturing this quote (and nothing else), this could be applied to anything you do in life. Am I overlooking something here?

You quote this as well:

Exercise generally causes an immediate response in the cardiovascular system. This response includes local blood flow changes which then cause reflexes that then cause an increased cardiac output (how much blood the heart is pumping out). From the cardiovascular standpoint, exercise is any activity that raises the resting oxygen consumption above basal levels. Thus swimming, walking with heavy gear, climbing ladders and performing heavy labor relating to diving are all sensed by the heart and cardiovascular system as forms of exercise and require an increased output.

I took this paragraph to talk about the physiology of exercise and how it relates to swimming, walking with heavy gear, climbing ladders and and performing heavy labor relating to diving. I don’t see any mention of predive exercise in this quote. Am I being too shallow in interpreting it?

I view the webpage by Dr. Campbell as information on how diving can be considered exercise and that it's targetted to people who are thinking about taking up diving so they have information about the exercise involved in diving. I can see how someone can interpret that you need to be physically fit (enough) for the activities involved with diving. I can also conclude that if you are tired before a dive (whether because of exercise or not), don’t do anything requiring excess physical exertion above and beyond your physical capacities. I’m unsure of how predive exercise fits into the picture. What did I miss?

Here’s a nice link that Vie put up in the other thread which is another good read about exercise & diving:
http://www.undercurrent.org/UCnow/articles/Exercise200403.shtml

ps I’m not on either side of whether predive exercise is beneficial or not. I am for proper referencing. In Spoon’s case, it may have unfortunately been a factor of his DCS. Especially since his joints were stressed (this is my interpretation).

I don't think you missed much at all. Good post, Chip. Since none of us really know what our EXACT limitations are in pre-dive exercise, I think not exceeding moderate exercise is a safe bet. I think that excessive exercise and what I got from the referenced article is that we might be absorbing N2 too quickly, and deeply, after exercise. In any event, I think we should follow DAN and PADi when they say don't overdo it, before or after dives.

BE SAFE

 

[pilot fish]

I do it regularly, but I usually only do 5 or 6 miles, but I've been known to go as much as 12 miles. The key is proper hydration. Yeah, I guess Aviation, Space, Enviromental Medicine is not PADI or DAN

Since DAN & PADI deal with ONLY diving, I would listen to them before I would A S E & E Meds. But, hey, you need to follow whatever you think is more reliable. Your choice.

 

[pilot fish]

Obviously it's hogwash!

Not sure this response adds to the friendly and informative discussion. You need to follow whatever practice you think is safe. I don't think hiking or running a few miles pre-dive is safe. You might get away with it a dozen times but it might bite you one day. Be careful and dive safely ,Jon.

 

[TCDiver1]

Here is Dans take on Exercise & Diving. It appears they recommend a minumum 2 to 4 hour wait to dive, after any exercise and recommend not exercising after diving. Sounds like good advise to me.

 

[pilot fish]

Here is Dans take on Exercise & Diving. It appears they recommend a minumum 2 to 4 hour wait to dive, after any exercise and recommend not exercising after diving. Sounds like good advise to me.

Thanks TC. yes, that is good advice. To be even more conservative, and err on the side of safety, keep pre-dive exercise to the moderate level and wait 4, 6 or even 8 hours. before diving, and don't go deep. Be safe.

 

[pilot fish]

Here is Dans take on Exercise & Diving. It appears they recommend a minumum 2 to 4 hour wait to dive, after any exercise and recommend not exercising after diving. Sounds like good advise to me.

DAN' s Dr. Peter Bennett recommends divers perform *no* strenuous exercise prior to diving.

 

[Spoon]

The things that caught my attention was the statement about completing 5 minutes of obligated deco, but then staying shallower than 30'. If this was a case of going up to 10', doing the deco, then back down to 30', that's not a good profile. A possibility, but not clear. If he cleared the deco obligation while puttering around in the 25-30' range, then that would have been a good thing.

There was also that bit about surge causing an abort of dive 2. Surge often causing up and down yo-yo action. Again, not good, but in a later post Spoon seems to say that didn't really happen.

Another thing that caught my attention was his reply to your post recommending 1-1-1 deco, in which he stated that he used the deco method he learned in DIR-F of 1 @ 30', 1 @ 20', 1 @ 10' on these dives while others in his group did 3@ 20'.

actually i did my deco at depth and stayed there for the remaining part of the dive, this was around 30-25ft range i mentioned in the other thread that my friend who has the same computer went up to 10ft to do his deco then come back down to 30' surprised he didnt get bent. reprimanded him for that

i also do my safety stops with my gf(dive buddy) at 30, 20, 10 while the other divers do it at 3 mins at 20' . all of my dives i make it a point to let the others know of my different safety stop

 

[pilot fish]

actually i did my deco at depth and stayed there for the remaining part of the dive, this was around 30-25ft range i mentioned in the other thread that my friend who has the same computer went up to 10ft to do his deco then come back down to 30' surprised he didnt get bent. reprimanded him for that

i also do my deco with my gf(dive buddy) at 30, 20, 10 while the other divers do it at 3 mins at 20' . all of my dives i make it a point to let the others know of my different safety stop

Spoon, what stops do you make on a normal dive to 100 ft or so? Half depth 1 min, 15 ft 5 min?

 

[Spoon]

Spoon, what stops do you make on a normal dive to 100 ft or so? Half depth 1 min, 15 ft 5 min?

i meant safety stops. i will usually beging my ascent slowly, air permitting but usually if i dont exceed 100ft then i just ascend at a normal rate and do my safety stops at 1 min 30', 1 min 20", 1 min 10"