Assessing DCI risk factors and adjusting dive plans

[nimoh]

Here's my method for not getting bent (or drowned or seasick). I make sure that:

• My ascent rate matches the plan (or computer).
• I feel good (inside)
• I feel good about the dive
• I'm happy with my buddy
• My DAN insurance is paid up
• Emergency services are available within a reasonable length of time.

I avoid over-analyzing things. If I happen to get bent within the no-deco limits or while following a valid, printed deco dive plan, it won't be severe, and I'll get to see what the inside of a chamber looks like. The chances of doing things right and taking a huge hit are from my perspective, nearly non-existent and don't rate a lot of concern.

The OP in the thread this was spun off from could just as easily have had a pinched nerve or some sort of other neuro event, as a DCS hit. Nobody really knows what happened and in any case, it resolved on O2 (might have resolved without O2 also).

flots.

the last two are part of your plan for if you get bent, rather than your plan for not getting bent, however I am guessing there is more to your list that you are leaving out such as planning conservative dives, staying hydrated, staying in shape...etc.

 

[pocky21]

Flots - your list is composed of all good things that all lead to safe, happy diving, and there is no disagreement on that. Whether the OP of the referenced thread was actually bent or not is irrelevant to this discussion, as I'm asking how each of us personally approaches our dive plans based on our own judgement calls.

To further clarify the question - when things aren't perfect, do you adjust your dive plans in specific regard to DCS mitigation and if so, how? "Not perfect" could mean any number of things - from the neighbor's party keeping you up, skipping breakfast, haven't been to the gym in a week, etc...

I ask this question because in evaluating an incident, we are quick to look to things that aren't "perfect" - yet we have little to no objective means of evaluating how "imperfect" these conditions are. We each have our own methods of evaluation and response to an imperfect scenario, so consider this an exercise in exploring that massive grey area we call "good judgement".

 

[diverrex]

I try to stay hydrated the night before and day of diving. I always ascend slowly and always do a stop. For deeper dives I may add a deep stop and/or extend my stop at 15'. I almost always am doing multi-level dives.

I don't adjust my dives because of lack of sleep or limited exercise that week, eating habits or other such things. The risk of DCS is already so low and the connection to other factors so unproven I don't consider them.

I believe in hydration, slow ascents, safety stops and keeping within NDL limits.

 

[Lorenzoid]

I don't take any supposed day-of-dive risk factors into account, but I always dive my conservative Suunto computer, stay hydrated, do a safety stop, and insist on a surface interval of an hour or so. People criticize the conservatism of the Suuntos, but it's great for those of us who don't want to spend our time thinking about whether to tweak how we execute a particular dive to mitigate some supposed short-term risk factor. I could crank up the computer's conservatism setting if I felt like I had some increased risk factor, but if I knew I had some day-of-dive risk factor, like serious lack of sleep, I would probably just not dive.

 

[SeaHawk12]

As a fairly active college student who has no known heart conditions and has good cardio conditioning, I don't particularly fall into the hugest risk group for DCS. However, I am a stickler for hydration in my daily life, and diving is no exception. I have a liter per dive rule which helps mitigate all of the nasty effects of dehydration. Additionally, I also ATTEMPT to get more sleep on diving days.

Ultimately, my decision on whether to dive or not comes down to how I feel the day of. If I don't believe I am either physically or mentally capable of dealing with the stress of the underwater world, I don't dive. Period.

 

[flots am]

Flots - your list is composed of all good things that all lead to safe, happy diving, and there is no disagreement on that. Whether the OP of the referenced thread was actually bent or not is irrelevant to this discussion, as I'm asking how each of us personally approaches our dive plans based on our own judgement calls.

To further clarify the question - when things aren't perfect, do you adjust your dive plans in specific regard to DCS mitigation and if so, how? "Not perfect" could mean any number of things - from the neighbor's party keeping you up, skipping breakfast, haven't been to the gym in a week, etc...

I ask this question because in evaluating an incident, we are quick to look to things that aren't "perfect" - yet we have little to no objective means of evaluating how "imperfect" these conditions are. We each have our own methods of evaluation and response to an imperfect scenario, so consider this an exercise in exploring that massive grey area we call "good judgement".

Things don't have to be perfect, however I have developed a sense for when I'm feeling tired or stupid or "accident prone" and will definitely skip the dive, but I'll probably go snorkelling. It's not a sacrifice. If I don't feel up to a dive, snorkelling or even taking a nap on the boat is also very nice.

OTOH, this probably has nothing to do with getting bent, unless "not feeling right" increases the chances of DCS.

flots.

 

[scubadada]

I don't take any supposed day-of-dive risk factors into account, but I always dive my conservative Suunto computer, stay hydrated, do a safety stop, and insist on a surface interval of an hour or so. People criticize the conservatism of the Suuntos, but it's great for those of us who don't want to spend our time thinking about whether to tweak how we execute a particular dive to mitigate some supposed short-term risk factor. I could crank up the computer's conservatism setting if I felt like I had some increased risk factor, but if I knew I had some day-of-dive risk factor, like serious lack of sleep, I would probably just not dive.

Less dive time will always equate to a lower risk of DCI, even if this means extremely, extremely low vs. extremely low. I am more than willing to accept the risk of diving the Oceanic DSAT algorithm of my VT3 and Geo2 compared to the Suunto algorithm.

 

[Lorenzoid]

Less dive time will always equate to a lower risk of DCI, even if this means extremely, extremely low vs. extremely low. I am more than willing to accept the risk of diving the Oceanic DSAT algorithm of my VT3 and Geo2 compared to the Suunto algorithm.

Yes, I believe that's my point. Suunto leaves a wide margin of safety by, of course, computing less total bottom time on average, encouraging long SIs, etc. My dives may be a few minutes shorter on average than people diving with less conservative computers, but--to address the what I believe was the original question--I feel the extra margin of safety that's ALWAYS present in a Suunto allows me to avoid the bother of making special allowances for supposed day-of-dive risk factors such as lack of sleep, dehydration, etc.

Of course, it's all voodoo in the end--risk factors and how to mitigate them aren't perfectly understood. For all I know, the supposed conservatism of the Suunto may be giving me a false sense of security, and perhaps I SHOULD take into account day-of-dive risk factors and make adjustments. But to answer the question, I do not presently do so.

 

[Mr Carcharodon]

I believe the factors that increase risk are things that change perfusion rates during the dive. High levels of exertion and getting chilled during the dive are chief among those. In response to those I will lengthen the time between 30 feet and the surface. Often adding an extra 5 or 6 minutes in that zone. That roughly doubles the time spent there.

Maybe it is too obvious to be said but by far the biggest risk factor is exposures that run right up to or beyond NDL. Doing so is certainly a trigger to be conservative on the last part of the dive.

 

[Bob DBF]

Things don't have to be perfect, however I have developed a sense for when I'm feeling tired or stupid or "accident prone" and will definitely skip the dive, but I'll probably go snorkelling. It's not a sacrifice. If I don't feel up to a dive, snorkelling or even taking a nap on the boat is also very nice.

OTOH, this probably has nothing to do with getting bent, unless "not feeling right" increases the chances of DCS.

flots.

It may have nothing to do with getting bent, but in my experience, it has a lot to do with the chances of the dive going badly. Being young and dumb, it took a while to correlate the two, but I finally realized that "not feeling right" on the surface did not magically get better with depth and sometimes it got much worse.


As for the original question, I may have a drink the evening before a dive, I don't go in feeling off, and if I am close to NDL I will extend the safety stop by using the remaining air in my tank.



Bob
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I may be old, but I'm not dead yet.