Decompression controversies

[Pullnglide]

I will have to look at the profile when I get home to know exactly. I think I recall my first stop being at 40'. I say average 95' but that can also be wrong, the cave is a lot of up and down which could have also contributed to my hit. Along with over exertion when my drysuit valve was bumped and hung open while removing a stage and also very cold for the last 45 mins at 20'. I have done many 100'+ dives with long bt and long deco. I have also since done several 200'+ and a 300' dive. Some 200'-250' with 25-30 min BT and I'm sure your aware the deco that comes with that. I've never had a problem since. I've since changed many things that could have lead to the hit And I've tried to learn as much as possible from it to make sure I minimize the risk as much as possible when planning my dives.

 

[kensuf]

Ginnie? Nitrox? Swimming? What was the BT?

I know a lot of people that have gotten hit there (myself included) doing 60-80 minute swim dives. I recently bent a friend there on a "simple" dive, 50 minute swim. I've heard someone speculate the shoot through the cornflakes / keyhole contributes a lot to it because you're going from 90' to 65' very quickly.

 

[Pullnglide]

It was Bozell, 30%, swimming. I think BT was @ 100 mins but I'll have to look. Keep in mind, it was 117' the entire dive, I'll also have to check the average. It's usually very high flow especially the first few hundred feet, I can't recall how it was that day but I don't remember it being that bad. It's definitely a sawtooth profile which was probably the leading cause. I'll post a picture of the dive profile when I get home.

 

[PfcAJ]

Sometimes people get bent. There doesn't have to be a special "cause" other than you went diving.

There's an element of chance involved.

 

[leadduck]

Along with over exertion when my drysuit valve was bumped and hung open while removing a stage and also very cold for the last 45 mins at 20'.

There's another NEDU study saying that being cold during deco is really bad: Don&#39t Dive Cold When You Don&#39t Have To — DAN | Divers Alert Network — Medical Dive Article
9°C difference during deco was comparable to 2x difference of bottom time.

 

[Pullnglide]

Sometimes people get bent. There doesn't have to be a special "cause" other than you went diving.

There's an element of chance involved.

Definitely agree!

 

[LiteHedded]

Sometimes people get bent. There doesn't have to be a special "cause" other than you went diving.

There's an element of chance involved.

pizookies.

 

[PfcAJ]

pizookies.

There is a strong pizookie correlation.

 

[leadduck]

Sometimes people get bent. There doesn't have to be a special "cause" other than you went diving. There's an element of chance involved.

Agreed, but I think it's smaller than the systematic factors for an individual diver.
In a study with many individuals doing the same profile, there is variance in the population. Some have a PFO, some are fat, some smoke. If all run the same profile and 5% get bent, you might read "5% DCS risk" as "this profile is too tough for 5% of the population". That's exactly what you want to know when making a table.
For one individual diver this kind of "randomness" does not exist. Either you have such a risk factor or you don't. One person repeating the same dive over and over again should show more consistent results. But you hardly ever do that anyway, so in the end it's the profiles and dive conditions that vary, and when you get bent you can only guess if it was because of the profile, dehydration, being cold, ..., or just bad luck.

 

[rddvet]

Ginnie? Nitrox? Swimming? What was the BT?

I know a lot of people that have gotten hit there (myself included) doing 60-80 minute swim dives. I recently bent a friend there on a "simple" dive, 50 minute swim. I've heard someone speculate the shoot through the cornflakes / keyhole contributes a lot to it because you're going from 90' to 65' very quickly.

I definitely did and learned alot more about DCS than I knew previous. Last year did a swim stage dive in Ginnie. It was no different than any other dive I've done there previously. Plan was to stay on mainline and see how far we would get in preparation for future stage dives in the area. Went home that night and got sweaty vipping some tanks. That night I had a couple of bruises on my shoulders that I attributed to a tight suit or carrying tanks, or anything other than DCS. I never thought a simple dive would cause issues. Next day did the exact same dive. My eyes were just a little blurry a couple hours after the dive, but only lasted a couple of hours. Later that night and next AM, I had alot more "bruises" on my shoulders and subq swelling that was slightly painful. I called DAN later that day and they suggested a trip to the ER and then the chamber. Although that would have been ideal, all neuro side effects were gone and I knew the skin hits would resolve with time and meds. Probably should have gone, but as a business owner I didn't have the luxury to take a day or two off of work, so I took my chances and stayed out of the water for 6 weeks.
In retrospect the most likely contributing factor other than needing to lose some weight in my opinion is the flow was high during that period and we were really working hard at the deepest point of our dive where its all silt bottom and there's nothing to pull and glide with. I'm sure not being extra slow exiting was a factor as well.

I also think that DAN is also correct that there are some factors that just can't be accounted for. Is there some odd genetic factor that plays a part? I believe so since some people get the niggles more than others. I was tested for a PFO and am negative. Since I was a kid I've bruised exceptionally easily, but there's no obvious medical cause for it. Could that potential be some untestable factor? I wonder since we're talking about prefusion on a tiny capillary basis.