How many decompression dives do you have?

[aainslie]

Please be as accurate as you can. I personally don't keep good logs, so my own entry is a guess - but please try not to exaggerate, there isn't an attractive single cavediver of the opposite gender listening to your response...

Sorry, that should be 101 to 200, not 1-1-200. Can a moderator fix that for me please?

Edit - an early observation, Russell, looks like you were right! This is getting interesting...

[tj]

Fixed

Sorry, that should be 101 to 200, not 1-1-200.

[BabyDuck]

where's the 'less than 10' category? :D

[amphipod06]

there was no differentiation among cave dives and other dives so they are all grouped in the response...

Dive safe,

Celia

[NorthWoodsDiver]

Every dive is a decompression dive... so I imagine your only asking about dives requiring mandatory in water decompression stops. Just thought I would clarify in case anybody was wondering. :smt064

[netmage]

Every dive is a decompression dive... so I imagine your only asking about dives requiring mandatory in water decompression stops. Just thought I would clarify in case anybody was wondering. :smt064

Pass the k00l-aid...

[amphipod06]

Pass the k00l-aid...

LOL....pass the pop corn now...

Dive safe,

Celia

[aainslie]

Pretty interesting. I was thinking people were getting bent every 1000 or so deco dives. Looks like it's more like one every 200-400. I haven't done the math very carefully, but it's of that order. and of course that's for users of THIS board only.

That's really high.

let me do some calcs and see what i come up with - in the interim, it'd be nice to get a few more responses, the response rate here is ay lower than on the "bent" question. It'll make me happier that biases are reduced if the response rates are similar.

[apitkin]

Pretty interesting. I was thinking people were getting bent every 1000 or so deco dives. Looks like it's more like one every 200-400. I haven't done the math very carefully, but it's of that order. and of course that's for users of THIS board only.

That's really high.

let me do some calcs and see what i come up with - in the interim, it'd be nice to get a few more responses, the response rate here is ay lower than on the "bent" question. It'll make me happier that biases are reduced if the response rates are similar.

Whatever your results, they will be biased by the fact that people who have been bent are more likely to respond to a poll of this kind. I am not sure you can derive any meaningful numerical conclusions.

Andy

[cwj]

have you seen the articles indexed in PubMed? agree with the bias issue, but hard to get good diving epidemiology data. can get hits that ended up in ER or hospitals via state hospital discharge databases but problem is getting a valid denominator.

interesting rates for crude comparison are in:

Decompression illness reported in a survey of 429 recreational divers.
Klingmann C, Gonnermann A, Dreyhaupt J, Vent J, Praetorius M, Plinkert PK.
Aviat Space Environ Med. 2008 Feb;79(2):123-8.

then look at related articles.

cheers.

[runawaylobster]

Every dive is a decompression dive... so I imagine your only asking about dives requiring mandatory in water decompression stops. Just thought I would clarify in case anybody was wondering. :smt064

Hehe.... I was going to say that, but well... :)

[NorthWoodsDiver]

Neither of the polls address when in the divers career they had a diving injury. Thats key information IMO.

I would think its more likely for someone to have an injury in their early days of decompression diving and after many years of decompression diving. but this is all based on my though process and no evidence.

-People who are newer to the idea may not have the skills or knowledge on the subject necessary to safely complete the dives thus leading to issues. as they do it more and more and continue training they will become better divers and more knowledgeable on the issues and will use caution and common sense to help avoid injury.

-People who have several hundred or thousand decompression dives have been doing it a while and usually find a system that they are comfortable with but I have seen several seasoned divers starting to switch things up and play with gradient factors and tables to try and push things a little. So I would bet some of these guys who decide to start modifying things or those who become complacent are the ones ending up with injury even though they have been diving a long time.

Its all theory but it makes sense to me. am I wrong?:smt102

[MengTze]

If you are going to correlate this to getting bent, should you not also differentiate the type of deco dive?

Depth, time, deco time, temp, types of gas etc?

[tflaris]

Add 2 more for me.

94 minutes at Ginnie
86 minutes at Ginnie

[tflaris]

Hehe.... I was going to say that, but well... :)

Hey I remember that from my NAUI Instructor manual also.

[aainslie]

Whatever your results, they will be biased by the fact that people who have been bent are more likely to respond to a poll of this kind. I am not sure you can derive any meaningful numerical conclusions.

Andy

I could equally claim that people who HAVEN'T been bent will tend to answer.

Do you have evidence for your claim? Because I sure don't for mine. Perhaps we should split the difference... :)

Anyway I just want to make the simple observation that assuming no biases in which of CDF's readers ansered iether or both polls (and it's a pretty high percentage of active readers anyway), CDF readers have a surprisingly high rate of getting the bends. About 40% have had some sort of incident, about 15% have taken rides (i.e. 25% (including myself) have had minor hits that they've treated themselves). Yet the average number of deco dives is way nearer 200 than 1000, leading to a hit rate of at LEAST 1 in about 500 dives - and I'm not even including victims of multiple hits (I've had two). I have NO causal variables, and I don't have the joint distribution - and franklly I'm not in a huge rush to collect those data. There MIGHT be bias in who chose to answer, but again considering the high percentage of respondents (especially to the first poll, which is probably the one most likely to induce bias), I doubt it.

But y'all take care out there - we're getting bent at a pretty high rate.

[netmage]

But y'all take care out there - we're getting bent at a pretty high rate.

And yet everyone seems to opt for schedules to 'rush out of the water'.....

[Slüdge]

Netmage, that's probably the most profound post made on the Forum in the last year. :clapper

[tflaris]

And yet everyone seems to opt for schedules to 'rush out of the water'.....


Well said

[aainslie]

And yet everyone seems to opt for schedules to 'rush out of the water'.....

Yep... I've done at least three big things on this:

1) I take an ipod touch into the water. On deco I catch up on TV. I'm much more willing to do an extra 15 minutes at the end of deco when watching TV.

2) I use GF 15/80 and VPM B/E conservative 5.

3) I do a few minutes substantially shallower than my computer suggests. At Ginnie, if my first stop is at 30, I spend about 5 mintues at 50 first.

Step up the conservative levels on those deco's!

[jj1987]

Something I've been debating posting, but I think I'm new enough at this that I'll gain some valuable insight here from some of your responses, so I'll go ahead.

When I first started deco diving not too long ago, obviously the fear of getting bent lead me to do a lot of reading up. From reading first hand accounts of being bent, I couldn't find any relationship between the deco algorithm used, and rates of being bent. Obviously this doesn't mean a lot, since very few people will admit to being bent, and if they do, I doubt they'd admit to violating a profile, screwing up their tables, or messing up avg depth. Honestly if you look at minor details of messing up a deco algorithm, it really doesn't throw your schedule off too much (maybe a few minutes?), so I'm guessing most cases aren't due to these factors.

One thing I did however notice, was that a surprisingly high number of cases were occurring on vacations. My own inference here is lack of sleep as well as dehydration (drinking the night before the dive?), but I'm just throwing that out there to see if others think it might be something worth considering? :smt102

I've also found it interesting to see HOW different people pad their safety margin.

Some work out and stay in shape, drink TONS of water (even bringing camel packs for during the dive), ensure they're diving dry with plenty of exposure protection to stay toasty warm, do at least 5min surface deco debriefing the dive, and get a good nights rest before any deco dive. From what I can tell, most of those who fall into this group don't pad their deco schedules much. Others will add 5min to their o2 time or something along those lines, or pad their overall schedule with time.

GUE has an interesting dvd about decompression, that if you haven't seen it, is worth your time and whatever they're charging for it these days. Much of it is over my head, but it does go into details of why decompression sickness remains such a mystery, and theories that are being tested to prevent it.

[FW]

One thing I did however notice, was that a surprisingly high number of cases were occurring on vacations. My own inference here is lack of sleep as well as dehydration (drinking the night before the dive?), but I'm just throwing that out there to see if others think it might be something worth considering? :smt102
Possibly they do most of their diving while on vacation. Not to mention more repetitive dives.

[FW]

3) I do a few minutes substantially shallower than my computer suggests. At Ginnie, if my first stop is at 30, I spend about 5 mintues at 50 first.
?? Deeper maybe?

[aainslie]

Yeah... OK, on that, I DO also try to hug the ceiling all the way to the bench - after that I change my strategy and hug the FLOOR, and move slowly. If I have a scooter I don't use it between the lips and my 50 ft stop. I start moving VERY slowly basically from the bench/keyhole on out.

Also this is on shorter Ginnie dives. In the deep section (I hit 167 ft, apparently it goes a little deeper), I often have a formal 50 ft stop by the time I get back to the lips. Of course, the whole passage from the Henkel out is a nice deco from that deep bit. Then I stop before the lips, just after the keyhole, for a few minutes in 60-70 ft. Puzzles the crap out of incoming groups, they sit there signalling at me to come past them, and on at least one occasion it tok a LOT of signalling to convince them to come past me. Good manners gone nuts :)

But you're right, I could start earlier. Key thing is, the computer's suggestion that 30 ft is cool is often NOT cool. nd it pays to slow down a LOT during the exit.

[FW]

shallower
What I meant by "deeper?" was you said "shallower" in your other post.

[aainslie]

What I meant by "deeper?" was you said "shallower" in your other post.

D'uh - sorry, I missed that!

[Bob Cree]

Yeah... OK, on that, I DO also try to hug the ceiling all the way to the bench - after that I change my strategy and hug the FLOOR, and move slowly. If I have a scooter I don't use it between the lips and my 50 ft stop. I start moving VERY slowly basically from the bench/keyhole on out.

...But you're right, I could start earlier. Key thing is, the computer's suggestion that 30 ft is cool is often NOT cool. nd it pays to slow down a LOT during the exit.

Perfect!



In the deep section (I hit 167 ft, apparently it goes a little deeper), I often have a formal 50 ft stop by the time I get back to the lips. Of course, the whole passage from the Henkel out is a nice deco from that deep bit. Then I stop before the lips, just after the keyhole, for a few minutes in 60-70 ft. Puzzles the crap out of incoming groups, they sit there signalling at me to come past them, and on at least one occasion it tok a LOT of signalling to convince them to come past me. Good manners gone nuts :)

2) I use GF 15/80 and VPM B/E conservative 5.


Having observed a part of one of these dives and on deco, I am curious what software you use to generate the GF 15/80? Given, there are plenty of unknowns on my part to be sure, but I believe (my) decoplanner using GF 20/80 would have resulted in a bit longer deco than what I observed - so I just assumed you were diving the computer (which I routinely find are significantly less conservative). Now, since learning you use GF 15/80, I am wondering if there is a significant difference between different software packages as well.

As a point of comparison, decoplanner 30% Nitrox, 110 feet square profile for 140 minutes w/100% O2 deco gas gives 106 minutes deco and 159% CNS. Since computation is our primary defense against getting bent, what software are you using and how does it compare?

Why I bring this up is that we all tend to follow our software - whether real time or tables - some conservative, others less so...do we truly know what it means? My bet is we are diving less conservative out of ignorance...and your polll data suggests that - biases and all. I think we are all just a bunch of human guinea pigs.

Glad to see you are using the 15/80 - I think it makes alot of sense for chronologically challenged divers.

[Bob Cree]

And yet everyone seems to opt for schedules to 'rush out of the water'.....

I agree with Sludge...Profound indeed...

After all, why the heck do we want to leave someplace we all try so hard to get to?

Is it because we are in such a big hurry to refill and get another dive in? Hmmm, now that I think if it, interesting link to what Rich said...if you are in an all fired hurry to get out and refill for another dive - seems there is a link to repetitive diving and exertion...

higher quality...lower quantity

[aainslie]

On your first post - I use GF on my Vision on the Inspo.

On the second - are you kidding me? Deco is excruciatingly boring!

[atedeschi]

i feel like my profiles are like dare devil profiles to what I am hearing. I use Vplanner on nominal, and usually throw a min or two in at half my max depth and a 5min saftey stop added to my last stop.

[aainslie]

i feel like my profiles are like dare devil profiles to what I am hearing. I use Vplanner on nominal, and usually throw a min or two in at half my max depth and a 5min saftey stop added to my last stop.

You're also half my age :)

[Bob Cree]

On the second

lol - touche', tongue and cheek...turned into a pretty good thread though. Truly, horribly boring, especially when it gets up there in time. You really know its bad when the fish get bored with you.

But I still do the deco - the true reason for a pee valve.

Ah, computer...by nature less conservative for the same algorithm due to following the profile. Have to admit in some cases to cutting special profile tables, like at Madison, 60 -120 - 60 feet, and use a deco mix on the outgoing shallow section. Not many places I would do this though. I dream on deco to do what my Nitek HE tells me to do. Damn decoplanner.

[atedeschi]

well since we are talking about deco, maybe we should see what type of conservation people are using and age of the diver.

I use Vplanner, nominal setting, and 5 mins to my 15min stop on O2, usually follow Dive Rite Duo when not using trimix, but average depth and v-planner are pretty close.

[Kelly Jessop]

In retrospect I realize my numbers would be skewed in that there was a cave diving era where nitrox wasn't readily available,or we'd use poor man's nitrox (topping air on top of a nitrox mix),so going into deco was quite prevalent,where the same dive today doesn't evoke decompression. I shiver at the thought of long air dives at Devils system,with long decompression times in a wet suit. Then again conversely,when nitorx was available we were diving 36% (and sometimes 38%-yikes),and we wouldn't hit deco,while a 32% diver would.

[netmage]

well since we are talking about deco, maybe we should see what type of conservation people are using and age of the diver.


35, VR3 SAFE 20 using VPM..., but thats mostly due to closed PFO & previous history... Probably equates to beyond a +5.

[apitkin]

I could equally claim that people who HAVEN'T been bent will tend to answer.

Do you have evidence for your claim? Because I sure don't for mine. Perhaps we should split the difference... :)

Anyway I just want to make the simple observation that assuming no biases in which of CDF's readers ansered iether or both polls (and it's a pretty high percentage of active readers anyway), CDF readers have a surprisingly high rate of getting the bends. About 40% have had some sort of incident, about 15% have taken rides (i.e. 25% (including myself) have had minor hits that they've treated themselves). Yet the average number of deco dives is way nearer 200 than 1000, leading to a hit rate of at LEAST 1 in about 500 dives - and I'm not even including victims of multiple hits (I've had two). I have NO causal variables, and I don't have the joint distribution - and franklly I'm not in a huge rush to collect those data. There MIGHT be bias in who chose to answer, but again considering the high percentage of respondents (especially to the first poll, which is probably the one most likely to induce bias), I doubt it.

But y'all take care out there - we're getting bent at a pretty high rate.

I have no more evidence than you, but what I am referring to is called recall bias in statistics textbooks and is one of the problems with this kind of retrospective analysis.

Having said that, I agree completely that cave diving is high risk for DCS and that we should all be conservative in deco planning.

Andy

[Bob Cree]

well since we are talking about deco, maybe we should see what type of conservation people are using and age of the diver.

As mentioned, I dive tables cut typically as square profiles from decoplanner 20/80 GF's. A while back, I used a Nitek Duo on its highest level of conservatism (SF2) as backup, and it matched up reasonably well with my tables as far as clearing on my last stop. Since the Duo does not give deeper stops (which I did anyway off my tables), it initially showed less deco obligation than the tables, but eventually caught up on the 20 foot stop. So I consider myself fairly conservative, but I am now 50 and have not been bent...knock, knock, knock...

One major cave/bends issue that I don't think has been mentioned is profile related. Sometimes back in the cave, the profile goes shallow suddenly and above the typical deep stop ceiling, then deep again. I have heard of people getting badly bent in these situations. One buddy of mine, years later, still suffers the consequences of this and they did get treatment.

[Randy Thornton]

Best thing I ever did to improve my deco was to install a pee-valve in my dry suit! Now, I am not in such a big hurry to get out of the water! :)