DCS and freediving

[NewWave]

Just read Sebastian's interesting article on freediving.biz about DCS and freediving. Now I'm a bit concerned about exposing myself to DCS dangers while freediving - especially during longer, endurance sessions with many dives.

I might be wrong, but surely it would be easy to put yourself in danger of DCS during a freedive session if say, a freediver did many (10, 20, 30) dives to even relatively shallow depths like 10 to 40 metres throughout the day?

Do we have to work to SCUBA DCS tables for this?
Is there a freediving DCS table available?

For most freedivers, I'd imagine the potential problem lies more in training than in competition (less warm ups during comps and less time spent at depth for the day compared to 'hardcore' training days with repetive dives)...

Any answers? : )

 

[vali]

Can Freediving Cause DCS?

 

[trux]

This is the most complete thread containin also tables to freediving DCS tables: http://forums.deeperblue.com/safety/75779-can-freediving-cause-dcs.html (different than the above link by Vali, despite the same title)

And further info, tables, and scientific documents are available here: DCS @ APNEA.cz

 

[NewWave]

Thanks! Read through that thread - quite technical. What I can deduce is that DCS should be taken very seriosuly by freedivers - especially since more and more people are repetitively (and easily) diving into 30 metre plus depths. Perhaps it should even become standard practice with freedivers.

Also got quite a scare after hearing about some DCS stories in dive that are nowhere near record depths. (Eric saying something along the lines of getting DCS hits after two 40 dives with fast ascent rates and brief surface intervals).

I read the document MAXIMUM NUMBER OF REPETITIONS BASED ON CALCULATED NITROGEN LOADING on your site, Trux. I see below the table that 'This table does not constitute a guideline neither can be used to prevent DCS during breath-hold diving'. Point taken. However, do you think we'd be diving in a relativily safe, user-friendly, practical zone if we followed the table - and made sure to 'bump up' our daily dive profile into the next category.

Example, instead of diving, say, 16 dives to 45m with 6min SI (at 1.3sec ascent/descent rate), 'bumping up' to 13 dives to 45m with 6min SI (at 1.3sec ascent/descent rate)?

Then, according to the table, doing faster ascent/descent rates lets you do more dives. However, this seems contrary to some of the DCS experinces mentioned in previous threads?

Any insights?!

​

​

​

​

​

​

​

​

​

​

 

[Newbie_spearo]

I may be completely off subject here, but I was always told spend twice as much time on the surface as you do at depth. So if your dive time is 3 minutes, then you spend a minimum of 6 mins on the surface? This might be nothing to do with DCS but thought it was good info.

 

[trullalla]

hi,
the way we teach in aida is to have surface intervals TWICE the divetime for dives SHALLOWER than 30 meters.
for deeper dives, divide the depth by 5 and that gives you the interval: ex 35m=7 minutes,
40m=8 minutes, 50m=10minutes and so on.
also, no reps for deep dives (60+)
obviously there's no proper research behind that, but it seems conservative enough to prevent possible problems.

linda

 

[efattah]

Many of the times I got bent I was following the rules. Once I got significant DCS after 9 dives to 25-33m, average dive time 2'44", average surface interval 6'50". This was within all the so called 'basic rules or guidelines.' And those were dives with pretty slow ascents. Speed up the ascents and it gets much worse.

The problem with the tables and guidelines is that it doesn't tell you how to avoid DCS from a single dive. For me a single dive to 65m+ results in minor DCS if I ascend very fast. I can avoid DCS by reaching the surface, hyperventilating hard for 2-3 minutes, and then immediately diving to 13-15m, where I hang for 30 seconds, and then begin an extremely slow ascent. I call this a recompression dive and it is incredibly beneficial for me during deep diving, especially on consecutive days. Doing a 100% O2 recompression dive is beneficial too, but I find that I must do at least one recompression dive in the 13-15m+ range, which is too deep for 100% O2. Doing regular air apnea deco at 8m isn't deep enough for me -- presumably bubbles which formed are not sufficiently crushed at 8m.

Another rule I follow is that I *never* end the day with a deep dive (anything over 30m). I force myself to always do shallow dives (<15m) to finish the day. This is true even if diving just for fun.

Summary of my rules which have worked great for me:

Fun Diving 30m+
1. Try to control ascent rate to less than 1m/s
2. Apnea deco stop at 6m on the ascent for 10 seconds
3. If unable to do that, then recompression dive immediately after to 10-15m
4. Never finish the day with a deep dive

Line diving 65m+
1. Recompression dive on regular air (apnea) 13-15m with ultra slow ascent
2. 100% O2 recompression dive to 6m if available

 

[DivingDane]

hmm interesting being a spearo particulalarly when diving in southern queensland repetative dives to over 25m+ are common and myself along with alot of other spearos here have doen substantially more that 15-20 25m= dives in a day before without any noticable problems, however surface interval times are always double the dive time if not more so i guess this is helping not to mention my ascent speed has always been very slow and relaxed. but it is something i have to consider more seriously now i think.

do we as a community have people with the expertise to design and test a set off APNEA DCS Tables that cold be published?

DD

 

[Mullins]

Test.....? :blackeye

I doubt you'd run into DCS problems doing repeat 25m dives - if series like that put you at risk then spearos all over the world would be dropping like flies. I think most guys who have been bent were diving 35-45m, often VW so long bottom times and fast ascents.

 

[DivingDane]

more research so we can develope tables similar to the PADI dive tables, didnt think it would be much of an issue, just interesting to see Eric's experience. your right the number of people diving those depths and much deeper is quite remarkable.

would just lke to see a "AIDA" apnea DCS table that has been researched and can be published huge undertaking but as a sport that is growing quite rapidly it is something we will have to consider seriously in the near future.

DD

 

[samdive]

another thing to bear in mind is hydration - which has a huge impact on DCS. If you are planning a long day's training with repetitive diving, however shallow, then make sure you have plenty of water with you. If you do have any symptoms then of course you should see a doctor, get on O2 etc... but I did once get rid of a minor skin bend from repetitive freediving by downing a couple of bottles of water once when doc/o2 etc was not easily accessible.... (got to say I know I'm prone to DCS, know what works for me and did consult a doc by phone to check on that one - but it did work!)

 

[Mullins]

more research so we can develope tables similar to the PADI dive tables, didnt think it would be much of an issue

DD, I was just having a laugh at the idea of testing it - any volunteers? Of course a proper, well-researched table for apnea will be pretty important in the future.

 

[DivingDane]

dont mind me Dave, just been really ill the last while and humour eludes me occassionally. my bad! but i agree being the crash test dummy for the table would suck, wonder how the original paddy test divers felt when doing the recreational dive planner (pretty sure it was military)

DD

 

[Kars]

At the World Team Championships in Canada 2004 (if I'm correct) there was a doctor doing a form of DCS research, micro bubbles, on the athletes. Maybe this technique can have some merit in sketching up a more detailed DCS avoidance table?

Love, Courage and Water,

Kars

 

[chrismar]

dont mind me Dave, just been really ill the last while and humour eludes me occassionally. my bad! but i agree being the crash test dummy for the table would suck, wonder how the original paddy test divers felt when doing the recreational dive planner (pretty sure it was military)

DD

The standard dive tables used are called US Navy Dive Tables.

Freediving DCS studies would be tough because you couldn't use a normal baro chamber; the rate of pressurisation just isn't fast enough.

 

[efattah]

I developed my own 'tables' and rules by experimenting on myself. Luckily I can detect very minor DCS symptoms which happen to me consistently and similarly each time. I've had probably 20 instances of minor symptoms and many sessions (obviously) without symptoms, and by comparing them I made conclusions.

However on one of the more severe DCS cases I had, I showed no results through the tear film analysis (bubble detection method), and I also showed no results on the doppler machine. For this reason I think that existing technologies to detect bubbles don't work properly on freedivers.

 

[chrismar]

I developed my own 'tables' and rules by experimenting on myself. Luckily I can detect very minor DCS symptoms which happen to me consistently and similarly each time. I've had probably 20 instances of minor symptoms and many sessions (obviously) without symptoms, and by comparing them I made conclusions.

However on one of the more severe DCS cases I had, I showed no results through the tear film analysis (bubble detection method), and I also showed no results on the doppler machine. For this reason I think that existing technologies to detect bubbles don't work properly on freedivers.

Your conclusion after tear film and doppler surprised me. What symptoms did you experience? What made you attribute them to DCS rather than another cause? I'd also be interested to hear why you believe the methods used wouldn't work on freedivers.

From reading your accounts of DCS, I've noticed you've encountered symptoms on much gentler dive profiles than several other people I've dived with or heard of. I take it you've been checked for the usual suspects like PFO, but do you have any idea why you might be more susceptible than others?

 

[wes]

Just a theory of why Eric may have more more DCS experiences then others.

It could be that he is experiencing a much more heightened dive response and vascoconstriction due to his dive training methods which enhance the dive response and also the cold water he typically dives in.

This enhanced vascoconstricition could concentrate a smaller amount of blood that cycles thru the lungs and heart and head so the nitrogen and CO2 loading would be higher then if the dive response was less and more total blood was circulating from the arms and legs.

Cheers Wes Lapp

 

[rafacuatic]

In my experience, after suffering a strong DCS five years ago, I am much more sensible to have more, for a brain injury, as I explained a hiperbaric doctor . I think the tables are handy for people who have never had DCS.
Rafa

 

[NewWave]

From a practical point of view, Linda, 'Surface intervals TWICE the divetime for dives SHALLOWER than 30 meters. for deeper dives, divide the depth by 5 and that gives you the interval: ex 35m=7 minutes, 40m=8 minutes, 50m=10minutes and so on.
also, no reps for deep dives (60+)' seems very user friendly and hopefully a good enough guide.
Also, Eric's 'Fun Diving and Line Diving guide' is, I can imagine, the kind of practical info that more and more freedivers will be needing.

The thing that still concerns me though, is that this seems like a pretty darn serious topic, and there sems to be no consensus on what to do.

I've often heard about spearos doing repetitive dives of over 30 metres through a session, and also competition freedivers doing handfuls of 50 metre plus freedives in a session.

I might be wrong on assuming this, but I'd imagine a scenario that plays itself out quite regularly is when a freediver trains his butt off with repetitive dives in his home town's local freedive spot (maybe maximum 30 metres) then heads off to Dahab or Deans Blue hole for a few weeks training and vigourously applies the same training model - but with new found, personal best depths - in the 50m's, 60m's 70m's etc.

Anyway, next time I go for a session in my local quarry, I'm reckon I'm going to double my (already conservative) surface interval times, stay better hydrated, try ascend slower (I normally increase my pace a lot when surfacing CWT), and maybe go for one max/deep dive instead of multiple deep(ish) dives.

Concerned freediving community citizen : )