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Surface Intervals

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

How long do you wait on the surface between freedives?

  • 1-2 minutes

    Votes: 7 13.5%
  • 2-4 minutes

    Votes: 27 51.9%
  • 4-6 minutes

    Votes: 9 17.3%
  • 6-8 minutes

    Votes: 3 5.8%
  • 8-10 minutes

    Votes: 1 1.9%
  • 10-12 minutes

    Votes: 3 5.8%
  • 12-15 minutes

    Votes: 0 0.0%
  • I neither know nor care

    Votes: 2 3.8%

  • Total voters
    52
Originally posted by samdive
no I got bent from scuba diving, but only from 11m. Had both pain and neurological symptoms so they are trying to advise me to be conservative on my freediving as I may be susceptible. 10 minutes is working well for me, but yes Alun, 15-20 is better before a max
thanks guys, we may be doing some more research on this, I will keep you posted

Sam

Small world Sam, i've had 2 incidents that were pretty much the same as yours <12mtr dives with type-II symptoms (on rich nitrox).

The doc suggested, very strongly, that i shouldn't scuba dive anymore, but didn't seem to have a problem with freediving.
 
for the record I have never given anyone any negative karma (don't think I know how actually!)

up to you guys - I spent most of last year trying to do negative dives, it didn't suit me, I stopped

and whatever I do... my letter from my dive doc says I need to do 10 minute surface intervals so thats what I'm sticking to... negative dives or not. I quite like the use of my legs and finding them numb and bent was kind of scary.

Sam
 
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Reactions: Pezman
Please guys I need some pieces of advice about DCS:

A friend of me is spear fishing (freediving, not scuba) in between 38 - 40 meters deep. He is very afraid abut DCS, so he asked me if I can make some questions to the deeperblue friends in order to avoid DCS problems.

During one complete morning of spear fishing he makes a maximum of 20 dives to a depth of 38 - 40 m. Duration of the dives: 2 to 2.20”, with a recovery time in between apneas of 8 min. No any apnea arrives to the limit, no any hard hypoxic signals, incidents or extreme difficulties. Everything is always under control. Only some soft headache appears the day after. He uses variable ballast to help himself in his dives, going down with 6 kilos and ascending with only one on his belt.

So the questions of my friend are:

- Can my friend increase the number of dives per day more than the 20 he is doing in this moment without being afraid of any DCS problem?
- Can my friend free dive two or three consecutive days, at this depth, or it must be always the day after to avoid DCS?
- 8 min of resting time in between dives is enough?
- If the number of dives is increased to 25 or 30 per day, the resting time must be increased also?

Thanks you very much guys.

Saludos Agustín.
 
I think 8 min is enough, but just barely enough. I think 10 min would be safer, but maybe 8 min is enough? I'm not qualified to say for sure. Ask an expert.


Eric Fattah
BC, Canada
 
Please Erik, what do you think about the other questions: the possibility of increasing the number of dives per day (currently 20) and the possibility of diving two or three consecutive days at 40 m?


Thanks Agustin.
 
Think of it this way; either the 8 minute interval is enough to 'off-gas' ALL of the nitrogen, or it isn't.

If the 8 minute interval is enough to off-gas all of the nitrogen, then your friend could continue his dives forever (200+ per day), every day.

If the 8 minute interval is a little too short, then eventually he would get DCS after more dives per day, or several days of diving.

Remember also that if he is COLD, or DEHYDRATED, or drinks alcohol, his risk for DCS increases. I think there are other factors -- perhaps some scuba divers could contribute.


Eric Fattah
BC, Canada
 
Hi Guss,

your question made me recall an incident where a spearo developed a CNS hit after competing in the an international competition held in SA. He was treated by Dr Van Niekerk who gave these pointers:
"An objective guideline would be to ensure that the total dive time does not exceed the no-decompression limits for compressed-air diving, even though it is known that repeated ascents while diving with compressed air increases the risk of developing the bends. Adequate hydration - the intake of 250 to 300 milliliters of fluid every hour - should be mandatory. Overall better record keeping of dive profiles by surface support personnel will lead to a better understanding of the problem and its scope" This incident is also documented in Terry Maas' "Bluewater Hunting and Freediving".

You may further find the following of interest:

Suk-Ki Hong in Breath-hold Diving section of Bove's 'Diving Medicine', p. 69. 1997.

Paulev, P. "DCS following repeated breath-hold dives". J.Appl. Physiol. 20(5): 1028-1031. 1965.

Edmonds, C. "Diving & Subaquatic Medicine". 1981.

Cross E.R., Taravana - Diving Syndrome in the Tuamotu diver. In 'Physiology of breath-hold diving and the ama of Japan.' National Academy of Science - National Research Council Publication 1341. 1965; 207-219.

Bove, A.A., 'Diving Medicine', Taravana

Wong, RM, Taravana Revisited: Decompression Illness After Breath-hold Diving, SPUMS Journal, Volume 29, No.3, September, 1999

Regards,
 
Lots of thanks to Erik and welwichia.

If somebody can help me with more info, I wil be very pleased to read your coments about this subject.

Saludos

Agustín Espinosa
 
Hi Guss

A quick quetion for you if you dont mind.

You said "During one complete morning of spear fishing he makes a maximum of 20 dives to a depth of 38 - 40m. Duration of the dives: 2 to 2.20”.

Do you have any idea how much of that 2 to 2.20 is spent at the bottom at 38-40m and how long his ascents and descents take?

Thanks

Ash
 
Hi ash

Normal bottom time is 40" to 1 min because he needs 40" to descent and 40" to ascent, average.

Saludos Guss
 
Hi Guss

Thanks for that information.

The reason I asked is that Welwichia’s post in this thread got me thinking about comparing scuba-based decompression limits with freediving.

Let’s say your friend takes 40 seconds to descend to 40m, spends 40 seconds at that depth and takes 40 seconds to ascend and he does this for 20 dives.

He is effectively spending about 13 minutes in total at 40m over the course of those 20 dives.

Keeping things simple, his average depth on the ascents and descents is 20m and he is spending almost 27 minutes at 20m.

If I plug this profile (multilevel air dive with 13min @ 40m and 27min at 20m) into GUE’s Decoplanner dive planning software, it shows this theoretical dive as requiring over 20 minutes of decompression.

So your friend is diving well outside of Dr Van Niekerk’s guideline, as I am sure are a lot of skilled spearfishermen all over the world, yet they aren’t getting DCS en masse.

The surface intervals are obviously working to stop DCS in the vast majority of cases but as your friend extends his dive times and does them over multiple days, he is pushing further and further into the unknown.

If he does 30 dives a day, the theoretical decompression required increases dramatically.

Your friend’s dives are well outside my meager capabilities but my advice to him would be to extend the surface intervals on the days where he is doing more than 20 dives a day.

I’ll see if I can get some more information on this topic from some hyperbaric experts.

Cheers

Ash
 
thanks

Thanks a lot Ash for your post, I will give all this information to my friend.

Saludos
Agustin.
 
Hi Guss

I received some feedback on this issue from a dive doctor. I thought you might like to read it :

>>>Free Diving

This is a question that we see frequently. There are at least two difficult questions here. These are nuclei formation and gas exchange.

Nuclei Formation

Free divers are an active bounce underwater if they are going to a deeper depth. This involves hard finning to reach the depth. This will possibly create micronuclei from the musculoskeletal activity as will a swimming ascent. This activity could be more than is accounted for in normal table development, and it is dependent on the skill of the diver.

Gas Exchange

The greatest uptake (from the lungs in a single breath) will occur with the diving being as active as possible while at depth. This is probably true with some freedivers. Since they will most likely rest while on the surface, the diver would go into a quite mode while on the boat. This will cause the circulatory system to shift to very low blood flows. Clearly this is bad for nitrogen elimination. To account for the rapid nitrogen uptake and slow elimination, I might suggest that at least five times the surface interval be maintained in comparison to the bottom time for any single dive.

One should recognize that none of this has been rigorously tested (controlled study) to my knowledge.

__________________
>>>Michael R. Powell, M.S., Ph.D.

Surface intervals of 5x the dive time may sound harsh but at the more advanced levels, it might make sense.

Cheers

Ash
 
Is the definition of bottom time still the time you start down to the time you start up? Five minute surface interval between 45 meter dives doesn't sound too long to me.
Aloha
Bill
 
Good question Bill. I would assume he's talking about the total dive time there, from the start of your descent until the time you surface.

I agree with you about the bigger dives but aiming for surface intervals of 5x the dive time for all freedives would probably be too conservative in some cases and not conservative enough in others from a DCS point of view.

Something like the tables Eric Fattah posted earlier in this thread would make more sense to me.

Ash
 
Umm, im a real newb, but im going out tomorrow afternoon. I was wondering what all this decompression stuff is. If i spend 1 min., lets say 30 ft. deep, how long should my recovery time be (i'm in pretty good shape i guess). I know that if you dive repeatedly, is that what you get the bends from? It all kind of confused me.
 
Your going to be too shallow, and not down long enough, to worry about the bends.

You should be more worried with being well rested, and your body re-oxygenated, before you dive again. Not always a set time limit on that- more on how you "feel".

Jon
 
Could you please explain decompression though, and what to do about it.
 
In a nutshell, Decompression is allowing enough time during your surface intervals to outgas (blow off) the excess nitrogen that has entered your body, by doing this the nitrogen will not come out of solution and cause all kinds of nasty problems, the worst being death. My advice if your concerned about the bends, get and open water SCUBA manual and read up on it, become familiar with the tables, If you have the money, get a computer. Above all, plan your dives and dive your plan. Stupid divers have gotten bent when they either didn't have a plan, or didn't follow it.
 
Ok, so does it matter how deep you dive? Lets say i dive 100 ft. down, with a bottom time of 2 minutes. Is decompression just breathing at the surface until the nitrogen receeds? Or is there some special technique?
 
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