Free-diving decompression tables

[DeepSeaApnea]

be careful now. CNS o2 tox and pulmonary o2 tox are two different things. CNS is 1.3-1.6 ata (depending on the person, it could go higher) is when oxygen becomes toxic. No amount of pseudoehiphidrines is going to make a difference. it depends on your body. and it is 2.4 ata dry or in a chamber, this is why you can breathe 100% at 60', try doing that underwater and you will more than likely have a convulsion. pulmonary tox is when you have been breathing o2 for a long period of time and you get a burning sensation in your lungs. can happen on surface in a chamber, or even at depth if you are sucking down bottle after bottle of o2.


DCS general knowledge.
Decompression sickness is generally divided into two categories. Type I decompression sickness involves the skin, lymphatic system, muscles and joints and is not life threatening. Type II decompression sickness (also called serious decompression sickness) involves the nervous system, respiratory system, or circulatory system. Type II decompression sickness may become life threatening. Because the treatment of Type I and Type II decompression sickness may be different, it is important to distinguish between
these two types. Symptoms of Type I and Type II decompression sickness may be
present at the same time.
When the skin is involved, the symptoms are itching or burning usually accompa-
nied by a rash. Involvement of the lymphatic system produces swelling of regional
lymph nodes or an extremity. Involvement of the musculoskeletal system produces
pain, which in some cases can be excruciating. Bubble formation in the brain can
produce blindness, dizziness, paralysis and even unconsciousness and convulsion.
When the spinal cord is involved, paralysis and/or loss of feeling occur. Bubbles
in the inner ear produce hearing loss and vertigo. Bubbles in the lungs can cause
coughing, shortness of breath, and hypoxia, a condition referred to as “the chokes.”
This condition may prove fatal. A large number of bubbles in the circulation can
lead to cardiovascular collapse and death. Unusual fatigue or exhaustion after a
dive is probably due to bubbles in unusual locations and the biochemical changes
they have induced. While not attributable to a specific organ system, unusual
fatigue is a definite symptom of decompression sickness.


Type I decompression sickness
includes joint pain (musculoskeletal or pain-only symptoms) and symptoms
involving the skin (cutaneous symptoms), or swelling and pain in lymph nodes.

 

[Deepwater]

be careful now. CNS o2 tox and pulmonary o2 tox are two different things. CNS is 1.3-1.6 ata (depending on the person, it could go higher) is when oxygen becomes toxic. No amount of pseudoehiphidrines is going to make a difference. it depends on your body. and it is 2.4 ata dry or in a chamber, this is why you can breathe 100% at 60', try doing that underwater and you will more than likely have a convulsion. pulmonary tox is when you have been breathing o2 for a long period of time and you get a burning sensation in your lungs. can happen on surface in a chamber, or even at depth if you are sucking down bottle after bottle of o2.


DCS general knowledge.
Decompression sickness is generally divided into two categories. Type I decompression sickness involves the skin, lymphatic system, muscles and joints and is not life threatening. Type II decompression sickness (also called serious decompression sickness) involves the nervous system, respiratory system, or circulatory system. Type II decompression sickness may become life threatening. Because the treatment of Type I and Type II decompression sickness may be different, it is important to distinguish between
these two types. Symptoms of Type I and Type II decompression sickness may be
present at the same time.
When the skin is involved, the symptoms are itching or burning usually accompa-
nied by a rash. Involvement of the lymphatic system produces swelling of regional
lymph nodes or an extremity. Involvement of the musculoskeletal system produces
pain, which in some cases can be excruciating. Bubble formation in the brain can
produce blindness, dizziness, paralysis and even unconsciousness and convulsion.
When the spinal cord is involved, paralysis and/or loss of feeling occur. Bubbles
in the inner ear produce hearing loss and vertigo. Bubbles in the lungs can cause
coughing, shortness of breath, and hypoxia, a condition referred to as “the chokes.”
This condition may prove fatal. A large number of bubbles in the circulation can
lead to cardiovascular collapse and death. Unusual fatigue or exhaustion after a
dive is probably due to bubbles in unusual locations and the biochemical changes
they have induced. While not attributable to a specific organ system, unusual
fatigue is a definite symptom of decompression sickness.


Type I decompression sickness
includes joint pain (musculoskeletal or pain-only symptoms) and symptoms
involving the skin (cutaneous symptoms), or swelling and pain in lymph nodes.

Old news -I dont how you figured that I thought the two were the same thing.

 

[DeepSeaApnea]

Old news -I dont how you figured that I thought the two were the same thing.

I was just pointing out the difference.

 

[Deepwater]

And I got them confused?

And for the record and to hear the sound of my own voice , I spent 11 hours in a chamber on pure O2 with the lung burning sensation or any other pulmonary issues.

You are ok doing deco at 1.6 as long as you are resting , not fining or working ( generation CO2 or straining your cardiac system).

A

 

[Rik]

Well, back to the topic of tables. I am currently studying two of them, the Thorsen table and the table of Heran. Heran wouldn't allow the first dive mentioned by Eric Fattah, and would note the second dive series as marginal safe. I don't have Thorsen in front of me, but remember that this table is a bit stricter then Heran, so probably both dive series wouldn't be allowed.

Like Eric however says, tables have one big problem: they don't adjust for the speed. Some reports in scuba diving suggest that a to quick or to slow ascent increases the risk on decompresion sickness. A fast ascent plays for sure a role in freediving.

The second problem is that a lot divers don't plan their dives. Both Heran and Thorsen assume that their users actually do think in advance to plan there dive. They both suggest a maximal amount of dives an hour, for a given maximal depth and maximal session time. It might be just me, but if I go diving, I do try to plan my dives, and adapt the amount of total dives to my goal, and time. I allow myself more dives if I dive shallow, and minimalise my total amount of dives if I dive deep. Often forgotten are the safety dives, who also should be taken into the account.

While these tables do not allow multi-depth adjustion, it would be logically to assume that deeper divers need more surface interval. This is also reflected in various publications on the topic. For those with acess to a university library, I would recommend the publication of Shipke. What is clear from those publications is that any dive below 50 meter has an increased risk on decompression sickness. Both mentioned tables are also only valid for dives shallower then 50 meters.

The big difference between SCUBA diving decompression sickness and Freediving decompression sickness is its presentation. Pure freediving often present itself with neurological (spinal) symptoms. It occurs fast, and can disappear fast too. This 'behaviour' has caused that freediving dcs isn't always recognised because by the time a doctor sees the divers, the symptoms are gone. Shipke also describes competition spearfishers who suffer from several bouts of DCS during the competition un recognised by themselves (or ignored),

When comparing the rule of thumb used by both AIDA and AA with the tables, it seems that these are too conservative on relative shallow dives, and unsafe on deeper dives. It might be of use to screen divers who dive below 50 meters on competition for DCS symptoms and evaluate if we need more strict rules on warming-up dives for these deep dives to avoid DCS during competition. This might be a nice project for the medical comitee's of the two organisations.

Just my 0.2 cents,


Rik Rösken


References

1. Thorsen HC, Zubieta-Calleja G, Paulev PE.,Decompression sickness following seawater hunting using underwater scooters.Res Sports Med. 2007 Jul-Sep;15(3):225-39.

2. Heran N. Les plongeurs en apnee peuvent-ils presenter un maladie de decompression. These de medecine, unversite montpellier, novembre 1990.

3. Schipke JD, Gams E, Kallweit O. Decompression sickness following breath-hold diving.
Res Sports Med. 2006 Jul-Sep;14(3):163-78.

 

[efattah]

My freediving DCS symptoms appear in the following order, from minor to severe:

1. One half of one big toe, or one half of one thumb, goes numb after I get out of the water. In other words, I have warm hands and feet, but the left or right side of a big toe or thumb is totally numb. Sometimes this is the only symptom I will get, and it indicates a minor hit.

2. In a more severe case, the half numb feeling hits several toes or fingers. I can be sitting in the sun warming up, and suddenly at some instant another finger or half a finger will go numb. It is amazing as it happens instantaneously. One moment I can feel that finger/toe, the other moment, it is numb or half numb.

The above symptoms are generally the only symptoms I get immediately after getting out the water. The rest of the symptoms come several hours later.

3. Skin prickles; strange spikes or prick feelings in my skin, all over my body at random places and random times. It is very disconcerting. I will be sitting talking or something, and suddenly it feels as if someone poked my skin with a needle. However the feeling happens slightly below the skin. It lasts for only a fraction of a second. On a bad DCS hit, I can get a skin prick feeling several times per minute for hours and hours.

4. Joint pains; pains and aches in my knuckles or elbows, mainly. Sometimes in the knuckles of my toes too. These pains can last for up to 3 weeks. Recompression in the chamber helps, but they still last for a while, and probably cause permanent damage and premature arthritis.

5. Exhaustion; on a more severe hit, the next morning I am extremely exhausted and weak. Unable to lift heavy objects. Extremely tired. Don't feel like getting out of bed. The danger is that this feeling is very similar to extreme dehydration, except that it will not go away no matter how much you drink.

 

[miguel-van]

Thanks a lot Eric!

I had the same symptoms of fingers getting numb for maybe an hour or two. Until now I was always thinking that maybe my glove was too small and that the blood did not circulate enough... I guess I was wrong about that.

Getting extremely exhausted at a point that I almost fell asleep at dinner... happened to me also. Since I dive in fresh water (lake Geneva in Switzerland) I said to myself that my body burned away a lot of calories to fight the cold... I guess I was wrong about that too!

Afther reading this thread I will definetely pay more attention to these symptoms.

Cheers
Miguel

 

[Aber]

Yes, thank you for shearing, Eric! This is very helpful .

 

[ILDiver]

Thanks a lot Eric!

I had the same symptoms of fingers getting numb for maybe an hour or two. Until now I was always thinking that maybe my glove was too small and that the blood did not circulate enough... I guess I was wrong about that.

Getting extremely exhausted at a point that I almost fell asleep at dinner... happened to me also. Since I dive in fresh water (lake Geneva in Switzerland) I said to myself that my body burned away a lot of calories to fight the cold... I guess I was wrong about that too!

Afther reading this thread I will definetely pay more attention to these symptoms.

Cheers
Miguel

miguel-van:
I'm the curious sort so I have to ask. If your in water that is warmer and your not wearing gloves, do you have this issue with your hands? I would tend to suspect the gloves and cold in your situation over DCS.

The fatigue factor, same thing. Exertion and cold rather than DCS. Your tired at dinner, but a good sleep you recover? I usually feel fine well after I dive, it's not until I get my gear put away and relax thet the fatigue hits me. But I'm fine after a good nights sleep. Eric refers to fatigue and weakness the next day.

(not saying you should brush it off, but make sure your not diagnosing a cold as cancer, you know)

Eric:
You mentioned that the chamber helps, but symptoms still last? Do the symptoms pass faster for you if you recognize them and get treated sooner? I never knew the symptoms stayed after the chamber ride. I thought they went away. I guess if I thought about it more, I have heard of people having to have more than one chamber treatment.

 

[samdive]

Sometimes you need loads of chamber trips - my record for one bend is 19 treatments.... admittedly as a result of scuba rather than freediving (and rather boring!)

 

[miguel-van]

Chris,

Of course when I'm tired after diving, basicaly a good night sleep and it's ok. But I was talking about just once where I was realy tired even after a day or two. But then again it only happened once so I'm not really alarmed. I will just pay more attention on next dives.

For the fingers, even in summer I wear gloves because below 30m it's only about 6 or 7 °C. But here again it doesn't happen every time I go out diving but stil I fet this feeling on a more regular basis. I'll try without the gloves a couple of times to see what happens.

Finaly the best solution for me is maybe to move somewhere closer to warmer waters...

Miguel

 

[ILDiver]

Finaly the best solution for me is maybe to move somewhere closer to warmer waters...

That is the plan I am working on for myself as well!

 

[danvolker]

It may be just semantics but IMHO the amount of O2 is not what is important in decompression. It's the partial pressure of N2. I don't have tables available to check but a local tech diver told me that decompression on 50% O2 is almost as good as on 100%(time wise) and doesn't require special equipment. I've never made a decompression dive so only interested in the freediving aspect.

I tech dive as well as freedive (DIR / see WKPP.org )the WKPP practice for deco would be 100% O2 at 20 feet..you would not use 50% O2 as a freediver--no way.
Also, the 100% not being safe in a normal reg is pretty much BS. It is dive shop nonsense. Get a shop that deals with techdiving to clean an 80 cu foot tank, and have it filled with 100% O2. They can clean the reg also, but I would not waste the money on this. Hang the tank from a float, and use it if you think you are pushing your offgassing limits.

Also, as a previous poster indicated, I would really consider the liklihood of a PFO causing the DCS...close to 25% of the general population has a PFO..they do not adversely effect a person above the water--you could even be a competitive cyclist and do fine with a PFO..but in scuba these are a huge part of what are frequently called "undeserved hits" ( where a scuba diver followed the tables, but got bent anyway). I have not read or heard about freedivers getting bent by the kind of profiles so far discussed here, which again, would suggest a PFO....but even with a PFO, the 100% O2 would be the best way to quickly get rid of the bubbling.

While the oxygen should work for this, a freediver who has been bent many times, and who has a PFO, should decide to have the PFO repaired, rather than trying to mitigate the problem with Oxygen.

Regards,
Dan Volker

 

[Deepwater]

I tech dive as well as freedive (DIR / see WKPP.org )the WKPP practice for deco would be 100% O2 at 20 feet..you would not use 50% O2 as a freediver--no way.
Also, the 100% not being safe in a normal reg is pretty much BS. It is dive shop nonsense. Get a shop that deals with techdiving to clean an 80 cu foot tank, and have it filled with 100% O2. They can clean the reg also, but I would not waste the money on this. Hang the tank from a float, and use it if you think you are pushing your offgassing limits.

Also, as a previous poster indicated, I would really consider the liklihood of a PFO causing the DCS...close to 25% of the general population has a PFO..they do not adversely effect a person above the water--you could even be a competitive cyclist and do fine with a PFO..but in scuba these are a huge part of what are frequently called "undeserved hits" ( where a scuba diver followed the tables, but got bent anyway). I have not read or heard about freedivers getting bent by the kind of profiles so far discussed here, which again, would suggest a PFO....but even with a PFO, the 100% O2 would be the best way to quickly get rid of the bubbling.

While the oxygen should work for this, a freediver who has been bent many times, and who has a PFO, should decide to have the PFO repaired, rather than trying to mitigate the problem with Oxygen.

Regards,
Dan Volker

Well well well-good to see you here Dan. I remember your from the old quest and techdiver list.
A

 

[kmo]

Thanks for the info Dan. Can you please explain what a PFO is and how you would get it repaired?

I've had that pin pricks in the skin feeling after multiple days of hard, repetitive diving in 15-20m, but hadn't ever considered deco sickness. Thought that it was more likely salt rash or similar. Still do to a degree, but it is food for thought.

Cheers
Cam

 

[samdive]

PFO - patent foramen ovale - basically a small hole in your heart that means blood can get through from one side to the other without going via the lungs, ie without getting rid of nitrogen bubbles. Its quite common and if you have one it makes you more susceptible to bends. If you've had an "undeserved" bend, then certainly in the UK, your doc should allow you to get tested for it (I got tested but didn't have one)

If you find you've got a PFO and plan on carrying on diving, it can be fixed surgically. They go in through a vein in your thigh and basically put a small piece of mesh across the hole in your heart so that tissue goes across it. A friend of mine had it done and hasn't had any problems since (used to get tired/grumpy and skin rashes after every dive)

best of luck

S

 

[danvolker]

Here are 2 decent articles on pfo's and diving...

Patent Foramen Ovale

Diving Doctor - Diver Magazine May 1999

While there has been no research done on freediving and PFO's ( that I have ever run accross), from what I have read, I would expect that the "packing" of lungs that some freedivers do prior to a drop, may help push bubbles in the bloodstream, through the PFO. But this is just idle speculation......any diver who has been bent more than once ( from a profile that is generally considered safe) , should get a pfo test, or stop diving. You can die from this !

Regards,
Dan V

 

[danvolker]

Well well well-good to see you here Dan. I remember your from the old quest and techdiver list.
A

Hey!
And while I miss the tech list, I don't miss the huge flame wars
Regards,
Dan

 

[Deepwater]

Hey!
And while I miss the tech list, I don't miss the huge flame wars
Regards,
Dan

You gotta admit, they were pretty funny sometimes

I should be up in Florida next year for Cave 1 and RB80

A

 

[danvolker]

You gotta admit, they were pretty funny sometimes

I should be up in Florida next year for Cave 1 and RB80

A

Plan on doing some dives with us off of Palm Beach.
Regards,
Dan