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Special Techniques for Apnea Performance?

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.


New Member
Jun 22, 2002

This post is dangerous, so be warned. My question is If I know some techniques that can be used for (at least theoretically) increasing apnea time significantly, but these techniques can be dangerous, should I disclose them anyway in this forum?

Be warned that I am a total newbie at holding my breath, so I cannot offer any world records as proof that this techniques work. But I do know a lot about biochemistry and a few subjects related to the physiological basis of breath holding. And since I have a passion for Philosophy and the development of brain power I have quite a few ideas about how to brake the apnea world records (hopefully) by a wide margin. By the way, what are the first prices for winning a static apnea competition? (he he, maybe I will use them on myself!).

Best Regards


Welcome to DB forums!

Your question is one that has been the subject of much debate on these forums before and not one that I particularly want to see flame up like last time.

These forums exist for free discussion on all topics, however we do reserve the right to moderate posts that seem to be defining very dangerous advice or that contradict the Forum Rules (i.e. flaming, liable, blatant commercial activity, etc..). Some people will see this as our form of censorship and that we are hiding facts/advice from the general public. This isn't the case, we just want to make sure any new Freedivers don't over-extend themselves and cause injury or (god forbid) worse.

So, to answer you question - go ahead, post your techniques - we have highly experienced freedivers on here who will help give you advice and discuss you training - however make sure that you make it clear what level your techniques are aimed at.

1st Technique

Stephan Whelan thank you very much for your kind words, stop me anytime if i brake any rule (thanks in advance).

1st Technique:

This is the least effective of the techniques and might not even work. It is intended only for advanced divers that know very well when they are in the danger zone while holding their breath.

Before disclosing this procedure it is important to consider this:

Respiratory Acidosis
If breathing is restricted, CO2 builds up and ultimately makes the blood more acidic (meaning decreasing its pH). This can cause headache, drowsiness, hyperventilation (as a way to compensate), cardiac dysrhythmias, gastrointestinal distress, nausea, vomiting, diarrhea, blurred vision. and abdominal pain. In the extreme it can cause death.

One possible solution to this problem is to do a "bicarbonate loading".

Here is a description of the technique as disclosed by is from the Blackrock Karate Club (©2000-2001 Blackrock Karate Club):

Sodium bicarbonate is a naturally occurring substance in the body. Its' main function is to help preserve the pH balance in intracellular fluid at a pH point around 7.35. The human body can only tolerate small fluctuations in the pH value and values +/- 1.00 (acidosis when the value falls below 7.35 and alkalosis when the value rises above 7.35). Sodium bicarbonate (NaHCO3) acts like a buffer when acidosis occurs bringing it back to near normal values.

To create energy for exercise activity the human body has a number of interlocking systems that allow it to generate varying amounts of adenosine tri-phosphate (ATP). ATP combines with phosphocreatine (PCr) to create the conditions where various chemical reactions can occur that allow muscle fibers to move against each other and so cause movement. The stored amounts of ATP and PCr in the body are small and need to be constantly regenerated. This is achieved through the interplay of three main energy producing systems. The ATP-PCr system is the easiest for the body to utilize. It is a purely chemical reaction and instant energy can be created for around 5-6 seconds of maximal activity. This system is backed up by anaerobic glycolysis and uses stored amounts of carbohydrate (glycogen) in muscle and the liver to help create ATP. It can last for 7-10 minutes at a maximal rate. However, the main bi-product called lactate is an acid and is one of the factors involved in slowing down the ATP-PCr chemical energy production and contributes to feelings of fatigue. Aerobic activity requires oxygen (O2) to produce ATP and as this is relatively slow at getting to the working muscle is the last system to generate energy. It can however, last for many hours and is the major source of human ATP.

Although anaerobic glycolysis is responsible for producing lactic acid (lactate) it is also a naturally occurring substance in the body, which can be tolerated, in small amounts. The normal fate of lactic acid (LA) is to be exhaled as H2O in breath or turned into pyruvate, which is used, in the chemical pathway that aids ATP production. However, when values start to reduce pH in working muscle, and subsequently the blood stream, causing acidosis to occur these two pathways are unable to cope with the increased amounts of LA. It is at this time NaCHO3 is used to buffer the free hydrogen ions (H+) causing the fall in pH to dangerous values. Maximal anaerobic exercise may cause pH to fall as low as 6.2-6.3, which, if not countered, can cause death.

The theory behind bicarbonate loading (the ingestion of extra amounts of bicarbonate) is that if it buffers LA in maximal anaerobic activity it could halt the pH decline and allow the activity to continue. This in turn might give one person an advantage over another allowing the 'loaded' athlete to compete harder for longer in continuous activity lasting for periods up to 10 minutes.

Research studies on the topic
Bicarbonate loading has been studied for around 60 years. The results from many of the studies pre 1970 were inconsistent due to variances in the study design and application. Often the administered dose of bicarbonate was too small to have an effect. However, from the 1970's onwards the doses used have been in the range of 0.20-0.30g/kg-body weight and generally administered 1-2 hours prior to exercise. This administration might have been by capsule, diluted solution or intravenously.

Depending on the actual dosage, gastrointestinal discomfort has been reported by subjects. This might involve vomiting, stomach cramps or diahorrea. Tissue sampling has been variously by blood sample or muscle biopsy or both. Varying exercise intensities have been used (normally related to % VO2 max) over varying work times and recovery periods. Swimming, cycling, running all feature in the exercise modes, which have included some, field-tests. Time to exhaustion, average power output over 30-120s, timed performances and perceived rate of exhaustion (RPE) have been the variables tested. Early studies were encouraged by observations that serum pH values at rest were increased after bicarbonate was administered and it is thought that the elevated serum pH facilitated the efflux of lactate from muscle. Williams (1992) suggests this to be "universally accepted".

Williams (1992) goes on to cite several studies that indicate inconsistent effects on VO2/VE from those that observed no changes to Cho et al (1990) who reported rises in VO2 max in trained cyclists. However, the main focus of attention has been in anaerobic type activities.

Several studies appear to report positive effects on the psychological perception of effort (RPE). Robertson et al (1987) used arm and leg exercise at 80% VO2 max and found reductions in RPE but at 20-60% VO2 max little/no change occurred. Later Swank and Robertson (1989) reported lower RPE values in repeated 5-min exercise bouts at 90% VO2 max with 10-min rest periods. This was attributed to blood alkalinity increasing and bicarbonate supplementation.

Laboratory studies involving maximal single exercise bouts of 30s - 10-min+ with short recovery periods have found that supplementation has not been effective in work periods around 30s. Speculation has been that PCr also acts as a buffer in these periods or that the time scale was too short for bicarbonate to have a positive impact on H+ efflux (Costill et al 1984). Lavender and Bird (1989) reported greater power outputs in repeated maximal cycle tests in 8 of 10 x 10s sprints. The greater differences being observed in the latter sprints (presumably when lactate accumulation was at it's greatest).

It would appear that repeated exercise bouts with some recovery periods offer the greatest opportunity for benefits from bicarbonate supplementation. McKenzie et al (1986) found that does of 0.15g/kg body weight (BW) and 0.30g/kg BW had a beneficial effect on time taken to exhaustion and total work possible in a test involving 6 x 1 min cycle sprints at 125% VO2 max with 1 min rest periods where the final work period was to exhaustion. Costill et al (1984) used a 0.2g/kg BW dose and reported a 42% increase in time to exhaustion in a similar test involving 5 x 1 min work periods with the final one being to exhaustion. Fox, Bowers and Foss (1994) report on several studies showing treadmill running to exhaustion times increasing from 4.5 min to 7.3 min and an 800m run study cutting almost 3s off the final time.

Field studies appear to support experimental research when using trained athletes. Simmonds and Hardt (1973), Gao et al (1988), Cho et al (1990), Wilkes et al (1983) and Goldfinch et al (1988) all reported improved performances in timed swims, 400-800m runs and cycle performances.

Practical applications
Bicarbonate loading/supplementation is not at present an illegal doping activity as described by the IOC or Sport England (the reader is recommended to inquire about its' status with Governing Body's before consideration). However, it may cause some gastrointestinal discomfort as described and prolonged use may cause severe alkalosis and other side effects such as apathy, irritability, cardiac arrhythmia's and more severe gastrointestinal problems. The dosage required (0.2g-0.3g/kg BW) may cause the user some difficulties and large amounts of fluid may be needed to aid ingestion (a 90kg man would need a dose of 18-27g according to most studies). .."

(©2000-2001 Blackrock Karate Club)

So as you can see, the practical application of this technique to free diving is in preventing acidosis and this in turn MIGHT improve apnea times. If some experienced divers try it, it would be very helpful if they share their experiences with the rest of us.

Thanks in advance.


PD (there are at least 9 more techniques, much more --hopefully-- effective than this one).
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Hi Gabriel,

I have read that before about the tests done with cycling sprints. The main advantage with Bicarb loading is that it delays the build up of lactic acid. I read that you would actually fail a doping test because it changes your blood PH to outside allowable limits.

I can't see how it would help in any way to hold your breath longer, especially for a static. It might possibly help for a dynamic or depth dive to reduce lactic acid build up.

But, I've seen a discussion before on this forum about changing blood PH, can have both positive and negative effects on breath hold time. Think Eric Fattah has already done quite a bit of research on the subject.

It's possible that it does help and maybe some people are already doing this, who knows.

I was going to try it out myself but not sure how safe it is. Took Bicarb once before exercise and it makes you burb big time ! :D
Tastes really salty.

Not a good idea

Bicarbonate loading doesn't help, because it inhibits the bohr effect. You need acidic blood to stay conscious; the O2 affinity of hemoglobin decreases with increasing blood acidity, and that keeps you conscious. If you artificially alkalinize your blood by either electrolyte drinks or hyperventilation, then you make your blood too alkaline to maintain consciousness. It is true that both bicarbonate/citrate and hyperventilation make holding your breath EASIER, but in the end you will black out SOONER than if you left your body alone. However, beginners who do not have the willpower to hold their breath to the point of blackout will always benefit from those techniques because they are not reaching a level of hypoxia where blood acidity is important.

As an example, if you decrease the O2 fraction in air, the blood remains alkaline (no CO2 build up), but you blackout around SaO2 = 55-70%. However, in the presence of CO2 build up, some freedivers get down below SaO2 = 20% without loss of consciousness or motor control; why? Only because the acidity is keeping them conscious.

Martin Stepanek does not hyperventilate for his world record level statics. He gets contractions around 4:00 - 4:30 and forces himself through 4 or more minutes of contractions. His ability to resist the huge CO2 is what keeps him conscious.

Eric Fattah
BC, Canada

that's very interesting what you have just said. Actually goes against discussions I've had with people about ventilating more to delay contractions, which can take extra energy, and getting longer times.

So your saying if you can tolerate the earlier contractions you get with a shorter breath up, it's possible to push longer without a blackout ?

I always thought there is also a chance of blackout from Hypercapnia - too much CO2 ?
Or does this depend greatly on the persons tolerance for high CO2 levels ?

Does the same principle aply for dynamics & depth dives ?

Re: Not a good idea

Originally posted by efattah
Martin Stepanek does not hyperventilate for his world record level statics. He gets contractions around 4:00 - 4:30 and forces himself through 4 or more minutes of contractions. His ability to resist the huge CO2 is what keeps him conscious.

...and, is this result from hard and long IHT-kind training, or more like something else?

2nd Technique

2nd Technique

Thank you very much for your response guys. They have been very enriching. I have one question for you Eric ¿Would artificially induced acidification of the blood help hold breath longer? (for example trough an Atkins type of diet). After Eric’s rebuttal we can forget about technique number 1.

Here is the second technique (FOR EXPERT DIVERS ONLY WHO KNOW THEIR LIMITS):


The idea is to load up on substances with oxygen sparing effect, either just before the competition, or on a regular basis. There are a lot of substances with this kind of effect so I will just mention the ones that seem safer.

1.- Vitamin E. It is an antioxidant. Recent research indicates that Vitamin E can prolong life by protecting us from the ravages of free radicals. Vitamin E also appears to have an "oxygen sparing" effect; meaning it helps organisms get by with less oxygen than is normally required. Vitamin E has also been shown to be an effective vasodilator. The antioxidant and neuroprotective properties of this substance make it (maybe) particularly useful for apnea performance. 3000 units per day (or before a competition) seem to be the right dosage.
2.-Malic Acid. This molecule is a vital component in the energy-producing Krebs cycle and plays many other roles in the body, including the maintenance of proper acid balance and the removal of toxic or undesirable metals by chelation. This process can be understood as the removal of excess calcium and other minerals that promote plaque formation, blood clotting, and atherosclerosis. Malic acid also has an oxygen-sparing effect (the ability to lower cellular oxygen consumption without affecting availability), and there are a number of indications that it is critical in controlling mitochondrial function in our cells. Malic acid also ATP and energy related factors. ATP is the universal energy source for the body (Adenosine Triphosphate) and is also the substance which stores energy that is created when the body burns carbohydrates and fats in the citric acid cycle. When energy is needed by the body (as, for example, in muscular contraction), ATP is broken down to release the stored energy. ATP is the universal energy molecule for the body in the same way that electricity is the universal energy source for a computer.

Requirement Conditions Postulated to Cause ATP Deficiency
Oxygen Hypoxia
Malate Deficiency
Magnesium Deficiency
Excess Aluminum
Excess Calcium
Substrate Severe Malnutrition
ADP Phosphate Deficiency
Inorganic Phosphate Magnesium Deficiency

3.- Magnesium. It enhances ATP and Related Energy Factors. The capacity of thiamine, riboflavin and pyridoxine are essential for the electron Respiratory Chain transport system in the respiratory chain. All three vitamins require magnesium dependent phosphate transfer reaction to become biologically active.
Mitochondrial Membrane Integrity Magnesium deficiency causes mitochondrial swelling, increases membrane permeability and uncoupling of oxidative phosphorylation.
A total daily dosage of 300-600 mg. of elemental magnesium and 1200-1400 mg. of malic acid are recommended for hypoxia resistance.

Researchers now believe that FM and related symptoms may be a result of deficiencies of substances needed for ATP synthesis. Synthesis of proteins, fats and carbohydrates necessary for cellular integrity, normal activity and function is dependent on ATP availability which supplies the energy for their synthesis and actions.
The synthesis of ATP by intact respiring mitochondria requires the presence of oxygen, magnesium, substrate, ADP and inorganic phosphate. The ingredients required for ATP synthesis are listed in the table on the left, together with some conditions which may cause a deficiency of each of these.(2)
Magnesium and Malic Acid Essential in Aerobic and Anaerobic Reactions Necessary for ATP Synthesis. They are also essential in both aerobic and anaerobic reactions necessary for the production of ATP. Both substances combined have a synergistic oxygen sparing effect.

4.- Organic Germanium. It is a metal-like element that is found in the soil and in several plants. Even as a trace mineral, most researchers did not recognize germanium as having great therapeutic benefit. In 1967, however, Dr. Kazukiho Asai, a brilliant Japanese chemist, created a new compound of germanium. This compound known as germanium sesquioxide (Ge-132), or simply as organic germanium, was found to have amazing curative capabilities. Organic germanium is most commonly used to aid the immune system and to improve oxygen flow to tissues. Research supports several clinical uses for Ge-132. Generally speaking, Ge-132 has been found to support the natural capabilities of the immune system. Studies have shown that organic germanium can restore normal function in the immune system. It is believed that organic germanium stimulates components of the immune system, such as interferon, macrophages, T-cells, and natural killer cells. These immune-supporting effects have been demonstrated in anti-tumor activity, for example. In addition, it may also combat viral infections, AIDS, and chronic fatigue. Organic germanium appears to act as a general tonic, balancing bodily functions; thus it can be utilized as both a preventative measure and to aid in the treatment of various conditions like allergies, rheumatoid arthritis, and cancer. It also has an oxygen sparing effect—it has been shown to lower oxygen requirements. IT IS ALSO VERY DANGEROUS IN HIGH DOSAGES SO ONLY USE THE DOSAGE RECOMMENDED BY THE MANUFACTURER (possible side effect of a mega dosage: DEATH).

5.- Ipriflavone. It has an oxygen sparing effect and affects energetics in a positive manner. Dosage: what the manufacturer recommends.
6.- Perhexiline maleate. It is an anti-angina agent. Its mechanism of action as an anti-angina agent has not been fully elucidated in humans; however, in vitro studies suggest that perhexiline causes inhibition of myocardial fatty acid catabolism (e.g. by inhibition of carnitine palmitoyltransferase-1: CPT-1) with a concomitant increase in glucose utilization and consequent oxygen-sparing effect. This is likely to have two consequences:
(i) increased myocardial efficiency, and
(ii) Decreased potential for impairment of myocardial function during ischemia.
Dosage: what the DOCTOR recommends (good luck trying to find a doctor who will prescribe this for apnea performance improvements).
Well that is about it. Let’s hope this technique survives “Eric’s Razor”. Any comment regarding the technique is most welcome!.

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Keep 'em coming

This is really good input Gabriel! Keep it coming!

I experiment a lot with various supplements/vitamins/minerals, but I don't experiment with drugs. I haven't tried Ipriflavon or perhexiline maleate--are those drugs? If you're interested in using drugs to improve your apnea, I can list a zillion which I have come across in journals (i.e. phenytoin)

Concerning the other substances (vitamin E, malic acid, magnesium, germanium), I have tried them. Unfortunately, when I experiment on myself, I can never make a completely controlled experiment. It can take quite a while for a particular supplement to show a statistical benefit, when I review the journals in which I record all my experiments. As you have shown with your quotes, I believe that the above four agents could help apnea, but magnesium has not helped me, I find that supplementing magnesium without calcium throws off my electrolyte balance. Vitamine E, malic acid, and germanium may show minor effects; certainly vitamin E, when taken in ENORMOUS doses, has shown huge capacity to improve survival rate of rats in extreme hypoxia, but vitamin E is fat soluble and if you take such big doses you'll rapidly accumulate too much in your body, eliminating its usefulness as a 'chronic' aid for apnea. I need to experiment more with Vitamin E/malic acid/germanium (as well as a huge list of others) before I can really comment on whether they help or not; the fact that I can't really tell yet means that the effect can't be that big.

Certain supplements and/or foods have good and bad effects. Take garlic for example. Raw garlic was eaten in excess by the polynesian pearl divers to increase breath-hold times. Does it work? In a sense yes; it increases your capacity to hold your breath, but it also increases the likelihood of a blackout. Garlic has tons of active compounds, including allicin, methyl-allyl-trisulfide, L-arginine, adenosine, and a small amount of organic germanium. It definitely vasodilates all your blood vessels, and it inhibits hypoxia induced pulmonary vasoconstriction. Allicin, L-arginine and methyl-allyl-trisulfide ALL act as vasodilators in different ways, and allicin also acts as an anti-bacterial compound similar to penicillin, hence the old practice of eating garlic to ward off illness. However, the vasodilation effect reduces your blood pressure so much that you tend to black out earlier than before...

In my experiments, there are only a couple of foods/supplements which have shown a massive, instant, repeatable effect. Keep guessing Gabriel; maybe you'll hit them!

Eric Fattah
BC, Canada
Very interesting what gabriel proposes about decreasing your blood PH, does have consecuences though , the more serious being the risk of suffering a B.O witha lower thresold (it´s the hypoxia, not the hypercapnia what causes it, it doesn´t matter if you have a very high blood CO2 content, like Eric Fattah states, you can learn to tolerate it, in fact high PCO2 triggers the drive to breath through brain chemoreceptors, if you hyperventilate or alkalinize blood by other means you alterate thid mechanism).

I do have some suggestions for those of you who are newbies or more advanced freedivers and want to improve your apnea time. The concept is simple, the more efficient your body utilizes its energy sources, the more time you get out of a single breath. these are my recommendations:

1. improve your aerobic metabolism: this means getting in shape. training in the aerobic zone ( swimming, jogging, bycicle, whatever you prefer). mantaining a heart rate between 70 and 85% of your maximun HR for age troughout the workout (220 - age=maximun Hr). for this i recommend using a heart rate monitor to keep track of your hear rate. this trainning improves your bottom time wen doing dynamic apnea. on the long run improves your static as well by decreasing basal heart rate and diminishing oxygen consumption.

2. increase your pulmonary capacity: there are several ways of doing this

a. elasticity: increasing your chest elasticity by doing stretching of rib cage and back
b. step breathing: like they do on yoga and pranayama: diaphragmatic (belly breathing) - thoracic breathing (chest wall) - clavicular. we can discuss this topic in detail if anyone wishes to.
c. PRANAYAMA: orientad style breathing. improves chest compliance and teaches how to proper breathe. very interesting
d. The powerlung and other devices improve chest wall capacity by creating resistance breathing.
e. resistance breathing while swimming or jogging: can be done simply by doing your exercise while breathing through a long, narrow snorkel.

3. anaerobic trainning: improves your tolerance to CO2 build up: doing repetition dives with short intervals of breathing between reps. should be guided and always spotted by someone.

Hope to hear some comments by gabriel, eric or anyone else interested in the subject.

alejandro Jiménez, M.D.
CO2 Blackout

As far as I know, CO2 itself can cause you to blackout. As the PaCO2 goes over 90mmHg, you enter CO2 narcosis; once you enter CO2 narcosis, you have around 2 minutes before you suffer from 'narcolepsy', or spontaneous falling asleep/loss of consciousness.

The most striking example of this was during the Duke study when subjects would inhale pure oxygen, then hold their breath and bike on a stationary bike. Their oxygen levels were monitored during the test. Some subjects couldn't resist the urge to breathe, but those who could first entered CO2 narcosis, then blacked out, despite having totally safe levels of oxygen dure to the inhalation of pure oxygen.

The question this brings up is one that me and my friends have been struggling with for ages: is CO2 narcosis caused by low blood acidity in general, or is it the CO2 itself? i.e. could lactic acidosis cause narcosis?

This is very important for me since I nearly blacked out from CO2 narcosis during a deep dive last year.

Because blackout from CO2 happens at depth, a safety freediver on the surface cannot help you....

Eric Fattah
BC, Canada

geeze I dont have a clue what you guys are talking about but it was interesting to know that stepanek dosen't hyperventilate and can hold 4 min of contactions, thats amazing I think im going to stop this stomach breathing stuff because it seems to be giving me the effects of hyperventilation, after this post Im going to try some dry statics with only taking 3 deep breaths before hand and see how long I can hold contractions.


ps does anyone know what martin does as a breathe up before statics cos im interested to try his techniques.

Re: Keep 'em coming

Originally posted by efattah
[ In my experiments, there are only a couple of foods/supplements which have shown a massive, instant, repeatable effect. Keep guessing Gabriel; maybe you'll hit them!


For the benefit of us in the great unwashed :) , are you at liberty share these?

Last edited:
reply to eric

interesting the subject of CO2 narcosis. I am not sure if this can happen in a non-controlled enviroment: e.g: without O2 supplementation. Do you have the reference where i can read about the experiment, i am really intersted. thanks for the feedback.
CO2 narcosis

CO2 narcosis can only occur when there is unusual amounts of oxygen available. This occurs either during pure O2 inhalation at atmospheric pressure, or during hyperbaric conditions, for example deep diving.

It is well known among variable-ballast divers that hyperventilating before the deep dive reduces the narcosis. I have confirmed that with my own experiments.

It is known that CO2 amplifies nitrogen narcosis, and it was previously assumed that by hyperventilating, you simply reduced the 'CO2-N2 amplification effect.'

But now, after the Duke study, we see for sure that there is such thing as narcosis induced only by CO2. If you do the math on the CO2 level of a deep constant ballast or variable weight diver, you will find a PaCO2 way over 90mmHg during the worst phase of the dive (around 1/3 the way up the ascent).

I had the Duke study on my old hard drive, but it has since crashed. Someone on the freedivelist has it I think.

Eric Fattah
BC, Canada
CO2 narcocsis happens all the time in scuba diving. It is one of the top arguments against deep air diving.

A friend of mine was teaching a deco class a couple of weeks ago and it hit a student at 150' on an air dive. This is the max depth we dive air to nowdays, I won't talk about what we used to do. The blank stare and mindless kicking gave it away. He got the guy up and it went away. Nothing serious happened, but it was a gentle reminder of why we got away from this type of diving.

Normal narcosis is compounded by the effect of exercise and co2 build up.
As goofy as it might sound, most of the people I dive with use helium in their mixes for most dives below 100'. I did a dive last night to 90' on a 30/30 trimix. It realy helps if you are doing any kind of work underwater.

There have been many cases over the yeears of divers blacking out at depths far shallower than those that Eric Fattah is reaching. Many of these were do to poor perfroming regualtors and too much exertion at depth. Many of these divers also died.

I still fiind it amazing that divers are pushing 300' on a constant ballast dive. There is a LOT of exertion, co2 build-up, and narcosis involved in swimming up from that depth.

My hats off to all those that can do it, or even come somewhat close.:cool:

i mean CO2 narcosis in freediving

I understand the mechanism where CO2 narcosis occurs in deep diving, because you use enriched O2 mixtures, my point is how can you have a BO when deep freediving, where you can say for sure that the cause is CO2 buildup instead of severe hypoxia? can it be a combination of both?

I invite anyone who has any comments on this subject to participate.
Deep Blackouts

The problem is further confounded by the possibility of blacking out at depth from oxygen toxicity. Pipin, Audrey and Stefano Makula have all blacked out (near the bottom) on the sled at 100+m. Because they were on the sled, they were not exerting themselves and producing lots of CO2. So I think we can say quite safely that they blacked out from oxygen toxicity. A freediver who blacks out from CO2 toxicity will likely be diving in physical discipline such as variable, constant, or free immersion. The blackout will likely happen around 1/3 of the way up, when he is the most negative, producing tons of CO2, and yet the pressure is so high that his lungs are still completely collapsed, so the CO2 has nowhere to go except the blood.

When Genoni was attempting 145m on the sled last year, he had a problem with the lift mechanism, so he had to pull himself up the line from that depth. He reported extreme narcosis/hallucinations during the ascent, and he was probably just on the edge of a CO2 blackout. He eventually blacked out around 10m from hypoxia.

So, during his descent on the sled, he risked a blackout from O2 toxicity. During the first 1/3rd of the ascent, he risked a blackout from CO2 toxicity. Then, in the last 20m, he risked a blackout from hypoxia (which actually occured).

There are many ways to black out...of course, if you exhale before you go down, there is only one type of blackout that can happen; hypoxia.

Eric Fattah
BC, Canada
Both gases

First I want to clarify that the mix in deep diving is actually hipoxic, not enriched.
I agree with Eric that there is many ways for a BO to occur, and hypercapnia is one of them.
Hypercapnia does cause unconsciousness, by the way it was used in 1928, by Leake, as anaesthesic agent in humans, but it produces too many convulsions.
It's narcotis effects probably is due to the alteration in the intracellular pH, because the narcotic effects correlated better with the cerebrospinal fluid pH, than with the pCO2.
Hypercapnia also causes vasoconstriction in the pulmonary circulation, an as Eric said the lung volume is reduced, so is very difficult to wash out the CO2 from blood.
Hypercapnia also has effects in myocardial contractility, heart rate and arrhytmias threshold. In isolated preparations of heart muscle the high pCO2 produce diminished heart rate and contractility, but in intact subjects (not freedivers) the cathecholamines production overshadow this effect. The study from Ferrigno in the Maiorca family showed a diminished Cardiac Output during deep freediving. Maybe the training and mental focus avoid a high adrenalin production in us. But the low cardiac output is another risk for BO, and if we count the cardiac arrhytmias the risk increases.
Another issue is that high pCO2 displaces O2, the N2 content also can contribute to the narcosis in freedivers.
We have to remember that the BO is not only and Hyperoxic or Hypoxic problem. We have to balance O2, CO2 and N2 in the inmersion.
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