my shallow water blackout nightmare

[Fondueset]

I agree - I find Lungfish's remarks unnecessarily adversarial and reacting to perceived intentions which do not seem to be present in any of the other posts.

I appreciate very much being able to watch informed disagreement in action but I do not appreciate judgemental bullshit. Lungfish's post is just noise on an otherwise informative and well-intentioned thread. As a novice in the context of this technical discussion I find it dissapointing to see the typical pattern of hostility which characterizes posts by people who are subject to the disinhibition so prevelant in Internet conversations. Deeper Blue is unique in having a very low percentage of these types of posts - which makes Lungfish's stand out all the more.

As I've mentioned - I dive mostly shallow depths. I'm sure given the opportunity I'll go deeper - and grow acusomed to it. But circumstance compells me to go for ease and speed of access at this time. Given my relative inexperience with safety protocols and the fact that I most often dive alone - I just don't push it at all. I figure the safest bet is long, slow breaths - accompanied by deep relaxation, though I do not consider this a guarantee.

When spearfishing, or taking pictures - I think it's important not to get greedy. It's strangely liberating to find myself just going for that extra rare shot and to simply let it go.

 

[Cliff Etzel]

I agree - I find Lungfish's remarks unnecessarily adversarial and reacting to perceived intentions which do not seem to be present in any of the other posts.

I appreciate very much being able to watch informed disagreement in action but I do not appreciate judgemental bullshit. Lungfish's post is just noise on an otherwise informative and well-intentioned thread. As a novice in the context of this technical discussion I find it dissapointing to see the typical pattern of hostility which characterizes posts by people who are subject to the disinhibition so prevelant in Internet conversations. Deeper Blue is unique in having a very low percentage of these types of posts - which makes Lungfish's stand out all the more.

As I've mentioned - I dive mostly shallow depths. I'm sure given the opportunity I'll go deeper - and grow acusomed to it. But circumstance compells me to go for ease and speed of access at this time. Given my relative inexperience with safety protocols and the fact that I most often dive alone - I just don't push it at all. I figure the safest bet is long, slow breaths - accompanied by deep relaxation, though I do not consider this a guarantee.

When spearfishing, or taking pictures - I think it's important not to get greedy. It's strangely liberating to find myself just going for that extra rare shot and to simply let it go.

I agree Fondueset with your position. Your perceptions of freediving are a healthy one and one that instills a healthy respect for the freedive itself. Enjoy the moment for the moment itself. It is a very zen like attitude that alot of DB members share - and one I am glad to share with like minded freedivers...

 

[jimqpublic]

:rcard Calling someone else's remarks judgemental bullshit is ... judgemental bullshit. I started following this thread hoping for some education on avoiding drowning and it turned into namecalling and "Your way is wrong, my way is right, you are unenlightened".:rcard

I'm a new diver and I find those with much more experience than I can't seem to even agree to polite discourse. Too sad.

EDIT: 12 hours later I wish I hadn't come across so strong. Sorry- One thing I learned from PFI was to cut caffeine out of my diet. Makes me cranky in the morning.

Jim

 

[Erik]

Evolution of anything means that we have to admit our mistakes or misconceptions, at least to the point where we're not selling theories that have changed with time and research.
I've had to swallow my pride a few times over the last 10 years or so, especially with the internet. Once you write it down, it's stuck there for eternity, or until WWIII Better to have a retraction printed somewhere too: "In the interest of not killing people with my advice, I retract said statement from 8 years ago (ie: purging 20 times is cool and I will therefore kick Herbert's ass in CW diving) and humbly admit that I am a human involved in the process of evolution"

C'mon back Lungfish- you're a smart guy, you're into the sport, you're passionate, you've got lots to contribute. Nobody's trying to dis you.
Erik Y.

 

[laminar]

It's a shame that Lungfish has abandoned Deeperblue and is not interested in working through this discussion in a more constructive way. We can all learn so much from there discussions.

I find this discussion very relevant to the beginning, recreational or relatively inexperienced freediver. The only way you can decide for yourself what it the best and safest techniques for YOU is by getting into these topics in as much detail as possible. Just taking one person's word for it, no matter what records they've set or how many people they've taught, is just silly. All techniques and safety guidelines evolve (hopefully) and no one can lay claim to knowing the perfect solution.

When I started freediving, the common understanding of what was optimal among all of us at the time in Vancouver, including Kirk Krack and Eric Fattah and everyone else associated with those two people, was that packing was great - no problemo - and that purging was something to do in certain circumstances.

So I started off doing both, purging and packing. I distinctly remember attending an introductory talk with Kirk and Brett LeMaster, in which we all purged for two minutes and attempted a dry static. I made 3'45", sitting in chair, and was amazed. Three weeks later, I did 5'05" in my bedroom. Cool!

But when I started training and learning what worked for me, I found purging very finicky as a preparation for a breath hold, especially in the competitive arena. Purge a little too much, have a hypocapnic blackout, purge a little too little, and feel horrible and underperform. The imprecision of this technique scared me for when I was diving in the ocean. I never used purges while diving because I always wanted to err on the side of having too much CO2. Sticking to this style served me well so far. I've never had a blackout or samba in the ocean. But I'm also cautious by nature.

The same thing happened with packing, although it took a little longer. Packing in the ocean allowed me to equalize deeper and perhaps, hold my breath longer, although, I question that logic these days. It was a quick way to get deep. Eric used it to do his world record (ironically, Umberto has never packed to my knowledge and has been to 98m!). I used it for my competition dive. Simple and effective. But not optimal. The more sustainable method would be to reduce residual volume through specific training techniques and improve mouthfill technique. Over years, not months. This is what I'm doing now.

Packing also had other consequences for me and other divers. I've posted a great deal about lung squeeze and it continues to be something I'm sensitive about in the diving community. I've found that the only way to avoid it (so far) is to make very gradual depth increases and never pack. I dive FRC exclusively now and find it much more enjoyable that the "pack and shove" method. So for me, packing is bad thing to do and while other divers use the technique without injury, I still think that every new diver takes a risk when they learn it. I know a fellow diver who's residual volume increased dramatically after learning the packing technique and now he can almost never dive below 15m without some sort of lung squeeze. There are other divers who have been sidelined by squeeze - packing is always a factor (I know that's not proof), but it sure is suspicious!

So yes both techniques are used successfully by a large number of divers. And yes the same techniques cause problems for a lot of divers, even world record holders, even PFI members.

I guess my philosophy is to choose techniques that are as danger-free as possible, since freediving does have risks.

So to new divers who are trying to sift through all the details of this and other threads, this is what I think it important:

1. Spend lots of time questioning and considering things people say online or in person at clinics. Never stop.
2. Try diving barebones first: no packing, no purging, no special breathe-up. Just relax and enjoy every second of the whole cycle of breathe-dive-breathe.
3. Take more than one course to learn safety protocols and techniques because they are very important. If you can't afford a course, then start a discussion on Deeperblue and with fellow divers to get as much information as possible. Keep updating your knowledge.
4. Learn CPR and First Aid and keep it current.

Pete

 

[Cliff Etzel]

The last thing I want is to come across as egotistical.

I love freediving and share it with whomever I can to raise interest in the sport. We can agree to disagree - agreeably. I may not agree completely with some peoples views, but We all love :inlove freediving and want to see it be as safe an activity as possible...

That was my only intent and I hope I didn't come across otherwise...

 

[Fondueset]

Well, okay, the JB line was a case of 'becoming what you despise' - my bad. I do not think any safety procedures have been torn apart here however - quite the opposite. I liked Lungfish's earlier posts - though they do seem edgy to me - I don't know why. But not much interesting happens without friction

The cool thing about this thread is that most of the participants have a good deal of experience - even if it's not in a petre dish. I don't see it as going for any absolute conclusions.

I'm not sure what 'egotistical' is - though I have heard of it.

 

[Jon]

I don't think anyone on here is try to "scare" new divers out of diving, it's just that they want them to do it in a safe way- that means proper buddy protocal and some sort of training.

Scuba had a huge number of deaths in the beginning, but self-regulated before the government took over and did it for us. Since there are no tanks to fill this can't happen to freediving; howver, with the advent of the internet we can now have access to data, and techniques, that were previously unavailable.

The worry of the people who run this site is that some 15 year old kid will read through a few threads and decide to make his own no-limits sled and try working on his FRC/wet-equalization techniques all at the same time while his 12 year old brother "spots" him from the back of the family boat.:head

I don't think there is any reason to flame anyone on here for their opinions or techniques, but I do think that we should point out any dangers, along with the benefits, associated with them. When I took the PFD clinic Kirk mentioned that he feared someone taking the course and using their new found techniques to surpass their abilities without a buddy around- because that was how they normally dive.

Making sure that you not only have a buddy, but that can actually assist you for the dive your doing is also essential- as has be shown in the past with tragic results.

Here's a few numbers I "borrowed" from the Safety-Vest site to illustrate reason for concern.


COUNTRY SWB DEATHS/YEAR
United States- Continental 3
United States- Hawaii 6
Greece 6
Australia 10
Italy 12
Portugal 3-5
NewZealand 2
SouthAfrica 0-1
France 8-10

(In 2003, 33 French freedivers died fromSWB)

Once again, this thread was not intended to scare someone away from freediving, just to try and instill a healthy respect for it and encourage proper back-up and training before someone gets in over their head.


Jon

 

[jimqpublic]

Now a question on packing.

It has been suggested that a full inhale while in the water wearing a wetsuit is only about 80% of a full inhale on dry land. It seems to me that packing back up to 100% of my normal dry volume would be safe. I understand there's still the question of whether it's efficient (due to time consumed and extra energy burned by raised heartrate from packing).

Is it safe? If not why? Also would strenthening the various breathing muscles let me get to 100% capacity in water/with wetsuit without packing?

Jim

 

[efattah]

Now a question on packing.

It has been suggested that a full inhale while in the water wearing a wetsuit is only about 80% of a full inhale on dry land. It seems to me that packing back up to 100% of my normal dry volume would be safe. I understand there's still the question of whether it's efficient (due to time consumed and extra energy burned by raised heartrate from packing).

Is it safe? If not why? Also would strenthening the various breathing muscles let me get to 100% capacity in water/with wetsuit without packing?

Jim

This is a complicated question. Packing to 'get back up' to your 'normal' lung volume, still poses similar risks.

The increased risk of squeeze and the chance of a vagal packing blackout are both causing by a 'higher than ambient' pressure in the lungs. If the pressure in the lungs is higher than the surrounding tissues, then it exerts pressure on the arteries (possible BO) and it pushes blood away from the lungs (increased risk of squeeze).

If you can't inhale to 100% in the water, it is likely because your chest is somewhat below the surface. By packing 'back up' to 100%, you are increasing the pressure in your lungs to higher than the ambient pressure. When you inhale naturally, you can only inhale up to ambient pressure, a sort of accidental natural safety mechanism.

 

[cdavis]

Support for Erik Y's point, Its very very hard to have a civil argument or express a controversial opinion on the internet without, in all innocence, sounding abrasive, judgemental, arrogant, you pick the negative feeling. I've done more than my share and probably still do, not for lack of trying. Chill everybody and stay around. Lungfish, you have some interesting things to report.

Connor

 

[JustinF]

I feel silly even posting in this tread, but this is the most I have learnt about Freediving since I began looking into it. Thank you to all the contributors! For the sake of other newbies reading this I will post something.

I'm with KMO on this one, I am new and my style is pretty much breath normally and swim around lol. I don;t feel I know enough to do anything else. Sometimes 30seconds into my dive I feel I have to breath so I go up, but I know it's better to at the surface then dead. I am also diving alone, as there are no other freedivers I can find in the country let alone area I am in.

I am looking into take a course right now!

I have only gotten down to about 75ft which is about 25m. Max time underwater is about 1:30. I thought this was very tame, now I am thinking that is way too dangerous.

I dive in the afternoon here and there is usually 1m-3m waves and gentle current.

Opinions?

Saftey first cause dieings the worst!

 

[tylerz]

Ok, so I will keep my opinions to myself.

Why, because we expressed ours? Any opinion of yours is wonderful, added perspective, and should be shared! But this is a discussion forum, therefore any opinion has to be expected to be discussed, and any so-called facts have to be expected to be peer reviewed. Your posts were filled with information that you presented as facts, even though they contained mainly opinion and various inconsistencies towards things that were close to fact. There is no reason to be offended that people feel inclined to clarify things with what is considered to be fact. Some of us who study the topics on our own could detect what was not accepted as fact and what was. The opinions that differed from yours either, stated their differences were opinion but backed them by details and experiences, or presented facts that could be verified.

Considering your post: [ame="http://forums.deeperblue.net/showpost.php?p=598875&postcount=26"]DeeperBlue Forums - View Single Post - my shallow water blackout nightmare[/ame]
whether intended or not, blanket discredited any of our information, then you have to understand that statements as such are distractions and implicitly manipulate those reading the discussion. Pursue the information and it is either credible or not. It doesn't matter who presents the information. Your post ended with a statement that essentially said all the so-called facts you presented were still fact, as though you had addressed the concerns that had been expressed towards your original points.

The problem somewhat seems to be that many of us seem to be distracted by the idea of opinion. Some comments are saying this topic is all about opinion. Sure, there have been various subjective ideas and unproven details passed back and forth. However, many of the arguments that have not been responded to regarding Lungfish's posts are facts and conclusions logically implied by such facts.

Simply stated, one of the arguments that has been going back and forth in this thread, which I am suggesting is not an argument of opinion, but fact is:
"If certain techniques need to be learned correctly, to avoid dangerous consequences, then the mere addition of these techniques implies additional danger, unless they remove to an equally, or greater extent, other elements of danger."

Does anybody see a subjective, arguable, opinion in that? A different topic in this thread has been "the opinion" of what diving practices/combinations of techniques that do add danger, are reasonable. I don't think anybody tried to say Lungfish was incorrect for standing by his approach for himself or others who were willing to employ the same risks. However, identifying those risks for those like SpearoPimp, who wish to comprehend more accurately what they are involved in, and back off to a more cautious, and effective approach, required clarifying the facts involved with any recommendations. Why that has been taken as "egotistical" and unconstructive, boggles my mind!? It is exactly what SpearoPimp asked for... if you are still out there SpearoPimp, have you not found those clarifications to be what you were looking for? Do they strike you as inappropriate fear-mongering?

I haven't seen your names on any relevent research of your own, nor do I see you teaching courses so you are all driven by something other than a desire to help weekender Joe Spearo and his buddies survive.

That is flawed logic. Because you haven't seen our names related to research or courses, we can not be driven by a desire to help people survive in this field? That is an amazingly incorrect statement. Looking through all the threads Lungfish posted in, they were all newbie threads where he responded. I have not seen him involved in discussions of any of the more advanced topics with any of the more advanced and experienced divers and doctors. Since, my first introduction to freediving, I have been gathering and working on a document to present freedivers a thorough overview of all the known dangers that are part of freediving and the various techniques. All novices to freediving who have met me find that I am quickly drawn to presenting the various dangers involved in freediving, in detail far beyond what was presented when I took PFI courses.

So, what is my drive then... got me, if it isn't genuine interest in their safety. Look, many of us meet lots of people interested in freedivomg because of our passion to freedive. Some people teach courses, others work with individuals in their free time. Who is more qualified? Who is driven by a purer motivation? I hope that isn't easy to answer.

By the way, there is publication of research, and then there is research. To be a researcher, does not require you to publish research. To be a teacher, does not require you to publically teach. And interestingly, you have seen many peoples' names on research. Many posts in these discussion forums are the conclusions of research efforts by the posters, who have taken various pieces of scientifically peer-reviewed information and find the meanings of such combinations, and finally present them here. That is why one has to go confirm for themselves the details of what is being presented, to know when something is based in fact and when it is based in opinion. They both have their place but interchanging them causes confusion. As you can see in this thread it allowed the confusion of discrediting people even though the information presented was directly from scientifically peer-reviewed sources.

Lungfish is outahere and www.deeperblue.net can rot.

Why?

I as well second the opinions that you should stick around. Grow, share, learn, and discuss. It is not a personal attack just because people try to point out what is accurate, what isn't, what is opinion, etc. If you voice your words, you obviously have an interest in their contents. If others respond back, then they are assisting your interest. Take it and make the most of it. It is in many, if not most of us that when we think we know something we suddenly feel the urge to make everybody else know it. But to be fair, to be helpful, it is important to check how thoroughly we know what we think we know.

 

[Mullins]

Eric mentioned above that packing "increases CO2 narcosis dramatically"

I've been experiencing significant narcosis at depths that aren't all that great compared to many competition freedivers (70-75m). It hasn't caused problems so far but if it gets much worse it may affect my coordination to the point where I can't grab a tag reliably and/or kick off the bottom without being clumsy and inefficient :crutch

If a beginner was to increase their depths rapidly (as I did) and suddenly run into this problem the effects may be quite serious.

I had assumed it was nitrogen narcosis, but from what I've been reading it may be caused by CO2. Will Trubridge mentioned that using a no-warmup strategy also make the narcosis a lot worse. I do 2 negative statics at 10m before a dive so I guess that's a 'minimal warmup' strategy. A couple of questions:

- roughly what proportion of divers experience significant narcosis?
- how does one know it's CO2 rather than nitrogen narcosis?
- why does packing make it worse?
- why does the no-warmup approach make it worse?


Thanks

 

[efattah]

I've been experiencing significant narcosis at depths that aren't all that great compared to many competition freedivers (70-75m).

- roughly what proportion of divers experience significant narcosis?
- how does one know it's CO2 rather than nitrogen narcosis?
- why does packing make it worse?
- why does the no-warmup approach make it worse?
Thanks

Your experience is very consistent with other divers. In my own experience in exploring the depths, I first experienced weak narcosis on a 57m dive. My first experience with severe narcosis was on a 67m (all these in dark, cold water). By the time I hit 82m the narcosis was extremely severe, and shortly thereafter I nearly died from narcosis on an 88m dive (at 53m on the ascent I forgot what to do, stopped kicking and started sinking again). Diving to 75m in clear, warm water produced about the same narcosis as on a 62-63m dive in cold dark water.

The Duke study on pure O2 apnea showed that narcosis from pure CO2 is possible, and they categorized the symptoms. So we know CO2 narcosis is possible. It is also well established in the scuba community that CO2 worsens N2 narcosis.

The way that most of the community concluded that the narcosis was primarily from CO2 was by a simple experiment: hyperventilation. If you dive to a fixed depth (say 80m) with a gentle breathe-up (high CO2), you'll find the narcosis is bad. Do the same dive with a much more aggressive breathe up (low CO2), and you'll find the narcosis is dramatically reduced (possibly eliminated if the hyperventilation is powerful enough). However, diving after hyperventilation causes premature blackout from the shift in the O2 dissociation curve. On the other hand, by reducing the deep-water narcosis, hyperventilating can drastically reduce the risk of deep-water blackout, at the expense of INCREASING the risk of shallow water blackout. However, if you only have surface safety divers (as most training divers do), then it is better to have a problem near the surface, rather than at the bottom. In the last days that I used to pack, I would deliberately over-breathe to reduce the risk of deep water blackout on 75m+ dives, and then rely on surface safety to take care of a samba.

The more energy that needs to be expended during the dive, the more CO2 is generated. At depth the CO2 has no where to go, since the lungs are collapsed, so the CO2 goes into the blood. If you pack a lot, you need to use more energy to get down, which generates more CO2 during the descent, which means your blood CO2 concentration will be worse at the bottom. If you pack, but just add weight to your belt to compensate for the extra buoyancy, then you will have to kick harder on the ascent, generating more CO2, again with collapsed lungs --> thus narcosis is again increased. To summarize, the greater the buoyancy change, the higher the narcosis on the bottom---it is unavoidable.

Diving without packing produces less buoyancy change, and therefore produces less narcosis. Diving without a wetsuit also reduces buoyancy change, but can increase your cold factor, which can counter the benefit.

Diving with less than a full breath (FRC), produces even less buoyancy change, and therefore even less narcosis --> usually none whatsoever. Since I started FRC diving I have never had narcosis of any kind, and I am very susceptible to narcosis.

On the other hand, in the days I used to pack, even doing 'fun' recreational dives to 40m+, I would get significant narcosis.

Why does the no-warmup method increase narcosis? This is a good question, and I don't think I know the answer for certain, but I can hypothesize. With the no warm-up method, the kidneys don't produce extra bicarbonate to buffer the acid from the warm up dives. So, I would guess you start the dive with less CO2 buffering capacity. Further, if you start the dive with a non-contracted spleen, and the spleen only contracts late in the ascent, then you lose the CO2 buffering capacity of the blood in the spleen, during the narcosis intensive bottom phase of the dive. Further, so-called 'warm-ups' are actually just an excuse to blow off CO2 for most divers. In many cases, the diver improves on each warmup dive not because of adaptations, but because each dive has successively less CO2. This is caused by the fact that the breathe-up for the dive blows off more CO2 than the dive accumulates -- and then the same breathe-up is repeated for the next dive, and then next, resulting in a lower and lower CO2 level for each dive, even with the same breathe up for each dive. Without warmups, this effect doesn't happen, and the body-water remains quite saturated with CO2.

In terms of comparing your experience with other divers, almost every diver I have ever spoken to who has gone to 70m+ has experienced narcosis. Some experience it erratically, some more, some less, but cold, darkness, fear and CO2 seem to be aggravating factors.

The worst effect that narcosis is produces can be the famous 'feeling of impending doom.' It is usually caused by a doubt in the mind on the ascent, which the narcosis amplifies 1000x to a feeling of extreme uncontrollable fear, irrational and without reason. The diver is overwhelmed with the feeling that death is imminent, and there is no hope for survival. I hated that feeling so much that I was willing to adopt any strategy to avoid it.

 

[tylerz]

Mullins, how many dives have you made in that range?

I first experienced Narcosis on a 45m dive, with packing and ventilating. 1 and a half years later I was doing a short stint of training and I had another case of it on a dive around 60m, with packing and ventilating. With each progression after that I seemed to get less severe Narcosis. On a 71m dive, with packing and ventilating, I had no noticeable Narcosis. A month or so ago, on a 60m dive, without packing or ventilating, in very dark conditions, I had another severe case of Narcosis, but had not done a deep dive since the 71m dive, two years earlier. A 50m dive this last weekend, without packing or ventilating, I did not have any Narcosis.

Somewhat, narcosis seems to be offset by training tolerance, but definately I felt cold and darkness were factors as well.

 

[tylerz]

Here is a response to a private message inquiring about finding ones' limit, and taking precautions in a recreational, spearfishing, and/or solo-freediving circumstances. Thought it strongly relates to this thread and continues the interest for newbies in various circumstances:

-------------------------

Originally, before looking into freediving, I just dove without any knowledge and always surfaced after feeling the urge to at the bottom. There was always enough time to make it up, but my depth was limited to 50 feet or less. This worked because without any form of breathup and a fairly ineffective preparation, CO2 would build up significantly before O2 would become low.

Since then, I definately advanced to a degree with my preparation, technique, and tolerances, therefore I had to relearn what constitues a safe dive for myself. I evolved with the introduction of line-diving, and diving with partners. This allowed me to challenge my max depth with the added security of a safety diver prepared for my surfacing. These challenges should only be done with small increments (1-2m) so that even if you push beyond your limit, it will be such a subtle push beyond, that you have a high chance of not having a complete BO. A samba at the surface, an extremely hard recovery, subtle inconsistencies or loss in your memory, and forgetting to recover properly are enough to tell you, under the condition you dove, you have reached your limit.

So, really, I think it is an important process to go through, where one has a partner and pushes their limits in a gradually incrementing fashion with the assistance of a weighted line. A static has nothing to suggest clearly about your max abilities. A dynamic could be a little more telling. But a constant line dive gives the most information in a relatively safe fashion. But if you have not reached the point of at least questioning whether you were on the edge of a samba/LMC, then in my mind you have no clue whether your limit is the next meter deeper or twice as deep.

Once you have seen that limit in constant weight line-diving, then you have to back off considerably when trying to assess a good profile for recreational diving. Recreational diving adds the element of lengthy, or intermittent finning, and much less tendency for blood shifting from the extremities to assist in countering this. You have to compare apples to apples, therefore on each dive, you should be watching yourself at the same time as diving, looking for actions that suggest a considerable change in your oxygen consumption, and noting each occurrence decreasing your intention of how long you will be down for and how deep.

I generally dive for 1-1:30 when alone. Yet, my longest dive has been for ~2:40 to 71m. Therefore cutting that in half you roughly get what I generally dive. When with other divers, I only minimally allow my time to increase to about 1:40-1:50, and that is dependant on how relevant their presence as a safety is, which is something often overlooked by many. Cutting my max time in half is just a guideline though. If I find myself kicking along the bottom and trying to maintain my position in the water column during negative or positive bouyancy, I notice and consider my time decreased. If I initiated my dive with less rest at the surface than general, I decrease my time. If I expelled more energy to reach neutral bouyancy, because of technique, or slowing down to watch something, then I decrease the time. Everything that suggests a change from the base safe recreational dive. Which I would describe my base dive as a dive where I go straight down to depth, 30-40m, immediately in the vicinity of what I am interested in, swimming for 10-20 seconds along the bottom, and then surfacing. The depth is not so important as the time spent in relaxation and whether oxygen conserving physiology is taking place.

If one has not had the opportunity to push their limits in a safe environment, then you have to be extremely cautious. So, the best thing to watch for is what you feel like during your recovery from one of your known deeper dives. If you find you feel quite strained and it takes considerable breathing to bring you back to a good state, then you may well assume your are near your limit, and should back off somewhat. The only problem is in differentiating between oxygen exhaustion and CO2 exhaustion. However, I think in more cases than not, in a recreational environment, they both go hand in hand close enough, that distinguishing between them generally won't change whether the dive was at the safe limit.

Which brings me back to breathe up. I have mentioned to you before that I do not ventilate in a considerable way when I dive alone. The sensation of CO2 really limits me from pushing much more. Which I employ to maintain a safe distance from a low O2 state. However, I am beginning to believe that is only effective if you have performed a significant and effective recovery between dives. Sometimes I find myself being very active at the surface in between dives and yes the CO2 makes me surface, but at the same time I did not necessarily allow for a proper reoxygenation, plus I have encouraged maintaining a high metabolism. Therefore the depletion of O2 will be considerably greater and closer to matching the increasing CO2.

Hope that assists.

 

[Mullins]

Great response, thanks Eric.

Makes sense that C02 buildup is exaggerated simply due to the greater buoyancy change associated with packing.

Deep water blackout (or 'deep water incapacitation', as per your account) sounds very nasty and could well be lethal if it happened to me on a deep dive. I use a lanyard, a 10kg baseplate and have at least 2 competent safety divers on the surface, one of whom comes down to 20m. By the time they knew something was wrong and managed to pull my weight + 10kg up to the surface from the bottom of a 75m line I would be in pretty bad shape (although I would have spent the time 'resting' so maybe those figures aren't quite as bad as they seem at first). Time to start looking at a counterweight system perhaps...

I pack regularly and have found it doesn't change my comfort level in any discipline (STA, DYF/DNF, CWT). I pack because I assume it will lengthen the time before a blackout but that is, as i say, only an assumption as I haven't yet samba'd or blacked out except for one static in competition. My project for the coming dive season may well be to try to match or better my PBs without packing.

One thing - if CO2 concentration in the blood during the dive is greatly increased, wouldn't that be a good thing as far as oxygen conservation is concerned? Big contractions, bad narcosis - but good vasoconstriction, bradycardia etc etc?


Tyler,

I've only done about 15-20 dives past 50m. I had been hoping that more time diving to those depths would offset the effects of narcosis. My depth increases went, as far as I can remember: 52m - 60m - 66m - 70m - 71m - 75m (comp situation, BAD narcosis. Difficult to grab tag, ended up with 2 ). Now, I realise that most coaches out there would be horrified by the size of those jumps. And by the fact that I nominated 4m deeper than my current pb in a comp... however, this was preceded by a lot of pool training - my dynamic pb remains, relatively speaking, greater than my CW pb. Those depths felt so far below my limits that I was completely confident bumping them up by several metres at a time. I'm not claiming that is the best way to progress though - those numbers go largely against what you outlined in that last post and are definitely more of an admission than a suggested approach!

All my dives have been in surface temps between 14-18 degrees, vis between 5-10m. Except for the last one in competition, which was 20 degrees and 30m vis

 

[Fondueset]

The kind of experiential discussion in this thread is really one of the most valuable ways of conveying information - in the broadest possible sense.. A book on freediving consisting entirely of stories and observations by freedivers - with perspectives freely expressed as just what they are would be wonderful and of tremendous value. A comprehensive reference section at the end would be sufficient for sorting out facts and terms.

There need be no big conclusions or unifying hypothesis. The narrative/experiential approach conveys much more useful and 'unpredigested' information than is possible with a more contrived approach and is far more conducive to the development of practical intelligence in the reader - at least in my experience.

Really impressive thread.

 

[efattah]

One thing - if CO2 concentration in the blood during the dive is greatly increased, wouldn't that be a good thing as far as oxygen conservation is concerned? Big contractions, bad narcosis - but good vasoconstriction, bradycardia etc etc?

I agree -- and from my experience, the high CO2 does lower metabolism, and the narcosis even reduces brain O2 consumption. Narcosis acts much like alcohol, affecting the NMDA receptors in your brain (NMDA = N-Methyl-D-Aspartate). By inhibiting the NMDA receptors, the brain activity is slowed down; thinking slows, and brain O2 consumption also slows.