Does "shallow water blackout" really exist?

[snorklebum]

Sorry, but I still a lot of trouble with the idea that you are at more risk in a pool than in deep ocean.
After reviewing this stuff, I am pretty much deciding there are individual propensities to blacking out. This might explain why hundreds of people never come close to it and others report several episode.
This is not all that unlikely. I learned during my law enforcement career that some people are a LOT more susceptible to losing consciousness when a "sleeper hold" is applied to them (carotid artery restricted) than others are. There is quite a bit of research that indicates black males are more sucseptible than either white or asian males.
So, I guess the thing to do is find out if this is a problem for you and if so be extra careful. Nothing I've read here makes me worry about having such an episode after all these years and I have still not found any UWH players who consider it a serious theat.
Thanks again or all this information, it'sbeen interesting in many ways.

 

[Tom Lightfoot]

I don't think you get it yet. This isn't about individual propensities or UWH players vs freedivers. Any one individual is more likely to blackout doing breath-hold or dynamic in a pool than he or she is to blackout playing underwater hockey or probably even deep diving.

With underwater hockey the risk is mitigated by the fact that the player starts every dive without the chance to hyperventilate. The urge to breathe comes early and hard and forces the player to return to the surface before any problem occurs.

With deep freediving the risk is mitigated by common sense. (usually) It's psychological, NOT physiological. Everyone knows that deep freediving is dangerous. The natural respect for the activity causes most people to progress incrementally and conservatively.

To summarize, the urge to breathe will save you in underwater hockey and fear will save you deep freediving. Practicing breath-hold or static (even without hyperventilation) reduces both of those factors without significantly reducing the risk.

I don't have any hard statistics but just thinking back now of incidents I know of in Canada, pool related sambas and blackouts outnumber ocean related sambas and blackouts by a ratio of 4:1.

Snorkelbum, I hope that you never do have one of these incidents but until you do, you'll just have to trust me on this.

Tom

 

[laminar]

Snorklebum,

I agree with Tom and have witnessed most of the blackouts and sambas he's talking about.

Tom and I have both saved Eric Fattah's life after a surface blackout from a deep dive. It can happen to anyone. I have been lucky so far, you might say, but another way of looking at it is prevention.

If you really want to see if blackout in a pool is possible, go to a pool, with a buddy (!) and some EMTs on hand and hold your breath on the surface until the earth goes black, you blow all your air and your buddy has to pull you out because you've gone limp. Hopefully, you will have a video camera to record the event, because you will feel disoriented and most likely be in denial of what happened (as most people are when they suffer a blackout or samba).

Really, though, I'm not asking you to black yourself out, but since you have questioned the opinions and information from people like Cliff and others who haven't experienced a blackout themselves (and me, I guess), why do you continue to play devil's advocate with those who have experienced it or have seen it first hand when you haven't either? I think the reason many of us feel so passionate about this discussion is that to deny the risk of blackout is dangerous to many of the people getting into the sport. If they hear that SWB, sambas and other risks are questioned, then they are most likely to ignore the risks. Most freedivers know of someone else who has died while practicing static apnea alone in a pool. On these message boards I have seen many posts by newcomers to the sport who are starting out alone without proper safety knowledge to keep safe. It scares me because it is an exciting sport and it is easy to get caught up in it. And it's a fine line between pushing your static time and coming up clean and losing control of your muscles and being unable to take your face from the water.... Think especially of all the young kids in their late teens who want to progress (a few of them are on this discussion board) and hold their breath like Umberto, Loic, Martin, etc.... Freediving has a huge challenge if we want it to be a sport that's accepted and supported by the public (unless there are some who like it ro remain a dangerous sport for crazy people). Snorklebum, I'd appreciate your thoughts on this issue of freediving safety.

I'd say the best thing for you to do is attend a competition where people are pushing themselves in the pool and you're likely to witness a samba or a blackout on the surface.

Peter
Vancouver, BC

 

[Thom]

It's threads like this that make me glad I stopped practicing static in the bath (alone!). Even though I never pushed myself 100%, the risks were just too high...

 

[Cliff Etzel]

Follwup on this thread...

What follows is taken from the PADI encyclopedia of recreational
diving 2nd ed, page 2-14:

"Shallow-water blackout gets it name because it occurs on ascent as the diver nears the surface. Dues to the remaining low carbon-dioxide level, there is no stimulus to breathe. Without this stimulus, the diver remains underwater using far more oxygen than he would on a normal breath-hold dive. the divers body depletes the oxygen supply but the increased partial pressure of oxygen at depth in the alveoli allows hemoglobin to continue consuming oxygen even after dropping below a level that would cause unconciousness at the surface.

When the diver ascends, the oxygen partial-pressure in the lungs falls rapidly, so the hemoglobin can no longer bond with oxygen and supply the body. Consequently, hypoxia results instantly, and the diver blacks out without warning."

Seems pretty cut and dry for me...

 

[Peter Sheard]

Shallow Water Blackouts . . .

Hi Guys;

It's reassuring to see that the topics I have written about in the past have actually anticipated questions that exist in the freediving community.

Part of the problem with discussion of SHALLOW WATER BLACKOUT is that it is based on a misnomer. SWB is NOT what is described by the PADI Encyclopedia of blah, blah, blah! PADI is simply buying into the popular misconception of what SWB is. What they are describing has been reported in the scientific literature for decades as ASCENT BLACKOUT.

SWB, in its original definition, is totally irrelevant to the world of under water hockey as it was first used to describe instances of quite sudden blackout in military closed circuit divers.

For the UWH crowd the major concern is BREATH HOLD BLACKOUT.

For a brief history, and physiology, of the three different blackout scenarios as accepted in the scientific literature, please refer to:

Sheard, Peter (2001) Blackout: What's in a name? Freediver 12: 18-19. ISSN 1466-089X

I will close by adding the definitions included at the end of that article:

SHALLOW WATER BLACKOUT -- a state of unconsciousness preceded by carbon dioxide retention; usually associated with the use of underwater breathing apparatus.

BREATH-HOLD BLACKOUT -- a state of unconsciousness preceded by the gradual onset of hypoxia; risk is compounded by hyperventilation or increased (shallow) underwater activity.

ASCENT BLACKOUT -- a state of unconsciousness preceded by sudden onset of hypoxia during ascent; risk is compounded by hyperventilation or increased (shallow) underwater activity.

I hope that clears the decks for a more agreeable discussion with a better understanding and a common vocabulary.

Cheers,
Pete

 

[Cliff Etzel]

Thanks Peter on giving clarification on this. Unfortunately, what literature that is out there many times is taken for gospel - hence my Reference to PADI's encyclopedia was an attempt to find valid documentation on this topic

Nice to see someone who can put this to rest(?)

 

[Tom Lightfoot]

Thanks Peter!

Thank you, Peter, thank you. When I read the definition of those three terms I felt like the clouds had just parted.

Tom

 

[snorklebum]

Cliff, thanks for that reference. Which confirms the impression I am getting here, that SWB has to do with returning from depths, a difference in pressure--it says nothing about shallow diving.

Tom, I'm not sure you get it, actually. You say this has nothing to do with individual propensity, but you have no way of knowing that. Barring the confusion of terms here (some calling SWB the technical stuff from cliff's reference, some holding breath in pool, some seem to think you're in danger anytime you're in shallow water) I'd say that if there IS an idividual propensity for blackouts (and similar breathing weirdness is commonly documeted in medicine) it would behoove us to think in that direction and to know whethere or not we are more liable to have it. To just "write off" that possibility seems dangerous and irresponsible to me, actually. And the dismissal of the concept doesn't seem to be basedon any reason, research or even giving it a thought.
To me it explains a lot of the inconsistencies that prompted my question in the first place and I don't think it's something that should be ignored. I just don't think thre are enough hard finding in this field to justify the force of some of these opinions.
One thing I would definiely say: If you've had a blackout or several, you should assume that you get them and be extremely careful, maybe talk to a Doc about it.

 

[hydro]

Come on Snorkelbum, this has gone far enough. SWB is not a medical condition. It sounds like you still think some people just don't black out obviously putting yourself first in that category.
It is not rocket science, ANYONE can black out given the circumstances.

Hydro

 

[Cliff Etzel]

Let's keep it civil guys...

Although much of what Snorkelbum has been asking seems annoying, it has led to some very interesting information that all of us have benefited from.

Each of us has to find out for ourselves the who, what, when, where, why and how of freediving and things happen the way they do.

But I do agree that this has been beat to death. Let's now dive deeper (pun intended) and understand even more about this very important topic that can affect all of us who participate in the awesome and extreme sport of freediving!

 

[laminar]

Well, Snorklebum, let's ask an expert.

Peter Sheard, what is the (or is there a ) technical, physiological difference between a blackout from a dynamic or static apnea within 0-4m from the surface and a blackout from a deeper dive deeper than say 10m (ascent blackout)? What are the factors that increase the risk of each?

My assumption is that ascent blackout is from the partial pressure differential and that a surface blackout is just plain O2 deficiency and/or CO2 accumulation.

I still believe, Snorklebum, that whatever kind of blackout you call it, whether it be "shallow water," "ascent" "hypocapnia," "surface" or "jeez, I dunno what happened" blackout, that the risk of blackout is something all freedivers should watch out for, whatever the depth and whatever the activity. Whether or not you believe that is your prerogative, but I know that when I invite new people into the sport of freediving, I let them know the risks as I understand them and always err on the side of being overly cautious. It's pretty simple for me: If you push yourself in any underwater environment on a breath-hold, you put yourself at risk.

You may be right about some people being more susceptible to blacking out than others, but that doesn't lessen YOUR risk of blacking out. Especially if you believe that since it has never happened to you that it never will (if you're pushing yourself).

Pete (laminar)

 

[Peter Sheard]

Shallow Water Blackout?!?

Hello Again;

In response to "Laminar Pete's" direct query re: Shallow water blackouts I will forward the two (brief) more-or-less-relevant articles I have written for Freediver (UK) Magazine for Stephan to post on DeeperBlue.

Cheers,
Pete

P.S. Subscribe to Freediver (UK) and get great freediving info 'hot off the press!' www.freediver.co.uk

 

[Stephan Whelan]

On its way

I've received the articles and are just going through the editorial process with them - they should be up on the site later today (Friday).

I have to back Peter when he says that you should subscribe to Freediver (UK) at http://www.freediver.co.uk - whilst they are a competitor (in some shape or form) they are also an awesome print magazine for Freedivers...Peter appears regularly in there as well.

 

[snorklebum]

Thanks again for all the help on this.

 

[Cabo Kid]

This is the one that caused me to register.
I don't see what's so "annoying" about the questions being asked here. I can see what Snorkelbum is getting at, and can't udnerstand why everybody is getting mad or putting their head in the sand over this. If this is something certain people are prone to, it would be good to know about it.
Here's another thought that came to me about this: what if you are blacking out because you are doing it wrong? What if there are techniques needed to prevent this from happening. Wouldn't that be worth knowing something about? That would make more sense to me than this "Don't dare go in the water without holding somebody's hand" stuff.
The prevailing attitude here reminds me of cavemen cowering in a cave discussing lightning or sabertooths. Random events that kill a guy, nothing you have any control over.
Is there ANYBODY out there who has any opinion or information about being able to prevent this SWB stuff?

 

[Cliff Etzel]

Here we go again...

Have you read any of the previous posts???

This isn't about not giving specific information or that somehow we are with holding information. There are certain things one can do to reduce the chance of SWB - and they have been discussed in the previous posts.

To summarize:

1. Don't dive until the urge to breathe
2. Give yourself at least 5 minutes of surface interval to recover from your previous dive
3. Do not dive if you are overly tired or have been drinking the night before
4. Make sure that you dive within your limits
5. Always dive with a buddy if you know that you'll be pushing your limits
6. Never train without a spotter or partner when attempting a skill or depth that you have never tried before
7. Know when to say when
   [/list=1]
   
   These simple steps can reduce your chances of SWB - but there is no guarantee that it still won't happen.

 

[cjborgert]

Reply to Cabo

I agree with you that Snorkelbum has asked some valid questions. I think he is right that sometimes the impression is given the blackout is totally unpredictable and can occur if you even get too close to running tapwater. However, I also think others have made valid points about the seriousness of ascent or breath-hold blackout, and the passion of their replies stems much less from a cretan mentality than from having lost friends to blackout.

You asked the key questions though - is there any information out there to:
1) identify sensitive individuals
2) prevent blackout

There are actually some very good sources of information. For example, Terry Maas' books have good information (Freedive!, a popular book of basic information about freediving, and Blue Water Hunting and Freediving) about blackout, who is most often victim; how to make sure you aren't, etc. I'd start there, and I've seen those books recommended by others as well.

Unfortunately, there is not a physiological exam or DNA test that will identify sensitive individuals. Despite the much-heralded human genome project, I seriously doubt that we will ever find the "SWB gene." That does not mean we can't identify some folks that are more likely to black out, or that we don't know how to prevent blackout . . . and it doesn't mean having your mom there every time you dive.

Blackout can happen to anyone, if he exceeds his physiological limits for oxygen levels in the blood, period. Regardless of the condition that helps to provoke it - hyperventilation; ascent - blackout WILL occur if there is too little oxygen in the blood to support consciousness. No one is immune (although those with the least brain tissue and highest hemoglobin count may require the longest to succumb). Everyone has a limit. Some folks know their limits and pay close attention to them; others get sidetracked.

Sensitive individuals are intermediate level fdivers; then experts. Intermediate fdivers because they are increasing their capacity and do not always know when to say when. Experts may know their own limits better, but often are very goal oriented and ignore physiology for the sake of achievement. Beginners, fortunately, are usually too scared to push far enough to black out.

How to prevent; pay close attention to your limits and don't push it . . . don't even come close to pushing it. A dive buddy is a good idea for a lot of reasons, but if you never push your limits, you won't ever need him to bail you out of a black out.

It is not true that your limits change every day and so prevent you knowing how much you can do, but it is true that some of your capacity for breath-hold can be taken up by other things besides your dive - dehydration, insufficient sleep, anxiety, etc. If you can learn to pay sufficiently close attention to your body, you'll know where you are on your own capacity scale and not exceed your limits.

It is really that simple. The tough part is knowing your body well enough to know where you are on that scale each day, and as you become more comfortable with being underwater, to continue to pay close attention to your body and be sufficiently cautious about your down times and exertion levels during breath hold. I think people with experience generally agree that it is damn difficult to know exactly how close to your own limit you are each day. Personally, I prefer to dive with a buddy if I want to try anything remotely strenous . . . I'd rather not gamble on how attuned I am to my physiology every day.

 

[Cliff Etzel]

What I was trying to say...

but didn't put it in such eloquent and specific terms...

I am now getting on my soap box to express my views on this and other matters:

This topic hits at the very issue of why I feel that some level of certification for freediving is important.

There will be those who feel that they shouldn't have to get a cert card to freedive. You don't need one to snorkel, why should you for freediving?.

But snorkelers don't do what we do when we freedive. We try and push our limits - to find out who we truly are - in a sense.

Physiologically, we do more to our bodies than tank divers do. Also, many of the same principles of diving physics and physiology apply to both tank and freediving.

By participating in a sport with only a little bit of information makes that participant a danger to themselves.

I adhere to the notion of taking personal responsibility for ones own actions and decisions, but when one does so at the expense of others involved (leaving family behind because you were only thinking about yourself), I become quite annoyed.

Self centeredness as an excuse to prove that you somehow are better than anyone else because of an unhealthy self esteem (which is why many do things that get them killed in the first place) is a mind set that needs to be addressed.

I have kept quiet about many of these threads due to my wanting to get a better understanding of what was being asked.

But I feel I can no longer in good conscience do so.

There has been made available so much information regarding the sport of freediving over the last few years that anyone can obtain the necessary rudimentary information needed to understand the sport more fully - either through books or the internet.

People like Terry Mass, Peppo Biscarini, Kirk Krack and others like them are to be commended for the amount of research they have done to make much of the information available about our sport.

To not do something as simple as type in a search phrase in one of the search engines to gather information on the sport is, in my opinion just plain wrong - and lazy. I typed in the term "Shallow Water Blackout" and got back a total of 2,530 references on Google.com.

I step down from my soapbox for now...

as a closing statement - I am usually an easy going person, one who isn't typically prone to venting as I did above.

But I have also been in teaching sessions while interning for my divemaster cert and felt that, even in that setting, not enough information was being presented - at the expense to meet class quotas for a specific tank diving cert agency. I, as a result, was not willing to take responsibilty for these new students who were being pumped through in 4 weeks so that they could go diving legally. I stopped my divemaster at that point.

It is a catch 22 world we live in...

 

[cjborgert]

getting to politics

Cliff,
I really do agree with much of what you say, which is why I posted my "reply to Cabo." I agree that having more readily available and more affordable training in freediving would benefit everyone. We need more of the "YMCA" level courses for beginners (not promoting the Y, but that style of course) and we need to help organizations who could sponsor such courses ensure that their instructors are well trained and knowledgable. In fact, instructor certification might be a very good idea.

But, I shudder at the notion of requiring a certification in order to freedive! This is really going over the top in terms of removing personal freedom for the sake of "protecting the populace." You really have to take a liberal view of personal actions in order to project the risks of freediving to those who are simply related to the diver. This isn't like driving drunk. I cannot see how freediving imperils people other than the freediver, and perhaps his diving buddy (but you choose your buddy too, just like you choose with whom you ride in a car).

Who would police the waters for uncertified free divers? How would we determine whether someone is just snorkeling or is really "freediving." Would it be on the basis of length of submersion? Or would we be comprehensive and require a license and registration for buying a mask, snorkel and fins? Would there be a three-day cooling off period before you could buy them? How would we punish offenders? Who would be the governing authority? Would it be Kirk Kraack or Pipin, or Cliff Etzel?

This begins to smack of the elitist view that the enlightened should dictate how others live and act. You can get as annoyed as you want about what others do, but I think you have to pull up short of deciding that you have the intelligence and right to decide others' lives for them. What if some of us decide that freediving is of no benefit to society and too risky to be legal. Maybe we should outlaw freediving altogether; then only certified SCUBA would be legal. I'll bet I could drum up support for that one!

I think rather than try to restrict the freedom of people, we should be personally responsible as freedivers, meaning that we should do our best to disseminate accurate information in a reliable way. Perhaps our organizations could collect reliable information, agree upon it by consensus of members and "experts," and then offer it as the view of that organization (keeping in mind the liability issues). Folks would then know that that information has some weight behind it.

I specificially would NOT recommend that someone educate himself by simply punching up terms on an internet search engine. I think that is actually an irresponsible way of finding good information. I rely on electronic information finding for my scientific consulting business and hire professionals to assist me - believe me, the internet is NOT the way to go here. There is no way to determine what is good versus bad information on the internet. People have to remember that the internet is a free-for-all in terms of ideas - bad ideas do not come with a label. There is no "truth-in-information policy" on the internet.

So, I think there is a role here for certification and for freediving organizations to really help the sport. I would be the first in line for a good course if it were affordable and I had some assurance it provided information I don't already have, and I would volunteer time to help organize these things and become a certified instructor. BUT, moving toward restrictions on people is something I would fight tooth and nail. It would be bad for freedivers and ultimately bad for the very sport you are trying to promote.