Talk:Deep water blackout

SWB & DWB use of terms

I reverted the fairly major change to the definition of SWB for two reasons:

• 1. it is a significant change and requires some discussion and
• 2. it makes a nonsense of the preceding section.
• 3. (As a side issue Wikipedia provides facts and information it doesn't provide safety advice so the warning should go anyway.)

So I thought we could put it to discussion here. The article acknowledges that there are different usages of the term SWB by different swimming fraternities and then goes on to state that for the purposes of this article... etc. the terms are taken to mean the following... etc. The proposed changes would then have contradicted this and made a nonsense of bith SWB and DWB. If we want to put more weight on the different usages it can be done but it needs to be handled differently. There is a lot of confusion about the use of the terms SWB & DWB and most of it has to do with the evolving use of language. This is not surprising because different swimming interests use the terms to describe different things. The original use of SWB was associated with specific problems arising out of the way WWII closed-circuit rebreathers worked. Since the 1950's US scuba organisations have used the term SWB to describe blackout on ascent from depth. Outside of scuba/freedive use, in the swimming pool fraternity there is a growing use of the term SWB to describe blackouts occuring entirely in shallow water. The distinction between the DWB latent hypoxia and the SWB suppressed beathing reflex is very important to maintain because SWB is now being taught in pool swimming circles as SWB. When I learnt to dive in Australia DWB was associated with problems attributed depth such as nitrogen narcosis, latent hypoxia was just called latent hypoxia and SWB as described in the article SWB was not discussed at all because it was not a scuba related problem, actually we didn't know it existed. The base of the problem is that two groups are using SWB to refer to conficting mechanisms and these need to be accommodated without totally confusing the two articles; we can probably handle that but the solution needs some consensus. Suggestions? Ex nihil 00:43, 30 June 2006 (UTC)

The problem with the definition shallow water black-out is already mentioned in the '60 by the breath-hold diving research Craig. He advised to drop the use of the term Shallow Water Black-out due to its originally definition regarding rebreathers and carbon-dioxide poisoning during the second world war. The alternative he advised was using the term 'ascent black-out' for the black-out due hypoxia caused by the pressure differential and using hypoxic black-out or swimmingpool black-out for the shallower form. The trouble with adopting this, in my vieuw excellent, alternative is that the use of SWB is pretty common in its both definition. What I would advise is to include the term ascent black-out in the article and include the discussion on the definition and the trouble for it. Apneist 11:59, 13 August 2006 (UTC)

Boy, is the article in major need of some expertise! Not you, nihil, as your comments are on target. Or you, Apneist - you're on target, too.

Put simply, shallow water blackout is the result of intentional hyperventilation which reduces the body's CO2 levels and, correspondingly, the blood becomes more alkaline. It's almost always accompanied by significant exertion, which depletes blood O2 levels to less than those required for consciousness, but before sufficient CO2/acidity buildup induces an urge to breath.

In contrast, deep water blackout is the result of a diver depleting O2 levels to sub-conscious levels at the surface, but due to the additional partial pressure added by depth, no blackout occurs until the partial pressure is reduced as the diver ascends towards the surface.

I agree that DWB should be renamed to something having to do with ascent and/or the decreasing partial pressure. My vote would be "partial pressure blackout," as the exact same phenomenon occurs during rapid depressurization in aircraft, which pretty much cuts the time of useful consciousness in half of what it would be if the change in pressure were more gradual. In a similar vein, the other phenomenon resulting from the absense of a breathing reflex would best be termed "hyper-alkalosis blackout" or "respitory alkilosis blackout." The latter is more correct, medically speaking.87.177.42.132 (talk) 18:52, 24 October 2008 (UTC)

Major Rework Needed

I am afraid you completely misunderstood the role of Wikipedia, or encyclopedia in general. Its role is not setting new definitions, but simply documenting the existing ones, regardless if they are logical or not. With this Wiki entry you introduced new definitions that are the exact opposite of what they are generally used in the community, and on my mind that is completely wrong and unacceptable. The definitions used in the current Wiki entry are wrong, and going against the common use of the terms.

In freediving we deal with three basic types of blackout: - plain hypoxic blackout or Static Apnea Blackout - depth plays no role here, it can happen on surface as well as in depth. Hyperventilation is common reason for holding the breath beyond the safe limit. - Shallow Water Blackout - happen usually in shallow water on ascent from a deeper dive (and not unusually even after surfacing), and the reason is usually the combination of the depressurizing effect, hyperventilation with its consequent shift of the Bohr curve, and hence reduced hypoxic tolerance, but there may be also other contributing factors such as additional drop of PaO2 due to exhaling on the ascent, increased O2 consumption due to accelerated kicking, or tilting the head when looking up to the surface and reducing so the blood flow through the carotid arteries to the brain. - Deep Water Blackout - happens at depth before the ascent. The reasons may differ, but it can be also a hypercapnic blackout - in contrary to the cases described above, the excess of CO2.

Also the diagrams used on this page are incorrect, since they completely omit the effect of hyperventilation on the Bohr saturation curve. When hyperventilating, the consequent change blood pH results in change of oxygen affinity of hemoglobin. With less CO2, the oxygen is more strongly bind to hemoglobin, and cannot be discharged in the target tissue, hence the hypoxic tolerance is lower than in normal state, and the blackout happens earlier. It is false to think that the only effect of hyperventilation relevant to blackouts is the suppression of urge to breath.....

APNEA.cz 82.67.60.230 (talk) 11:48, 14 April 2010 (UTC)

Other stuff

• Ex nihil 00:22, 1 March 2006 (UTC) I'm putting in some references but they are all in my library which is not where I am now, so patience please. Feel free to add some 'though. I acknowledge that some scuba divers use the term deep water blackout to refer to blackouts caused by various physiological effects of pressure including nitrogen narcosis and, often poorly understood, neurological pressure related problems. Blackouts for these reasons have proper terminology to describe them each and seperately and I have considered the use of the term deep water blackout as a generic term to describe these as slang or short-hand and too imprecise to use here. It also collides with the term shallow water blackout, which outside of scuba circles seems to be the common term for blackouts occurring in dives confined to shallow water and caused by self-induced hypocapnia. I acknowledge that there is a nomenclature problem here and would welcome comment. I think the problem would be resolved if different water sports groups were a little more rigorous in how these terms were used. I am quite familiar with all the usage because I am a FAUI Divemaster, I indulge in free-diving and I assist my wife who works for a child water safety advocacy group in Australia.

Hi many freedivers are using the term SWB for what is described in this article. I think the note about scuba divers using this terminology should be expanded to both scuba divers and free divers. --hhanke 22:21, 16 June 2006 (UTC) Ex nihil 07:55, 19 June 2006 (UTC) I agree, and I wrote the original. I am a scuba diver, a skin diver and do stuff in pools and shallow water in Northern Territory rockholes. There is a nomenclature problem and it does cause confusion and I'm not sure what to do about it. It is rather unfortunate because there is now a lot of literature connected to pool deaths that use SWB and they need to keep that label. Why don't you just make the change as you describe?

On hypocapnia and acent black-out. In swimmingpools, the main cause of black-out is indeed often caused by hyperventilation. Although hypocapnia before the dive does play an important role in ascent black-out, it is the pressure change and the partial pressure of oxygen that is the main cause and it can also happen without hyperventilation. In Europe, to my knowledge, deep water black-out as describing nitrogen problems is not common used. I would prefer the use of nitrogen narcosis for describing any symptoms caused by the high partial pressure of nitrogen on depth. High oxygen pressures, contamination, but also non-diving related problems as stroke and heart attacks can cuse black-outs at depth. Personally I would believe the term Deep Water Black-out too general for any use in scuba diving since, like its sister shallow water black-out is easy misused and leads to confusing. Again we have the trouble that both deep water black out and shallow water black out is used in general so the only thing I can guess of to do is to explain the situation and let the reader know of the alternatives.Apneist 12:09, 13 August 2006 (UTC)

I believe you are quite correct in everything you say above. We could probably clarify this with a bit of thought. Nitrogen narcosis and other unpleasant things that might afflict people at depth are something separate, perhaps we mention these merely to put them in their proper place and link out, they are really mostly SCUBA things not apnea things. This article is just about latent hypoxia on ascent which may sometimes, but not necessarily, be exacerbated by hyperventilation over-extending bottom time. The rather loose usage of terms by different groups is a problem, it is tempting to impose a discipline of usage and I suppose if we were writing a textbook rather than an encyclopedia article perhaps we could have done that. However, I think that with a bit of thought we could come up with a coordinated form of words for the three articles NNarc, SWB and DWB that satisfies all groups and describes everything with such clarity that the terms would logically fall into place. Why not have a go? Ex nihil 00:09, 15 August 2006 (UTC)

Mechanism could really be clarified for laymen

I had a somewhat difficult time intuitively grasping what the mechanism was for this phoenominon. Compare to the shallow water blackout, which has a very simple and understandable description of the mechanism.

I'm extrapolating a bit from other articles, and I'm a total layman to this stuff. It seems to me that when holding breath, oxygen is absorbed into the bloodstream and (less massive) carbon dioxide fills the lungs, creating lower gaseous pressure (not explained in the article) but that the pressure of the water on the lungs compresses the lungs enough to offset this loss of gaseous pressure (also not really explained in this article) to keep the pressure levels sufficient for conciousness, but then upon rising to the surface, as the lungs expand again due to lower compression from the water, the lung gas density falls below what's necesary to maintain conciousness - hence they black out near the surface. Is that a correct interpretation of the article? In any case, it could definitely be explained more clearly for laymen to understand, as I'm not even sure if I'm reading the correct meaning for it. SenorBeef 12:15, 20 November 2006 (UTC)

Assessment

C class: Insufficient referencing to meet WP:WIABCA. B-class articles generally require at least one reference per section, and ideally at least one reference per paragraph. After making improvements, you may wish to consider the Good Article criteria. WPMED does not currently have a process for approving new A-class articles.

Additionally, this article could easily fall into the scope of more than one WikiProject. The addition of a banner by WP:WikiProject SCUBA might be appropriate (although the choice is ultimately up to their members). WhatamIdoing (talk) 19:24, 2 October 2008 (UTC)

Agreed, and have done so, now that I noticed. I suggest that if you spot any other articles that might be in the scope of WPSCUBA but has not been tagged to leave a note on the project talk page. Could have saved a few years! Cheers,• • • Peter (Southwood) ^(talk): 19:05, 13 January 2017 (UTC)

Wrong link to German Wikipedia

The link points to the German article "Tiefenrausch" but the meaning of this word is "nitrogen narcosis". PadH (talk) 17:58, 19 June 2009 (UTC)

Original work?

Whilst I have no good reason to doubt anything in this well-written article, I have to say that it does not read like an encyclopedia. This really does read like a single person's opinion based on personal research. There is nothing wrong with that in the right context, but an encyclopedia is not the right context. I also see that this has been flagged for five years... Deddly (talk) 14:15, 17 June 2013 (UTC)

• You are right aboutthe refs, but it isn't original work, there are plenty of potential references but they are mostly in books rather than webpages. I shall see if I can quote some. There is an added complication that the scuba diving fraternity tends to use the term to apply to oxygen toxicity and other problems experienced while at depth while the freediving fraternity refers it as it is here, blacking out from a latent oxygen deficiency incurred while at depth but manifested on ascent. Ex nihil ^(talk) 23:02, 17 June 2013 (UTC)

I thought the blackout was due to oxygen diffusing back into the lungs from the blood during ascent, thereby reducing the concentration/ppO2 in the circulation faster than it would be metabolised. We really do need some reliable references for this section. • • • Peter (Southwood) ^(talk): 19:25, 13 January 2017 (UTC)

The section name Possible mechanisms for deep water blackout actually states that the content is speculation. This makes it critically important to specify whose speculation it is, with verifiable references.

The first hypothesis basically suggests that the divers are holding their breath until they pass out. This does not explain a depth effect at all, and does not distinguish it from shallow water blackout in any meaningful way. (interrupted, more later). • • • Peter (Southwood) ^(talk): 17:07, 16 January 2017 (UTC)

Ex nihil, On further consideration I think a merge might solve several problems, see below.• • • Peter (Southwood) ^(talk): 07:53, 24 January 2017 (UTC)

Merge and rename?

I suggest a merge with Shallow water blackout and a rename to Freediving blackout with redirects and disambiguation where applicable.

There appear to be several aspects of blackout associated with freediving, with a significant amount of overlap in when they are likely to occur, and in causative factors, mechanism etc. There are also a wide range of alternative names. The only thing they all have in common, is their association with apnea diving, which suggests that they may be logically combined in one article. At present, the size of the combined article appears likely to be within the preferred range. The existing separate articles are both fairly small, and no articles appear to exist for the other types of blackout.

Redirects would probably include: Shallow water blackout, Deep water blackout, Blackout of ascent, Apnea blackout, Surface blackout, Hypoxic blackout and possibly others.

I have been looking for reliable sources and have so far found the following, some of which may be more reliable than others:

• Pollock, Neal W. (25 April 2014). "Loss of Consciousness in Breath-Holding Swimmers". Fact Sheets, Water Safety. National Drowning Prevention Alliance (NDPA.org). Retrieved 17 January 2017.
• Potkin, Ralph; Cheng, Victor; Siege, Robert (1 September 2007). "Effects of glossopharyngeal insufflation on cardiac function: an echocardiographic study in elite breath-hold divers". Journal of Applied Physiology. 103 (3). American Physiological Society: 823–827. doi:10.1152/japplphysiol.00125.2007. ISSN 1522-1601. Retrieved 17 January 2017.(with 27 refs)
• Johnson, Walter L. (12 April 2015). "Blackout" (PDF). www.freedivingsolutions.com. Retrieved 17 January 2017.
• Staff. "Freediver blackout". Education. Miami, Florida: DiveWise. Retrieved 24 January 2017.
• Etzel, Cliff (18 October 2001). "Rescue procedures for Freediver Blackout". Freediving. DeeperBlue. Retrieved 24 January 2017.
• Staff. "Freedive Safely". Resources. Norcross, Georgia: Shallow water blackout prevention. Retrieved 24 January 2017.
• Lindholm, Peter (2006). Lindholm, P.; Pollock, N. W.; Lundgren, C. E. G. (eds.). "Physiological causes of freediver blackout". Breath-hold diving. Proceedings of the Undersea and Hyperbaric Medical Society/Divers Alert Network 2006 June 20-21 Workshop. Durham, NC: Divers Alert Network. Retrieved 24 January 2017 – via DiveWise. (several references listed)
• Lindholm, P.; Pollock, N. W.; Lundgren, C. E. G., eds. (2006). Breath-hold diving. Proceedings of the Undersea and Hyperbaric Medical Society/Divers Alert Network 2006 June 20-21 Workshop. Durham, NC: Divers Alert Network. ISBN 978-1-930536-36-4 https://www.diversalertnetwork.org/files/UHMS_DAN_2006_Breath-hold_Workshop_Proceedings.pdf. Retrieved 24 January 2017. {{cite conference}}: Cite has empty unknown parameter: |1= (help); Missing or empty |title= (help) Full report (several references listed)
• Maas, Terry; Sipperly, David (1998). "Physiology part I". Freedive!. BlueWater Freedivers. Retrieved 24 January 2017.
• Maas, Terry (1997). "Shallow-water blackout". BlueWater Hunting and Freediving. BlueWater Freedivers.
• Campbell, Ernest (1996). "Free Diving and Shallow Water Blackout". Diving Medicine Online. scuba-doc.com. Retrieved 24 January 2017.
• Scott, Duke (24 October 2005). "Shallow Water Blackout" (PDF). YMCA Scuba Currents Articles. www.aquaticsafetygroup.com. Retrieved 24 January 2017.
• Brothers, Alex. "Shallow water blackout (swb)" (PDF). Swimming Canada. Retrieved 24 January 2017.
• Staff (20 September 2015). "Hypoxic Blackout vs. Shallow Water Blackout". USA Swimming. Retrieved 24 January 2017.
• Staff. "Hypoxic Blackout In Aquatic Activities Is Deadly Serious" (PDF). American Red Cross. Retrieved 24 January 2017. (terminology - Hypoxic vs Shallow water)
• Pearn, John H.; Franklin, Richard C.; Peden, Amy E. (2015). "Hypoxic Blackout: Diagnosis, Risks, and Prevention" (PDF). International Journal of Aquatic Research and Education. 9 (3). Human Kinetics Inc.: 342–347 – via ScholarWorks@BGSU. (with long list of references)
• McCafferty, Marty (Spring 2016). "Hypoxia in Breath-Hold Diving". Alert Diver. Durham, North Carolina: Divers Alert Network. Retrieved 25 January 2017.

Comments and discussion please. • • • Peter (Southwood) ^(talk): 07:20, 17 January 2017 (UTC)

• Support per PBsouthwood rationale--Ozzie10aaaa (talk) 13:28, 24 January 2017 (UTC)
• Support IMO related enough and small enough to justify a merge. Doc James (talk · contribs · email) 01:59, 25 January 2017 (UTC)
• Support I started SWB and DWB, see my comment in Discussion below, happy for it to move on. Ex nihil ^(talk) 02:54, 25 January 2017 (UTC)
• Support I am happy to support this sensible merge.CV9933 (talk) 10:12, 25 January 2017 (UTC)

Discussion

Both articles were created by the same editor Ex nihil at the same time, so I imagine there was a good reason to keep them separate then. Would be useful to get their input. CV9933 (talk) 15:07, 24 January 2017 (UTC)

• I am Ex nihil ^(talk) 02:40, 25 January 2017 (UTC) and I did indeed start both articles. The main reason for the separation was that SWB was the name of an article I wrote for Surf Life Saving Australia after a series of tragic shallow water deaths in swimming pools and Northern Territory natural swimming holes arising from hyperventilation as preparation. I wrote DWB shortly after to avoid confusion between the mechanisms but there was always a bit of tension in the naming as the scuba fraternity talk about DWB under an entirely different mechanism and different circumstances. I am happy to see a merge and deal with it all under one article, just have to sort out the nomenclature but I shall defer to Peter (Southwood) on that; think I'll stay out of it and see what you guys come up with. I wrote both under a bit of a non-Wiki sense of personal mission to stop people killing themselves so could do with a review. The important thing is to differentiate between the shallow water hyperventilation mechanism and the ppO2 drop on ascent mechanism so people understand why they are placing themselves in danger. I appreciate being consulted. Ex nihil ^(talk) 02:54, 25 January 2017 (UTC)
  • Ex nihil, Thanks for your explanation of the history. I would appreciate your further contribution to the discussion and articles as someone who appears to have taken a long-term interest in the broader topic, as well as a significant contributor to both articles and other diving articles. One of the reasons for suggesting the merge is that by having both mechanisms described in the same article, the similarities and differences can be more directly compared, which I think fits in well with your priority of discriminating between the mechanisms. I plan to go ahead with the merge with the acceptance that if it doesn't work, or if at any stage it becomes clear that the subject matter is too much for a single article, it can always be split again. If you know of, or can find, any good sources explaining what happens in the ascent and how it happens, please let me know. I have not yet found anything definitive, and may have to resort to e-mailing some contacts.
  • In particular, are you happy with Freediving blackout as the title? It seems to be fairly popular with some freediving websites as can be seen from the list of possible references above, and clearly distinguishes it from blackouts during scuba (like oxygen hits and hypoxia in rebreathers) or those unrelated to diving. Cheers, • • • Peter (Southwood) ^(talk): 05:43, 25 January 2017 (UTC)
    • That all seems sensible. Let's see how it turns out. I shall follow with interest. Ex nihil ^(talk) 07:41, 25 January 2017 (UTC)

Merged and converted to redirect, then a disambiguation.

The article content was merged into Freediving blackout as discussed, and the title redirected to Freediving blackout, but that did not cover the alternative usage for deep air diving blackout, so I changed it again to a disambiguation page with a short referenced explanation of the alternative meanings and links to the relevant articles. If anyone thinks there is a better way to handle this, please let me know. Cheers, · · · Peter Southwood ^(talk): 07:16, 26 July 2019 (UTC)