Underwater Swim Training- Shallow Water Blackout

[dumpsterDiver]

I totally disagree with Ratliff stated.

I believe that SWB is based on another point of view and I will not go to great depths to explain it but:
Since the number one mechanism that controls the respiratory system (in most people) is the increase in CO2 (hypercapnia). Some people hyperventilate on the surface to "blow" off CO2 thus decreasing their drive to take a breath. Now the second mechanism that controls the respiratory system (again in most people) is the lack of oxygen (hypoxia). Both chemicals are picked up by chemoreceptors in the brain and heart but, these chemoreceptors (in most people) are more sensitive to CO2 than O2. When a swimmer blows off CO2 then they reply upon the hypoxic drive to signal them to breathe. The downside to this method is that, sometimes, by the time the signal is addressed the swimmer's oxygen is so low that they have depleted their oxygen to the point that they blackout at the surface. Now you have either a death or a person with an anoxic brain injury. I can provide rescue breaths, intubation, life support, etc to bring back someone with a very high PaCO2 level but not a super low PaO2 level. OBTW, as CO2 increases the pH decreases (respiratory acidosis) and can be tolerated to the lowest level I have ever seen someone come back from 6.9 whereas the normal range is 7.35-7.45.

Please read this: https://www.swimmingworldmagazine.com/news/shallow-water-blackout-the-silent-killer-of-swimmers/

You are very much incorrect. There is no evidence that a shallow water blackout will cause death or an anoxic brain injury. it is my understanding that a BO is actually a PROTECTIVE mechanism and essentially ALL BO victims are recoverable without death or brain injury... if the proper aid is provided quickly.

This is not a minor distinction either. BO is not that unusual in spearfishing and especially in freedive competitions. When a buddy provides aid quickly.. the victim is usually just "done for the day"... If nobody is there to provide support.. the victim is almost always just "done".

Proper aid is EXTREMELY effective in preventing injury.. This is why good buddy diving is so essential.. i think most all of my serious freedive buddies have had at least one BO and all of them have witnessed one as well...or maybe we are all just drain bamamaged.

 

[John C. Ratliff]

John:

Wikipedia seems to contradict your definition of Taravana.

And shallow water blackout is generally used to describe a BO caused by a diver ascending from a significant depth into shallow water. A diver who stays shallow and just blacks out while swimming is .... not sure what they call that.. hypoxia?


https://en.wikipedia.org/wiki/Taravana

I will take a look at the wiki write-up in a few minutes. Before doing that, let me relate that I did not somply pull this information out of my mask. I have been researching this since the 1960s and have a number of references. I will get some of these soon. I used this information to put together one of the first explanations of SWB in the 1970s, and have briefed Pararescue teams on SWB too when I was in the USAF.

Concerning Taravana, E.R. Cross first wrote of thIs malady in the September 1962 issue of Skin Diver Magazine. He was the one who publicized the name when he titled this article, "
"Taravana."

Translated from Paumotan, the language of the Tuamotus, Taravana means to fall (tara) crazily (vana). Many of the divers who fall crazily back into the lagoon as they emerge from a dive are rescued from the water by the tete or helper only to die later in the village. Those who survive may be paralyzed or mentally incompetent for days, weeks, and sometimes for the rest of their lives...

This article is the first description, and E.R.Cross went on for four double-column pages describing this problem, describing the detail of these diver's experiences with what they named "taravana." Here is his description of the probable cause in this 1962 article:

The most likely cause of taravana is the lack of oxygen to the blood and tissues. The simple phenomina of anoxia...

I am aware of the possibility of decompression sickness, as U.S. navy submarine tank divers have suffered confirmed cases of decompression sickness from breath-hold dives. But I used the term "taravana" for this paper in the 1970s when the E.R. Cross definition was applicable to SWB.

Dr. Anne Dumitru and Dr. Hamilton discussed the mechanism of SWB in their April 1964 artical, "Underwater Blackout, A Mechanism of Drowning" in the magzine, GP. They illustrated two near-drowning situations. Albert B. Craig, M.D. wrote of 12 cases, and documented three in detail, in an article ( which I think was in the Journal of the American Medical Association in the late 1960s describing one death in which the swimmer could not be resuscitated despite immediate efforts.

The other references I used were:
Bell, Geoge H., J. Norman Davison and Harold Scarbough, Textbook of Physiology and Biochemistry, 7th Edition, The Williams and Wilkins Company, Baltimore, 1968.

Reseck, John, Jr., SCUBA Safe and Simple, Prentice-Hall Inc., Englewood and Cliffs, New Jersey, 1975, pp52-58.

Pierce, Albert L., "Underwater Blackout and the Diving Reflex," Preceedings of the Sixth International Conference on Underwater Education (IQ6), NAUI, 1975, pp 312-316.

SeaRat

PS: I had to clean this up, as I wrote it on an iPad and there were some misspellings and other problems endemic to writing on the iPad. Also, I wrote this above paper 40 years ago. But the mechanisms haven't changed in these forty years. If someone has other findings from medical sources, and wants to update my paper, feel free. Handle it as if it were a historical document, but you must present valid, scientific sources for your information. The Textbook of Physiology and Biochemistry that I used then and today's references probably won't change much the facts that a person will black out at about 34mm Hg (that's millimeters of mercury partial pressure in the blood).

Now, about "proper aid EXTREMELY effective in preventing injury," cited by DumpsterDiver above. There are a number of cases where aid, including CPR, was administered within a minute of recovery of the diver/swimmer, and the diver/swimmer did not survive. I will relate one of my own experiences below.

 

[TONY CHANEY]

You are very much incorrect. There is no evidence that a shallow water blackout will cause death or an anoxic brain injury. it is my understanding that a BO is actually a PROTECTIVE mechanism and essentially ALL BO victims are recoverable without death or brain injury... if the proper aid is provided quickly.

This is not a minor distinction either. BO is not that unusual in spearfishing and especially in freedive competitions. When a buddy provides aid quickly.. the victim is usually just "done for the day"... If nobody is there to provide support.. the victim is almost always just "done".

Proper aid is EXTREMELY effective in preventing injury.. This is why good buddy diving is so essential.. i think most all of my serious freedive buddies have had at least one BO and all of them have witnessed one as well...or maybe we are all just drain bamamaged.

dumpsterDiver,
Did you actually watch the thread that I posted? I would guess not. What you cannot understand is that it can happen in a pool in just than 3 feet of water. Please watch the thread and think it over. But on the other hand you are an Instructor and I am only a Tech Dive Master and a Respiratory Therapist. But then again what the heck does a Respiratory Therapist know. With your own example it can be equated to OSA...where even a little of brain starved oxygen can create adverse effects of your brain, which in your thinking it may have already taken place. Please watch the thread I posted and do not teach your students what you think. OBTW, "Proper aid is EXTREMELY effective in preventing injury" is not the way to go! Proper planning and precautions Prevent injuries and proper aid is given to victims who are already are in trouble. DaXn, I cannot believe that you post this s^&t!!!

 

[John C. Ratliff]

Here is an e-mail I wrote about a year ago to a Pararescue colleague about PJ training and Shallow Water Blackout:

I have written quite a lot on shallow water blackout, both on vintage diving websites and with NAUI years ago. As a former PJ, and also a NAUI Instructor (#2710, inactive), shallow water blackout (SWB) is a considerable concern in both civilian and military training. With breath-holding underwater, normally the CO2 in the blood stream will build up to a "must breath" level of about 50 mm of mercury (Hg). This normally will happen in about a minute. However, if a diver hyperventilates a lot, the diver will blow off enough CO2 to be able to extend that time until the oxygen level goes down below the blackout level (about 34 mm Hg).

This can further be complicated by depth. At depth, the oxygen level is increased by the partial pressure of oxygen in the bloodstream. But as the diver ascends, that partial pressure lessens, and there can actually be a transfer of oxygen from the blood back into the lungs. Blackout occurs at about 10 feet underwater when breath-hold diving to depth.

SWB can be prevented by not hyperventilating more than about two or three breaths before diving. I have long advocated using a "rhythm diving" method too, where you dive underwater until first feeling the "must breath" signal, then surface. Breath normally for about two minutes, then dive again. Over time (15-20 minutes) you'll be extending your time underwater by relaxation and your body's adaptation to the breath- holding.

To show what this hazard is, here is my story of SWB. I was on the YMCA Swim Team in Salem, Oregon as a kid. My friend, Tom Lengyel had just swam four lengths of a 20 yard pool, and I wanted badly to beat his record. So I hyperventilated over a minute, enough to get a bit dizzy, then dove in and swam underwater breast stroke. The first two lengths were easy. On the third length, I was beginning to feel the urge to breath, but suppressed it. Coming into the turn at the end of the fourth length, I said to myself, "I'll make the turn, take one stroke underwater, then surface and swim to the side of the pool." And, that's exactly what I did. The trouble is that I did not remember anything after the pushoff of the turn. The next thing I knew, I was at the pool's edge and dizzy, regaining consciousness. I told our swim coach, who was Margaret Lengyel, mother of Tom, and also an Olympic Silver Medalist in breast stroke in the 1930s from Hungary (unconfirmed, but that's what we heard), and she immediately stopped all underwater competitions.

This may not fit with the military training for PJs or SEALs, but it is about the only way to prevent SWB. By pushing people into SWB, the risk is that it won't be recognized by the instructors or buddy, and that the person will die. Had I not pre-programmed my mind to surface, I would not have, and would have continued swimming underwater until I was dead! This has been documented in professional physiology journals since the 1960s. So simply waiting for symptoms to "show" during military training may actually be too late to revive the diver.

http://www.ncbi.nlm.nih.gov/pubmed/25996093

After reading the Craig paper above some years ago, I'm convinced that had I not pre-programmed my brain to surface, I would have continued swimming underwater until I had effectively died. I did continue swimming while unconscious; it was that close.

SeaRat

 

[archer1960]

No, it is SWB. (See the paper I enclosed above.)

Concerning the "15m rule," I have not heard of that rule. However, as the former Finswimming Director for the Underwater Society of America, and having access to the rules for Finswimming competition worldwide, the competitive limit for breath holding under CMAS rules is 50m. Using a monofin, the world record is somewhere less than 16 seconds for 50m underwater breath-hold men's swim.

Under Olympic freestyle rules, there is a 15m limit after the start or turn, by which time the swimmer must be breaking the surface.

 

[dumpsterDiver]

dumpsterDiver,
Did you actually watch the thread that I posted? I would guess not. What you cannot understand is that it can happen in a pool in just than 3 feet of water. Please watch the thread and think it over. But on the other hand you are an Instructor and I am only a Tech Dive Master and a Respiratory Therapist. But then again what the heck does a Respiratory Therapist know. With your own example it can be equated to OSA...where even a little of brain starved oxygen can create adverse effects of your brain, which in your thinking it may have already taken place. Please watch the thread I posted and do not teach your students what you think. OBTW, "Proper aid is EXTREMELY effective in preventing injury" is not the way to go! Proper planning and precautions Prevent injuries and proper aid is given to victims who are already are in trouble. DaXn, I cannot believe that you post this s^&t!!!

Just because I am a dive instructor does not make me correct. You should not put yourself down just because you are not an instructor. However, you are absolutely incorrect with the assertion that a BO victim is going to suffer a brain injury or death,

This is incorrect and has been proven thousands of times. Your assertion is refuted on a daily basis.

As for John's comments about using 40 yr old sources... well a lot has been learned in the last 40 years... Back then, people doubted that a freediver could get the bends from one or two freedives. Now we see really deep freedivers being very aware of it and using techniques to avoid it - including immediate, post dive decompression on pure oxygen to prevent the bends. It is my understanding that the short immersion and very rapid ascent causes decompression issues in fast tissues of freedivers, which tends to affect the nervous system.

 

[John C. Ratliff]

Under Olympic freestyle rules, there is a 15m limit after the start or turn, by which time the swimmer must be breaking the surface.

I think this has to do with the advantages of being underwater for streamlining, and that freestyle is a surface stroke. Its does not have to do with SWB.

SeaRat

 

[John C. Ratliff]

...As for John's comments about using 40 yr old sources... well a lot has been learned in the last 40 years... Back then, people doubted that a freediver could get the bends from one or two freedives. Now we see really deep freedivers being very aware of it and using techniques to avoid it - including immediate, post dive decompression on pure oxygen to prevent the bends. It is my understanding that the short immersion and very rapid ascent causes decompression issues in fast tissues of freedivers, which tends to affect the nervous system.

Cite some sources. Here's one study:

South Med J. 2010 Jul;103(7):650-3. doi: 10.1097/SMJ.0b013e3181e10564.
Prevention of needless deaths from drowning.
Modell JH1.
Author information

Abstract
OBJECTIVE:
To determine whether faulty pool maintenance and substandard lifeguard performance critically delayed retrieval and resuscitation of a significant number of pool drowning victims.

METHODS:
One hundred and eighty drowning incidents that resulted in litigation from 1998 to 2008 were studied to determine whether faulty pool maintenance and/or substandard lifeguard performance delayed retrieval and thereby contributed to the death of these persons. A total of 180 swimming pools-commercial and private-were included. Ninety-seven of these pools were manned by lifeguards. Subjects who underwent the drowning process and suffered severe brain injury or death were reviewed to determine the rescue and resuscitation attempts by lifeguards or bystanders at the pool.

RESULTS:
One hundred and seventy-seven of the 180 persons who underwent the drowning process died. Cases were analyzed as to whether faulty pool maintenance and/or substandard lifeguard performance contributed to their demise. At fault were cloudy or dirty water; drain pipes that created underwater suction to trap victims; inadequate fencing around pools through which small children gained access; permitting small children to be at the pool without adult supervision; permitting dangerous exercises such as hyperventilation while underwater swimming, resulting in shallow waterblackout; lifeguards not being attentive, being distracted by other persons, performing nonrelated chores, leaving their positions without proper relief, while failure to enter the water when told persons were submerged.

CONCLUSION:
Faculty pool maintenance and substandard lifeguard performance critically delayed retrieval and resuscitation of a significant number of pool drowning victims.

PMID:

20531066

[PubMed - indexed for MEDLINE]

Here's another one concerning brain damage from breath-hold diving, this one concerning DCI and breath-hold diving.

PLoS One. 2014 Aug 12;9(8):e105006. doi: 10.1371/journal.pone.0105006. eCollection 2014.
Brain damage in commercial breath-hold divers.
Kohshi K1, Tamaki H2, Lemaître F3, Okudera T4, Ishitake T5, Denoble PJ6.
Author information

Abstract
BACKGROUND:
Acute decompression illness (DCI) involving the brain (Cerebral DCI) is one of the most serious forms of diving-related injuries which may leave residual brain damage. Cerebral DCI occurs in compressed air and in breath-hold divers, likewise. We conducted this study to investigate whether long-term breath-hold divers who may be exposed to repeated symptomatic and asymptomatic brain injuries, show brain damage on magnetic resonance imaging (MRI).

SUBJECTS AND METHODS:
Our study subjects were 12 commercial breath-hold divers (Ama) with long histories of diving work in a district of Japan. We obtained information on their diving practices and the presence or absence of medical problems, especially DCI events. All participants were examined with MRI to determine the prevalence of brain lesions.

RESULTS:
Out of 12 Ama divers (mean age: 54.9±5.1 years), four had histories of cerebral DCI events, and 11 divers demonstrated ischemic lesions of the brain on MRI studies. The lesions were situated in the cortical and/or subcortical area (9 cases), white matters (4 cases), the basal ganglia (4 cases), and the thalamus (1 case). Subdural fluid collections were seen in 2 cases.

CONCLUSION:
These results suggest that commercial breath-hold divers are at a risk of clinical or subclinical brain injury which may affect the long-term neuropsychological health of divers.

PMID:

25115903

[PubMed - in process]
PMCID:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4130625/#!po=2.94118
PMC4130625

SeaRat

 

[John C. Ratliff]

Okay, I have read the wiki link on Taravana, and most agree that this is associated with DCI, which is also consistent with the paper above on Ama divers and brain injury.

However, Wiki also has two sites devoted to shallow water blackout. The first one has graphs much like mine (without the actual numbers for blood pp readings):
https://en.m.wikipedia.org/wiki/Shallow_water_blackout

Wiki also differentiates between shallow water blackout and deep water blackout, which. Is consistent with my discussion of two different mechanisms.
https://en.m.wikipedia.org/wiki/Deep_water_blackout

It seems that this phenomena has not changed much in the last 40 years.

SeaRat

 

[dmaziuk]

I think this has to do with the advantages of being underwater for streamlining, and that freestyle is a surface stroke. Its does not have to do with SWB.

The unofficial story is that there were a few near-drownings, too, when people tried to do the whole 100 underwater and found out the hard way that swimming at competition speeds requires a bit more oxygen than they had in their lungs and bloodstream. The official reason is "unfair advantage" of dolphin kick underwater.

And no, freestyle is "any style", it's just that front crawl is the fastest surface style so nobody swims anything else.