Free-diving student blacks out training - Taiwan

[John C. Ratliff]

Thanks for the detailed explanation on BO!

Not sure it’s an accurate explanation, though.

SeaRat

 

[John C. Ratliff]

I did a freediving class with Kirk Krack (the training/safety guy for Avatar), and I'm pretty sure he said they were prebreathing O2. It would be dumb not to really. I was also able to get to a 4 minute static breath hold after about 20 minutes of training. I would say that was somewhat due to my previous experience with freediving, but my dive partner, who had never freedove before, also made it to 4 minutes.

I wasn't even having contractions at the 4 minute mark, so I probably could have made 5 minutes, but 4 was the pre-determined max time. Again this was static, floating at the surface, with a buddy literally hands on, under supervision.

Okay, think about what you are saying. Air is 21% oxygen. If you breathe 100% oxygen, that is almost five times the oxygen as in a breath of air. If one minute on air is comfortable, breathing pure oxygen (100% oxygen), and pre breathing it too to rid your body of nitrogen, will extend your easy breath-holding ability by 4x to 5x the time of the air breathing time.

Now, I’m disturbed that there doesn’t seem to be an actual understanding of the two different mechanisms physiologically for shallow water blackout. I have experienced it several times, the first in a pool during swim team practice at the Salem, Oregon YMCA where our North Salem High School swim team was practicing in about 1963. I have a write up upstairs on my experiences, and how physiologically shallow water blackout occurs. But I have not seen here a real physiological explanation of shallow water blackout. It seems that each generation must learn the same lessons without the help of the older divers experiences. I’ll attach that paper here a bit later.

Here’s a paper about shallow water blackout from the NIOSH Morbity and Mortality Weekly Report:

MMWR Morb Mortal Wkly Rep

2015 May 22;64(19):518-21.

Fatal and nonfatal drowning outcomes related to dangerous underwater breath-holding behaviors - New York State, 1988-2011​

Christopher Boyd, Amanda Levy, Trevor McProud, Lilly Huang, Eli Raneses, Carolyn Olson, Centers for Disease Control and Prevention (CDC)

• PMID: 25996093
• 
  
• PMCID: PMC4584570

Free PMC article

Abstract​

Drowning is an important cause of preventable injury and mortality, ranking fifth among leading causes of unintentional injury death in the United States. In 2011, two healthy young men died in a drowning incident at a New York City (NYC)-regulated swimming facility. The men became unconscious underwater after performing intentional hyperventilation before submersion. The phenomenon of healthy swimmers becoming unconscious underwater has been described elsewhere as hypoxic blackout. Prompted by this incident, the NYC Department of Health and Mental Hygiene (DOHMH) in collaboration with the New York State Department of Health (SDOH) conducted a case review of New York state fatal and nonfatal drownings reported during 1988-2011 to investigate similar behaviors in other incidents. DOHMH identified 16 cases, three in NYC, with a consistent set of voluntary behaviors associated with unintentional drowning and designated this class of behaviors as "dangerous underwater breath-holding behaviors" (DUBBs). For this small sample, the frequency of different DUBBs varied by age and swimming level, and practicing more than one DUBB increased the risk for fatality. This research contributes to the literature on drowning by focusing on contributing behaviors rather than drowning outcomes. NYC recently enacted public health education and regulations that discourage DUBBs; these interventions have the potential to effectively reduce unintentional drowning related to these behaviors and could be considered by other municipalities and jurisdictions.

Fatal and nonfatal drowning outcomes related to dangerous underwater breath-holding behaviors - New York State, 1988-2011 - PubMed

Drowning is an important cause of preventable injury and mortality, ranking fifth among leading causes of unintentional injury death in the United States. In 2011, two healthy young men died in a drowning incident at a New York City (NYC)-regulated swimming facility. The men became unconscious...

pubmed.ncbi.nlm.nih.gov

SeaRat

 

[John C. Ratliff]

Here’s a write-up I sent to the U.S. Air Force Pararescue personnel some years ago:

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.
Fatal and nonfatal drowning outcomes related to dangerous underwater breath-holding behaviors - New York State, 1988-2011 - PubMed

I have another paper that I wrote decades ago which shows graphically what happens with shallow water blackout. I’ll post that later today in a different post.

SeaRat

 

[John C. Ratliff]

Okay, I'm uploading two papers, one by me, and one by E.R. Cross titled "Taravana." In years past, I have used the South Seas Islands term, "Taravana," as a synomym of Shallow Water Blackout, but today that term is now associated with decompression sickness experienced by freedivers. I thought you'd like to see the original paper by E.R. Cross that got me interested in SWB in the 1960s. My original paper, never published, was written in the 1970s, with now two revisions.

DAN now has a paper available titled Taravana: Fact or Fallacy? This includes the latest research on Taravana (decompression sickness associated with repetitive, deep freediving). Here are their conclusions:

CONCLUSION
The main conclusions of this research are threefold:

• Significant intracardiac bubbling has been observed following repetitive breath-hold diving. This supports the idea of a bubble-related cause of taravana.
• Current decompression models are unsuitable for predicting breath-hold related bubbles and, consequently, the risk of developing taravana.
• It is noteworthy that the experimental dive profiles used for the study, which produced bubbling, are more conservative than those used regularly in the open ocean. Until we find better predictors of taravana, we strongly recommend that all divers follow the empirical precautionary principle of spending at least three times the duration of their dive at the surface in order to recover.

Research is ongoing. Breath-hold divers who are interested in participating in this research are welcome to contactresearch@dansa.org

Taravana: Fact or Falacy?

The condition, known as “taravana” amongst pearl divers of the Tuamotus (a chain of islands and atolls in French Polynesia), has increasingly become accepted as a unique form of DCI

www.dansa.org

Enjoy,

SeaRat

 

[Angelo Farina]

The good news is that it's really hard to pass out in a pool. It either demands a lot of self control or use of beta blockers or some similar drugs. The need to breathe in those last 10-15 seconds is so bad that I have never managed to black out even when trying.
The other good news is that blacking out does no permanent damage if you are revived in the next 30 seconds or so, so again freediving in a pool is very safe.

You can easiky pass away in a pool. It happened twice to me whike performing a 50m underwater swim.
The urge of breathing comes from an high level of CO2, not from a low level of oxygen.
If you learn to swim properly with long freediving fins, your muscles will produce very little CO2, while burning a lot of oxygen. So you can easily reach the blackout point without feeling any urge to breath.
Of course poor swimmers wasting a lot of muscle energy doing inefficient kicking with short, rigid fins do not incur in this problem.
But I have seen students blacking out while training in static apnoea, as they exceeded in hyperventilation before.
My wife also had a student who did not perceive any need to breath wathever the CO2 level. He passed out several times during the diving course, and my wife had to revive him at least three times.

 

[DandyDon]

But I have seen students blacking out while training in static apnoea, as they exceeded in hyperventilation before.

Oh, yeah, as a dumb kid killing time riding a country school bus, I used to do that for kicks,