Underwater Swim Training- Shallow Water Blackout

[dumpsterDiver]

There are some people who believe that supervision tends to INCREASE the frequency of BO. This "theory" makes sense to me - a diver who "knows" a buddy has his back and is watching him, may well decide to push things harder than if he knew he was solo. The answer to this is, of course, "never rely on your buddy being there"..

The reality of the situation is that it would be extremely rare to require CPR. A freedive class will stress safety and rescue procedures. A quick synopsis (based on taking a 1-day course, 3-4 yrs ago)... is

Watch the diver.
In some cases, you may want to descend and accompany the diver for the final ascent (where most all problems occur)
If a LMC or BO occurs, protect the airway.
Get the diver to the surface, protect the air way.
Probably ditch lead.. few freedivers have the mental capacity to ditch lead when in trouble.
Remove the mask
Blow on the cheeks
Talk to the victim and firmly tell them to breathe (often the diver may be paralyzed or a LMC may be occurring and they may be blinded, but often the diver can still receive audible input). In fact visual disturbances, tunnel vision, seeing stars etc.. can often be valid warning signs to a diver that a BO is imminent.
tap on the cheeks
tap, blow talk..The reason for this.. is apparently the brain can often retain some level of function. Normally the airway is closed automatically (a protection mechanism) and when the brain detects that the face is now dry - then this will often stimulate the victim to resume breathing on their own.
I think this is supposed to be repeated for maybe 25 seconds, if recovery does not occur. Then a few rescue breaths should be provided and continue the tap, blow talk routine.
It is important to do this immediately and not waste time trying to remove the diver from the water.
If a diver does not recover from this procedure relatively quickly... I think you have a real problem.

The video of them working on that female BO victim was pretty much textbook , as far as I know.

The recovery protocol is different from what a lifeguard would be trained to do, if they recover a victim unconscious on the bottom of a pool

I'm not really sure, but I think there may be some people who are advocating for administration of a rescue breath almost immediately and to forgo the tap and blow stuff.

I only carry an oxygen (scuba bottle) for scuba first aid..

Incidentally, I spent hundreds of hours solo freediving (before I knew any of this stuff) and even now, National spearfishing contests are basically run with each diver on their own. They have had fatalities at the national tournaments.

 

[John C. Ratliff]

DD,

Okay, we had a semantics problem; I had a different meaning for "supervision" than did you. You were talking about the buddy "supervising" the dive. I was thinking of supervision as a management concern for contests, setting up the logistics, ensuring everyone was accounted for, etc. I was not thinking of a buddy team. 'Just thought you'd like to know of this difference in perspective.

SeaRat

 

[adfitzer]

There are two points of discussion in this thread: the first, accurately defining SWBO; the second, preparednesss when undertaking inherently risky activities. I previously posted my opinions/understanding of these two points. I would like to state that this thread has now changed my understanding of what is appropriate to define as SWBO. I was not convinced by the resources provided. I decided to review what was said in Bove and Davis' Diving Medicine. In their section on breath hold diving, they state, 'the primary hazard entailed in [breath-hold diving] is hypoxic loss of consciousness (HLOC). HLOC has often been called shallow-water blackout becase divers are at increased risk for HLOC as they ascend at teh end of the dive and the partial pressure of oxygen decreases, but HLOC may also occur without a change in depth if divers ignore the urge to breath and oxygen in the lungs is depleted." So contrary to my originally held opinion, I now am in agreement with Chaney and SeaRat in regards to proper usage of the term SWBO. Thank you for further developing my understanding of diving.
BTW, SeaRat, what is the purpose of the dime on your card?

 

[John C. Ratliff]

adfitzer,

At a time long, long ago, but not so far away, a dime could be inserted into a pay phone to initiate a local phone call. (see the link above)

By the way, you referenced one of the classic books on diving medicine, Bove and Davis' Diving Medicine. I have an older book, Underwater Physiology edited by C.J. Lambertsen, but it is a 1971 book, and in leu of the discussion about using older references, I decided it would not be helpful here. Another good reference is Bennett and Elliott's Physiology and Medicine of Diving.

One other point is that Loss of Motor Control (LMC) does not necessarily happen immediately. A diver or underwater swimmer can loose consciousness and continue swimming, as I described happened to me in one of my early posts here. In that case, the diver/underwater swimmer will continue motor activity pre-programmed in his or her brain until LMC happens, but may not be conscious in the time before that happens. This phenomena decreases the time available for resuscitation, as the brain has been hypoxic for a longer period of time. It also explains the deaths of underwater swimmers who are immediately recovered, but cannot be resuscitated.

SeaRat

 

[TONY CHANEY]

Thanks Adfitzer. John, good picture of a pay phone and we are truly showing our age. HaHaHa. Remember when parents always made sure you had enough change to make a phone call if you need them? Thanks to DumpsterDiver. I have learned a lot from you pertaining to free diving, which BTW, I suck at but admire those that can do it.

 

[dumpsterDiver]

Ok thanks... An attentive buddy who takes t

There are two points of discussion in this thread: the first, accurately defining SWBO; the second, preparednesss when undertaking inherently risky activities. I previously posted my opinions/understanding of these two points. I would like to state that this thread has now changed my understanding of what is appropriate to define as SWBO. I was not convinced by the resources provided. I decided to review what was said in Bove and Davis' Diving Medicine. In their section on breath hold diving, they state, 'the primary hazard entailed in [breath-hold diving] is hypoxic loss of consciousness (HLOC). HLOC has often been called shallow-water blackout becase divers are at increased risk for HLOC as they ascend at teh end of the dive and the partial pressure of oxygen decreases, but HLOC may also occur without a change in depth if divers ignore the urge to breath and oxygen in the lungs is depleted." So contrary to my originally held opinion, I now am in agreement with Chaney and SeaRat in regards to proper usage of the term SWBO. Thank you for further developing my understanding of diving.
BTW, SeaRat, what is the purpose of the dime on your card?

I didn't read the text book, but it sounds to me like they are indicating that HLOC is a general term and SWBO is a special case of HLOC - which is specifically associated with an ascent from depth and the concomitant drop in PP of O2..

Not worth arguing over since it is not much more than semantics, but the SWBO term (in my opinion) has value in that it has the potential to help explain to the new diver, why exactly the ascent is so dangerous and why your buddy is NOT safe, simply because he reached the surface on his own power.

Also, this is obvious, but it is easy to see why people would tend to call BO's that occur in shallow water -- a SWBO. An uphill battle to try to explain why the term has meant something else.

It sounds like the opinions of several people in this thread are coming closer into agreement.

 

[John C. Ratliff]

DumpsterDiver,

It might surprise you to find out that the term "Shallow Water Blackout" was first described in 1944 by Dr. K.W. Donald, and referred to closed circuit divers who blacked out in shallow water.
http://archive.rubicon-foundation.o.../123456789/6311/SPUMS_V26N3_14.pdf?sequence=1

http://archive.rubicon-foundation.o...56789/4954/RANSUM_Project_8-68.PDF?sequence=1

As you can now see, it is the freediving community which is taking this term (SWB) as its own from another discipline.

As I said before, it seems that the freediving community has its own mythology to explain thIs condition of what doctors refer to as hypoxia loss of consciousness. Yes, I agree that it is easier as an instructor to explain this phenomina by using the term SWB, and relating it to ascent and the decreasing partial pressures. But the same situation occurs via a slightly different mechanism, for underwater distance swimmers.

I see this as analogous to the situation for decompression illness/sickness, which divers commonly called "the bends." We now know that it is caused via at least two mechanisms: the use of scuba to stay at depth long enough to have inert gases dissolve into the blood, and ascending without adequate decompression; AND the breath-hold diver who dives repeatedly to depths, probably greater than 60 feet, over a long period of time to cumulatively dissolve enough nitrogen into the blood so as to result on bubble formation. These are two different mechanisms for the same illness.

My thought is that SWB can also have two different mechanisms which result in the same illness, blacking out in shallow water.

My understanding of "hypoxia loss of consciousness" (HLOC) is that this is an umbrella term with many different mechanisms. When I was in the USAF, we were prohibited from flying higher than 10,000 feet because we were not carrying oxygen, and over that altitude the USAF had determined that pilots were susceptible to HLOC. This caused us some interesting situations when we flew two helicopters from Florida to Vietnam, the first trans-Pacific flight of helicopters, in Alaska, when we could not go over 10,000 feet because of the helicopters, and had to refuel them in valleys with mountains high above us and an overcast just over the 10,000 foot level. The same is true of mountaineers at high altitude. SWB would also fall under this umbrella term.

We try too hard to make complex physiology simple, when it is not simple. You want something complex, try explaining the effects of the dioxin which was in Agent Orange to a group of Vietnam veterans. I'm currently working on that presentation, set for March 2016.

SeaRat

 

[dmaziuk]

Most pool and lifeguards will NOT allow people to do such things Pete. There is a big push from the "pool safety" people to ban all breathhold activities.

You jinxed it: last night the lifeguard asked me for the first time ever to please limit my underwater swims to one per workout because rules don't allow "extended breath holding". The scary thought is she'll graduate and have a degree in whatever it is she's studying here...

 

[covediver]

This is kinda scuba as it's training related. If you are training yourself for an underwater swimming requirement, understand what shallow water blackout is.

Dartmouth Swimmer Died Trying to Do 4 Laps Without Breathing

This guy lived:
Darren Harrity — Shallow Water Blackout Prevention

Same guy now:
Coast Guard swimmer rides a rip tide to conserve energy in daring nighttime rescue that saved 4 | OregonLive.com

Thanks for this information. Underwater fin swimming in the form of monofin swimming and bifin swimming is not taught much in the US, but is more popular and a competitive sport in other countries in events sanctioned through CMAS. I have taught both at local sport club pools and regularly practice both at local pools. I have also played underwater hockey. In each case, participants are warned about the dangers of blacking out underwater, especially where they are practicing drills that some people call "lung busters" where one attempts to swim underwater as long and as far as they can. I understand that this is also a technique that many water polo players practice and one that has been banned by some high school sports federations. press reports mention deaths by drowning every so often when people practice this technique.

In any event, blackouts in extended underwater swimming is a condition that really started being emphasized in pool safety and American Red Cross lifeguard classes a few years ago. (I am a Lifeguard Instructor and lifeguard). Safety signage started to appear warning people of the practice, if not outright banning it as part of the risk management strategy. The guards at the pool where I swim generally enforce a one-length-or-one-lap-per-breath rule. We can argue over what the mechanism is called that causes the drowning, the fact of the matter is people do die and need to be reminded of the hazard. I do note that under-21 teams are being formed in the US to advance underwater rugby and finswimming, so these warnings are timely.

 

[dmaziuk]

The guards at the pool where I swim generally enforce a one-length-or-one-lap-per-breath rule.

:sigh: Lifeguards with brains. Where can I get guards like these...