Dangers of Breath-Hold Diving

[Benny17441]

In another thread there has been brief discussion of reports of the tragic death of a fellow boater who, according to one report, dove on his anchor to free it, as it evidently had become fouled on something. The depth of the water was not mentioned. But regardless of the full set of circumstances leading to the above-mentioned tragedy it has occurred to me that while people don't much think about it, breath-hold diving can be a dangerous activity, especially in cold water. People trained in SCUBA diving are given some instruction, but since most recreational SCUBA divers are trained by instructors of sport shops looking to expand the sport (and sales), training in breath-hold diving is not a priority item. Even among some types of professional diver training,

King the average depth of the water at that location is 16 ft. and the water temperature was in the 70s weather conditions were good. He was a 38 year old Navy serviceman attached to SOCOM at Macdill AFB. NCIS investigators were on the scene to determine the actual cause for the death. There were reports that he indeed carried some type of breathing apparatus and that could very well be a source of complications if Boyle's laws were disregarded.

 

[JamesG161]

First rule of diving...
NEVER DIVE ALONE OR UNATTENDED!

Second rule (non professional)...
NEVER DIVE A WRECK OR CAVE!

Jim...

 

[Skipper]

Stuck anchor remedy: pic

A call to a tow boat is going to be drastically more expensive than a new anchor. Our local surplus shop has hundreds of them new and used for half of usual $. Of course there's also the chain to buy.... and shackle... and many feet of lost rode... but likely still less than paid assistance.
And immeasurably less than loss of life.
Most sailors carry spare anchors and rode anyway.
I'm not a diver. But am pretty good with a knife, and an expert at price shopping for new gear.
I've never had a stuck anchor. There are numerous recovery tactics. But if it ever sticks unrecoverable, there it will stay.

 

[Ken Cross]

Anybody have any experience with this?
http://www.anchorrescue.com/

I've seen a steel ring about 6 inches in diameter tied to a line. Put it over the rode. dinghy out away from the direction you think the anchor is set and pull. I understand it works great.

Ken

 

[PotomacDaysailer]

I had never heard of shallow water blackout before. Sure glad I read about it here. Thanks for truly life-saving information!

 

[Dan_Y]

as a professional diver, I know what all this means, but lets try to help the ones that dont know..... without the training necessary to know better, all these ppo2's and atm's and ppn2's are

Sorry to offend your sensibilities centerline. It's hard to simplify this aspect of the explanation. Ken gave a great non-math version, as did you, and this was simply another perspective for those that cared to take the time to read through and understand more what the mechanism is. This was not very mathy, although I did use addition, ha.
Edit: changed 'dumb down' to simplify... didn't wish to offend anyone else...

 

[centerline]

Sorry to offend your sensibilities centerline. It's hard to dumb down this aspect of the explanation. Ken gave a great non-math version, as did you, and this was simply another perspective for those that cared to take the time to read through and understand more what the mechanism is. This was not very mathy, although I did use addition, ha.

you didnt offend me.. just trying to make a point that with all the abbreviations, which are ok for the divers and advanced members of the group who already know the stuff you posted, it offers very little to those that dont know what all the abbreviations mean.....

 

[Kings Gambit]

It's "fixable", as follows:
Another way to explain shallow water blackout is that as you descend from the surface where the partial pressures of oxygen and nitrogen are about 0.2 and 0.8 atmospheres (ATM), respectively ( i.e., totaling one ATM) to 33 feet, you are now at two absolute ATMs of pressure - one for the surface pressure and one for the weight of the water at 33 feet. Thus, the oxygen partial pressure of the air in the compressed lungs is now 0.4 ATM and that of nitrogen 1.6 ATM as they must add to 2 ATM. I seem to recall that you need about 0.1 ATM of oxygen partial pressure or a tad +/- to remain awake. As your body burns oxygen its partial pressure drops. If you were to stay at 33 ft until your blood oxygen fell from 0.4 to to say 0.2 ATM, and then ascend to the surface your oxygen partial pressure would drop to 0.1 absolute ATMs as you neared the surface (due to lung re-expansion) and you could lose consciousness. Remember, gas pressures in the blood are in equilibrium with those in the lungs. The rebreather example is a good one. If you don't keep sufficient oxygen pressure in the breathing loop, even if your carbon dioxide scrubber is working fine, you black out even at the bottom of a shallow pool. In both cases you are hypoxic, as pointed out above.

Note: Atmospheric pressure of air is composed of the additive pressures of each of its constituents. If oxygen is 20% of the composition of the air, it's contribution to total atmospheric air pressure at sea level, i.e., its "partial pressure", would be 0.2 ATM, i.e., 1 ATM x 0.2 oxygen component = 0.2 ATM partial pressure of oxygen. Under two absolute atmospheres, say at 33 ft, you have 2 ATM x 0.2 = 0.4 ATM partial pressure of oxygen in the compressed lungs.

KG

 

[marke14]

The body of a well-known local spearfisherman (Mr. Poznik) was recovered from the waters off Palos Verde a couple of weeks ago.

Thanks for sharing this story in this context, KG. I didn't know this guy but this hits close to home - we're from the same area and he was about a year older than me. RIP

Good topic, I'm glad I read this because I am a free dive "enthusiast" whenever we are on vacation and snorkeling. I will push the limit less now that I've read this.

 

[kimelmore]

SWB can happen even in a pool. My Nephew was in great shape. A triathlete in his 30's with a bride of little more than a year. He was practicing holding his breath under water in a pool with his wife sitting reading less than 25 feet away. She looked up from her book and he was sitting on the bottom in the shallow end of the pool. When she looked up a few minutes later he was floating on the surface face down. It only took her a minute to realize something was wrong. The doctors told the family it was an embolism but I knew better after doing some research. I was a life guard for many years. We never ever did any diving without a partner. It was a real shock to the family and a terrible tragedy but my point is that age and fitness does not keep it from happening. I know that I am much more careful diving on my boat (snorkeling) and make it clear to those watching to be vigilant when I am out of sight. More than likely he blacked out from excess CO2 and then took a deep breath of water. They did find water in his lungs. All of this in the shallow end of the pool. Be careful out there.

 

[Dan_Y]

It's "fixable", as follows:
Another way to explain shallow water blackout is that as you descend from the surface where the partial pressures of oxygen a...
KG

Thanks for the constructive improvement KG! One last point here that was an ah ha explanation when I first heard it. Recall that a healthy body is reminded to breath by the build up of carbon dioxide in the blood as sensed in the brain, not the lack of oxygen. Hyperventilating prior to a free dive may increase the oxygen saturation of the blood in a healthy individual from maybe 96-97% to maybe 98-99%, i.e., doesn't do much. But it can reduce the carbon dioxide level in the blood somewhat, pushing off the the urge to breath when holding your breath. So at depth you can go a little longer before you feel the urge to breath, but are getting closer to becoming hypoxic at depth, then heading to the surface and potentially getting in trouble.

 

[marke14]

I think of all the deep dives I've made over the years. Not to mention a ton of idiotic teenage risky stuff, cavalier and reckless. We used to train to swim underwater, 25 yards and back in a pool (with a wall turn of course). For fun, more or less.

I am so thankful to have more or less survived my young and adolescent years.

"The things that I used to do, Lord, I won't do no more ..."

 

[kimelmore]

One of the Navy safety sites recently had a very in depth article about this very subject that I found while researching my nephews accident. I will try to find the link and post it here.

 

[Kings Gambit]

One of the Navy safety sites recently had a very in depth article about this very subject that I found while researching my nephews accident. I will try to find the link and post it here.

Please do; I'd like to see it.

 

[thinwater]

I remember as young lad that underwater tag lost it's interest when we all learned to swim 25 meters underwater, through a crowded pool, with ease. I've snorkeled a lot and am quite comfortable down to about 15 feet.

But I've always avoided pushing breath holding even a little bit, even when working. The reason is practical. Once you push it just a little, you are going to get very little done on subsequent dives. Thus, I never push beyond a very low percentage of how long I can stay down, or how long I can work. It is simply not productive. And yes, once or twice I realized I'd been down a little too long and it smartened me up. Little bites are safer and ultimately more productive.

Freeing an anchor? First, always take a rope with a carabiner clip. Most of the time all you need to do is clip the tripping eye or roll bar and bolt for the surface. There is no future in trying to do heavy work, when the boat is right above you with winches. The most you should be doing underwater is looking over the situation and attaching lines (sometimes another object needs lifted).

Cutting rope free? Make sure you are properly dressed; always have a wet suit or dry suit if you aren't in the tropics. Take short trips; you are NOT going to get it done in one dive anyway. Worried about dropping tools or a knife? Don't use a lanyard, they can get stuck. Instead, wear a suit with pockets and don't worry if you drop it. You should have taken a cheap one.

 

[shemandr]

I am so thankful to have more or less survived my young and adolescent years.
"The things that I used to do, Lord, I won't do no more ..."

Amen. It was close a few times.

 

[Kings Gambit]

I remember as young lad that underwater tag lost it's interest when we all learned to swim 25 meters underwater, through a crowded pool, with ease. I've snorkeled a lot and am quite comfortable down to about 15 feet.

But I've always avoided pushing breath holding even a little bit, even when working. The reason is practical. Once you push it just a little, you are going to get very little done on subsequent dives. Thus, I never push beyond a very low percentage of how long I can stay down, or how long I can work. It is simply not productive. And yes, once or twice I realized I'd been down a little too long and it smartened me up. Little bites are safer and ultimately more productive.

Freeing an anchor? First, always take a rope with a carabiner clip. Most of the time all you need to do is clip the tripping eye or roll bar and bolt for the surface. There is no future in trying to do heavy work, when the boat is right above you with winches. The most you should be doing underwater is looking over the situation and attaching lines (sometimes another object needs lifted).

Cutting rope free? Make sure you are properly dressed; always have a wet suit or dry suit if you aren't in the tropics. Take short trips; you are NOT going to get it done in one dive anyway. Worried about dropping tools or a knife? Don't use a lanyard, they can get stuck. Instead, wear a suit with pockets and don't worry if you drop it. You should have taken a cheap one.

Although we may never know in the cited cases, I suspect that repetitive breath-hold dives with short surface intervals is the likely culprit. Imagine going down to do work, like freeing an anchor. You're concentrating on that, pushing the limit to get the job done, but perhaps it doesn't. Return to the surface, take 3 or 4 gulps, and then back down. You may clear the carbon dioxide--but do you replace all of the blood oxygen that was depleted? Blood oxygen has two components--oxygen bound to the hemoglobin and oxygen dissolved in the blood plasma, which is a considerably smaller fraction. You might be restoring the oxy-hemoglobin with a short surface interval but I wonder if the blood receives its full saturation. When I've breath-hold dived while snorkeling my surface interval is always at least a full minute of "normal" breathing, but usually more. I'm thinking one needs a surface interval of a few minutes to be safe (rather than "pop and drop")--but just my opinion. I might sound like one to somebody, but I'm not a physician or a respiratory physiologist!!

 

[IH82BL8]

As a diver and dive instructor, here are a few of my thoughts. Free diving safely is taught as part of SCUBA training. The rule is three deep breaths, hold the third one and dive. More than three breaths can result in SWBO. Also, never dive without a knife that includes a line cutter.

It's also wise to think through in advance what to do in an emergency situation where you might be too stressed to think clearly. Then if an emergency arises you'll be better mentally prepared for it.

If you are a certified diver, there's no reason not to take SCUBA gear with you when you sail. You never when you might need it.

 

[JamesG161]

Also, never dive without a knife that includes a line cutter.

Or Alone or unattended!
Jim...

 

[waterpirate]

How you breath up or not has little effect on SWB. Just like narcosis or deep air, the phrase I like to use is " On any given Sunday ". What it means is that no matter how manly we think we are, there are factors at play that we do not control. What we did yesterday and got away with may not be replicated with the same outcome today. Sort of like flying a cat solo on the ragged edge, tomorrow you may or may not pitch.
Eric