DAN Report on Diving Fatalities

[The Chairman]

Sorry. I just don't see the "difference". You occlude your airway when you free dive (aka breath holding or apnea diving). There is no egress of air in or out of your pulmonary system during the actual dive. What am I missing here?

Free divers, apnea divers and breath hold divers don't have to worry about Boyles' Law. They take in one lung full of air at the surface and while it might be a bit compressed during the dive, it's still only one lung full by the end. They simply don't have to worry about lung over expansion injuries. I tell my students that Boyles is really an acronym: Breathe Or Your Lungs Explode, Stupid. It gets the point across. However, it only applies to those breathing compressed air at depth.

 

[boulderjohn]

Okay, NetDoc and BoulderJohn, I'll ask a very simple question. Is a whale, a penguin, or a seal holding its breath when a continuous stream of bubbles comes out of the animal during its dive? When I do a breath-hold dive, I count the time of breath-holding from the time I take the breath and leave the surface until I return to the surface, regardless of whether I am exhaling or not. When, in a buddy breathing situation, a diver gives up the regulator to the other diver (whether the person with the good reg or receiver), if that person is exhaling the person is the person breathing? Not exactly; that person without the regulator will drown, as shown above, if the other person hogs the regulator and he or she stays underwater.

I agree with Pete (Netdoc) on the difference between holding a breath of compressed air and holding a breath of air taken at the surface, but I don't think that is the question here. I am honestly not sure I understand your point in the last two sentences above. I think I have a sense of what you mean, though, and as I understand it, you are not arguing anything about technique; you are arguing over the definition of holding your breath. You seem to be saying that if you are not inhaling, you are holding your breath. If that's the way you want to define your term, that's OK with me. I am just pointing out that a lot of people do not define holding their breath that way. Most people include exhaling as a part of the breathing process, while you include only inhaling. Fine. Just remember that if you are using that term in a discussion, other people will be using a different definition, and you will want to be sure to define your terms to avoid confusion--such as we have now.

 

[Ken Kurtis]

I tell my students that Boyles is really an acronym: Breathe Or Your Lungs Explode, Stupid.

I like that a lot. I'll be stealing that one (and will try to remember to give proper attribution).


- Ken

 

[John C. Ratliff]

I agree with Pete (Netdoc) on the difference between holding a breath of compressed air and holding a breath of air taken at the surface, but I don't think that is the question here. I am honestly not sure I understand your point in the last two sentences above. I think I have a sense of what you mean, though, and as I understand it, you are not arguing anything about technique; you are arguing over the definition of holding your breath. You seem to be saying that if you are not inhaling, you are holding your breath. If that's the way you want to define your term, that's OK with me. I am just pointing out that a lot of people do not define holding their breath that way. Most people include exhaling as a part of the breathing process, while you include only inhaling. Fine. Just remember that if you are using that term in a discussion, other people will be using a different definition, and you will want to be sure to define your terms to avoid confusion--such as we have now.

You know, this started out when Thalassamania took Dennis Graver to task for using the word "breath holding" for the person without the regulator when buddy breathing. Now, you finally realize that there are more than one way of looking at "breath holding" as a term. Yes, one should define what they mean. But yes, also, the term can change in 30+ years.

Now, let's get back to buddy breathing. If you'll analyze your breath holding ability, you can do it either with a closed mouth or open mouth. Opening your mouth does not automatically allow air out, as we can close down our throat too. But to exhale during buddy breathing takes a voluntary effort. When we take a regulator out of our mouth, we "hold our breath" automatically. This keeps water from coming down our throats. To exhale, we need to decide to do it. If, as the regulator exchange is occurring, a diver is interrupted by some other event (the other diver touches him, equipment doesn't do what it's supposed to do, etc.), we will continue breath holding without exhaling, probably as we ascend. This could cause lung overpressure, and was what Dennis Graver was warning about.

SeaRat

 

[boulderjohn]

Now, you finally realize that there are more than one way of looking at "breath holding" as a term.

I'm pretty sure I realized it from the start. This is what I wrote before:

I see what you mean in the way you define holding one's breath, but others use a different definition. For most people that I know, holding the breath involves closing the airway so that air cannot pass--either in or out. If your airway is open--even if you are neither inhaling nor exhaling, then you are not holding your breath. The key for safety purposes is that if the airway is open and the air in the lungs has expanded to the point that it needs to come out, then it will come out. If you are exhaling, then you are definitely not holding your breath by the definition most people I know use.

Now, let's get back to buddy breathing. If you'll analyze your breath holding ability, you can do it either with a closed mouth or open mouth. Opening your mouth does not automatically allow air out, as we can close down our throat too. But to exhale during buddy breathing takes a voluntary effort. When we take a regulator out of our mouth, we "hold our breath" automatically. This keeps water from coming down our throats. To exhale, we need to decide to do it. If, as the regulator exchange is occurring, a diver is interrupted by some other event (the other diver touches him, equipment doesn't do what it's supposed to do, etc.), we will continue breath holding without exhaling, probably as we ascend. This could cause lung overpressure, and was what Dennis Graver was warning about.

I'm pretty sure I said that as what he meant, too.

 

[billt4sf]

The official dive death rate is one in 200,000 in the US.

The DAN papers referenced above quote a rate of 16 annually per 100,000 DAN insured divers.

• Annual death rate among insured DAN
members members 2000 2000 –– 2006 2006 = 16 per 100 000 = 16 per 100,000

That's well above 1 in 100,000 but still low. The same DAN paper quotes a rate of deaths for jogging of 13 in 100,000 annually.

- Bill

 

[Mr Carcharodon]

That makes diving seem realatively dangerous since most people run (not jog) a lot more than they dive. Of course I'd guess the realtivly fit are underrepresented in fatilities.

 

[Thalassamania]

You are missing the point. Dennis was making a point using accidents that never happened. There has never been, as far as as I know, a pair of divers who ascended while buddy breathing and got to the surface with one of them with an AGE. All embolism cases that featured buddy breathing as part of the incident, also featured re-separation of the divers and a bolt for the surface. You can indite buddy buddy breathing for being too complex, for requiring too much practice, or for being plain old too hard to do, but Dennis' analysis is way off base. By the way, it is quite possible to keep your glottis open, even whilst neither inhaling nor exhaling, or even while free diving.

 

[vincent54]

When I have a heart attack in bed while sleeping, is it considered a sleeping accident or preexisting illness. The numbers for dive accidents should be reconfigured to eliminate heart/cardiac conditions.They really aren't accidents, but weak hearts that are stressed. Diving seems to be safe when common sense is used. HAPPY NEW YEAR

 

[John C. Ratliff]

You are missing the point. Dennis was making a point using accidents that never happened. There has never been, as far as as I know, a pair of divers who ascended while buddy breathing and got to the surface with one of them with an AGE. All embolism cases that featured buddy breathing as part of the incident, also featured re-separation of the divers and a bolt for the surface. You can indite buddy buddy breathing for being too complex, for requiring too much practice, or for being plain old too hard to do, but Dennis' analysis is way off base. By the way, it is quite possible to keep your glottis open, even whilst neither inhaling nor exhaling, or even while free diving. (emphasis added--jcr)

Thalassamania, in my post #75, there is a description of an accident which did involve a single fatality from buddy breathing? It was not overpressure, but it was a buddy breathing failure. Hilbert V. Schenck, Jr., and John J. McAniff were concerned enough about these incidents to state:

...It is difficult to escape the impression that had the victim attempted an immediate, emergency surfacing maneuver rather than remaining at depth and attempting the regulator exchange, both might have survived. Once again we stress what has been observed in dozens of shared-breathing cases through the years: The possession of one's own regulator is decisive in an air-lack emergency...Buddy breathing has surely saved many lives, but it can and does fail. Had these two persons been using octopus units, we believe they would both have lived.(emphasis added--jcr)
United States Underwater Fatality Statistics 1975

If they make it to the surface buddy breathing, usually all is well. It's what happens on the way up that can be problematic. And, it doesn't have to result in an overpressurized lung to be a fatal situation.

In your last sentence, it seems you agree that it is possible to breath hold while allowing air to expand out of the lungs. Is my impression correct?

SeaRat