DAN Report on Diving Fatalities

[Thalassamania]

No agency demands it, a few prohibit it. There are many NAUI Instructors who still teach it as an ancillary skill.

 

[boulderjohn]

Thanks for you comments John. I have to take on Dennis' piece head on though. Let's look at this piece. Dennis states that one diver breaths while the other holds his breath - WRONG! One diver breathes while the other exhales by slowly blowing bubbles.

The wording confused me. Looking at the entire context of the quote, I think he mis-wrote it. I could easily be wrong, but the sentences that follow suggest that he meant that in the stress of the situation, dives forget that they are supposed to be exhaling and will instead hold their breath.

 

[Thalassamania]

Yes, your read of Dennis' piece is correct. But it is Dennis that was wrong ... all BB fatalities that I know of began with a separation of the divers, e.g., a bolt for the surface. None involved a diver who forgot to exhale during a BB ascent. The problem was always after the BB event had turned into a bolt style ESA.

 

[reefduffer]

Just a couple of observations. I'm just a recreational diver, neither a diving or medical professional.
But I read and remember, and this thread is missing some important stuff from previous similar discussions.

I think wrt the cardiovascular issues, the routine advice about lifestyle and prevention may be a little too pat.
See this post by JonKranhouse in post #69 here: http://www.scubaboard.com/forums/accidents-incidents/331412-diver-dies-islamorada-2.html#post5185219
An excerpt:

.... But consider these comments from the UHMS’ 1997 Near Drowning Workshop.

page 32/38 of PDF (excerpts, emphases added):

Dr. Lundgren: ...in immersion, say, at the surface, head out, the redistribution of blood...is quite marked. We've measured with dye dilution technique up toward a liter of blood being forced into the chest. You have a profound distention of the heart and increase in preload-and distention of the heart is arrhythmogenic by itself [i.e. causes abnormal electrical heart rhythm]...with the diving response we have seen amazing levels of arrhythmia in these healthy people. One of our subjects had a period of 45 seconds without a single sinus peak.

Dr. Neuman: ...there is no pathologic evidence for a fresh myocardial infarction, microscopically...the problem is that in these people who die sudden arrhythmic deaths [which could be aggravated by the immersion phenomenon], there is no way of telling what has happened to them, and you can only look for sort of corollary evidence that they may have a risk factor for a sudden arrhythmic death... And so this is one of the epidemiologic problems that you have to face, that we simply are going to have to accept the fact that it may not be possible to tell.

Dr. Dueker: I think that is absolutely beyond doubt, and if some one has an arrhythmic death, which certainly can occur, without coronary calcifications, but even with coronary problems, the pathologist isn't going to be able to help [and call it a drowning]
​

In my opinion, THIS 70-PAGE PDF SHOULD BE MANDATORY READING FOR ALL DIVE PROFESSIONALS. Training agencies should require mastery of this knowledge by DMs. Doing so could save lives and IMPROVE OUTCOMES: Near Drowning Workshop.

I found this workshop report quite interesting, although a slow slog in places as someone with no medical training.

In particular, see the paper Drowning with Scuba by Carl Edmunds starting on page 19 of the pdf. On page 22 fatalities were broken down by Buddy Diver/Group Practice. There's more detail, but this captures the gist:
In fact, 80% of the victims did not have a genuine buddy by virtue of their elected diving practice. In less than 1 in 10 deaths was there a continued contact with the buddy or group during and following the incident. The fatalities seemed to flagrantly disregard the "buddy" system, as did their companions, the organization which conducted the dive, or the "dive leader".

Speaking as a non-professional, it would seem that there's some low-hanging fruit in terms of both dive instruction and resort DM practices.

And another gem that struck me on page 28, discussing "Depth of Incident" among contributing factors [Bolding is mine]:
... This demonstrates that it is not so much the environment that is the problem, but the diver's experience of that environment. The danger of "diving deeper" without extra prudence and supervision is apparent. Any dive deeper than that previously experienced should be classified and treated as a "deep dive", irrespective of the actual depth.

 

[John C. Ratliff]

Thanks for you comments John. I have to take on Dennis' piece head on though. Let's look at this piece. Dennis states that one diver breaths while the other holds his breath - WRONG! One diver breathes while the other exhales by slowly blowing bubbles. As far as I know there has never been an incident (e.g., controlled exchange of regulator from depth to the surface) that resulted in an embolism. All of the cases I can remember involved a FAILED attempt to buddy breathe which resulted in a battle over the regulator followed by an bolt for the surface (or just a bolt for the surface) that resulted in an AGE. The divers are not together forgetting to exhale, they are separated, bolting to the surface. The article has many good points, unfortunately they are rather randomly distributed amongst pure fabrications.

Thalassamania, a couple of points. I was very specific to state that this was Dennis' opinion "at the time." These were mimiographed handouts for our ITC, as I recall, on blue paper. I have scanned them as I received them. This was a time when our thinking on buddy breathing was evolving, and Dennis put this together to stimulate thought. It was not a formal publication of Dennis'. I have saved it, and put it up on the Vintage Scuba website. I presented it here as a vintage piece of history, and not as a definitive statement. Dennis Graver went on to become one of the leading figures in NAUI, and for IQ8 (November 1976) published an article titled In Support of Emergency Ascent Training. Here is the abstract:

Significant controversy currently exists regarding Emergency Ascent training. Such training for sport divers is advocated and arguments in favor of the training not previously considered are presented. Contributing factors to accidents occurring during Emergency Ascent training are set forth. Recommended training procedures to offset the contributing factors are presented.

Dennis did not mention buddy breathing at all in this paper. I'll write more on buddy breathing from articles in NAUI News in the 1970s a bit later.

Second, on "holding one's breath," I consider that I am holding my breath even when I exhale. That is because I am not "breathing," but am controlling my breath. When I was free diving for fish, I would sometimes exhale on my way to the surface to suppress the urge to breath. I am exhaling, but I am also still "holding my breath" by not inhaling. Do you get my drift?

Third, I have a copy of the United States Underwater Fatality Statistics 1975, put out by the U.S. Departemnt of Commerce, NOAA and the U.S. Dept. of Transportation and the U.S. Coast Guard Underwater Safety Project, and printed on March 1977 by NAUI. It is an analysis of 637 skin and scuba diving fatalities. Of that, 555 were scuba fatalities. These were recorded in the USA over the period 1970 to 1975. The authors reported this case:

The accident involving an oceanographic specialist gathering specimens occurred in the Caribbean area. Although this incident involved research divers of the most skilled sort, who had made many such dives together, the case presents a typical failure of buddy breathing. The victim and buddy were ascending from 90 ft when the victim indicated zero air on a submersible pressure gage. Since both divers started with similar amounts of air and the buddy still had some 700 lb/in2 in his tank, different air consumption rates cannot be explained. The victim breathed many times before returning the regulator, at which point the buddy was in a partially drowned state, having swallowed water. He free-ascended and ditched his belt, but, on looking down, saw the victim supine on the bottom. Being light now, the buddy could not return to depth, but it is evident that he was in no shape to perform a rescue. After recovery, the victim's life vest was found to be operable, but lacking the two CO2 cartridges required. Two such items were found in the deceased's effects on the beach. The description of witnesses and the buddy's deposition make it evident that this was almost a double accident, even though it occurred in clear, warm and quiet waters under almost ideal conditions. 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-bretahing cases through the years: The possession of one's own regulator is decisive in an air-lack emergency. Seldom does the person with his own regulator die. Even though this buddy was so choked with water that he could not breath, he managed to achieve the surface with the regulator in his mouth. 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... (pages 15-16)
This report was producted by Hilbert V. Schenck, Jr., Professor of Mechanical Engineering and Applied Mechanics, and John J. McAniff, Research Associate and Diving Officer, College of Engineering and Special Instructor, Department of Physical Education, University of Rhode Island, Kingston, Rhode Island 02881.

SeaRat

John C. Ratliff, CSP, CIH, MSPH
NAUI #2710 (retired)

 

[boulderjohn]

Second, on "holding one's breath," I consider that I am holding my breath even when I exhale. That is because I am not "breathing," but am controlling my breath. When I was free diving for fish, I would sometimes exhale on my way to the surface to suppress the urge to breath. I am exhaling, but I am also still "holding my breath" by not inhaling. Do you get my drift?

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.

 

[The Chairman]

I define it the same way, John. If the airway has been occluded, then you are holding your breath. You can pause in the breathing cycle without occluding your airway. Unfortunately, holding your breath is part of the mammalian reflexes we have to deal with in regards to water. That's why there were so many accidents: people have to overcome their primordial reflexes in order to successfully do this. Some are more effective while others only fail.

 

[John C. Ratliff]

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.

What the exhaling is doing is relieving lung overpressure upon ascent. Technically, at depth a person has enough air in his or her lungs to make it all the way to the surface in an ascent if not delayed. Frederic Dumas, as described in JY Cousteau's The Silent World in some of the earliest scuba classes in the world, describes a free swimming ascent from 100 feet as his graduation from the class:

At the end of the course the honor students swim down to a hundred feet, remove all equipment and return to the surface naked. The baccalaureate is an enjoyable rite. As they soar with their original lungful, the air expands progressively in the journey through lessening pressures, issuing a continuous stream of bubbles from puckered lips.
(page 180)

One of the things to remember is that concepts change over time. We are comparing what Dennis Graver wrote in about 1972 with today's usage. I am attempting to show that the terms may have changed a bit in that time.

My understanding of the mammalian diving reflex is somewhat different too, in that it is a slowing of the heart rate and re-distribution of blood flow during a dive away from the limbs caused not by breath-holding so much as cold water on the face.

SeaRat

 

[The Chairman]

I'll ask a very simple question. Is a whale, a penguin, or a seal holding its breath

Of course it is. It takes a breath at one atmosphere of pressure. It doesn't matter how deep it goes as it has only one lung full of air. A diver, however, takes a breath at more than one atmosphere. The excess has to be vented as the pressure decreases or a lung over expansion injury will occur. Apnea or breath hold divers just don't have to worry about such things.

 

[John C. Ratliff]

NetDoc, Dennis Graver was also a snorkel diver. This was a time when we did both, regularly. The terminology for breath-holding in free diving and scuba was a bit different than today, where these are now considered by most as separate sports. All I'm saying is don't judge Dennis' statement by today's standards; judge it by the time period (1972) in which it was written.

SeaRat