This is a 2-for-1 response. Or, in the current vernacular of 'special offers', maybe it can be called a BOGO.
JamesBon92007:
I can see how that would be an issue if cave diving or getting lost inside a shipwreck etc, but in open water, how does someone just "run out of gas (air)"?
The 'how' is outlined in the post that started this entire discussion, specifically in the document for which a link is provided in the very first line of that post.
Did not read all the answers but , to my knowledge there is - at least in france - a large number of fatal accidents due to "surpession pulmonaire " in other words "too high pressure in the lungs" that creates "explosions" of the lung alveoles , difficulties to oxygenate blood and therefore death. So I am rather surprised that you all seem to focus on loss of air and lack of weight ditching as the main cuprit. . . . Did I misread most of your discussion?
No, you did not misread the discussion. But, perhaps you just didn't read the very first post in this thread, specifically the very first line.
I do not make these comments to be critical of either comment, rather to identify a particular post, which happens to be the first post in the thread, and one that probably provides particularly useful context to facilitate understanding of the overall discussion.
And, in fairness to those who joined the discussion midstream, the thread has taken a rather tortuous and difficult to follow course at times, complicated by egregious misunderstandings and misinformation with regard to proper weighting, and some unfortunately extraneous and irrelevenat detour discussions about issues such as the weight of a diver's head. The comments about (over)weighting, in particular, have primarily evolved from the text of one of the linked 'references' -
http://www.divingmedicine.info/Ch 34 SM10c.pdf. And, on the surface the comments from that source appear to be applicable to the discussion. In fact, the observational study alluded to, but not directly referenced, in this chapter, while probably a seminal work,
for its time, is better described in 2016 as a 'vintage' study. The observational study - of 100 divers - which was the basis of the statistics cited in the chapter, was conducted between 1980 and 1989 (30 years ago), and (as far as can be determined) has not been updated with any subsequently collected data. Several posters in this thread have focused on the chapter authors' assertions about significant overweighting as a cause of diver deaths, without assessing the merits of the calculations the authors used to determine that overweighting was a legitimate factor in the diver deaths (somewhat arbitrary,
entirely retrospective and presumptive, and consequently flawed beyond any reasonable credibility). There is simply no contemporary evidence to support that presumption.
This thread originated with a question about a DAN summary of diver deaths, based on a substantial body of contemporary data. Those data indicate that, once medical events have been eliminated, a primary factor in diving incidents and accidents is an interruption in the gas supply. It may be that, in selected regions, the primary factor is something else (e.g. barotrauma associated with rapid ascent, medical events, etc.). But, the most important message - divers need to pay close attention to their gas supply - remains pre-eminent.
