Thanks for sharing. Following the comments on youtube and the wikipedia page [1] I found this scientific analysis [2] about probable causes of the accident. M

Thanks for sharing. Following the comments on youtube and the wikipedia page [1] I found this scientific analysis [2] about probable causes of the accident. My layman summary: rising pressure of respired gas at high depth (about 26 atmospheres at the bottom) increases the respiratory resistance both in the diver (lungs, larynx) and the diving equipment. There is a limit to exhaled volume flow-rate called "effort independent flow" where compression of air-ways due to exhalation keeps air-flow from increasing further. This limit lies at lower flow-rates when breathing high-pressure gas. Physical exertion causes increased CO2 production by the diver which needs to be matched by correspondingly increased air-flow for CO2 removal. Once point of effort-independence is reached, lots of respiratory effort is wasted, contributing to further CO2 production. This causes a downward spiral of increased CO2 accumulation in the diver that could only be broken by switching to alternative breathing equipment that reduces respiratory effort (i.e. open-circuit gear). Seems that close-circuit diving equipment is generally more risky to use [3] due to difficult to detect and non-correctible failure modes. [1] https://en.wikipedia.org/wiki/David_Shaw_%28diver%29 https://en.wikipedia.org/wiki/David_Shaw_%28diver%29 [2] http://www.ingentaconnect.com/content/asma/asem/2007/00000078/00000002/art00001 http://www.ingentaconnect.com/content/asma/asem/2007/0000007... [3] https://en.wikipedia.org/wiki/Rebreather_diving#Risk https://en.wikipedia.org/wiki/Rebreather_diving#Risk