Posted by Kendall Raine on March 20, 2001 at 08:54:49:
In Reply to: Re: - A Quick Follow-Up Poll - posted by Jeff B on March 19, 2001 at 13:55:12:
Jeff
Interesting question. I think you mean, is deep air equally problematic if you're diving a hose. My answer: yes and no. Diving a hose means not running out of air. Diving a hose means comms. Diving a positive pressure system means you don't have an issue with breathing resistence-just dead space. Diving a helmet means your head is warm and maybe you have hot water in your suit. All help you deal with the inherent problems of narcosis.
On the other hand, you still have all that nitrogen in your body and brain. Let's face it, N2 at elevated partial pressures is hard on the body. Reb blood cell rigidity is one problem with nitrogen which potentially leads to a host of others-like isobaric osteonecrosis. You still also have the narcotic properties of nitrogen and you still have to manage the mission and your hose. A commercial diving friend of mine told me some days on deep air he just has to scram the dive and come up because he's too impaired to do the job right. You can also still have an emergency on a hose and have to deal with it quickly and decisively. Then there's CNS toxicity. Yes, you're far more likely to survive a convulsion diving a helmet, but you're still incapacitated on the bottom of the oceam. You can still embolize. The final issue is cost. If you've got the support and money to dive surface supply, why worry about the cost of helium?