There are several issues with freediving on nitrox:
1. You would still have to follow the scuba tables for the max depth to avoid O2 toxicity
2. There are reports that breath-holding on any elevated oxygen mixture causes strange physiological changes which decrease your ability to hold your breath on regular air. If you are not worried about your ability to hold your breath on regular air, then maybe you are willing to continue the nitrox.
3. The elevated O2 will suppress the breathing reflex even more, so that even the CO2 will not cause a breathing reflex. This puts you in danger of A) CO2 narcosis, B) CO2 blackout. In other words, even though you have minimized the risk of shallow water blackout, now you risk a blackout at the bottom due to extreme CO2 levels. (Imagine a scuba diver performing skip-breathing on nitrox--he would blackout very quickly)
So, an experienced freediver diving on nitrox might experience something like this:
- He starts the dive, and feels great. After several minutes on the bottom, he still feels great. Soon, his CO2 is massively elevated, but the extreme O2 inhibits his breathing reflex. Soon he starts getting confused and disoriented due to CO2 narcosis. Suddenly he realizes something is really wrong and he starts for the surface. The few hard kicks to get off the bottom generate enough CO2 to cause a CO2 blackout. He loses consciousness and promptly sinks back down to the bottom. Out of range of his surface freedivers, the grim reaper awaits him....
The risk of CO2 blackout, for me, would be enough to say no to nitrox.
Eric Fattah
BC, Canada
|
