Quote:
| Originally Posted by milldog just a follow on from the thread deep air, as i don't want to hijack Brains thread
if your last stop on a dive was 36 minutes on O how would you break that up if at all?
would you count the back gas breaks as part of the deco?
if you don't break it up how long would you stay on O before you would have breaks?
or are you happier using the 80%?
Graham |
Our concerns with high POP gases are the effect that the O2 has on the lungs. As we know O2 is an irritant and anything above 0.5 PPO2 has a negative effect. So it does not really matter whether you use 80% or 100% both over time will have act as an irritant to the lungs ( pulmonary toxicity)
So what we are attempting to do with air breaks is to reduce to a minimum the effect of the O2 and keep the alveoli running at full speed.
Pulmonary toxicity is time dose dependent, so if you had been running high PPO2's during the bottom phase of the dive, then additional high exposures during deco would not only increase pulmonary tox, but also the likelihood of Oxtox.
Due to the effect of the gas breaks our lungs maintain a greater level of efficiency than without - I guess the secret is the how often should the gas breaks be? (a gas break is a break to the lowest breathable PPO2 that you have with you)
Over long periods of time 20 on and 5 off seems to start frying lungs, but anecdotally 12 on 6 off does not appear to have the same impact.
So with Graham's 36 minutes on O2, you could do 12 on 6 off, 12 on and 6 up. This keeps the clock running
Andy
PS I would not use 80%, as it still contains Nitrogen, and I would still be ongassing Nitrogen.