| CCR in O2 mode as a "Deco Check"....
OK, I have been thinking. I run my unit as an O2 CCR on deco starting from about 7m briefly to get the buzzer sounding, then at 6m to keep the PPO2 nice and high (and hence maximise the inert gradient). After a reasonable exposure dive (particularly with Helium in the dil) it is apparent that I am still offgassing as the loop PPO2 drops - (before anyone who's not thought about this properly says, "But the PPO2 will drop because you're metabolising O2" - this is not the case, if the unit is running as an O2 breather, there should always be 100% O2 in the loop, and any drop is caused by the addition of inerts from your body, not the metabolisation of O2)
So my question is this: Could you use the monitoring of the rate of PPO2 drop whilst running a CCR in O2 mode as an indication that you are "clean"? For example if you're at 6m, and you flush the loop and get 1.6bar, you know you've got 100% in the loop, if after 5 minutes that's only dropped down to say 1.58 bar, could you assume that you are no longer off gassing as a rate that gives a hightened risk of DCS. (obviously I only picked the numbers 1.58bar and 5 minutes arbitrarily, more investigation would be required...)
In the case that your body is still loaded, but because of some external factor is not offgassing efficiently (for example like el_presidente frezing his nads off after a suit flood) this check would tell you that you might as well get out early, blow the stops, get on O2 and call the chopper as the stops are not working efficiently anyway, and even if you do them, you'll probably still be loaded. Would save possibly complicating a bend with hypothermia...
Any thoughts on this as a possible additional "cleanliness check"? |