Just a question for MAC and ginger nut.
Being an engineer and a diver if folk have probs with stuff getting blown back in. How about blowing it out with 1 bar of pressure. ie stick them in a chamber and take them down slowly to 10m let them sit for a bit on 1.6 bar partial o2 and let the free radicals do there stuff then a reasonable sharpish accent?.
I was always amazed at the amount of snot, more than a mouth full, that could be held in ones head that was produced in the last 10m. I never got colds etc when diving 30m plus regularly. My sister who's job it is to research the green slime in sewage farms which eats poo reckoned we where making the bugs burn out with high PP of o2.