Strangely on OC dives I always used to plan for 1.4 on the bottom. So my first 100m dive OC was 1.4pp02 on the bottom and 1.6 at 66m (21/35) 1.6 @ 33m (36%) and 1.6 at 10m on 80%
For some strange reason I was always perfectly happy using the 1.4pp02 on the bottom of all my dives and often went above slightly due to fill errors. Id be happy pushing CNS to 150% but after that id start doing 15on/5off air breaks.
Then I read some GUE stuff several years ago which suggested I shouldn't be running such high pp02s on the bottom and I should only use 1.6 from 21m and up. The research appeared to make a strong link between working and high PPo2 but I didn't quite follow why I couldn't use 1.6 on deep deco (deep for me being 66m)
I decided to stick with my deep 1.6 as the stop times were so short it hardly seemed to matter.
Then in 04 when I switched to CCR things got a lot more complicated due to the constant PP02. Now I was running 1.3 for everything. I did three dives between 96m and 105m running 1.3pp02 all the way. On one dive lasting just under three and a half hours I noticed signs of lung irritation. This was on a multi day trip with several dives below 60 that week.
After this event I started introducing air breaks past 120 cns
I haven't suffered any lung irritation since. Whilst I very rarely go past 90m I do do a lot of diving over 100% CNS due to long bottom times in the 60-80m range.
A dive past 100m is a major event for me so Ill err on the side of caution. Because CCR has the odd spike and trough in PP02 I have gone with the generally accepted idea of running 1.2pp02 on the deeper dives.
I believe in a max END of 25m so I tend to run a lot of He in the mix. I understand more He will reduce breathing resistance and decrease C02 retention. This to me is a good thing.
I would never do any intentional hard work below 90m. If i found the telegraph it can just stay there. I am much more concerned about my level of work / stress at great depth than I am about my PP02 or He percentage.
Since switching to CCR i have always ran 1.3 for deco till the last stop depth. Then I will run 100% 02 for the final 20mins of any dive. If possible Ill do this at 4m but if not ill do it at 6.
Running pure 02 for the last segment of deco has resulted in a noticeable improvement in post dive condition.
So in summery: deep is 80m+ and ill run 1.2 on the bottom 1.3 on deco and finish with 100% for the last 20mins
So far, so good
I am 44, fit ish (badminton three times a week golf twice) but a light smoker moderate drinker and at least two stone overweight.
ATB
Mark