Quote: (Originally Posted by
UKSteve)
As someone who always looks over the fence and likes to learn from others I found this a really interesting post. The subject has been debated before on here but I don't recall this rationale being mentioned before.. but I might of course simply be having a senior moment!!
It also made me think... what is the "right" response to looking at your handsets and seeing 0.20 0.18 and 0.19? Other than "Oh sh1t!!" I guess you have a choice - hit the manual O2 button or hit the manual Dil button (or suck hard and fire the ADV) .. but which?
I am trying to recall what (if anything) I was taught on my courses. Am away from home at moment - but my instinct is at depth, hit the dil button and dil flush and in the shallows - 6m or less, hit the O2 button. Based on that the rationale above only makes sense in the shallows .. but perhaps that is where you are most at risk of a sudden drop in ppO2?
Interested in others thoughts...
Steve
I don't dive a Meg, or indeed an ECCR, but like to mentally kick around problem scenarios as I believe it helps develop a "mental toolbox" which can be useful in emergencies.
On an ECCR if you look at your handsets and they are "0.20 0.18 and 0.19" then several of things come to mind: If they are reading correctly then you are breathing a perfectly life-sustaining gas mix. If they are reading correctly your ECCRs O2 addition system has failed in some way. If they are all incorrect (some major problem with software, frozen display, etc) then you may have no idea what you are breathing - about to pass out from hypoxia, or have a hyperoxic convulsion.
Therefore my first response would probably be to bail out to BOV unless I was sure the displays were reading correctly to avoid hypoxia/hyperoxia, and then reassess. If no BOV then you are into a debate as to whether O/C bailout is quicker than breathing dil by triggering ADV. If firing ADV gets dil to you fast then that sounds like a good plan, progressing to dil flush to check cell function. I probably wouldn't immediately try to add O2 even if I believed displays were right as 1. I may not be judging it well if hypoxic, 2. If O2 delivery has failed it may not work! immediate realisation that O2 is turned off, and displays are right, would be the only circumstance I wouldn't go to breathing dil by whatever route - in this case no big rush as still on life-sustaining mix, turn on O2 and bring up PO2.
Just my thoughts - but then I'm an MCCR diver at present
Neil