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UKSteve · 17th April 2008, 17:16

Quote: (Originally Posted by jkaterenchuk)

Direct from the source....

Hi John,

This is a fairly common question, at first glance injecting oxygen on the inhale side would seem counter intuitive. However, CNS is not a condition that "strikes" with a breath of pure O2, it is a combination of time and level of PO2. If your operating envelope is anywhere near normal PO2 range a CNS hit is not an issue from a an occasional injection of O2. On the other side of the envelope if your PO2 had dropped to dangerously low levels and you were on the edge of Hypoxia you may not have the 3 or 4 breaths left to pull O2 from the exhale side, through the loop to your lips before you pass out. The overall design of the Meg is based on crictical controls being assessable to either hand and the ability of a diver on the edge of unconsciousness from whatever cause to have the best chance of self rescue. As you mentioned it is easy to switch the O2 to the exhale side and when I dive a 4 cell lung that is what I do to maintain a stable reading on the 4th cell.

Best Regards,

Jerry Whatley
General Manager
InnerSpace Systems Corporation

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

17th April 2008, 17:16	#5 (permalink)
UKSteve Still a novice... Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Jul 2005 Location: Weymouth, UK Posts: 557	Re: O2 slug Quote: (Originally Posted by jkaterenchuk) Direct from the source.... Hi John, This is a fairly common question, at first glance injecting oxygen on the inhale side would seem counter intuitive. However, CNS is not a condition that "strikes" with a breath of pure O2, it is a combination of time and level of PO2. If your operating envelope is anywhere near normal PO2 range a CNS hit is not an issue from a an occasional injection of O2. On the other side of the envelope if your PO2 had dropped to dangerously low levels and you were on the edge of Hypoxia you may not have the 3 or 4 breaths left to pull O2 from the exhale side, through the loop to your lips before you pass out. The overall design of the Meg is based on crictical controls being assessable to either hand and the ability of a diver on the edge of unconsciousness from whatever cause to have the best chance of self rescue. As you mentioned it is easy to switch the O2 to the exhale side and when I dive a 4 cell lung that is what I do to maintain a stable reading on the 4th cell. Best Regards, Jerry Whatley General Manager InnerSpace Systems Corporation 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
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