Mailing List Archive Mailing List Archive
> Whoooaaa. This is getting circular. I was labouring under the > impression that counterintuitively, high ppO2 was exactly what you > wanted - not because of the high O2, but because of the low diluent. Yes, generally high PO2 is what you want - but not BECAUSE of the O2 (for the most part) - it's BECAUSE of the reduced inert gas content. > The > point being that shifting from one diluent to another doesn't work; by a > number of theoretivcal observations, and more significantly by > observation. Errr...well...I don't think the jury is completely in on how multiple diluents function for calculating deco schedules (by the way, what is a "theoretical observation"). Point being, most deco models calculate deco stops based on total, combined inert gas content without regard for what the ratio of the different inert gases are. HOWEVER, the rates at which "ongasing" and "offgasing" occurs are calculated based on the "speed" of the gas (helium is "fast", nitrogen is "slow") and the GRADIENT between the inspired partial pressure of each inert gas and the theoretical dissolved concentration in the blood. By switching from heliox to nitrox, you increase the average helium gradient across the alveolar membranes, and thus increase the rate at which helium is theoretically removed from the body. > Just because the flushing route (basically the blood) is > emptying of He, does not mean that it can now carry far more He, because > now it's full of N. If you fill it with O2, the O2 then metabolises away > and lets more He out - high O2, not low He, is what you want. But this is where the relative "speeds" of helium and nitrogen come into play. Because helium is "faster" (smaller), it will be coming out of your body faster than the rate at which nitrogen is going in - so the combined dissolved inert gas total will (theoretically) decline. That's why it's not as efficient to decompress on heliox after a nitrox dive. That's also why Exley and others considered using argon as a decompression gas (it's "slower" than nitrogen). > So running two separate algorithms, one keyed to He, one to N2, > and ignoring the effect that each has, whilst groovy by that cat Billy > of Occam, doesn't quite mix the pickle . Huh? > Why do the pros no longer shift to Nx? Who are the "pros"? What are they decompressing on? If by "pros" you mean saturation commercial divers, then the reason they stay on heliox all the way out is because helium is a "faster" molecule, and therefore it's better to stay with helium for the duration when coming out of saturation. We "tech" divers are very-much sub-saturation divers, and therefore it works out to our advantage (theoretically) to swap to a heavier (slower) inert gas during decompression. Let me know if you'd like further elaboration on this. > How common do you think your preHPNS symptoms are? This is an > oddity, and there are several things about Narcs that might apply - i) > some old manuals state Narcs is a problem below 50m. Nothing about the > lab reports measuring it at 15m. Hence if you get a figure of 500 feet > and you find it at 250, don't be surprised. I dunno - how many people 1) breathe heliox in the 250-500 range, and 2) pay close attention to how their thought patterns are flowing? I would have thought that the commercial or Navy guys would have noticed or published something about it, which makes me think I'm an anomaly. On the other hand, every non-military, non-commercial deep diver (i.e., "tech" diver) that I've spoken to who has breathed a high-helium gas mixture (<50 feet EAD) below about 200 feet has told me they've felt the same way. > > Secondly, Cousteau, ever a genius for stating the blindingly > obvious and claiming it for his own, noted that 'intellectuals' suffer > more from 'rapture' than others. A higher self awareness and dependance > on higher functions is likely to detect any impairment earlier - this > *is* observed in divers. Anyone who says he isn't narced at 40m is > either i) lying, ii) brain dead, iii) on the Y. My experience has been the opposite RE: "intellectuals", but then again, I think Jaques' experience dwarfs mine. By the way, what does "on the Y" mean? > What would be interesting to know is if your symptoms are > exacerbated by cold, dark, stress, tiredness, physical condition or drug > use; as narcosis is. You'll have to find another test subject, because I avoid diving in water that's colder than what I can spend 3 hours in wearing only a t-shirt and swim suit; I don't do much night diving and I don't dive in holes in the ground (i.e., no dark); I have incredible grace under pressure so I never get stressed (that deserves a :-) I think), I don't get tired, I'm not terribly out of shape, and I believe that all drugs (including aspirin) are placebos so I never take them. > Is it my imagination or is TD a more pleasant place to be these > days? Seems to be.... Aloha, Rich
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]