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Brad May wrote: > > Devon E Bowen wrote: > > > > Somebody (no attribution) wrote: > > > > > > One item you wrote that interested me was the fact that you'd adjust > > > for the altitude. Exactly how would you do that? > > > > What I was suggesting was adjusting the tables as you would for any > > altitude dive. [Adjust for 8000' (cabin pressure)...] > > In the example you give, you are diving at sea level. By adjusting your > table for 8000' you are ignoring the fact that your tissues are already > saturated at a higher pressure of 1 ATA. All you table calculations will > be off because this initial N2 load is not accounted for. > > Now, if you dive for 24 hours (or whatever 3x the longest compartment > half-time in your particular table is) this initial error will have > dissipated away, and what you propose would be valid [...] I take that back, after 24 hours of diving, diving on a table adjusted to 8000' feet *still* wouldn't be valid, because in doing your adjusted table calculations you assume that when you surface you are at 8000'. In reality you are still at sea level (1 ATA), so you are not offgassing as fast or as completely as your calculations say. This will still be very conservative for intermediate dives, because you never really "surface" to 8000' between dives, you remain "submerged" at an equivalent depth of Ceiling_Depth = (1 ATA - p(8000')) * 33 FSW/1ATA. Sorry, don't have a table here to know the equivalent pressure for 8000'. But when your week of divng is over and it's time to board your plane and "surface" to 8000' equivalent cabin pressure, you must consider that you effectively haven't surfaced all week, but have in reality done a single week-long multilevel dive with a minimum effective depth as calculated above. Your tissues (especially the longer compartments) are more saturated than your calculations assume. I've never taken an altitude class, so take this with a grain of salt, but it makes sense to me. Comments? Brad May (bmay@co*.ci*.co*)
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