Dennis Guichard
Registered
I've got my mind into a muddle thinking through all this decompression theory and hoping someone can kindly switch my light bulb back on...
Where I dive it has become common practice to do the last dive deepest simply because people controlling the dives think that a short deep dive (31m for 40 minutes) is safer than a long shallow one (say 18m max for 60 minutes)... so we would have done two 18-24m-ish dives on Friday, same again on Saturday, and then a 'quick' deep dive on the Sunday before getting away to drive back home after the long weekend away.
On the one hand I understand that tissue saturation is a time vs depth equation... it's driven by half-life's of the various tissues... so on a short dive you'd in-gas the fast tissues but not as much of the slower tissues as you would on a longer dive. But Henry’s Law of diving physics states that the amount of gas absorbed by a tissue is directly proportional to the partial pressure of the gas in contact with the tissue...
I know that decompression theory is not a 'simplistic' thing but is it rather at a simple level just a time driven thing, based on tissue half life's...?
In recreational no-deco-stop diving, IS a deep short dive safer than a longer shallower dive, assuming all else is equal in terms of ascent rate control, safety stops, hydration, etc...?
Research debated at the "Reverse Dive Profiles Workshop", conducted at the Smithsonian Institution in Washington D.C., in October 1999, resulted in the conclusion that in fact reverse profile diving (on the same dive or over a sequence of multi-day dives) was perfectly acceptable as long as the generally accepted 40m depth limit was not exceeded and that any repetitive dive was not more than 12m deeper than the preceding dive. This has subsequently however been disputed more recently (2013) in some dive medical books I've read and all seems to be endlessly in debate (as much around decompression theory seems to be).
If on both dives a diver has breathed their cylinder 'empty' (from say 230bar down to 50bar), haven't they both in fact breathed and thus in-gassed the same volume of inert gas? As an aside I've always questioned in my mind whether gas loading is influenced or not then by our breathing rate too rather than just something time-based...? So, to my original question, if you breathe the same volume of gas on both the deep and shallow dives isn't the in-gassing near enough the same and thus one isn't necessarily safer than the other at all...?
I appreciate and value any guidance and clarity...
Where I dive it has become common practice to do the last dive deepest simply because people controlling the dives think that a short deep dive (31m for 40 minutes) is safer than a long shallow one (say 18m max for 60 minutes)... so we would have done two 18-24m-ish dives on Friday, same again on Saturday, and then a 'quick' deep dive on the Sunday before getting away to drive back home after the long weekend away.
On the one hand I understand that tissue saturation is a time vs depth equation... it's driven by half-life's of the various tissues... so on a short dive you'd in-gas the fast tissues but not as much of the slower tissues as you would on a longer dive. But Henry’s Law of diving physics states that the amount of gas absorbed by a tissue is directly proportional to the partial pressure of the gas in contact with the tissue...
I know that decompression theory is not a 'simplistic' thing but is it rather at a simple level just a time driven thing, based on tissue half life's...?
In recreational no-deco-stop diving, IS a deep short dive safer than a longer shallower dive, assuming all else is equal in terms of ascent rate control, safety stops, hydration, etc...?
Research debated at the "Reverse Dive Profiles Workshop", conducted at the Smithsonian Institution in Washington D.C., in October 1999, resulted in the conclusion that in fact reverse profile diving (on the same dive or over a sequence of multi-day dives) was perfectly acceptable as long as the generally accepted 40m depth limit was not exceeded and that any repetitive dive was not more than 12m deeper than the preceding dive. This has subsequently however been disputed more recently (2013) in some dive medical books I've read and all seems to be endlessly in debate (as much around decompression theory seems to be).
If on both dives a diver has breathed their cylinder 'empty' (from say 230bar down to 50bar), haven't they both in fact breathed and thus in-gassed the same volume of inert gas? As an aside I've always questioned in my mind whether gas loading is influenced or not then by our breathing rate too rather than just something time-based...? So, to my original question, if you breathe the same volume of gas on both the deep and shallow dives isn't the in-gassing near enough the same and thus one isn't necessarily safer than the other at all...?
I appreciate and value any guidance and clarity...
