Saturation
Medical Moderator
Very welcome, folks. A take home msg fundamentally is the more diluted the information comes from the original source, the higher the likelihood of misinterpretation ... in this case Divernet's article misses a number of important issues included in Dr. Flooks' original report. However, in its reported facts, it indeed is 100% accurate, but it is strung together to read, in my interpretation, that yoyo diving to 100' is not such a bad idea, it is, and is not supported by Flooks' paper. Flooks' paper suggests safety is really in the 60' and shallower zone.
Often, a more precise description is a press release from Dr. Flooks' representative, but the best printed reference is the actual study itself, and later quering Dr. Flook in a press conference. If it reads somewhat difficult and is not entirely clear, it probably is the issue is not so clear cut too.
The overall msg of Flook's report is that offgassing in short dives to ~ 50' is quite clean for the profiles done by the fishtrap divers, however she defines what short is. Since ongassing in the early phase of dives is ~ linear, then 10min of bottom time, is almost fully offgassed by a 10 min SIT, thus critical controlling compartments are suitably cleaned out, in this case the CNS and blood. However, if the same time is spent entirely at depth, then the gas uptake enters a different slope, because ongassing is logarithmic, and thus, the tissues have ongassed more.
However, in dives past 60', and more clearly at 100' and deeper, the rate of ongassing is great enough that the yoyo dives provide no benefit in offgassing.
These model reports are independent of the effects of ascent rate or nucleation ... Flook focuses more on inert gas tissue tensions.
A more reasonable lesson from this report is in relation to reinforcing the safety of the procedures done by fish trap divers for shallow depths and for open water instructors, who dive similar profiles. For instructors that is, repeated pool work for several student groups over a day, and later shallow check-out dives to 20-30' often require yo-yo like profiles. DAN's recent accident report suggests a higher accident rate [bends] among instructors though, but doesn't clarify the conditions that led to the accidents.
Often, a more precise description is a press release from Dr. Flooks' representative, but the best printed reference is the actual study itself, and later quering Dr. Flook in a press conference. If it reads somewhat difficult and is not entirely clear, it probably is the issue is not so clear cut too.
The overall msg of Flook's report is that offgassing in short dives to ~ 50' is quite clean for the profiles done by the fishtrap divers, however she defines what short is. Since ongassing in the early phase of dives is ~ linear, then 10min of bottom time, is almost fully offgassed by a 10 min SIT, thus critical controlling compartments are suitably cleaned out, in this case the CNS and blood. However, if the same time is spent entirely at depth, then the gas uptake enters a different slope, because ongassing is logarithmic, and thus, the tissues have ongassed more.
However, in dives past 60', and more clearly at 100' and deeper, the rate of ongassing is great enough that the yoyo dives provide no benefit in offgassing.
These model reports are independent of the effects of ascent rate or nucleation ... Flook focuses more on inert gas tissue tensions.
A more reasonable lesson from this report is in relation to reinforcing the safety of the procedures done by fish trap divers for shallow depths and for open water instructors, who dive similar profiles. For instructors that is, repeated pool work for several student groups over a day, and later shallow check-out dives to 20-30' often require yo-yo like profiles. DAN's recent accident report suggests a higher accident rate [bends] among instructors though, but doesn't clarify the conditions that led to the accidents.
