I WOULD LIKE TO ASK THE MEDICAL AND DECOMPRESSION GURU's on the Board to give their opinion to this report's findings.
In reading the report and the conclusions prepared on Yo Yo Diving (refer to the reference in RossH above), which not only looks at fish farm work but also includes a look at dive instructor's diving, the following statements are made in the conclusion of the report;
". . . One conclusion that can be drawn for all depths is that No-D diving puts the brain at particular risk. The rates of ascent though generally slow enough to protect the faster tissues are not slow enough to protect the brain. In general the accepted No-D tables do not protect the brain."
"A second conclusion that can be drawn for all depths is that tables drawn up for repet diving to not take into account the way in which the presence of bubbles slows down the removal of gas from the body. Though not a major part of this report this aspect of decompression is touched on in discussion of the profiles shown in Figure 7. These two conclusions lead the author to believe that dive computers currently in use may not be suitable as a means of determining safe yo-yo diving procedures."
NOTE THAT AS THIS IS A 2004 REPORT, THE REFERENCE TO DIVE COMPUTERS CURRENTYY IN USE MUST BE ASSUMED BY THE READER TO BE CONTEMPORANEOUS COMPUTERS/
While the report's conclusion goes on to state "The main conclusions from this work are that yo-yo diving of the type traditionally practiced in fish farm diving can be very safe . . .", it should be noted that this report used 4 ATA for dive instructors and typically 2 ATA or less for fish farmers.
FOR READERS NOT METRIC ORIENTED, 2 ATA IS 10 METERS OR 33 FEET, AND 4 ATA IS 30 METERS OR 100 FEET.
MY QUESTION/CONCERN IS FURTHER COMPLICATED BY THE REPORT CONCLUSION'S FINAL STATEMENT;
"Though, as far as we have the requisite knowledge, it seems that for the depths covered in this report bubble formation in the brain does not reach levels which can be said to be dangerous, once bubbles form there is a random element to the risk."
It seems to contradict itself twice. Once on the risk to the brain of No-D diving and once on the danger of Yo Yo diving in that they note that it can be very safe, and even safer than following a standard dive table profile, but yet note that dive computers may not be safe for Yo-Yo diving. While I can understand that the dive computer would follow the actual dive profile and thus have less bottom time than a square dive profile none-the-less, there is the general assumption throughout the report that it is evaluating bubble formation within No-Deco time limits.
