Effect of varying deep stop times and shallow stop times on precordial bubbles after dives to 25 msw (82 fsw)
Bennett, P.B.; Marroni, A.; Cronje, F.J.; Cali-Corleo, R.; Germonpre, P.; Pieri, M.; Bonuccelli, C.; Leonardi, M.G.; Balestra, C. (2007). Effect of varying deep stop times and shallow stop times on precordial bubbles after dives to 25 msw (82 fsw). Undersea Hyperb. Med. 34(6): 399-406
In: Undersea and Hyperbaric Medicine. The Society: Bethesda, Md.. ISSN 1066-2936, more
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| Authors | | Top |
- Bennett, P.B.
- Marroni, A.
- Cronje, F.J.
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- Cali-Corleo, R.
- Germonpre, P., more
- Pieri, M.
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- Bonuccelli, C.
- Leonardi, M.G.
- Balestra, C., more
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| Abstract |
Bennett PB, Marroni A, Cronje FJ, Cali-Corleo R, Germonpre P, Pieri M, Bonuccelli C, Leonardi MG, Balestra C. Effect of varying deep stop times and shallow stop times on precordial bubbles after dives to 25 msw (82 fsw). Undersea Hyperb Med 2007; 34(6):399-406. In our previous research, a deep 5-min stop at 15 msw (50 fsw), in addition to the typical 3-5 min shallow stop, significantly reduced precordial Doppler detectable bubbles (PDDB) and "fast" tissue compartment gas tensions during decompression from a 25 msw (82 fsw) dive; the optimal ascent rate was 10 msw (30 fsw/min). Since publication of these results, several recreational diving agencies have recommended empirical stop times shorter than the 5 min stops that we used, stops of as little as 1 min (deep) and 2 min (shallow). In our present study, we clarified the optimal time for stops by measuring PDDB with several combinations of deep and shallow stop times following single and repetitive open-water dives to 25 msw (82 fsw) for 25 mins and 20 minutes respectively; ascent rate was 10 msw/min (33 fsw). Among 15 profiles, stop time ranged from 1 to 10 min for both the deep stops (15 msw/50 fsw) and the shallow stops (6 msw/20 fsw). Dives with 2 1/2 min deep stops yielded the lowest PDDB scores - shorter or longer deep stops were less effective in reducing PDDB. The results confirm that a deep stop of I min is too short - it produced the highest PDDB scores of all the dives. We also evaluated shallow stop times of 5, 4, 3, 2 and I min while keeping a fixed time of 2.5 min for the deep stop; increased times up to 10 min at the shallow stop did not further reduce PDDB. While our findings cannot be extrapolated beyond these dive profiles without further study, we recommend a deep stop of at least 2 1/2 mins at 15 rnsw (50 fsw) in addition to the customary 6 msw (20 fsw) for 3-5 mins for 25 meter dives of 20 to 25 minutes to reduce PDDB. |
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