NAUI Master Scuba Diver 156 Decompression and Recompression 5 10 20 terpart, providing less time at depth. They also provide an extremely conservative repetitive dive procedure, since all repetitive dives are combined and worked as single dives, regardless of surface interval (table 5-2). The Royal Navy tables were in use by the British Sub-Aqua Club as recently as 1972. The divers using the Royal Navy tables had to add bottom times of repetitive dives made within 12 hours of a dive to 9 m (30 ft) or more. The total combined dive time and the deepest depth reached in either dive were used in the tables to determine decompression requirements. Once the diver had spent his 60 minutes at 18 m (60 ft), he could not return to that depth without stage decompression until 12 hours had passed. The 1980 BSAC Decompression Table Workbook uses the BSAC/Royal Navy Physiological Laboratory (RNPL) tables. These tables are based on a more recent theory than the R.N. tables and allow more time at depth than the R.N. tables and less time than the U.S. Navy tables. A technique has also been introduced to allow some surface interval credit for second dives, although more than two dives per day must still use the “multiple dive rule” of adding all bottom times and using the deepest dive depth. The BSAC/RNPL tables have been produced with very easy to remember decompression stop times. Unlike the U.S. Navy tables, where the first stop over the NDL varies from two to ten minutes at ten feet depending on dive depth, in the RNPL tables the first stop over the limit is always five minutes at five meters for dives shallower than 20 meters, and always “five at five” and “five at ten” for deeper dives. Swiss Theory The Haldane theory also provides the origin for the Swiss theory as developed by Professor A.A. Buhlmann at the Laboratory of Hyperbaric Physiology at the University of Zurich. Swiss theory utilizes 16 tissues, with half-times of 2.65 to 635 minutes, to determine no-decompression limits for single and repetitive dives, as well as decompression requirements for longer dives. Unlike Haldane theory and its British and American descendants, Swiss theory is extended to altitude diving. The M-values, or maximum surfacing nitrogen pressures, are not constant but rather are mathematical functions of atmospheric pressure. This further complicates an already complex situation, but tables and computers based on the theory 0 10 40 75 30 meters 100 feet 20 30 40 50 60 70 80 Dive 1 Time (Minutes) FIGURE 5-7. UPTAKE OF GAS IN ROYAL NAVY MODEL ON A DIVE TO 30 M (100 FT).
20047TC
To see the actual publication please follow the link above