Testing of Decompression Algorithms for Use in the U.S. Navy Underwater Decompression Computer
Final rept. on Phase 2
NAVY EXPERIMENTAL DIVING UNIT PANAMA CITY FL
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Results of the second phase of man-testing a computer algorithm for computing decompression profiles breathing 0.7 ATA oxygen in nitrogen are presented. This algorithm is primarily for use with the MK 15 or MK 16 closed circuit UBA. This Phase II testing was designed to lengthen the no-decompression limits established in the previously reported Phase I testing and to gain more experience in the 100-150 FSW depth range. Some 228 man dives resulting in 11 cases of Type I decompression sickness were conducted. During the course of Phase II testing, the decompression model had to be changed. Initially, the model used in Phase I testing was used exponential gas uptake and offgassing, 9 tissues ranging from 5 min to 240 min halftime, but testing showed this model predicted inadequate decompression profiles for repetitive dives. The Phase I model was modified so gas uptake was exponential but gas elimination was linear. This linear offgassing modeled the elimination of a gas phase with instantaneous diffusion in a well-mixed compartment. Three different sets of ascent criteria were tested using this modified model. The final set of ascent criteria produced an acceptable algorithm with an expected maximum incidence of decompression sickness less than 3.5 assuming that occurrence followed the binomal distribution at the 95 confidence leVel. The report gives complete details of the decompression model derivation as well as detailed flow charts for all algorithms. All tested ascent criteria and test profiles are presented along with complete descriptions of all cases of decompression sickness.
- Life Support Systems