The TDM was used to record depth-time profiles of dives performed by three Navy diving units during surface-supplied harbor cleanup dives; WAL-18M decompression tables were used to determine decompression times. The decompression times required by the tables were compared against decompression times prescribed by the TDM running the WAL-18M real-time algorithm. For 309 dives conducted, there were matching written and uncorrupted TDM records for 17 in-water decompression dives and 142 surface decompression dives. The primary reasons for TDM records being unavailable were failure to charge the batteries and cable connection problems. Decompression required by the TDM would have been a mean of 7.9 min shorter for in-water decompression and a mean of 9.5 minutes shorter for surface decompression dives than the limits required by the tables-reductions of 69% and 26%, respectively. For these near square profiles, the time savings are small for each dive, but over the course of several dives they would have allowed time to dive additional teams each day. Real-time decompression calculations afford operationally relevant savings in decompression times for surface-supplied diving.

This project developed and evaluated a new mathematical decompression model with asymmetrical gas kinetics. The intended application was to support U.S. Navy diving operations involving surface decompression with oxygen (02) following air diving (Sur-D 02). Before this effort, the most sophisticated model for predicting human risk of decompression sickness (DCS) following exposure to elevated 02 mixtures was one developed in 1998 and based on only a small amount of Sur-D 02 data. The present effort added more than 4,000 dives, particularly dives with high 02 and/or Sur-D 02, to the data for calibration of the new model. About half of the added dives were experimental exposures involving rats, in the hope that higher-risk animal dives would improve prediction accuracy for higher-risk human dives. It was also thought that sharing parameters between the species, particularly those parameters defining the effect of 02 on decompression risk, might enhance model performance. However, we were unable to demonstrate an advantage of the rat-human model over the human-only or the 1998 models. We used all three models to evaluate three possible alternative Sur-D 02 procedures, each alternative having more flexibility than those currently in use but varying in amounts of DCS risk. The Navy can now evaluate changes in Sur-D 02 procedures by using all three models. When new procedures are considered for Fleet use, this approach may enhance decision making without requiring a manned dive trial. CONTENTS