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An extract from Mathematical Evaluation of Mulit-Level Diving, U.S. Dept. of Commerce (NOAA), University of Michigan

INTRODUCTION
Over the past few years people in the diving community have been exposed to a new diving technique called Step Diving, or Multi-Level diving. This technique allows divers to extend their bottom time past the Navy's no-decompression limits and still surface without any decompression. The question to be considered is: is this type of diving technique safe to the divers who are practicing it? The answer to this question could affect a trend that is becoming more pronounced each year in the diving community. Already at some Caribbean resorts this type of diving has become common practice. These practices warrant further investigation before they spread into other areas of the diving community.
The step diving or multi-level technique is analyzed in this paper through mathematical evaluation of certain multi-level dive profiles. The Navy's model for nitrogen absorption and elimination in the body is used to check the nitrogen pressure present in the body tissues when the diver surfaces. Calculations were run on a Hewlett Packard 67 calculator specifically programmed for this study.


CALCULATION PROCEDURES
In order to calculate the nitrogen pressure in the different tissue groups, a program was developed for a Hewlett-Packard HP-67 programmable calculator. This program is a modification of two previous programs that were developed to calculate non-standard decompression schedules (Bassett 1974). These programs take multilevel dive profiles into account. The program that was developed for this project is listed in Appendix I along with directions for its use. It can calculate the tissue pressures for dive profiles up to 19 steps long with a maximum duration at each step of 999 minutes. It will display the final tissue pressures at the end of the profile, the tissue pressures at the end of each step, or, if the profile includes a combination of dives, it can display the tissue pressures at the end of each dive. The general display sequence is, first - the tissue group half-time, second - the nitrogen pressure in that group, and last - the % of M.A.P. for the tissue group.

APPENDIX I
DETERMINATION OF N2 BUILDUP DURING STEP DIVING


Appendix I utilizes the 'standard' HP program form(s) - excellent documentation throughout.

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