Graphical Analysis: Decompression Tables and Dive-Outcome Data
Abstract
We use a graphical approach to compare prescriptions for ascent given by various air decompression tables with outcomes of experimental dives compiled in the U.S. Navy' Decompression Database. For a given dive depth, we plot times at decompression stops plus time to travel from depth to the surface (TDT) on the Y-axis end bottom time on the X-axis. The analysis dramatizes the large differences among alternative decompression instructions: tables from different sources require markedly different TDTs. For the same depth/bottom-time combinations, the TDTs for USN57 (the current U.S. Navy Standard Air table) are about one-third as long as those for VVal-18 (a table developed for the U. S. Navy). Many profiles that resulted in decompression sickness (DCS) have longer TDTs then those of the USN57 table; thus, divers developed DCS despite spending more time at stops then the table requires. To a lesser extent, the same is true for the table used by the Canadian forces. A few DCS cases occurred in profiles having longer TDTs than those of the VVal-18 table or a table prepared at the University of Pennsylvania. A table developed St Duke University enables divers to avoid DCS by avoiding long bottom times. The NMRI `99 table (generated by a U.S. Navy probabilistic model, evaluated for 2.2% risk) has far longer TPTs than almost all the experimental dives that resulted in DCS cases, end in many cases the TDTs are more than twice as long as those for VVal-18.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2004
- Accession Number
- ADA442657
Entities
People
- E. T. Flynn
- H. D. Van Liew
Organizations
- United States Navy Experimental Diving Unit