VVal-18 and VVal-18M Thalmann Algorithm Air Decompression Tables and Procedures.

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VVal-18 and VVal-18M Thalmann Algorithm Air Decompression Tables and Procedures.

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Title: VVal-18 and VVal-18M Thalmann Algorithm Air Decompression Tables and Procedures.
Author: Gerth, WA; Doolette, DJ
Abstract: The Thalmann Algorithm parameterized with the VVal-18 parameter set is a well-documented decompression algorithm developed at Navy Experimental Diving Unit (NEDU) to produce 0.7 atmospheres absolute (ata) constant PO2-in-N2 decompression schedules. The algorithm was more recently used with a modified VVal-18 parameter set, designated VVal-18M, to produce a candidate set of air diving decompression procedures. This report documents the modifications to the VVal-18 parameter set that result in VVal-18M and describes the accompanying updates to the Thalmann Algorithm that are required to correctly implement these modifications. Complete sets of air, air with in-water oxygen (Air/O2), and air with surface decompression using oxygen (SurDO2) decompression tables are provided as calculated with the algorithm with VVal-18 and VVal-18M parameter sets. In the absence of extensive man-testing, probabilistic models of DCS incidence and time of onset were used to assess the risks of decompression sickness (PDCS) of the schedules in these tables. Estimated risks and total decompression times of the schedules were compared to those of current U.S. Navy Standard Air and Air SurDO2 decompression procedures. Schedules for air with in-water O2 decompression (Air/O2) and air with surface decompression using oxygen (SurDO2) are recommended for use as prescribed by either the VVal-18 or VVal-18M Thalmann Algorithm. Schedules for air-only decompression prescribed by either the VVal-18 or VVal-18M Thalmann Algorithm are recommended with less enthusiasm because such schedules prescribe large decompression time increases that afford only relatively small DCS risk decreases from those incurred by current procedures over the range of commonly accepted DCS risk. This imbalance is mitigated by allowing a 10 fsw last decompression stop instead of the 20 fsw last stop imposed in the nominal VVal-18M procedures. Both the VVal-18 and VVal-18M air diving procedures integrate Air, Air/O2, and SurDO2 schedules into a single table that can be used with the same Surface Interval Credit Table that accompanies existing U.S. Navy VVal-18 0.7 ata and 1.3 ata constant PO2-in-N2 Tables, a use that would simplify table-based repetitive diving. Under all procedures, PDCS of schedules in a dive depth group increases with increasing total decompression stop time (TST). The integrated table of either VVal-18 or VVal-18M schedules will require insertion of an exceptional exposure limit line for air-only decompressions in each dive depth group to indicate when the schedules first incur unacceptable DCS risk as bottom time increases. Such lines are not required for the Air/O2 or SurDO2 schedules.
Description: Citation Status: Active; Citation Classification: Unclassified; Title Classification: Unclassified; Report Classification: Unclassified; Identifier Classification: Unclassified; Abstract Classification: Unclassified; Distribution Limitation(s): 01 - APPROVED FOR PUBLIC RELEASE; Information provided by the Department of Defense and the Defense Technical Information Center (http://www.dtic.mil/) is considered public information and may be distributed or copied unless otherwise specified. Use of appropriate byline/photo/image credits is requested.
URI: http://archive.rubicon-foundation.org/8349
Date: 2007

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