[abstract] COMPARISON OF U.S. NAVY AIR DECOMPRESSION TABLES: NEW VS OLD.

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[abstract] COMPARISON OF U.S. NAVY AIR DECOMPRESSION TABLES: NEW VS OLD.

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Title: [abstract] COMPARISON OF U.S. NAVY AIR DECOMPRESSION TABLES: NEW VS OLD.
Author: Survanshi, SS; Parker, EC; Thalmann, ED; Weathersby, PK
Abstract: The U.S. Navy is releasing new air decompression tables based on a probabilistic model of human decompression sickness (DCS). The model parameters were estimated by fitting to a calibration data set of carefully controlled and recorded experimental dives. A large dive trial (709 man-dives) was conducted to validate the model. These trial dives were added to the calibration data set, totaling 3322 man-dives, and a final parameter set was derived by fitting to the combined data set. The decompression schedules were then computed using a "sliding risk" strategy: acceptable probability of DCS (P(DCS)) level is increased from 2.3% to 5% as total decompression time (TDT) increases from 20 min to 60 min, acceptable P(DCS) level is further increased from 5% to 10% as TOT increases from 180 min to 220 min and schedules are considered to be exceptional exposure schedules. The old U.S. Navy tables, which were developed in 1956 and tested with 568 single man-dives and 62 double repetitive-dives, are evaluated using the new model. Average estimated values of P(DCS) for the old schedules increase as TDT increases as shown below: TOT (min) 0-20 21-60 61-120 121-240 241-Longer P(DCS) 2.7% 5.3% 9.1% 14.2% 18%-36% In general, the new tables are more conservative, Le., allow shorter no-D times and require longer decompression times with the exception of deep short dives. For dives 90 fsw and deeper the new tables allow slightly longer no-D times but the decompression times at these depths are longer as bottom time increases. Graphs of decompression time vs bottom time at various depths comparing old and new tables are presented. P(DCS) values for schedules in the old table are compared to corresponding schedules in the new table. The dive data upon which both tables are based are also compared. (Supported by NMRDC Work Unit #63713N M0099.01A-IOO2)
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 22-26, 1994. Westin Hotel, Denver, Colorado (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/5696
Date: 1994

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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