Effect of compression rate on use of trimix to ameliorate HPNS in man to 686 m (2250 ft)

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Effect of compression rate on use of trimix to ameliorate HPNS in man to 686 m (2250 ft)

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Title: Effect of compression rate on use of trimix to ameliorate HPNS in man to 686 m (2250 ft)
Author: Bennett, PB; Coggin, R; McLeod, M
Abstract: Previous man dives, in a series designed to evaluate the physiological effects of helium, nitrogen, and oxygen (trimix), investigated the comparative effects of 5 percent vs. 10 percent nitrogen with fast compression (12 h 20 min) to 460 m (1509 ft) and subsequent compression over 2.5 d to 650 m (2132 ft). In 1981 three divers were compressed twice as slowly as for these earlier dives to 650 m over a period of 6 d 8 h using 10 percent N2 in heliox. An extensive series of studies were made over 4 d 15 h at 650 m before further compression to 686 m (2250 ft) for a stay of 24 h with extensive tests of psychological and neurophysiological performance, pulmonary function, reflex, Doppler, and other studies. High pressure nervous syndrome (HPNS) tremors and EEG theta activity increases were effectively controlled with no nausea, vomiting, or somnolence (microsleep). Some euphoria was present. At 686 m there was a 20percent to 30percent impairment of concentration and attention; otherwise the physical condition of the divers was fine and they completed all tasks without difficulty. Slow compression prevented the initial large performance decrement of 40percent to 50percent on Day 1 as found in previous fast-compression dives. Otherwise the performance tests showed much the same decrement of 15percent to 20percent seen in earlier dives; deeper than 570 m (1870 ft), however, the addition test was worse, with a decrement of 35percent. The results are discussed with respect to the previous two dives with faster compression, and the possible nonlinearity of nitrogen antagonism of HPNS is considered.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: PMID: 7168098
http://archive.rubicon-foundation.org/2920
Date: 1982

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  • Undersea Biomedical Research Journal
    The Undersea Baromedical Research journal was published by the Undersea Medical Society, Inc. (now the Undersea and Hyperbaric Medical Society) quarterly from 1974 to 1992 when the name changed to the Undersea and Hyperbaric Medicine Journal.

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