[abstract] Bubble recordings after nitrox dives with a semi closed demand controlled rebreather

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[abstract] Bubble recordings after nitrox dives with a semi closed demand controlled rebreather

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Title: [abstract] Bubble recordings after nitrox dives with a semi closed demand controlled rebreather
Author: Gennser, M; Blogg, L; Franberg, O
Abstract: Introduction: The Swedish Armed Forces have used the Interspiro Demand Controlled Semi Closed (DCSC) mechanical rebreather mine clearance set successfully for 15 years. At depths deeper than 30 msw the machine is fed a nitrox gas with 28% oxygen, giving a mixed gas containing 22-23% oxygen according to the manufacturer’s specification. Decompressions have been made according to the Swedish Navy air tables (based on USN56 tables). Given its excellent track record, it was of interest to investigate the amount of venous gas emboli (VGE) after deep square dives with the DCSC. Methods: A total of 12 dives to 33 msw for 20 minutes, 12 dives to 40 msw for 20 minutes, and 10 dives to 57 msw for 15 minutes were carried out using DCSC with 28% oxygen/72% nitrogen. Swedish air tables were used for decompression. After the dives the divers were checked for VGE for two hours post-dive with both ultrasound Doppler and 2D-ultrasound imaging. Results: One dive to 40 msw resulted in a limb bend, which was treated with USN TT6. The other dives were uneventful. The median maximum Kisman-Masurel Doppler scores varied between KM 3 and KM 3+ for the different depths. The maximum median 2D scores also varied between 3 and 3+ on the Brubakk-Eftedal scale for the various depths. Conclusion: Despite an excellent safety record with the DCSC, squared dives using decompression tables based on the USN56 air tables gave rise to one case of DCS and to high VGE scores post-dive, indicating a large decompression stress. This occurred despite the assumed added safety factor of a slightly higher oxygen fraction \than in air. In future tests the oxygen fraction in the breathing loop will be monitored.
Description: Undersea and Hyperbaric Medicine : Journal of the Undersea and Hyperbaric Medical Society, Inc.
URI: http://archive.rubicon-foundation.org/9887
Date: 2011

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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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