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DAVID RHEA PHOTO/GUE.COM Technical Diving Conference Proceedings January 18-19, 2008 Richard D. Vann, B.A., B.S., Ph.D. Simon J. Mitchell, M.B., Ch.B., Ph.D., DipDHM, FANZCA Petar J. Denoble, M.D., D.Sc. T. Gavin Anthony BSc, MSc, CChem, CSci, FRSC Editors Technical Diving Conference Proceedings 1 Technical Diving Conference Summary Recommended Citation: Vann RD, Mitchell SJ, Denoble PJ, Anthony TG, eds. Technical diving. Proceedings of the Divers Alert Network 2008 January 18-19 Conference. Durham, NC: Divers Alert Network; 2009. ISBN# 978-1-930536-53-1 Copyright © 2009 by Divers Alert Network 6 West Colony Place Durham, NC 27705 This book is available for download at no cost as a pdf file from the Divers Alert Network Website (http://www.dan.org/). Opinions and data presented at the Conference and in these Proceedings are those of the contributors and do not necessarily reflect those of the Divers Alert Network. Cover design by Rick Melvin. ISBN 978-1-930536-1 Technical Diving Conference Proceedings 2 Technical Diving Conference Summary CONTENTS Acknowledgments 6 CONFERENCE SUMMARY Richard D. Vann 8 PHYSIOLOGY WORKSHOP CHAIRMAN’S SUMMARY Simon J. Mitchell 10 RESPIRATORY ISSUES IN TECHNICAL DIVING Simon J. Mitchell 12 CENTRAL NERVOUS SYSTEM OXYGEN TOXICITY Richard D. Vann, Robert W. Hamilton 38 NITROGEN NARCOSIS, OXYGEN NARCOSIS, AND THE HIGH PRESSURE NERVOUS SYNDROME Peter B. Bennett, Simon J. Mitchell 67 THERMAL CONCERNS IN COLD WATER DIVING Marshall L. Nuckols 99 DECOMPRESSION WORKSHOP CHAIRMAN’S SUMMARY Richard D. Vann 109 PATHOPHYSIOLOGY OF DECOMPRESSION ILLNESS Richard E. Moon 112 RISK FACTORS FOR DECOMPRESSION SICKNESS David J. Doolette, Richard D. Vann 119 DEEP STOPS AND THEIR EFFICACY IN DECOMPRESSION Wayne A. Gerth, David J. Doolette, Keith A. Gault 138 ASSESSING THE RISK OF DECOMPRESSION SICKNESS Richard D. Vann, Petar J. Denoble, David J. Doolette 158 Technical Diving Conference Proceedings 3 Technical Diving Conference Summary THERAPY FOR DECOMPRESSION ILLNESS Simon J. Mitchell, Richard Pyle, Richard E. Moon 178 REBREATHER WORKSHOP CHAIRMAN’S SUMMARY T. Gavin Anthony 204 TESTING DIVERS’ UNDERWATER BREATHING APPARATUS: THE U.S. NAVY PERSPECTIVE Dan E. Warkander 206 DIVING RE-BREATHING APPARATUS TESTING AND STANDARDS: UK/EU PERSPECTIVE T. Gavin Anthony 218 REBREATHER ACCIDENT INVESTIGATION John R. Clarke 236 MANUFACTURERS PANEL DISCUSSION Gavin Anthony, Alex Deas, Paul Haynes, Jarrod Jablonski, Gene Melton, Pete Nawrocky, Martin Parker, Peter Readey, Leon Scamahorn, William Stone 259 TRAINING WORKSHOP CHAIRMAN’S SUMMARY Petar J. Denoble 289 RISK ASSESSMENT ANALYSIS: EXPEDITION BRITANNIC 2006 John Chatterton, Richie Kohler 291 COMMON CAUSES OF FATALITIES IN TECHNICAL DIVING Petar J. Denoble 303 TRAINING PANEL DISCUSSION Petar J. Denoble, Steven Barsky, Jeffery Bozanic, Sean Harrison, Tom Mount, Karl Shreeves, Paul Haynes, David Pence, Jarrod Jablonski 311 Technical Diving Conference Proceedings 4 Technical Diving Conference Summary WRITTEN ANSWERS TO TRAINING QUESTIONS Steven Barsky, Jeffery Bozanic, Sean Harrison, Tom Mount, Karl Shreeves, Paul Haynes, David Pence, Jarrod Jablonski 342 APPENDIX A. Glossary 393 APPENDIX B. Schedule 396 APPENDIX C. Attendees 397 Technical Diving Conference Proceedings 5 Technical Diving Conference Summary ACKNOWLEDGMENTS Office of Naval Research Chief of Naval Operations Naval Sea Systems Command Suunto Vantaa, Finland www.suunto.com Curby’s Technical, Inc. 91 Exeter Drive Ottawa, Ontario, Canada K2J 1V6 Micropore, Inc. 350 F Pencader Drive Newark, DE 19702 www.extendair.com PADI 30151 Tomas Street Rancho Santa Marguerita, CA 92688 www.padi.com Silent Diving Systems/Ambient Pressure Diving 204 Fulford Point Road Elizabethtown, Ontario, Canada www.silentdiving.com The Rubicon Foundation, Inc. 5708 Catskill Ct. Durham, NC 27713 http://archive.rubicon-foundation.org/ Thanks to Peter Golding, editor of Diver Magazine, for providing 150 copies of the December issue for conference attendees Additional thanks to Cindi Easterling for skillful logistics management. Technical Diving Conference Proceedings 6 Editors: Richard D. Vann, B.A., B.S., Ph.D. Divers Alert Network Center for Hyperbaric Medicine and Environmental Physiology Duke University Medical Center Durham, North Carolina, USA Simon J. Mitchell, M.B., Ch.B., Ph.D., DipDHM, FANZCA Department of Anaesthesiology University of Auckland Auckland, New Zealand Petar J. Denoble, M.D., D.Sc. Divers Alert Network Durham, North Carolina, USA T. Gavin Anthony BSc, MSc, CChem, CSci, FRSC QinetiQ Alverstoke, UK Technical Diving Conference Proceedings 7 Technical Diving Conference Summary TECHNICAL DIVING CONFERENCE SUMMARY Richard D. Vann, Ph.D. Divers Alert Network Center for Hyperbaric Medicine and Environmental Physiology Department of Anesthesiology Duke University Medical Center Durham, NC, USA The Divers Alert Network (DAN) held a two-day technical diving conference on January 18-19, 2008 in Durham, NC. Included were four half-day workshops that addressed relevant issues pertaining to physiology, decompression, rebreathers, and training. These proceedings are the written record of the conference. Presentations and discussions are also available as video recordings.1 Topics covered in the workshops are described below. Physiology Workshop. The objectives of technical diving are to dive deeper and stay longer which exposes a diver to physiological stresses absent at sea level. Carbon dioxide is a particular concern. The lungs must be adequately ventilated with fresh gas to eliminate carbon dioxide or there are risks of headache, shortness of breath, unconsciousness, and increased likelihood of narcosis and oxygen toxicity. Many factors that influence the occurrence of oxygen toxicity, nitrogen narcosis and the high pressure nervous syndrome (HPNS) are well-understood, but their thresholds are ill- defined. Hypothermia is exacerbated by long dives, and insight into its physics and physiology is useful for understanding new active and passive thermal protection. Decompression Workshop. Longer and deeper dives require slow ascent to avoid decompression sickness (DCS). Much is known but much is uncertain. Bubbles have acute physical effects and delayed biochemical effects. Mechanisms leading to objective signs and subjective symptoms differ in according to affected tissues. Several environmental factors can cause large increases or decreases in DCS risk. Available evidence concerning deep decompression stops does not support their effectiveness. DCS is probabilistic, not deterministic. Risks can be reduced but not realistically abolished. DCS severity differs widely with probabilities that depend on dive conditions and inert gas species. Recompression on oxygen remains the gold standard for therapy, but methods that provide rapid intervention, such as in-water recompression, deserve consideration. 1 The PowerPoint® and mp4 video files may be viewed on line at the DAN website (www.dan.org) or downloaded to your computer by right-clicking on the file name. A high-resolution DVD is available at no cost. Please contact DAN Member Services at (800) 446-2671, Option 3, and ask for Product # 171-0010. Technical Diving Conference Proceedings 8 Technical Diving Conference Summary Rebreather Workshop. Rebreathers are an essential part of technical diving as they allow ready extension of depth and endurance due to their low gas consumption. Unmanned and manned testing is essential to ensure minimum performance capability, however. Standard U.S. Navy (USN) and European Union (EU) tests and their rationale were described. Common standards are under negotiation. Carbon dioxide toxicity is a major and unappreciated concern. Except for the few cases reviewed by the USN and EU, diving accident investigation is poorly-funded, non- standard, and lacks a competent investigative body. A panel discussion of nine rebreather manufacturers addressed key aspects related to design, manufacture, and operation. Training Workshop. Complex equipment and procedures allow long underwater penetrations but with numerous challenges whose mastery requires systematic training, experience and currency. Accidents happen nonetheless. Causes of fatalities were reviewed for recreational diving, cave diving and rebreather diving. During a sequence of adverse events, a diver may be incapable of self-help but might be rescued if adequate resources were available. Planning is essential for reducing risk, and an expedition risk assessment plan was presented as an example. A training agency panel discussed formal courses, compliance with training procedures, diver self-reliance, and role models. Communication within the diving community was recommended as a means of improving safety and efficacy. Technical Diving Conference Proceedings 9 Physiology Workshop Chairman’s Summary PHYSIOLOGY WORKSHOP: CHAIRMAN’S SUMMARY Simon J. Mitchell, M.B., Ch.B., Ph.D., DipDHM, FANZCA Department of Anaesthesiology University of Auckland Auckland, New Zealand Technical diving techniques are usually employed to facilitate either (or frequently both) of two goals: to visit greater depths or to extend underwater duration. Fulfillment of these goals exposes the diver to several problematic physiological stressors, which we have chosen to address in this workshop. Simon Mitchell describes the dependence of CO2 elimination on ventilation of the lungs with fresh gas. He points out that the use of any given gas mix at increasing depths requires the diver to respire a denser gas. This increases resistance to the