Diving and Hyperbaric Medicine The Journal of the South Pacific Underwater Medicine Society and the European Underwater and Baromedical Society Volume 46 No. 2 June 2016 Conservatism settings in dive computers Inner-ear barotrauma and Eustachian tube function Perilymph fistula from inner-ear barotrauma Inner-ear decompression sickness in trimix divers Critical flicker fusion and diver performance Different carbon dioxide absorbants are not equivalent 15 years of decompression sickness in Denmark Print Post Approved PP 100007612 ISSN 1833-3516, ABN 29 299 823 713 Diving and Hyperbaric Medicine Volume 46 No. 2 June 2016 PURPOSES OF THE SOCIETIES To promote and facilitate the study of all aspects of underwater and hyperbaric medicine To provide information on underwater and hyperbaric medicine To publish a journal and to convene members of each Society annually at a scientific conference SOUTH PACIFIC UNDERWATER EUROPEAN UNDERWATER AND MEDICINE SOCIETY BAROMEDICAL SOCIETY OFFICE HOLDERS OFFICE HOLDERS President President David Smart <[email protected]> Jacek Kot <[email protected]> Past President Vice President Michael Bennett <[email protected]> Ole Hyldegaard <[email protected]> Secretary Immediate Past President Douglas Falconer <[email protected]> Costantino Balestra <[email protected]> Treasurer Past President Peter Smith <[email protected]> Peter Germonpré <[email protected]> Education Officer Honorary Secretary David Wilkinson <[email protected]> Peter Germonpré <[email protected]> Chairman ANZHMG Member-at-Large 2015 John Orton <[email protected]> Karin Hasmiller <[email protected]> Committee Members Member-at-Large 2014 Denise Blake <[email protected]> Robert van Hulst <[email protected]> Simon Mitchell <[email protected]> Member-at-Large 2013 Janine Gregson <[email protected]> Pierre Lafère <[email protected]> Webmaster Liaison Officer Joel Hissink <[email protected]> Phil Bryson <[email protected]> ADMINISTRATION ADMINISTRATION Membership Honorary Treasurer and Membership Secretary Steve Goble <[email protected]> Patricia Wooding <[email protected]> 16 Burslem Avenue, Hainault, Ilford MEMBERSHIP Essex, IG6 3EH, United Kingdom For further information on SPUMS and to complete a membership Phone & Fax: +44-(0)20-85001778 application, go to the Society’s website: <www.spums.org.au> The official address for SPUMS is: MEMBERSHIP c/o Australian and New Zealand College of Anaesthetists, For further information on EUBS and to complete a membership 630 St Kilda Road, Melbourne, Victoria 3004, Australia application, go to the Society’s website: <www.eubs.org> SPUMS is incoprorated in Victoria A0020660B DIVING AND HYPERBARIC MEDICINE <www.dhmjournal.com> Editor: Editorial Board: Michael Davis <[email protected]> Michael Bennett, Australia PO Box 35 Alf Brubakk, Norway Tai Tapu 7645 David Doolette, USA New Zealand Christopher Edge, United Kingdom Phone: +64-(0)3-329-6857 Peter Germonpré, Belgium Jane Heyworth, Australia European (Deputy) Editor: Jacek Kot, Poland Lesley Blogg <[email protected]> Simon Mitchell, New Zealand Editorial Assistant: Claus-Martin Muth, Germany Nicky Telles <[email protected]> Neal Pollock, USA Journal distribution: Monica Rocco, Italy Steve Goble <[email protected]> Martin Sayer, United Kingdom Erika Schagatay, Sweden Journal submissions: David Smart, Australia Submissions should be made at http://www.manuscriptmanager.com/dhm Robert van Hulst, The Netherlands Diving and Hyperbaric Medicine is published jointly by the South Pacific Underwater Medicine Society and the European Underwater and Baromedical Society (ISSN 1833-3516, ABN 29 299 823 713) Diving and Hyperbaric Medicine Volume 46 No. 2 June 2016 69 and gradient factors has been introduced. The reasons for The Editor’s offering doing this were that both these design elements will become more prevalent in recreational diving computers in the next Carbon dioxide (CO2) absorption in rebreathers few years, but were not available at the time of the original testing. It was considered that to not address both of these Translating new findings into everyday practice usually introductions in a paper that will most likely be the only takes many months or even years. However, the grapevine one for some time that covers this overall subject would be in technical diving is such that the findings by the Auckland an obvious omission. group, published in the March 2015 issue,1 have already found their way into changes in the way divers are trained Whilst accepting this technical review is somewhat limited, on some closed-circuit rebreathers (CCR). Their conclusions as only one example of each computer was tested, previous were that, whilst there are several reasons for a ‘pre-breathe’, work by this group has shown that dive computers show identifying a carbon dioxide (CO2) absorber problem is not minimal and insignificant variation at the single model one of them. In this issue, Harvey et al compare the duration level.6 It is an important message that there is variation in of Sofnolime™ and Spherasorb™ CO2 absorbants in a CCR conservatism methods even between models by the same under standard conditions and demonstrate a significant manufacturer and that both consumers and medical advisors difference in performance between the two.2 Thus, a diver should be made aware of this. cannot assume similar durations for the two products before CO2 ‘breakthrough’ occurs. Society meetings Of considerable importance for CCR diving safety is the With 103 full delegates, SPUMS’s Annual Scientific Meeting fact that when CO2 breakthrough does occur, the rise in in Fiji, just finished, was its largest gathering ever, and PCO2 in the rebreather circuit is rapid, leading to increased attendees heard a range of excellent talks from the Guest ventilation and work of breathing, which can be catastrophic Speakers, Drs Chris Lawrence and Simon Mitchell and John at depth. Rebreather circuits, of which there are many Lippmann from DAN AsiaPacific. I wish EUBS the same varieties, mostly semi-closed, show this rapid change once a success with their meeting in August in Switzerland. rate-limiting point resulting in CO2 accumulation within the circuit is reached. For instance, in the Magill (Mapleson A) References anaesthetic circuit this point is when the fresh gas flow into the circuit is reduced to less than alveolar minute volume, 1 Deng C, Pollock NW, Gant N, Hannam JA, Dooley A, Mesley at which point expired alveolar gases reach the reservoir P, Mitchell SJ. The five-minute prebreathe in evaluating carbon bag in the circuit.3 dioxide absorption in a closed-circuit rebreather: a randomized single-blind study. Diving Hyperb Med. 2015;45:16-24. 2 Harvey D, Pollock NW, Gant N, Hart J, Mesley P, Mitchell User settings on dive computers SJ. The duration of two carbon dioxide absorbents in a closed-circuit rebreather diving system. Diving Hyperb Med. The paper by Sayer et al arose from discussions at the 2016;46:92-7. SPUMS Annual Scientific Meeting 2014 in support of the 3 Conway CM, Davis FM, Knight HJ, Leigh JM, Preston TD, SPUMS/UKSDMC joint statement on persistent (patent) Tennant R. An experimental study of gaseous homeostasis foramen ovale (PFO) and the need for divers to add an and the Magill circuit using low fresh gas flows. Br J Anaesth. element of conservatism to their diving.4,5 It was originally 1976;48:447-54. devised with the aim of informing medical advisers about 4 Sayer MDJ, Azzopardi E, Sieber A. User settings on dive how dive computers may be used by divers with PFOs or computers: reliability in aiding conservative diving. Diving Hyperb Med. 2016;46:98-110. who are returning to diving after PFO closure or having had 5 Smart D, Mitchell S, Wilmshurst P, Turner M, Banham N. a decompression illness incident. In these circumstances, Joint position statement on persistent foramen ovale (PFO) there may be a wish to use dive computer personal settings and diving: South Pacific Underwater Society (SPUMS) and/or nitrox while decompressing for air as safety factors. and the United Kingdom Sports Diving Medical Committee Little information is provided by computer manufacturers (UKSDMC). Diving Hyperb Med. 2015;45:129-31. about the underlying principles of ‘conservatism’ factors 6 Sayer MDJ, Azzopardi E, Sieber A. Decompression built into their products. management by 43 models of dive computer: single square- wave exposures to between 15 and 50 metres’ depth. Diving The authors had limited time and resources to do a Hyperb Med. 2014;44:193-201. comprehensive study and did not consider that one was necessary to bring most of the nuances of dive computer use Michael Davis to a readership that may have to provide guidance to a diver with a PFO. However, after peer assessment, it was decided Front page photo, by Dr Martin Sayer, shows Dr Cathy that an element of review was necessary in order to cover Meehan wearing the eight different makes/models of dive all aspects of computer-controlled diving conservatism. In computer used by her diving group on a wreck dive in particular, some discussion of dual algorithm computers Truk Lagoon in June 2015. 70 Diving and Hyperbaric Medicine Volume 46 No. 2 June 2016 overseas. Educational responsibilities include the teaching The President’s pages faculty of the ANZHMG and RAN SUMU courses and David Smart, President SPUMS setting up the Tasmanian Occupational and Offshore diving course. Along with the Royal Adelaide Hospital basic and At the time of writing this report, I am contemplating the advanced courses and the Western Australian short course, 2016 year ahead. This report precedes our Annual Scientific there are great opportunities to make diving medical training Meeting being held in Fiji in May. Fortunately the hotel was more consistent internationally. not seriously affected by the cyclone. By the time this is published, the meeting will have been completed. One challenging area for the Executive in the past has been succession planning.