Does diving affect the hearing of Asian military divers? A study in the Republic of Singapore Navy

OBJECTIVE

This study examined whether military diving during a National Serviceman's two-year term of service affected his hearing threshold levels.

METHODS

A retrospective cohort study was designed to examine the hearing thresholds of divers (mean age 20.9 years) who enlisted between 2001 and 2010 (n = 748). Their pre-enlistment and pre-discharge audiograms were collected. All made dives using scuba dive sets, averaged 200 dives over two years and depths of 30 meters of sea water/msw or less.

RESULTS

The divers' hearing levels in the left ear were not affected except for a marginal decrease in hearing level at the 2kHz level. There was a marginal decrease in hearing level in 0.5, 1 and 2 kHz in the right ear. These changes are physiologically insignificant. There were more low-frequency (0.5, 1 and 2 kHz) changes compared to high-frequency (4 and 8 kHz) changes in both ears, with a larger number of changes noted in the right ear, as compared to the left. However, no diver had a hearing threshold increase greater than 20dB or exceeded the hearing threshold levels required of military divers.

CONCLUSION

There was no decrease of clinical significance in hearing function of the Republic of Singapore Navy national serviceman naval divers after diving for two years.

Provisional report on diving-related fatalities in Australian waters 2009

INTRODUCTION

An individual case review of diving-related deaths reported as occurring in Australia in 2009 was conducted as part of the DAN Asia-Pacific Dive Fatality Reporting Project.

METHOD

The case studies were compiled using reports from witnesses, the police and coroners. In each case, the particular circumstances of the accident and details from the post-mortem examination, where available, are provided.

RESULTS

In total, there were 21 reported fatalities (two more than in 2008), including 18 males and three females. Twelve deaths occurred while snorkelling and/or breath-hold diving, eight while scuba diving and one while using surface-supply breathing apparatus. Apneic hypoxia continues to be a problem with breath-hold divers and appears to have caused the death of three victims in this series. Cardiac-related issues were thought to have been the disabling injury in the deaths of at least three snorkel divers and at least three scuba divers. One of the victims was a student who became separated from her instructor on an introductory scuba dive in poor visibility.

CONCLUSIONS

Apneic hypoxia, pre-existing medical conditions, snorkelling or diving alone, separation and inadequate supervision were once again features in several deaths in this series.

Conservation of the critically endangered eastern Australian population of the grey nurse shark (Carcharias taurus) through cross-jurisdictional management of a network of marine-protected areas

Between 2001 and 2009, 26 marine-protected areas (MPA) were established on the east Australian seaboard, at least in part, to manage human interactions with a critically endangered population of grey nurse shark, Carcharias taurus. This network is spread across six MPA systems and includes all 19 sites outlined in the National Recovery Plan for C. taurus, though five sites remain open to some forms of fishing. The reserve network has complex cross-jurisdictional management, as the sharks occur in waters controlled by the Australian states of New South Wales (NSW) and Queensland, as well as by the Commonwealth (Federal) government. Jurisdiction is further complicated by fisheries and conservation departments both engaging in management activities within each state. This has resulted in protected area types that include IUCN category II equivalent zones in NSW, Queensland, and Commonwealth marine parks that either overlay or complement another large scaled network of protected sites called critical habitats. Across the network, seven and eight rule permutations for diving and fishing, respectively, are applied to this population of sharks. Besides sites identified by the recovery plan, additional sites have been protected as part of the general development of MPA networks. A case study at one of these sites, which historically was known to be occupied by C. taurus but had been abandoned, appears to shows re-establishment of an aggregation of juvenile and sub-adult sharks. Concurrent with the re-establishment of the aggregation, a local dive operator increased seasonal dive visitation rates at the site fourfold. As a precautionary measure, protection of abandoned sites, which includes nursery and gestating female habitats are options that may assist recovery of the east coast population of C. taurus.

Fate of abstracts presented at the annual scientific meeting of the Undersea and Hyperbaric Medical Society

INTRODUCTION

The full-text publication of abstracts presented at any given scientific meeting in peer-reviewed journals is accepted as a measure of scientific quality of that particular meeting. The aim of this study is to determine the full-text publication rate of abstracts presented at the 2005 Scientific Meeting of the Undersea and Hyperbaric Medical Society (UHMS).

METHODS

We identified the scientific abstracts presented at the 2005 UHMS meeting and searched the PubMed database (June 2005 to July 2010) for their corresponding full-text publication. We recorded the following parameters for each of the abstracts: number of authors, number of centers involved in the study, statistical methods used, country of origin of the study, study type, and subject of the abstract. We recorded the time to publication and the title of the journal if the abstract had been published in a peer-reviewed journal.

RESULTS

Overall, we identified 187 abstracts presented at the 2005 UHMS meeting. Two of the abstracts were excluded from the study because they had been retracted from the meeting and six more because they had been already published as full-text articles at the time the meeting was held. Of the 179 abstracts, 62 (34.6%) were published as full-text articles within the succeeding five years. The mean (+/- SD) time to publication was 18.5 (+/- 13.6) months. Multivariate analysis with logistic regression identified "country of origin" and "the subject of the abstract" as independent predictors of full-text publication.

CONCLUSION

We found that only one-third of the abstracts presented at the 2005 UHMS meeting were published as full-text articles within the succeeding five years. Although this rate is consistent with similar studies from various disciplines, further research is needed to identify the specific barriers to full-text publication of abstracts in the field of underwater and hyperbaric medicine.

Analysis of recreational closed-circuit rebreather deaths 1998-2010

INTRODUCTION

Since the introduction of recreational closed-circuit rebreathers (CCRs) in 1998, there have been many recorded deaths. Rebreather deaths have been quoted to be as high as 1 in 100 users.

METHODS

Rebreather fatalities between 1998 and 2010 were extracted from the Deeplife rebreather mortality database, and inaccuracies were corrected where known. Rebreather absolute numbers were derived from industry discussions and training agency statistics. Relative numbers and brands were extracted from the Rebreather World website database and a Dutch rebreather survey. Mortality was compared with data from other databases. A fault-tree analysis of rebreathers was compared to that of open-circuit scuba of various configurations. Finally, a risk analysis was applied to the mortality database.

RESULTS

The 181 recorded recreational rebreather deaths occurred at about 10 times the rate of deaths amongst open-circuit recreational scuba divers. No particular brand or type of rebreather was over-represented. Closed-circuit rebreathers have a 25-fold increased risk of component failure compared to a manifolded twin-cylinder open-circuit system. This risk can be offset by carrying a redundant 'bailout' system. Two-thirds of fatal dives were associated with a high-risk dive or high-risk behaviour. There are multiple points in the human-machine interface (HMI) during the use of rebreathers that can result in errors that may lead to a fatality.

CONCLUSIONS

While rebreathers have an intrinsically higher risk of mechanical failure as a result of their complexity, this can be offset by good design incorporating redundancy and by carrying adequate 'bailout' or alternative gas sources for decompression in the event of a failure. Designs that minimize the chances of HMI errors and training that highlights this area may help to minimize fatalities.

Provisional report on diving-related fatalities in Australian waters 2008

INTRODUCTION

An individual case review of diving-related deaths, reported as occurring in Australia in 2008, was conducted as part of the DAN Asia-Pacific dive fatality reporting project.

METHOD

The case studies were compiled using reports from witnesses, the police and coroners. In each case, the particular circumstances of the accident and details from the post-mortem examination, where available, are provided.

RESULTS

In total, there were 19 reported fatalities (the same as for 2007), 17 involving males. Twelve deaths occurred while snorkelling and/or breath-hold diving,and six while scuba diving. One diver died while using surface-supply breathing apparatus. Two breath-hold divers appear to have died as a result of apnoeic hypoxia, at least one case likely associated with hyperventilation. Two deaths resulted from trauma: one from impact with a boat and the other from an encounter with a great white shark. Cardiac-related issues were thought to have contributed to the deaths of five snorkellers and at least two, possibly three, scuba divers.

CONCLUSIONS

Trauma from a marine creature, snorkelling or diving alone, apnoeic hypoxia and pre-existing medical conditions were once again features in several deaths in this series.

An analysis of the causes of compressed-gas diving fatalities in Australia from 1972-2005

In order to investigate causative factors, root cause analysis (RCA) was applied to 351 Australian compressed-gas diving fatalities from 1972-2005. Each case was described by four sequential events (trigger, disabling agent, disabling injury, cause of death) that were assessed for frequency, trends, and dive and diver characteristics. The average age increased by 16 years, with women three years younger than men annually. For the entire 34-year period, the principal disabling injuries were asphyxia (49%), cerebral arterial gas embolism (CAGE; 25%), and cardiac (19%). There was evidence of a long-term decline in the rate of asphyxia and a long-term increase in CAGE and cardiac disabling injuries. Asphyxia was associated with rough water, buoyancy trouble, equipment trouble, and gas supply trouble. CAGE was associated with gas supply trouble and ascent trouble, while cardiac cases were associated with exertion, cardiovascular disease, and greater age. Exertion was more common in younger cardiac deaths than in older deaths. Asphyxia became less common with increasing age. Equipment-related problems were most common during the late 1980s and less so in 2005. Buoyancy-related deaths usually involved loss of buoyancy on the surface but decreased when buoyancy control devices were used. Countermeasures to reduce fatalities based on these observations will require validation by active surveillance.

Current status of decompression illness in China: analysis of studies from 2001-2011

OBJECTIVE

To analyze the studies on decompression illness (DCI) in China in the past 10 years.

METHODS

We searched three Chinese databases and collected studies on DCI for further analysis. On the basis of findings, we proposed the issues on DCI in China.

RESULTS

There are more than 50,000 active divers in China, the majority of whom are fishing divers. Among them, the incidence of DCI is still at a high level because they have little or no knowledge of diving and diving medicine, the quality of diving equipment is poor, and divers generally do not follow the regulations of diving. There are few dive physicians in China, and the general clinicians have poor knowledge about, or pay little attention to, dive medicine. This might be the major cause of the poor quality of studies on DCI. There is no consensus in the classification of DCI and treatment tables for DCI treatment. These are factors affecting systemic review and further meta-analysis of available studies on DCI.

CONCLUSION

It is imperative to generalize knowledge in not only divers and diving-related practitioners but general practitioners as well.

The incidence of decompression illness in 10 years of scientific diving

BACKGROUND

The American Academy of Underwater Science (AAUS) constitutes the single largest pool of organizations with scientific diving programmes in North America. Members submit annual summaries of diving activity and any related incidents.

METHODS

All diving records for a 10-year period between January 1998 and December 2007 were reviewed. Incidents were independently classified or reclassified by a four-person panel with expertise in scientific diving and diving safety using a previously published protocol. Subsequent panel discussion produced a single consensus classification of each case.

RESULTS

A total of 95 confirmed incidents were reported in conjunction with 1,019,159 scientific dives, yielding an overall incidence of 0.93/10,000 person-dives. A total of 33 cases were determined to involve decompression illness (DCI), encompassing both decompression sickness and air embolism. The incidence of DCI was 0.324/10,000 person-dives, substantially lower than the rates of 0.9-35.3/10,000 published for recreational, instructional/guided, commercial and/or military diving.

CONCLUSIONS

Scientific diving safety may be facilitated by a combination of relatively high levels of training and oversight, the predominance of shallow, no-decompression diving and, possibly, low pressure to complete dives under less than optimal circumstances.

Alcohol and UK recreational divers: consumption and attitudes

INTRODUCTION

Scuba diving demands information processing, recall, reasoning, decision making and the ability to take control of situations under different scenarios. Anecdotal evidence suggests that some divers consume alcohol to excess around the time of a dive. This study investigates alcohol consumption and attitudes to alcohol in United Kingdom (UK) recreational divers.

METHODS

A questionnaire addressing diving demographics, general health, type and frequency of alcohol consumption, and attitudes to drinking alcohol around the time of diving was available for anonymous completion online between September 2010 and January 2011.

RESULTS

Records from 818 divers were analysed. Older divers were more likely to exceed the weekly alcohol units recommended by the UK government compared to younger divers (P < 0.001), but binge drinking was associated with younger divers (P = 0.014). Diving when considering themselves unfit to drive a car was reported by 151 (18.5%) respondents and 187 (22.9%) had witnessed a diving incident which they felt was attributable to alcohol. Only 313 (38.3%) respondents reported a responsible attitude to alcohol by their dive clubs both under normal circumstances and whilst on a dive trip.

CONCLUSION

Some divers undertook diving activities when potentially over the legal limit to drive a car and demonstrated a possible lack of understanding of the effects of alcohol beyond dehydration. Divers considered club attitudes to drinking and diving to be less responsible when on a diving trip. Some divers took a more responsible attitude to alcohol consumption having witnessed a diving incident which was potentially related to alcohol.

Lower risk of decompression sickness after recommendation of conservative decompression practices in divers with and without vascular right-to-left shunt

INTRODUCTION

A vascular right-to-left shunt (r/l shunt) is a well-known risk factor for the development of decompression sickness (DCS). No studies to date have examined whether divers with a history of DCS with or without a r/l shunt have a reduced risk of suffering recurrent DCS when diving more conservative dive profiles (CDP).

METHODS

Twenty-seven divers with a history of DCS recommended previously to dive more conservatively were included in this study and retrospectively interviewed by phone to determine the incidence of DCS recurrence.

RESULTS

Twenty-seven divers performed 17,851 dives before examination in our department and 9,236 after recommendations for conservative diving. Mean follow up was 5.3 years (range 0-11 years). Thirty-eight events of DCS occurred in total, 34 before and four after recommendation of CDP. Four divers had a closure of their patent foramen ovale (PFO). A highly significant reduction of DCS risk was observed after recommendation of CDP for the whole group as well as for the sub-groups with or without a r/l shunt. A significant reduction of DCS risk in respect to r/l shunt size was also observed.

DISCUSSION

This study indicates that recommendations to reduce nitrogen load after DCS appear to reduce the risk of developing subsequent DCS. This finding is independent of whether the divers have a r/l shunt or of shunt size. The risk of suffering recurrent DCS after recommendation for CDP is less than or equal to an unselected cohort of divers.

CONCLUSION

Recommendation for CDP seems to significantly reduce the risk of recurrent DCS.

Provisional report on diving-related fatalities in Australian waters 2007

INTRODUCTION

An individual case review of diving-related deaths reported as occurring in Australia in 2007 was conducted as part of the on-going Divers Alert Network (DAN) Asia-Pacific dive fatality reporting project.

METHOD

The case studies were compiled using reports from witnesses, the police and coroners. In each case, the particular circumstances of the accident and details from the post-mortem examination, where available, are provided.

RESULTS

In total, there were 19 reported fatalities, comprising three females and 16 males. Nine of the deaths occurred while snorkelling and/or breath-hold diving, eight while open-circuit scuba diving, one while using a closed-circuit rebreather, and one while using surface-supply breathing apparatus. Cardiac-related issues were thought to have contributed to the deaths of at least three but possibly up to six snorkel divers and possibly two scuba divers. One diver is believed to have died as a result of immersion pulmonary oedema of diving. Six of the compressed-gas divers were very inexperienced, three being certified within 14 days prior and dying while under the guidance of an instructor.

CONCLUSIONS

Inexperience, pre-existing medical conditions and buoyancy issues were highlighted in several deaths in this series.

A review of 17 years of telephone calls to the Australian Diver Emergency Service (DES)

INTRODUCTION

The Diver Emergency Service (DES) in Australia provides specialised medical advice on diving incidents 24 hours a day to divers, dive operators, families and health professionals. It is operated from the Hyperbaric Medicine Unit of the Royal Adelaide Hospital where the physician-on-call also carries the DES phone (1800-088200 or +61-8-8212-9242).

METHODS

Data from calls to the service have been compiled into a computer database since 1991. Calls for the 17 years from 1991 through 2007 were analysed.

RESULTS

A total of 6,083 calls were logged, an average of 358 calls a year. Calls from Queensland and New South Wales each accounted for 25% of calls. Calls originating from outside Australia have been increasing and now make up 25% of calls. The diver themselves initiated the call 50% of the time and 66% of the calls were about male divers. The age range of divers was 12 to 95 years old. The mean age has increased from 30 to 36 years, with a greater proportion of calls from divers aged 50 years or older (from 2% to 14%). The largest group of calls (37%) related to whether symptoms might be the result of decompression illness (DCI). DCI was considered to be the probable diagnosis in 17% of calls, and possible in a further 12%. Other common findings were barotrauma (11%) and questions regarding fitness to dive (15%). Older divers were more likely to call in relation to a medical problem.

CONCLUSION

Interpretation of these data is qualitative but the prolonged collection period of 17 years allows some consideration of trends as to who calls the DES and why.

Diving-related deaths in Hong Kong waters, 2006-2009

Diving is a popular recreational activity in Hong Kong, and there is an associated incidence of mortality. This individual case review of reported diving-related deaths occurring in Hong Kong waters between 2006-2009 inclusive, was conducted as part of the ongoing DAN Asia-Pacific dive fatality reporting project. The eight reported deaths involved one snorkeler and seven scuba divers. Six of the victims were male and two were female. The disabling injury in at least one death, possibly two, appeared to have been cardiac-related; two involved trauma from impact with boats; and asphyxia was believed to be the disabling injury in four or five fatalities. Two of the deaths occurred during open-water diver training and one during advanced diver training. Inexperience, pre-existing medical conditions, poor supervision, solo diving and poor sea conditions were key factors in these deaths. It is hoped that this review provides a suitable model for others to emulate in reporting dive fatalities.