UNASSIGNED: Central retinal artery occlusion (CRAO) presents suddenly causing painless loss of vision that is often significant. Meaningful improvement in vision occurs in only 8% of patients with spontaneous reperfusion. Hyperbaric oxygen treatment (HBOT) is considered to be of benefit if commenced before retinal infarction occurs. The Undersea and Hyperbaric Medical Society (UHMS) guidelines on the management of CRAO were last amended in 2019. This survey questioned Australian and New Zealand (ANZ) hyperbaric medicine units (HMUs) about the incidence of CRAO cases referred and compared their subsequent management against the UHMS guidelines.
UNASSIGNED: An anonymous survey via SurveyMonkey® was sent to all 12 ANZ HMUs that treat emergency indications, allowing for multiple choice and free text answers regarding their management of CRAO.
UNASSIGNED: One-hundred and forty-six cases of CRAO were treated in ANZ HMUs over the last five years. Most (101/146) cases (69%) were initially treated at a pressure of 284 kPa. This was the area of greatest difference noted in CRAO management between the UHMS guidelines and ANZ practice.
UNASSIGNED: Few ANZ HMUs strictly followed the UHMS guidelines. We suggest a more simplified management protocol as used by the majority of ANZ HMUs.

BACKGROUND: This study aimed to describe recently active adult scuba divers in the United States (US) and compare their characteristics with other active adults. The research question was: do active scuba divers have different health and wellbeing characteristics, compared with adults active in other pursuits?
METHODS: The Behavioural Risk Factor Surveillance System (BRFSS) is a proportionally representative annual survey of adults in the US. It is the largest continuous population health survey in the world. Since 2011, data on scuba diving is collected biannually. A comparison group were matched on age, sex, being physically active and state of residence.
RESULTS: The dataset comprised 103,686,087 person-years of monthly behavioural data, including 14,360 person years of monthly scuba data. The median weekly frequency of recent scuba diving was 1.0 times per week and the median weekly duration was equivalent to two dives each of one hour. Compared with the comparison group, divers more often earned > USD$50,000 per year, were less frequently married, with fewer children in the house, which they more often owned. They reported being able to afford a doctor if needed within the previous year, but more often reported excellent/good health and excellent/good mental health, despite the divers being 16% more frequently overweight.
CONCLUSIONS: The results demonstrate a relatively healthy cohort of active scuba divers, confirming previous survey results that active divers are commonly college-educated, unmarried, without children, home owning, often overweight, they often currently drink alcohol, and smoked tobacco in the past, but commonly gave up smoking ten years or more ago.

BACKGROUND: As the diving population is ageing, so are the diving instructors. Health issues and the use of prescribed medications are more common when ageing. The death of two diving instructors during one weekend in 2017 in the Netherlands, most likely due to cardiovascular disease, motivated investigation of the prevalence of relevant comorbidities in Dutch diving instructors.
METHODS: All Dutch Underwater Federation diving instructors were invited to complete an online questionnaire. Questions addressed diving experience and current and past medical history including the use of medications.
RESULTS: A response rate of 27% yielded 497 questionnaires (87% male, average age 57.3 years [SD 8.5]). Older instructors were over-represented among responders (82% of males and 75% of females > 50 years versus 66% of males and 51% of females among the invited cohort). Forty-six percent of respondents reported no current medical condition. Hypertension was the most commonly reported condition followed by hay fever and problems equalising ears and sinuses. Thirty-two percent reported no past medical condition. Problems of equalising ears and sinuses was the most common past medical condition, followed by hypertension, joint problems or surgery, and hay fever. Fifty-nine percent used non-prescription medication; predominantly analgesics and nose or ear drops. Forty-nine percent used prescription medicine, mostly cardiovascular and respiratory drugs. Body mass index (BMI) was > 25 kg·m-2 in 66% of males and 38% of females. All instructors with any type of cardiovascular disease were overweight.
CONCLUSIONS: Nineteen percent of responding diving instructors suffered from cardiovascular disease with above-normal BMI and almost 60% used prescribed or non-prescribed medication. Some dived while suffering from medical issues or taking medications, which could lead to medical problems during emergency situations with their students.

BACKGROUND: We aimed to identify the possible chain of events leading to fatal scuba diving incidents in Australia from 2001-2013 to inform appropriate countermeasures.
METHODS: The National Coronial Information System was searched to identify scuba diving-related deaths from 2001-2013, inclusive. Coronial findings, witness and police reports, medical histories and autopsies, toxicology and equipment reports were scrutinised. These were analysed for predisposing factors, triggers, disabling agents, disabling injuries and causes of death using a validated template.
RESULTS: There were 126 known scuba diving fatalities and 189 predisposing factors were identified, the major being health conditions (59; 47%), organisational/training/experience/skills issues (46; 37%), planning shortcomings (29; 23%) and equipment inadequacies (24; 19%). The 138 suspected triggers included environmental (68; 54%), exertion (23; 18%) and gas supply problems (15; 12%) among others. The 121 identified disabling agents included medical-related (48; 38%), ascent-related (21; 17%), poor buoyancy control (18; 14%), gas supply (17; 13%), environmental (13; 10%) and equipment (4; 3%). The main disabling injuries were asphyxia (37%), cardiac (25%) and cerebral arterial gas embolism/pulmonary barotrauma (15%).
CONCLUSIONS: Chronic medical conditions, predominantly cardiac-related, are a major contributor to diving incidents. Divers with such conditions and/or older divers should undergo thorough fitness-to-dive assessments. Appropriate local knowledge, planning and monitoring are important to minimise the potential for incidents triggered by adverse environmental conditions, most of which involve inexperienced divers. Chain of events analysis should increase understanding of diving incidents and has the potential to reduce morbidity and mortality in divers.

Diving by persons with diabetes has long been conducted, with formal guidelines published in the early 1990s. Subsequent consensus guidelines produced following a 2005 workshop helped to advance the recognition of relevant issues and promote discussion. The guidelines were intended as an interim step in guidance, with the expectation that revisions should follow the gathering of additional data and experience. Recent and ongoing developments in pharmacology and technology can further aid in reducing the risk of hypoglycemia, a critical acute concern of diving with diabetes. Careful and periodic evaluation remains crucial to ensure that participation in diving activity is appropriate. Close self-monitoring, thoughtful adjustments of medications and meals, and careful review of the individual response to diving can assist in optimising control and ensuring safety. Open communication with diving partners, support personnel, and medical monitors is important to ensure that all are prepared to effectively assist in case of need. Ongoing vigilance, best practice, including graduated clearance for diving exposures and adverse event reporting, are all required to ensure the safety of diving with diabetes and to promote community understanding and acceptance.

BACKGROUND: This study identified pre-existing medical conditions among scuba diving fatalities in Australia from 2001 to 2013, inclusive, and assessed whether these conditions likely contributed to the deaths.
METHODS: The National Coronial Information System (NCIS) was searched for scuba diving-related cases during 2001-2013, inclusive. Coronial findings, witness and police reports, medical histories, and autopsy and toxicology reports were scrutinised for pre-existing medical conditions and autopsy findings. Predisposing factors, triggers, disabling agents, disabling injuries and causes of death were analysed using a validated template.
RESULTS: There were 126 scuba diving-related fatalities identified during the study period. Forty-six (37%) divers were identified as having a significant medical condition which may have contributed to their incident. The most common condition was ischaemic heart disease (IHD) which had been diagnosed in 15 of the divers. Thirty-two (25%) deaths were attributed to cardiac disabling injuries (DI) such as ischaemic heart disease and arrhythmias, although a cardiac DI was thought likely in another six. Respiratory conditions were implicated in eight (6%) deaths, at least four associated with cerebral arterial gas embolism. At least 14 (11%) divers who had contributory pre-existing medical conditions had been cleared to dive by a medical practitioner within the year prior.
CONCLUSIONS: Chronic health-related factors played a major role in almost half of these deaths; primarily cardiac conditions such as IHD and cardiac arrhythmias. Although fitness-to-dive (FTD) assessments have limitations, the high incidence of cardiac-related deaths indicates a need for \'older\' divers to be medically assessed for FTD.

BACKGROUND: Scuba diving is physically and cognitively demanding. Medical guidance regarding physical and mental health (MH) issues and related prescribed medication is often based on limited evidence. There is a paucity of data concerning diving with MH issues. This survey aimed to investigate the prevalence of MH issues and use of prescription medications among United Kingdom (UK) sport divers, and the rate of non-compliance with current guidance among divers suffering depression and anxiety. The positive effects of scuba diving on MH were also considered.
METHODS: An anonymous online survey was publicised through diving exhibitions and social media. Measures included diver and diving demographics; GAD-7 Anxiety and PHQ-9 depression questionnaires; diagnosed current and/or past MH conditions; medication usage; comorbid medical conditions/treatments; disclosure of past/current MH issues; and perceived MH benefits of diving.
RESULTS: Data from 729 respondents revealed MH issues at rates comparable with the general population. Current and/or past MH issues were reported by 111/729, with 60 having active diagnoses, and 45/60 taking prescribed psychotropic medications; 21/45 did not declare their medication on diver self-certification medical forms. The activity of diving was thought to be beneficial to MH by 119/729 respondents.
CONCLUSIONS: Divers experienced expected levels of MH issues, but did not comply with current medical guidelines on modifying or abstaining from diving activity or reporting their MH condition. Changes may be needed to diver training to encourage more accurate reporting and aid development of evidence-based protocols. Guidelines could be reconsidered in light of current diver behaviour, risks and potential MH benefits.

Dr Sherlock asks for clarification on the approach adopted by the European Committee on Hyperbaric Medicine (ECHM) to assessing evidence for establishing indications for hyperbaric oxygen treatment (HBOT). Firstly, regardless of the strict process of editing and proof-reading of tables included in the above-mentioned publication, we received comments from some readers that identified imperfect layout of Table 1 and incorrect layout of Table 2 which significantly changed the conclusions to be drawn from them. This concerned both the details of the methodology used and description of the ECHM recommendations and associated levels of evidence. Therefore, those tables are republished in their correct forms in this issue, hoping that this will explain at least some of the doubts and misunderstandings. Both the Editor and ourselves apologise for these errors of publication. Secondly, in the ECHM Consensus Conference methodology, we scored the evidence for clinical studies requiring double-blind randomised controlled trials (RCT) as Level A and B when, at the same time, some scoring scales require simply \'RCT\', as correctly pointed out by Dr Sherlock. Long experience in organising evidence based medicine (EBM) meetings and discussions has taught us that RCTs that are not double blinded are often criticised as having serious potential bias and so are denied as level A evidence. Although we acknowledge that double blinding a clinical study in HBOT is a source of difficulty, we chose a priori to consider only double-blinded RCTs in our grading scale to avoid endless discussions about this potential bias. We are well aware that doing so means that Level A evidence is a difficult target for the hyperbaric community. We agree that many evidence scoring systems have a low level of inter-observer agreement. This is why we treat the Consensus Conference as a valuable tool that provides a better opportunity for discussing the evidence than analysis by a small group of \'experts\'. This is because the whole process is transparent and available to all participants\' comments and input. The final process of voting by the audience after the general discussion thus truly reflects the position of the professional hyperbaric community in Europe on the issued recommendations. By these two mechanisms, the blind application of disputable evidence scoring systems may be avoided or, at least, decreased. Thirdly, the problem of \'sham\' treatments in hyperbaric research has been raised. While this has been discussed many times in the past, hyperbaric research is not the sole field where such sham treatment raises some difficulty. Surgery is probably the best example where RCTs with control arms utilising sham surgical procedures (possibly including the administration of anaesthesia) are rare and can raise major ethical problems. Nevertheless, from an EBM viewpoint, the difficulty of designing a double-blind study is never taken into account during evaluation of clinical studies. Finally, Dr Sherlock pointed out her doubts on the recommendations issued by the ECHM on idiopathic sudden sensorineural hearing loss (ISSHL). While there is no possibility to cite here the full experts\' report on that issue presented during the conference, we understand that a detailed report from the Conference is being prepared for publication. In brief, the strength of evidence has been scored as Level B, in general agreement with the last Cochrane review and the UHMS Committee report. Based on this level of evidence, the Type 1 recommendation was issued with the agreement of the large majority of the Consensus Conference participants.

The ECHM Consensus Conference on indications for hyperbaric oxygen treatment (HBOT) was a welcome update of the evidence for HBOT use. However, clarification is requested in relation to how the GRADE system (Grades of Recommendation, Assessment, Development and Evaluation) was modified and how levels of evidence were applied in the case of idiopathic sudden sensorineural hearing loss (ISSHL). GRADE has a low kappa value for inter-observer agreement, so is modification valid? The original GRADE criteria, using consensus, grades evidence (defined as high, low and very low) and uses this to adjust the strength of recommendations. Randomised controlled trials (RCTs) score highly. The ECHM have modified the GRADE system without explanation, assigning grades as levels 1 to 4 and have asserted that RCTs which are double-blinded constitute level 1 or 2 evidence. This has important implications for HBOT research. The term double-blinded is not used in the abstract, which leads the reader to wonder; where do RCTs which are not double-blinded fit in? The ECHM, by including the term double blinded as a requirement for level 1 or 2, has lifted the evidence bar. Does this constitute a form of research \"bracket creep\"? Double-blinding is viewed by many to require a \'sham\' treatment in hyperbaric research. Many conditions require multiple doses requiring daily hospital attendance with associated costs of lost time from work and daily transport costs. Even with a crossover after the sham, a requirement of many ethics committees, the lost time for a patient is a considerable burden. Delaying HBOT until crossover in those randomised to the control group in a disease that has a narrow therapeutic temporal window, such as idiopathic sudden sensorineural hearing loss (ISSHL), may affect the chance of recovery. Double blinding is logistically difficult with HBOT. A sham treatment may be achieved by using air instead of oxygen; however, this exposes the non-intervention group to a risk that the intervention group does not have, that of decompression sickness (DCS). This may be considered to be unethical. Researchers have used hypoxic air mixtures to compensate for the higher oxygen partial pressure at depth as the control, but this is complex and increases the nitrogen load (and thus the risk of DCS). RCTs which control by other methods should still be considered high level evidence (as the original GRADE system recognised). Many indications for HBOT have multiple therapies against which to compare, which could act as a control. The requirement for double-blinding to achieve level 1 or 2 evidence may hamper research; an unintended negative consequence. There is lack of consistency of definitions in relation to levels of evidence used by the ECHM. The authors state that for clinical research the levels of evidence are; levels A to F, which they defined. The ECHM jury used a grading scale of level 1 to 4. For ISSHL, this results in a recommendation to treat based on level B evidence. Is this the same as level 2 in their modified system? This is confusing. The authors have not explained why they modified the GRADE system which is itself non-validated. The lack of references to the publications which provide the foundation for the strength of the recommendations leaves the reader unable to determine the true strength of the evidence. The GRADE system has been criticised as it dissociates recommendations from the evidence that the recommendation is founded upon. Further, the application of the GRADE system has been questioned when strong recommendations are made with it as this may cause ethics committees to question whether equipoise exists, further hampering research. How do we present a well-designed trial for ISSHL to an ethics committee when a strong recommendation has already been made despite the Cochrane review on ISSHL concluding there is a need for large, well designed RCTs in this area?

Scuba diving is a popular recreational and professional activity with inherent risks. Complications related to barotrauma and decompression illness can pose significant morbidity to a diver\'s hearing and balance systems. The majority of dive-related injuries affect the head and neck, particularly the outer, middle and inner ear. Given the high incidence of otologic complications from diving, an evidence-based approach to the diagnosis and treatment of otic pathology is a necessity. We performed a systematic and comprehensive literature review including the pathophysiology, diagnosis, and treatment of otologic pathology related to diving. This included inner, middle, and outer ear anatomic subsites, as well as facial nerve complications, mal de debarquement syndrome, sea sickness and fitness to dive recommendations following otologic surgery. Sixty-two papers on diving and otologic pathology were included in the final analysis. We created a set of succinct evidence-based recommendations on each topic that should inform clinical decisions by otolaryngologists, dive medicine specialists and primary care providers when faced with diving-related patient pathology.