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Exploring the use of full-face masks for ventilation in dive rescue

Elizabeth A Blizzard^1,2,3, Andrew A Grandin^2,3,4,5, Dalelynn Sims⁶

¹ Rutgers New Jersey Medical School, Newark, New Jersey, USA 
² Capital Health Life Support Training Center, Pennington, New Jersey, USA
³ Grand Ideas Medical Consulting, Burlington, New Jersey, USA
⁴ Capital Health Emergency Medical Services, Pennington, New Jersey, USA
⁵ ChristianaCare LifeNet, New Jersey, USA 
⁶ Brunswick SCUBA, Freeman, Virginia, USA

Corresponding author: Elizabeth Blizzard, 43 Bertrand Dr, Princeton, NJ 08540, USA
ORCiD: 0009-000 2-3070-8811
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Keywords
Diving medicine; Diving research; First aid; Life support; Rescue; Resuscitation

Abstract
(Blizzard EA, Grandin AA, Sims D. Exploring the use of full-face masks for ventilation in dive rescue. Diving and Hyperbaric Medicine. 2026 31 March;56(1):2−7. doi: 10.28920/dhm56.1.2-7. PMID: 41875436.)
Introduction: Early oxygenation is essential in a non-breathing scuba accident victim, but the need to exclude water has thus far prevented underwater ventilation, causing significant delay. The full-face mask (FFM) is a potential solution, but its safety and feasibility in this context has not been established. This is a preliminary study into the utility of FFMs for underwater ventilation.
Methods: The tidal volume and peak inspiratory pressure delivered by the OTS Guardian and Neptune III FFMs were measured using a RespiTrainer Advance Airway Management Trainer and an open circuit scuba system. Ventilations were tested with varying lengths of purge valve depression and degrees of tightness of the FFM. A tidal volume of 350–560 mL was considered ideal. Thresholds considered to be high risk were 700 mL for volutrauma and peak inspiratory pressure 
> 3.4 kPa for barotrauma.
Results: In all trials, the delivered pressure remained well below the 3.4 kPa threshold. The delivered volume was consistently less than 700 mL in at least one trial condition per FFM, although this required the fastest possible release of the Guardian purge valve without maximal mask tightening. The Neptune remained below 700 ml regardless of technique but required a one second purge valve depression to deliver sufficient volume (> 350 mL).
Conclusions: Recommendations need to be tailored to specific masks styles or brands. However, this form of ventilation could be feasible. Our findings are most directly applicable to ventilation at the surface. Further testing of these and other FFMs in simulation at depth will be necessary to evaluate the masks’ use for ventilation. These results merit further investigation.

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The full article is currently under embargo for 12 months and will be made available on our website and PMC after this period. If you would like to access the article before it becomes publicly available, you can purchase it for personal use directly on our website. Alternatively, you may join SPUMS or EUBS to gain access to the entire issue.

An echo from the past: open access repository of over 10,000 annotated Doppler audio recordings of venous gas emboli

S Lesley Blogg^1,2, Arian Azarang³, Rachel Lance^4,5, Frauke Tillmans^4,6, Richard Moon⁵, Virginie Papadopoulou³, Peter Lindholm^1,7

¹ Department of Emergency Medicine, University of California San Diego, USA
² SLB Consulting, c/o Home Park Barn, Kirkby Stephen, Cumbria, UK
³ Department of Radiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
⁴ Divers Alert Network, Durham, North Carolina, USA
⁵ Departments of Anesthesiology and Medicine, Center for Hyperbaric Medicine and Environmental Physiology, Duke University, Durham, North Carolina, USA
⁶ Lampe Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, North Carolina, USA
⁷ Department of Physiology and Pharmacology, Karolinska Institute, Sweden

Corresponding author: Professor Peter Lindholm, 200 W Arbor Drive, MC8676, San Diego, CA 92103, USA
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Keywords
Artificial intelligence; Bubbles; Decompression sickness; Measurement; Venous gas embolism

Abstract
(Blogg SL, Azarang A, Lance R, Tillmans F, Moon R, Papadopolou V, Lindholm P. An echo from the past: open access repository of over 10,000 annotated Doppler audio recordings of venous gas emboli. Diving and Hyperbaric Medicine. 2026 31 March;56(1):8−12. doi: 10.28920/dhm56.1.8-12. PMID: 41875437.)
Introduction: Doppler ultrasound measurements have been recorded since the 1970s across the world and provide a valuable data resource for learning, analysis, and potential training of deep learning algorithms to recognise and grade venous gas emboli (VGE) allowing assessment of decompression sickness (DCS) risk.
Methods: We collected a ‘big database’ of Doppler recordings and associated metadata. Audio tapes with recorded Doppler data were converted to digital files, then cut into individual recordings and matched with their metadata, including subject and pressure profile information. The audio signals and their Doppler grades were then processed further for suitability to train an algorithm to identify VGE.
Results: A total of 10,099 Doppler ultrasound recordings were compiled. Divers (n = ≤ 311; 170 identified, ≤ 141 unidentified) were male, with a median age of 31.5 years among the 170 identified divers. The maximum depth of the dives included ranged from 24 m (80 feet) to 91.4 m (300 feet). The timing of the Doppler measurements ranged from two minutes post-dive to 594 min post-dive, with a median time of 52 min. Breathing gases included air, nitrox, and heliox. DCS was noted in only 12 individuals. The dataset centred around lower VGE loads (Spencer Grades 0, I, and II).
Conclusions: This database represents a landmark in DCS investigation as the audio dataset and metadata collected have been released under a public domain license for further use. The large number of data points has also allowed the development of a deep learning algorithm that can grade bubble loads without a human operator.

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Changes in lung ultrasound presentation induced by breath-hold diving in a simulated depth competition at Taiwan

Ying-Jen Chi¹, Hsiu-Yung Pan², Po-Chun Chuang², Chi-Yung Cheng², Han-Yu Li³, Meng-Huan Wu²

¹ Department of Emergency Medicine, Pingtung Hospital of the Ministry of Health and Welfare, Pingtung, Taiwan
² Department of Emergency Medicine, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taiwan
³ Department of Family Medicine, E-Da Dachang Hospital, Kaohsiung, Taiwan

Corresponding author: Dr Meng-Huan Wu, Department of Emergency Medicine, Kaohsiung Chang Gung Memorial Hospital. No. 123, Dapi Road, Niaosong District, Kaohsiung 833, Taiwan
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Keywords
Freediving; Imaging; Immersion pulmonary oedema; Lung

Abstract
(Chi Y-J, Pan H-Y, Chuang P-C, Cheng C-Y, Li H-Y, Wu M-H. Changes in lung ultrasound presentation induced by breath-hold diving in a simulated depth competition at Taiwan. Diving and Hyperbaric Medicine. 2026 31 March;56(1):13−20. doi: 10.28920/dhm56.1.13-20. PMID: 41875438.)
Introduction: Acute respiratory symptoms after diving are common among competitive breath-hold divers. These symptoms, including shortness of breath, cough, haemoptysis, and chest discomfort, are often linked to immersion pulmonary oedema (IPO) or pulmonary barotrauma. This study aimed to evaluate the incidence, clinical presentation, and risk factors of IPO using portable ultrasound devices in a depth competition for breath-hold divers in Taiwan.
Methods: This observational study was conducted during a competition around Liuqiu Island, Taiwan. Twenty-five breath-hold divers participated. Lung ultrasonography was performed pre- and post-diving, along with measurements of basic vital signs. Symptoms and diving history were recorded. The primary outcome measure was B-line score before and after diving.
Results: Following the dive, 7/25 (28%) of divers reported acute respiratory symptoms, 10/25 (40%) showed ultrasound evidence of increased extravascular lung fluid, and 2/25 (8%) met the clinical criteria for IPO, presenting with both symptoms and hypoxaemia (SpO2 ≤ 95%) alongside positive B-lines. B-line scores significantly increased from a median of 4 (range 1–4) to 7 (range 3–13) (P = 0.048). Male sex, higher body mass index, and elevated pre-dive systolic blood pressure were significantly associated with positive ultrasound findings. Among all factors, only diving depth remained statistically significant associated with increased post-dive B-line scores (regression coefficient = 0.046) (P = 0.007).
Conclusions: The incidence of post-dive acute respiratory symptoms was 28%, and 8% of participants exhibited clinical features of IPO. Positive lung ultrasound findings were observed in 40% of divers, mostly asymptomatic. Maximum diving depth was significantly associated with increased post-dive B-line scores.

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Full article available here - this is an immediate release article.

Review of excursion procedures used in commercial heliox saturation diving

Jean-Pierre Imbert¹, Lyubisa Matity², Jean-Yves Massimelli³, Christian Cadieux⁴, Jan Risberg⁵, Philip Bryson⁶

¹ Divetech EURL, 1543 chemin des vignasses, 06410 Biot, France
² Hyperbaric and Tissue Viability Unit, Gozo General Hospital, Victoria VCT 2520, Malta
³ Centre Hospitalier Universitaire de Nice, 30, Voie Romaine, 06001 Nice, France
⁴ CCO Ltd, 52/2 moo 3 Tambon Tarpo - Phitsanulok 65000, Thailand
⁵ NUI, Gravdalsveien 245, 5165 Laksevag, Norway
⁶ TAC Healthcare Group, Wellheads Industrial Estate, Aberdeen, United Kingdom

Corresponding author: Dr Philip Bryson, TAC Healthcare Group, Wellheads Industrial Estate, Aberdeen, AB21 7GA United Kingdom
ORCiD: 0000-0002-7815-1218
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Keywords
Decompression sickness; Decompression tables; Excursion dives; Occupational diving; Oxygen

Abstract
(Imbert J-P, Matity L, Massimelli J-Y, Cadieux C, Risberg J, Bryson P. Review of excursion procedures used in commercial heliox saturation diving. Diving and Hyperbaric Medicine. 2026 31 March;56(1):21−40. doi: 10.28920/dhm56.1.21-40. PMID: 41875439.)
Introduction: This study reviews heliox saturation procedures used in offshore commercial diving and focuses on bell excursion dives. It excludes initial compression and final decompression. Our first objective was to trace the history and the reasons behind the successive changes that led to the current practice. Our second objective was to review the current practice and identify problem areas and perspectives.
Methods: We first present the background of excursion diving and reference key procedures from the US Navy, Comex, and international standards. We then review the procedures of 13 anonymised diving companies and compare their sources, designs, and operation parameters.
Results: The current excursion procedures are derived from a few original procedures (US Navy, Comex). It appears that, without relevant scientific support since the 1980s, companies have empirically adapted these procedures to their needs. Two designs prevail: excursions from storage depth and excursions from the deepest depth. Recent innovations offer ‘standard’ and ‘extended’ excursions, sliding excursion windows, as well as shallow and deep excursions. Companies participating in the study have a low risk of DCS with excursion diving. Excursions rarely produce immediate DCS symptoms but associated bubble formation could impact the final decompression. The trend is towards reduced excursion distances and explicit post-excursion intervals. Oxygen toxicity remains a general concern in saturation diving, but the PO2 values used in the procedures reviewed are unlikely to cause pulmonary toxicity according to the dose models in use.
Conclusions: We observed a trend towards harmonisation under the pressure of international standards and through cooperation within industry association committees. We recommend scientific monitoring of saturation divers to measure the decompression stress and support further research and development. We recommend that companies document their procedural developments to record and thus keep the lessons learned.

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Treatment success in relation to timing of hyperbaric oxygen therapy in idiopathic sudden sensorineural hearing loss 

Cheuk-Yin Lun¹, Kwan-Leong Au Yeung¹, Yuk-Fai Lau2, Wing-Wa Yan³, Kin-Bong Tang³

¹ Accident and Emergency Department, Queen Elizabeth Hospital, Hong Kong SAR, China
² Department of Ear, Nose and Throat, Pamela Youde Nethersole Eastern Hospital, Hong Kong SAR, China
³ Hyperbaric Oxygen Therapy Centre, Pamela Youde Nethersole Eastern Hospital, Hong Kong SAR, China

Corresponding author: Dr Cheuk-Yin Lun, Accident and Emergency Department, Queen Elizabeth Hospital, 30 Gascoigne Road, Kowloon, Hong Kong SAR, China
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Keywords
Hearing loss, sudden; Hyperbaric oxygen treatment; Otologic emergency; Outcomes; Treatment latency; Pure-tone audiometry

Abstract
(Lun C-Y, Au Yeung K-L, Lau Y-F, Yan W-W, Tang K-B. Treatment success in relation to timing of hyperbaric oxygen therapy in idiopathic sudden sensorineural hearing loss. Diving and Hyperbaric Medicine. 2026 31 March;56(1):41−47. doi: 10.28920/dhm56.1.41-47. PMID: 41875440.)
Introduction: Idiopathic sudden sensorineural hearing loss (ISSNHL) is an otologic emergency for which hyperbaric oxygen therapy (HBOT) is a potential treatment. This study aimed to evaluate the effectiveness of HBOT in treating ISSNHL, with a focus on the timing of treatment and its impact on hearing outcomes, while also considering other factors such as demographic characteristics, clinical parameters, and treatment methods.
Methods: This retrospective cohort study analysed 70 ISSNHL patients (April 2019 to August 2024) who received steroid treatment (oral, intratympanic or both). Patients were divided into early HBOT (< 12 days), late HBOT (13–22 days), salvage HBOT (> 22 days), and no HBOT groups. Hearing improvement, measured by pure-tone audiometry (PTA), defined the treatment outcome.
Results: Significant PTA improvements were observed in most groups (median changes: early HBOT 33.8 dB [n = 15], late HBOT 6.9 dB [n = 16], salvage HBOT 0.0 dB [n = 5], no HBOT 11.9 dB [n = 34]), with early HBOT showing greater gains than late HBOT (P < 0.001), salvage HBOT (P = 0.001), and no HBOT (P = 0.002). Receiver operating characteristic (ROC) analysis indicated that treatment within 10.5 days predicted marked improvement (AUC = 0.883, P < 0.001), and linear regression showed that each day’s delay reduced PTA improvement by 0.832 dB (P < 0.001).
Conclusions: HBOT is effective in restoring hearing in patients suffering from ISSNHL and early treatment is associated with better outcome.

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Scuba tank fill survey in Victoria, Australia, 1 July 2024 to 30 June 2025

John Lippmann¹

¹ Australian Diving Safety Foundation, Canterbury, Victoria, Australia

Corresponding author: Dr John Lippmann, Australasian Diving Safety Foundation, PO Box 478, Canterbury VIC 3126, Australia
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Keywords
Compressors; Cylinder fills; Decompression illness; Dive numbers; Diving deaths; Diving industry

Abstract
(Lippmann J. Scuba tank fill survey in Victoria, Australia, 1 July 2024 to 30 June 2025. Diving and Hyperbaric Medicine. 2026 31 March;56(1):48−51. doi: 10.28920/dhm56.1.48-51. PMID: 41875441.)
Introduction: This study’s aim was to determine the number of scuba tank fills done in Victoria, Australia from 1 July 2024 to 30 June 2025 to provide an estimate of the number of scuba dives conducted during that period and, from that, estimates of the fatality and decompression illness rates.
Methods: Suppliers of compressed gas for scuba diving in Victoria were identified through internet searches, industry liaison and the Australasian Diving Safety Foundation records. Those identified were emailed an invitation to participate in the tank fill survey and provided with dedicated spreadsheets. Email reminders were sent to collect monthly data on air, nitrox and ‘other’ fills. Data were compiled and, at the end of the survey period, non-regular participants were approached to provide actual numbers or estimates of the year’s fills.
Results: Overall, 38/40 (95%) identified current suppliers participated in the survey, with 27 submitting regular monthly data and the remainder providing actual or estimated annual fills. There were 46,720 reported fills, including 39,386 air, 6,758 nitrox, and 576 others, with proportions of 84%, 15% and 1%, respectively. During that period, 11 scuba divers were treated for decompression illness (DCI) (eight of whom had dived locally) and there were two fatalities.
Conclusions: It is estimated that around 50,000 scuba tank fills were provided, equating to approximately 50,000 dives conducted in Victorian waters during from 1 July 2024 to 30 June 2025. During that period, there were eight open circuit divers who had dived in Victoria treated for DCI and two scuba diving fatalities, yielding estimates of 16 DCI cases and four deaths per 100,000 dives.

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Decision regret and shared decision-making in patients undergoing hyperbaric oxygen therapy

Joost R Meijering1,2,*, Nurseda Risvanoglu3,*, Julia D van Waard3, Johanna H Nederhoed1, Rigo Hoencamp2,4,5, Robert A van Hulst3, Dirk T Ubbink1

¹ Surgery, Amsterdam University Medical Center, Amsterdam, the Netherlands
² Surgery, Alrijne, Leiderdorp, the Netherlands
³ Anaesthesiology, Amsterdam University Medical Center, Amsterdam, the Netherlands
⁴ Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands
⁵ Department of Surgery, Erasmus University, Rotterdam, the Netherlands
^* Drs Meijering and Risvanoglu contributed equally to this study

Corresponding author: Dr Joost Meijering, Amsterdam University Medical Center, Amsterdam, the Netherlands
ORCiD: 0009-0004-3667-0353
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Keywords
Communication; Health surveys; Personalised medicine; Questionnaire; Side effects; Treatment sequelae

Abstract
(Meijering JR, Risvanoglu N, van Waard JD, Nederhoed JH, Hoencamp R, van Hulst RA, Ubbink DT. Decision regret and shared decision-making in patients undergoing hyperbaric oxygen therapy. Diving and Hyperbaric Medicine. 2026 31 March;56(1):52−58. doi: 10.28920/dhm56.1.52-58. PMID: 41875442.)
Introduction: Hyperbaric oxygen therapy (HBOT) is used for various medical conditions. HBOT is demanding and varies in effectiveness. This intensity combined with logistical challenges may lead to patients regretting undergoing HBOT. Therefore, shared decision-making (SDM) seems applicable when considering HBOT. The goal of this study was to assess the level of SDM as perceived by HBOT patients and relate this to post-hoc regret about choosing HBOT.
Methods: Patients referred for ≥ 10 sessions HBOT, were recruited for this prospective cohort study. Participants completed the SDM-Q-9 and SDM-K-Q questionnaires within one week of HBOT initiation. At least six weeks after HBOT completion or discontinuation participants completed the Decision Regret Scale (DRS) questionnaire. Multivariable linear regression analysis was applied to find factors influencing decision regret and SDM.
Results: Sixty-two patients (mean age 61.5 years; 36 female), primarily treated for radiation-related injuries, were included. Minor complications, including fatigue and temporary visual changes, were common. Mean SDM-Q-9 and SDM-K-Q scores were 61.9% and 72.1%, respectively. Among 54 patients completing the DRS, mean regret score was 13.4%. Lower regret correlated with symptom improvement (B = −16.56, P = 0.036) and more side effects (B = −6.81, P = 0.014). Males tended to report more regret (B = 8.26, P = 0.081), while age and SDM-Q-9 scores were not significant predictors. No factors significantly affected SDM-Q-9 scores.
Conclusions: HBOT patients reported limited involvement in decision-making and low levels of regret. Interestingly, minor complications were associated with less regret, suggesting complex dynamics in patient experience and treatment justification. These findings highlight the importance of individualised shared decision-making and patient education in the context of HBOT to ensure treatment choice aligns with patient values and expectations.

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Transgender people and occupational diving: a new challenge for diving physicians?

Pieter-Jan AM van Ooij^1,2, Annemarije R Bek¹, Robert A van Hulst³

¹ Diving Medical Centre, Royal Netherlands Navy, Den Helder, the Netherlands
² Department of Respiratory Medicine, Amsterdam University Medical Centre (AUMC), University of Amsterdam, Amsterdam, the Netherlands
³ Department of Anesthesiology and Hyperbaric Medicine, Amsterdam University Medical Centre (AUMC), University of Amsterdam, Amsterdam, the Netherlands

Corresponding author: Pieter-Jan van Ooij, Diving Medical Centre, Royal Netherlands Navy. PO Box 10,000 1780 CA Den Helder, the Netherlands
ORCiD: 0000-0002-2108-320X
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Keywords
Fitness to dive; Gender affirming hormone therapy; Medical conditions; Review article; Risk factors

Abstract

(van Ooij PJAM, Bek AR, van Hulst RA. Transgender people and occupational diving: a new challenge for diving physicians? Diving and Hyperbaric Medicine. 2026 31 March;56(1):59−70. doi: 10.28920/dhm56.1.59-70. PMID: 41875443.)
The gender identity of transgender people is not fully aligned with their sex assigned at birth. It has been estimated that approximately 355 of 100,000 people in the general population consider themselves transgender. Transgender people are increasingly choosing to transition through gender-affirming hormone therapy, including treatment with testosterone or oestrogens and gender-affirming surgeries. Occupational diving is performed in a unique, highly hostile physiological environment. An occupational diver should be free of pulmonary, cardiovascular, neurological, and psychological risk factors that could increase the risk of diving-associated adverse events. Dive medical assessments can identify these risk factors. The increasing number of people openly identifying as transgender raises the likelihood that more will want to participate in occupational diving. To date, however, no guidelines have been specifically designed for safe occupational diving by transgender individuals. This review, involving 43 systematic reviews and/or meta-analyses, was therefore designed to assess the long-term health effects in transgender individuals and how these influence occupational diving. Although transgender people face some additional health risks that could affect occupational diving, these risks can be managed by adhering to regular occupational fitness-to-dive guidelines.

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The full article is currently under embargo for 12 months and will be made available on our website and PMC after this period. If you would like to access the article before it becomes publicly available, you can purchase it for personal use directly on our website. Alternatively, you may join SPUMS or EUBS to gain access to the entire issue.

Outcomes in the treatment of inner ear decompression sickness with hyperbaric oxygen therapy, a systematic review

Rosanna J Stokes^1,2, Jonathan Marsden¹, Doug Watts², Gary Smerdon², Stephen D Hall¹, Lisa Bunn¹

¹ Brain Research and Imaging Centre, University of Plymouth, Plymouth, UK
² DDRC Healthcare, Plymouth Science Park, Plymouth, UK

Corresponding author: Dr Rosanna J Stokes, DDRC Healthcare, Plymouth Science Park, Plymouth, UK
ORCiD: 0009-0006-4501-0634
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Keywords
Diving; Sharpened Romberg test; Review article; Vertigo; Vestibular

Abstract
(Stokes RJ, Marsden J, Watts D, Smerdon G, Hall SD, Bunn L. Outcomes in the treatment of inner ear decompression sickness with hyperbaric oxygen therapy, a systematic review. Diving and Hyperbaric Medicine. 2026 31 March;56(1):71−82. doi: 10.28920/dhm56.1.71-82. PMID: 41875444.)
Introduction: The primary objective of this review was to evaluate the effectiveness of hyperbaric oxygen therapy (HBOT) in the treatment of inner ear decompression sickness (IEDCS). Secondary objectives were to summarise the diver characteristics, HBOT parameters and outcome measures.
Methods: All descriptive observational study designs including case series and individual case reports involving divers suffering IEDCS treated with HBOT were included. PubMed, Scopus, CINAHL and EMBASE were used to search for texts reporting the outcome for divers treated with HBOT. Eligible studies were appraised by two independent reviewers and any disagreements resolved via the third reviewer. Data were extracted using standardised tools and narrative synthesis was undertaken.
Results: 3,683 records were identified with 24 included in the final review representing 539 cases of IEDCS. Mean age was 44, average (in-water) dive depth 29 metres of seawater and dive duration 38 minutes. Mean onset of symptoms was 32 minutes and 74% had a right sided lesion. Only 37% had residual symptoms on discharge despite 68% showing dysfunction on laboratory testing. Follow-up duration and assessment methods were variable. Vestibular rehabilitation was underutilised and only 46% of divers went on to have patent foramen ovale (PFO) screening despite the well-established link to IEDCS.
Conclusions: A standardised method of examination and assessment of symptoms should be considered along with vestibular rehabilitation (or referral to this service). All divers should be counselled on PFO screening. A standard 3-month follow-up is recommended to allow for assessment of residual dysfunction / symptoms and discussion regarding returning to diving. Further research should focus on assessment of vestibular deficit / symptoms over time to assess efficacy of HBOT including the effects of delay to recompression and number of treatments. Laboratory testing should be utilised to determine the mechanism of injury and recovery.

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Efficacy and safety of potential irrigation diluents following ‘caustic cocktail’ ingestion 

Adam Lee^1,*, Catherine Moore^1,*, Adam Griffiths¹

¹ Underwater Medicine Department, Institute of Naval Medicine, Portsmouth, UK
^* Drs Lee and Moore contributed equally to this paper

Corresponding author: Adam Lee, Surgeon Lieutenant Commander Royal Navy, Institute of Naval Medicine, Gosport, Portsmouth, UK
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Keywords
Diving medicine; First aid; Injuries; Military diving; Rebreathers - closed circuit; Treatment

Abstract

(Lee A, Moore C, Griffiths A. Efficacy and safety of potential irrigation diluents following ‘caustic cocktail’ ingestion.  Diving and Hyperbaric Medicine. 2026 31 March;56(1):83−87. doi: 10.28920/dhm56.1.83-87. PMID: 41875445.)
Closed circuit rebreather (CCR) diving sets use soda lime, a sodium hydroxide-based ‘scrubber’ substance to remove CO₂ from exhaled breathing gas thus prolonging dive time and efficiency. Inadvertent water ingress into the set may result in reaction with the scrubber and a highly alkaline solution known as a ‘caustic cocktail’ may be formed. Ingestion or aspiration of this solution can cause severe chemical burns. Irrigation with freshwater is the mainstay of initial treatment of ‘caustic cocktail’ injuries in CCR divers. Published advice advises divers never to use acidic diluents to irrigate and neutralise a caustic cocktail solution due to concerns over the potentially exothermic nature of the neutralisation reaction. However, there is limited available evidence to support this advice, and it was felt that further research into the best treatment options available for caustic cocktails is required. This study used an in vitro model of an ingested caustic cocktail to investigate pH and temperature changes after adding different diluents (including acidic diluents orange juice or coca cola) to a solution of sodium hydroxide. Acidic diluents reduce pH significantly more than neutral diluents with a respective mean drop in pH of 5.99 compared to 0.78 (P = 0.015). There is no statistically significant difference in temperature change noted between the two types of diluent (P = 0.32) with no exothermia generated. We propose that orange juice or coca cola are more effective irrigation solutions than fresh or seawater, and that advice to divers who use CCRs could change.

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Dual rebreathers in practice: example experiences from the Wetmules and COBRA Divers

Daniel Lee¹, Craig Challen², Gareth Lock³

¹ COBRA Dive Team, Darmstadt, Germany
² Wetmules Dive Team, Perth, Australia
³ The Human Diver, Wilts, UK

Corresponding author: Daniel Lee, COBRA Dive Team, Mathildenstrasse 43, 64285 Darmstadt, Germany
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Keywords
Cave diving; Deep diving; Equipment; Rebreathers - closed circuit; Remote locations; Safety; Technical diving

Abstract

(Lee D, Challen C, Lock G. Dual rebreathers in practice: example experiences from the Wetmules and COBRA Divers. Diving and Hyperbaric Medicine. 2026 31 March;56(1):88−94. doi: 10.28920/dhm56.1.88-94. PMID: 41875446.)
Closed-circuit rebreathers have opened new frontiers in technical diving, but rebreathers are not invulnerable and therefore a ‘bailout’ gas supply is required. For extreme dives, open-circuit bailout is logistically impossible. This has led teams to adopt dual rebreather configurations, where a second rebreather serves as bailout. This article presents operational experiences from the Wetmules and COBRA Divers, who independently developed dual rebreather practices for extended range diving. The teams evolved contrasting approaches through extensive field testing. The Wetmules initially adopted partially integrated configurations, sharing components between rebreathers to reduce complexity for deep dives with straightforward access to dive sites. COBRA Divers used fully independent dual rebreathers, prioritising complete redundancy for remote locations with challenging logistics. Both developed techniques to ensure the operational status of the inactive rebreather including gas content variability, buoyancy control, and fault detection. Real-world experience validated theoretical benefits while revealing additional considerations. Both teams significantly reduced open-circuit bailout requirements, enabling extended penetrations and depths that were previously extremely difficult. Key operational insights included maintaining breathable gas mixtures in inactive loops, regular integrity checks, and managing variable buoyancy. The approach introduced new challenges: increased task loading, maintenance requirements, and novel failure modes specific to inactive rebreathers, showing that equipment redundancy does not automatically enhance safety. Dual rebreathers extend operational envelopes but introduce significant complexity. Benefits include eliminating gas switches during emergencies and maintaining optimal decompression profiles. However, inactive rebreathers remain vulnerable to undetected failures and demand higher operator proficiency. The contrasting approaches - integration versus full independence - reflect different operational priorities and mission parameters. This article contributes operational experience to support informed decision-making within the technical diving community.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

The full article is currently under embargo for 12 months and will be made available on our website and PMC after this period. If you would like to access the article before it becomes publicly available, you can purchase it for personal use directly on our website. Alternatively, you may join SPUMS or EUBS to gain access to the entire issue.

Liver disease and the Diver Medical Participant Questionnaire

Andrew George Watson¹, Tiong Yeng Lim¹

¹ Department of Hepatology, Royal London Hospital, Barts Health NHS Trust, London, UK

Corresponding author: Dr Andrew George Watson, Department of Hepatology, Royal London Hospital, Barts Health NHS Trust, London, UK
ORCiD: 0009-0007-0517-7197
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Keywords
Fitness to dive; Liver, Medical-diving; Questionnaire; Recreational divers; Risk assessment

No abstract.

doi: 10.28920/dhm56.1.95-96. PMID: 41875447.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

The full article is currently under embargo for 12 months and will be made available on our website and PMC after this period. If you would like to access the article before it becomes publicly available, you can purchase it for personal use directly on our website. Alternatively, you may join SPUMS or EUBS to gain access to the entire issue.

Comment on 'Effects of fluid loss on the physiology of closed-circuit rebreather divers after 100- and 45-metre dives by Tuominen, et al.'

Peter T Wilmshurst¹, Christopher Edge²

¹ United Kingdom Diving Medical Committee, UK
² Imperial College, Department of Life Sciences, London, United Kingdom

Corresponding author: Dr Peter T Wilmshurst, United Kingdom Diving Medical Committee, Atcham, SY5 6QE, UK
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Keywords
Bubbles; Deep diving; Diuresis; Immersion; Weight change

No abstract.

doi: 10.28920/dhm56.1.96-97. PMID: 41875448.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

The full article is currently under embargo for 12 months and will be made available on our website and PMC after this period. If you would like to access the article before it becomes publicly available, you can purchase it for personal use directly on our website. Alternatively, you may join SPUMS or EUBS to gain access to the entire issue.

Reply to comment by Peter T Wilmhurst and Christopher Edge

Laura J Tuominen¹, Anne K Räisänen-Sokolowski², Richard V Lundell³

¹ Tampere University Hospital, Centre for Prehospital Emergency Care, Finland
² Helsinki University Hospital and Helsinki University, Pathology, Finland
³ Centre for Military Medicine, Finnish Defense Forces, Diving Medical Centre, Finland

Corresponding author: Dr Laura J Tuominen, Tampere University Hospital, Centre for Prehospital Emergency Care, Annalankatu 17 D 15, Tampere, Finland
ORCID: 0000-0003-0826-4679
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Keywords
Diving medicine; Letters (to the Editor); Physiology; Safety; Technical diving

No abstract.

doi: 10.28920/dhm56.1.97-98. PMID: 41875449.

Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.