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.
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.
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.
Introduction:During clinical use of extracorporeal membrane oxygenation (ECMO) in hyperbaric conditions at our centre, upward titration of indicated sweep gas flow rates is required to maintain adequate CO₂ clearance. This project measured the impact of hyperbaric pressure on oxygen flow rates delivered by the Comweld Ezi-Flow flowmeters used in our centre. Methods:Oxygen flow rates through Comweld Ezi-flow standard and low oxygen gas flowmeters were set at 101.3 kPa (1 atmosphere absolute [atm abs]) and then measured at intervals up to 284 kPa (2.8 atm abs) using a calibrated gas flow analyser, with cross verification against a small Douglas bag test type apparatus. During testing, the chamber was compressed and decompressed at a rate of 10 kPa·min⁻¹. Flow rates during chamber compression and decompression were compared. Results:The indicated rate of oxygen gas flow through the unadjusted flowmeters changed minimally - typically rising by a maximum of half of the diameter of the indicator ball. The actual (volumetric) flow, tested across indicated flow rates from 3 to 12 L·min⁻¹, was consistently reduced by approximately 50% as the chamber pressure increased from 101.3 to 284 kPa (1 to 2.8 atm abs). A slightly smaller reduction was observed when assessing the low flowmeter across the same pressure range; reductions of 40.0 and 43.3% were demonstrated at 0.3 to 0.6 L·min⁻¹ respectively. Differences in flow rates between compression and decompression were minor except at the very lowest flows. Conclusions:At 284 kPa (2.8 atm abs), actual volumetric flow of oxygen through Comweld Ezi-Flow flowmeters is dramatically reduced and this needs appropriate compensation to ensure therapeutic aims are achieved.
Introduction:Transoesophageal echocardiography (TOE) is claimed to be the investigation of choice for detecting a persistent foramen ovale (PFO) with almost 100% diagnostic accuracy. If true, TOE would detect all large/clinically significant PFOs. Methods:Retrospective analysis to determine the sensitivity of TOE for detection of clinically significant PFOs. Patients were from a consecutive series of 150 patients who had transcatheter closure of a PFO following events attributed to paradoxical embolism (decompression sickness or stroke). In each patient, transthoracic echocardiogram with bubble contrast showed a clinically significant atrial right-to-left shunt. The data reported are from the sub-group of the 150 patients with a clinically significant PFO who also had a TOE performed in other hospitals. Results:Twenty seven of 150 consecutive patients had a total of 31 TOEs performed at 22 United Kingdom regional cardiac centres. TOE failed to detect a PFO in 17 of the 27 patients. Four patients had a TOE on two separate occasions and in each case both of the TOEs failed to show a PFO. TOE gave a false negative test in 21 of 31 investigations (sensitivity 32%). The mean PFO diameter was 9.4 mm (median 9 mm, range 5-16 mm) in the 21 patients in whom balloon sizing was performed and 9.8 mm (median 10 mm, range 5-16 mm) in the 13 patients in whom balloon sizing was performed and a TOE failed to show a PFO. Conclusions:These finding demonstrate that the precision of TOE for detecting a PFO in real world clinical practice is considerably lower than generally believed.
Cerebral arterial gas embolism (CAGE) is a recognised complication of diving-related barotrauma and of medical procedures whereby gas enters the vascular system. CAGE is a principal indication for hyperbaric oxygen treatment (HBOT). In contrast, CAGE resulting from HBOT itself is exceedingly rare. We describe the case of a 73-year-old man undergoing his first session of HBOT for a chronic lower limb wound, who developed acute focal neurological deficits during decompression. He had no known respiratory disease or smoking history. Immediate assessment demonstrated stable physiology. Initial computed tomography (CT) scan of the brain and neck vessels and perfusion imaging did not show any evidence of thrombus or intravascular gas, and partial neurological recovery occurred over several hours. Subsequent magnetic resonance imaging of the brain demonstrated acute infarction involving the left precentral and postcentral gyri. High-resolution CT chest revealed multiple bilateral thin-walled pulmonary cysts, including a left upper lobe cyst with an air-fluid level consistent with recent barotrauma. A transient broncho-venous fistula allowing arterial oxygen embolisation during decompression was considered the most plausible mechanism. The patient improved with supportive management and was discharged with minimal residuae. This case highlights an exceptionally rare but serious complication of HBOT and underscores the importance of vigilance during decompression and careful consideration of occult pulmonary pathology.
Introduction:Fitness-to-dive after otologic surgery is often approached conservatively, with some procedures historically labelled as absolute contraindications despite limited empirical evidence. The available literature is heterogeneous and includes clinical reports, experimental pressure studies, guidance documents, and manufacturer specifications, leading to uncertainty in clinical counseling. We aimed to characterise the available evidence regarding fitness-to-dive after otologic surgery and to develop an evidence-informed clinical decision aid. Methods:A scoping review was conducted in accordance with PRISMA-ScR guidance. PubMed/MEDLINE, Embase, Scopus, and relevant non-indexed sources were searched. Eligible sources included clinical reports and series, experimental or hyperbaric chamber studies, guidance or consensus documents, and manufacturer statements providing explicit pressure- or depth-related information. Data were charted descriptively by procedure type and evidence stream. Results:The search identified 324 records; after removal of duplicates and screening, 40 sources were included. The evidence base was predominantly non-comparative. Across procedures, recommendations emphasised postoperative stability and reliable pressure equalisation rather than surgical history alone. Canal wall down mastoidectomy was consistently portrayed as incompatible with diving, whereas selected middle ear reconstructions and stapes surgery were commonly described as potentially compatible in appropriately selected individuals. For cochlear implantation, guidance was mainly conditional and based on hyperbaric testing, limited clinical diving reports, and manufacturer-specified pressure or depth limits. Communication emerged as an additional practical consideration in cases of significant hearing loss. Conclusions:Relevant evidence is limited and heterogeneous, and does not consistently support blanket prohibitions for all otologic procedures. A function-based, individualised approach is supported, while specific higher-risk scenarios warrant restriction. Prospective registries and standardised outcome reporting are needed to refine procedure-specific recommendations.
Introduction: Quantifying inert gas uptake and washout is critical for understanding decompression sickness (DCS). However, the limited amount of data has made it difficult to integrate inert gas kinetics into risk models for DCS. Measuring whole-body inert gas kinetics during submersion is technically challenging. This study presents a novel method for quantifying inert gas uptake and washout in human divers using a rebreather-based system. Methods: During constant-depth diving with a closed-circuit system that maintains a constant oxygen partial pressure, changes in buoyancy will reflect the kinetics of inert gas. Two divers completed four dives each, with a bottom phase at 2.5 bar and a decompression phase at 1.3 bar or 1.4 bar. Load cell data were converted into equivalent changes in volume of nitrogen standardised for temperature and pressure (VN2, STP). Power analysis was conducted to quantify the resolution by which the method could detect nitrogen uptake and washout volumes. Results: Distinct uptake and washout curves were obtained, comparable to previous studies using other techniques. Mean VN2 uptake during the bottom phase was 0.96 L (SD 0.29), while mean washout during decompression was 0.67 L (SD 0.26). The minimal mean detectable difference (MDD) with eight dives was 0.28 L for the bottom phase and 0.26 L for the decompression phase, considering standard 80% power and a 0.05 significance level. Conclusions: This novel method quantifies inert gas kinetics during submersion with acceptable precision and accuracy. It could facilitate the collection of inert gas kinetics data during submersion, potentially yielding valuable correlations with the risk of DCS.
Retinal artery occlusion (RAO) is an ophthalmic emergency that causes sudden, painless vision loss due to retinal ischaemia. Hyperbaric oxygen therapy (HBOT), when initiated early, may help preserve photoreceptor function by increasing retinal oxygenation. A 69-year-old woman with a history of hypertension presented with sudden visual loss in the left eye and was diagnosed with RAO. HBOT was initiated within six hours of symptom onset (253 kPa [2.5 atmospheres absolute] for 90 minutes per session), and 20 sessions were planned. During the seventh session, the patient reported a marked improvement in visual acuity in the contralateral (right) eye, previously diagnosed with choroidal neovascular membrane (CNVM) and untreated with anti-vascular endothelial growth factor (VEGF) therapy. Optical coherence tomography demonstrated regression of the CNVM and complete resolution of subretinal fluid. To our knowledge, this is the first report suggesting that HBOT administered for unilateral RAO may also promote structural and functional improvement of CNVM in the contralateral eye.
Introduction: Technical diving, involving rebreathers and/or helium-based gas mixtures for deeper and longer dives, may influence risk and clinical presentation of injuries due to helium's properties, equipment constraints, or exposure conditions. This study aims to describe the specific characteristics of this accidentology. Methods: A retrospective study was conducted across five French coastline hyperbaric units. Medical records of technical divers presenting with decompression sickness (DCS), immersion pulmonary oedema (IPO), or gas-toxicity between 2010 and 2024 were reviewed. Results: 127 technical divers were included, three declined participation, leaving 124 cases for analysis. DCS was the most frequent condition (n = 105) followed by IPO (n = 16) and gas toxicity (n = 3). Median age was 45 [IQR 37-53] years, and 113 (91%) were male. Rebreathers were used in 94 (75.8%) cases and helium-based mixtures in 77 (62%). Previous diving-related accidents were reported in 36 (29%) cases. IPO occurred mainly after shallower dives in wetsuits and was frequently associated with procedural errors. Among DCS cases isolated musculoskeletal DCS predominated (n = 36), whereas spinal involvement was less frequent. When indicated, median recompression delay was 238 [IQR 135-555] minutes. Unfavourable outcomes occurred in 26 (25%) DCS cases, primarily with bone or inner-ear involvement. Conclusions: Technical diving accidents exhibit distinct patterns from recreational diving, notably greater musculoskeletal involvement and a possible increased risk of dysbaric osteonecrosis (DON). Current evidence does not support different management, but the risk of potential initially silent bone lesions should not be overlooked. Further research on helium-related risks and hyperbaric treatment's role in DON prevention is needed.
Introduction:The aim of this review was to synthesise current knowledge and propose structured evidence-based recommendations for long-term care of individuals with spinal cord decompression illness (scDCI) drawing on experience from French clinical settings and the international literature. Methods:We conducted a systematic search of international and French guidelines for decompression illness (DCI) and spinal cord injury (SCI), including systematic reviews and consensus statements. Additional literature searches were performed in PubMed® (1996-2025) to identify evidence relevant to long-term care. Key domains were predefined based on SCI guidelines: lower urinary tract and gastrointestinal function, thromboembolic, autonomic dysreflexia, pulmonary function, pain, and spasticity. Results:Our findings confirmed the absence of specific long-term follow-up protocols for scDCI. Evidence from SCI guidelines was therefore adapted to this population. We propose structured, evidence-based recommendations that include systematic neurological and urological screening even in apparently recovered patients and risk-adapted follow-up during the first two years. Conclusions:Long-term outcomes after scDCI remain poorly defined, but sequelae are frequent and may be underdiagnosed. Structured follow-up based on adapted SCI guidelines may improve prognosis, harmonise care, and generate robust data for future prospective studies.
Introduction:The Divers Alert Network (DAN) aims to provide safety information for all types of diving. Assessing the number of active closed-circuit rebreather (CCR) divers is difficult, as pertinent information is often not available. This review aims to give an overview of global use and safety of CCR diving equipment from 2013-2022. Methods:Data were combined and assessed from various DAN internal and public sources on CCR diver demographics, fatalities, and CCR sales. Results:Over the past 10 years, the number of certified CCR divers has increased from an estimated 2,000 in 2013, to 3,000 in 2022. There has been an increase in growth in CCR sales over a five-year period from 2018, with around 25,000 to 35,000 units on the market today; rebreather divers are a growing community. There were 241 confirmed CCR fatalities from 2013-2022, mean 24 (SD 6) per year. Most fatal accidents involved dives made between 40-80 m (130-260 ft) depth. Cause of death is difficult to establish due to lack of detail and dive-specific training for the medical examiner. The estimated death rate is 1.8-3.8 deaths per 100,000 CCR dives although these values are derived from limited data. Conclusions:Not enough information is made available to address CCR accident analysis effectively, perhaps stemming from family reticence to discuss the incident, fear of litigation, and/or lack of diving knowledge reducing the useful information. DAN continues to collect CCR data, but increased collaboration between training bodies, equipment providers, and comprehensive reporting of incidents is needed to reveal the true picture.
Introduction: Rebreather diving carries an increased risk of hypercapnia. Hypercapnia can cause impaired cognition, breathlessness, and increase the risk of oxygen toxicity. We investigated whether a prior unblinded hypercapnia experience, compared to reading about hypercapnia symptoms, would improve divers’ ability to recognise hypercapnia and initiate self-rescue. Methods: Forty divers were recruited and randomised to receive either an unblinded hypercapnia experience (partial pressure of end-tidal carbon dioxide [PETCO2] of 8.5 kPa) or an information leaflet explaining hypercapnia symptoms. At least one month later, participants in each group were further randomised to undergo blinded exposure to hypercapnia or normocapnia, allocated at 3:1. The primary outcome was the proportion of participants who self-initiated bailout prior to reaching PETCO2 8.5 kPa. Continuous cardiorespiratory data (PETCO2 and PETO2, tidal volume, respiratory rate, minute ventilation, heart rate, and blood pressure) were also recorded. Subjective symptoms associated with hypercapnia were assessed with a visual analogue scale. Results: Thirteen of 15 participants (87%) who received the unblinded hypercapnia-experience self-initiated bailout compared to 10/15 information leaflet participants (67%) (P = 0.149). There was no difference in cardiorespiratory physiology parameters at bailout between the groups. Shortness of breath, light-headedness, and disorientation were the most intensely reported symptoms. Approximately half (47%) of participants who received a hypercapnia training experience had a correlated symptom response during their subsequent hypercapnia testing session. Conclusions: Although no significant training benefit was shown, becoming familiar with the sensations associated with hypercapnia under appropriate supervision could be useful to rebreather divers both recreationally and within occupational settings.
Bipolar disorder is a recurrent psychiatric condition characterised by episodic mood disturbances, residual functional impairment, and high rates of psychiatric and medical comorbidity. While many individuals achieve symptomatic remission, persistent deficits in cognition, emotional regulation, and insight may remain, raising concerns for participation in safety-critical activities such as scuba diving. This systematic review synthesised evidence from psychiatric, occupational, aviation, and diving medicine literature to examine the clinical course of bipolar disorder, treatment considerations, functional outcomes, and safety-relevant factors pertinent to fitness-to-dive assessments. Bipolar disorder exhibits marked heterogeneity in syndromal and functional outcomes. Even during euthymia, subtle impairments in attention, executive functioning, and decision-making may persist. Pharmacological stability is essential for diving, but treatment regimens, particularly lithium use, polypharmacy, and antidepressant therapy, introduce additional considerations. Comorbidity, circadian disruption, sleep deprivation, and reduced insight during early relapse further complicate risk assessment. Empirical data on diving outcomes in individuals with bipolar disorder are scarce, necessitating reliance on expert opinion and extrapolation from related safety-critical domains. Fitness-to-dive assessments in bipolar disorder should prioritise sustained functional stability, reliable treatment adherence, and illness insight over symptom absence alone. A cautious, individualised approach is warranted, incorporating medication effects, comorbidity, operational context, and relapse-prevention planning, supported by collaboration between mental health professionals and diving medical examiners.
Pyomyositis is a serious bacterial infection of the skeletal muscles, usually treated with antibiotics and surgical drainage. The success of medical or surgical treatment is often delayed or less effective when tissue hypoxia is present. Hyperbaric oxygen therapy (HBOT) is currently being studied as a helpful additional treatment for various conditions, especially those involving complications of tissue hypoxia. In this case report, we describe a 29-year-old male who developed chronic pyomyositis and a right lower leg ulcer after failure of multiple surgeries, including fasciotomy, debridements, skin grafts and antibiotics to treat compartment syndrome and tuberculosis of the right knee. HBOT was administered for 80 sessions at 243 kPa (2.4 atmospheres absolute) for 90 minutes. The patient showed significant clinical improvement, as evidenced by the development of healthy granulation tissue, reduction in swelling and discharge, and better mobility. This case highlights the potential of HBOT as an additional treatment option for complex soft tissue infections such as pyomyositis caused by tuberculosis, especially in cases where traditional treatments have been ineffective.
Pulmonary vein isolation (PVI) is an established rhythm-control therapy for atrial fibrillation (AF), yet the electrophysiological response of post-PVI individuals exposed to hyperbaric environments remains undocumented. Similarly, the in-vivo performance of implantable loop recorders (ILRs) and external patch-based electrocardiographic (ECG) devices under increased ambient pressure has never been reported. We describe the first hyperbaric electrophysiology assessment in a post-PVI diver undergoing both underwater immersion and dry hyperbaric exposure with dual-modality cardiac rhythm monitoring. A 46-year-old experienced diver with successful PVI underwent: a scuba dive to 42 m in a warm water pool, monitored with a marinised 12-lead ECG Holter system; and a stepwise hyperbaric chamber compression to 284 kPa (2.8 atmospheres absolute) in ambient air, with single-lead surface ECG recordings obtained at static pressure plateaus. In both cases, the subject was monitored as well by his ILR. No AF recurrence or other dysrhythmias were detected during either exposure, with stable heart rate trends. The ILR maintained full functional integrity after both the 42 m dive and the 284 kPa chamber compression. The external ECG patch yielded interpretable tracings during static phases. Telemetry failed due to electromagnetic shielding by the steel chamber walls. This case suggests that carefully selected post-PVI individuals may tolerate controlled underwater and hyperbaric exposure without rhythm destabilisation. Both implantable and external monitoring devices preserved operational integrity under moderate hyperbaric conditions, providing a foundation for the emerging field of hyperbaric electrophysiology monitoring and informing fitness-to-dive assessment in post-ablation patients.
(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.
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.
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.
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 orbrands. 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.
