Hypoxia exposure blunts angiogenic signaling and upregulates the antioxidant system in endothelial cells derived from elephant seals

BACKGROUND

Elephant seals exhibit extreme hypoxemic tolerance derived from repetitive hypoxia/reoxygenation episodes they experience during diving bouts. Real-time assessment of the molecular changes underlying protection against hypoxic injury in seals remains restricted by their at-sea inaccessibility. Hence, we developed a proliferative arterial endothelial cell culture model from elephant seals and used RNA-seq, functional assays, and confocal microscopy to assess the molecular response to prolonged hypoxia.

RESULTS

Seal and human endothelial cells exposed to 1% O2 for up to 6 h respond differently to acute and prolonged hypoxia. Seal cells decouple stabilization of the hypoxia-sensitive transcriptional regulator HIF-1α from angiogenic signaling. Rapid upregulation of genes involved in glutathione (GSH) metabolism supports the maintenance of GSH pools, and intracellular succinate increases in seal but not human cells. High maximal and spare respiratory capacity in seal cells after hypoxia exposure occurs in concert with increasing mitochondrial branch length and independent from major changes in extracellular acidification rate, suggesting that seal cells recover oxidative metabolism without significant glycolytic dependency after hypoxia exposure.

CONCLUSIONS

We found that the glutathione antioxidant system is upregulated in seal endothelial cells during hypoxia, while this system remains static in comparable human cells. Furthermore, we found that in contrast to human cells, hypoxia exposure rapidly activates HIF-1 in seal cells, but this response is decoupled from the canonical angiogenesis pathway. These results highlight the unique mechanisms that confer extraordinary tolerance to limited oxygen availability in a champion diving mammal.

SEC-Clinical Cardiology Association/SEC-Working Group on Sports Cardiology consensus document

The practice of recreational scuba diving has increased worldwide, with millions of people taking part each year. The aquatic environment is a hostile setting that requires human physiology to adapt by undergoing a series of changes that stress the body. Therefore, physical fitness and control of cardiovascular risk factors are essential for practicing this sport. Medical assessment is not mandatory before participating in this sport and is only required when recommended by a health questionnaire designed for this purpose. However, due to the significance of cardiovascular disease, cardiology consultations are becoming more frequent. The aim of the present consensus document is to describe the cardiovascular physiological changes that occur during diving, focusing on related cardiovascular diseases, their management, and follow-up recommendations. The assessment and follow-up of individuals who practice diving with previous cardiovascular disease are also discussed. This document, endorsed by the Clinical Cardiology Association of the Spanish Society of Cardiology (SEC) and the SEC Working Group on Sports Cardiology of the Association of Preventive Cardiology, aims to assist both cardiologists in evaluating patients, as well as other specialists responsible for assessing individuals' fitness for diving practice.

Decompression sickness of the inner ear and relationship with a patent oval foramen: a study of 61 cases

OBJECTIVE

To discuss the link between inner ear decompression sickness and patent foramen ovale.

MATERIALS AND METHODS

Monocentric and retrospective study on decompression sickness of the inner ear requiring hyperbaric chamber treatment, from 2014 to 2021.

RESULTS

Sixty-one patients of inner ear decompression sickness were included in this study. Twenty-four patients had vestibular injuries, 28 cochlear injuries and 9 cochleo-vestibular injuries. Compression chamber treatment was given, using an oxygen-helium mixture with oxygen partial pressure (PIO2) limited to 2.8 atmosphere absolute (ATA). All vestibular accidents completely recovered without clinical sequelae. For cochlear accident only 10 out of 37 patients (27%) recovered completely. A right-left shunt (patent foramen oval or intra-pulmonary shunt) was found in 31.1% of patients with inner ear decompression sickness (p > 0.05).

CONCLUSION

The presence of patent foramen oval in patients with inner ear decompression was not statistically significant in our study. Understanding of the pathophysiology of decompression illness and the physiology and anatomy of the labyrinth would suggest a mechanism of supersaturation with degassing in intra-labyrinthine liquids.

Breath-holding as model for the evaluation of EEG signal during respiratory distress

PURPOSE

Research describes the existence of a relationship between cortical activity and the regulation of bulbar respiratory centers through the evaluation of the electroencephalographic (EEG) signal during respiratory challenges. For example, we found evidences of a reduction in the frequency of the EEG (alpha band) in both divers and non-divers during apnea tests. For instance, this reduction was more prominent in divers due to the greater physiological disturbance resulting from longer apnea time. However, little is known about EEG adaptations during tests of maximal apnea, a test that voluntarily stops breathing and induces dyspnea.

RESULTS

Through this mini-review, we verified that a protocol of successive apneas triggers a significant increase in the maximum apnea time and we hypothesized that successive maximal apnea test could be a powerful model for the study of cortical activity during respiratory distress.

CONCLUSION

Dyspnea is a multifactorial symptom and we believe that performing a successive maximal apnea protocol is possible to understand some factors that determine the sensation of dyspnea through the EEG signal, especially in people not trained in apnea.

First Real-Life Data on the Diving Response in Healthy Children

Swimming and diving are popular recreational activities, representing an effective option in maintaining and improving cardiovascular fitness in healthy people. To date, only little is known about the cardiovascular adaption to submersion in children. This study was conducted to improve an understanding thereof. We used a stepwise apnea protocol with apnea at rest, apnea with facial immersion, and at last apnea during whole body submersion. Continuous measurement of heart rate, oxygen saturation, and peripheral resistance index was done. Physiologic data and analysis of influencing factors on heart rate, oxygen saturation, and peripheral vascular tone response are reported. The current study presents the first data of physiologic diving response in children. Data showed that facial or whole body submersion leads to a major drop in heart rate, and increase of peripheral resistance, while the oxygen saturation seems to be unaffected by static apnea in most children, with apnea times of up to 75 s without change in oxygen saturation.

Within-diver variability in venous gas emboli (VGE) following repeated dives

Introduction

Venous gas emboli (VGE) are widely used as a surrogate endpoint instead of decompression sickness (DCS) in studies of decompression procedures. Peak post-dive VGE grades vary widely following repeated identical dives but little is known about how much of the variability in VGE grades is proportioned between-diver and within-diver.

Methods

A retrospective analysis of 834 man-dives on six dive profiles with post-dive VGE measurements was conducted under controlled laboratory conditions. Among these data, 151 divers did repeated dives on the same profile on two to nine occasions separated by at least one week (total of 693 man-dives). Data were analysed for between- and within-diver variability in peak post-dive VGE grades using mixed-effect models with diver as the random variable and associated intraclass correlation coefficients.

Results

Most divers produced a wide range of VGE grades after repeated dives on the same profile. The intraclass correlation coefficient (repeatability) was 0.33 indicating that 33% of the variability in VGE grades is between-diver variability; correspondingly, 67% of variability in VGE grades is within-diver variability. DCS cases were associated with an individual diver's highest VGE grades and not with their lower VGE grades.

Conclusions

These data demonstrate large within-diver variability in VGE grades following repeated dives on the same dive profile and suggest there is substantial within-diver variability in susceptibility to DCS. Post-dive VGE grades are not useful for evaluating decompression practice for individual divers.

Risk assessment of SWEN21 a suggested new dive table for the Swedish armed forces: bubble grades by ultrasonography

Introduction

To develop the diving capacity in the Swedish armed forces the current air decompression tables are under revision. A new decompression table named SWEN21 has been created to have a projected risk level of 1% for decompression sickness (DCS) at the no stop limits. The aim of this study was to evaluate the safety of SWEN21 through the measurement of venous gas emboli (VGE) in a dive series.

Methods

A total 154 dives were conducted by 47 divers in a hyperbaric wet chamber. As a proxy for DCS risk serial VGE measurements by echocardiography were conducted and graded according to the Eftedal-Brubakk scale. Measurements were done every 15 minutes for approximately 2 hours after each dive. Peak VGE grades for the different dive profiles were used in a Bayesian approach correlating VGE grade and risk of DCS. Symptoms of DCS were continually monitored.

Results

The median (interquartile range) peak VGE grade after limb flexion for a majority of the time-depth combinations, and of SWEN21 as a whole, was 3 (3-4) with the exception of two decompression profiles which resulted in a grade of 3.5 (3-4) and 4 (4-4) respectively. The estimated risk of DCS in the Bayesian model varied between 4.7-11.1%. Three dives (2%) resulted in DCS. All symptoms resolved with hyperbaric oxygen treatment.

Conclusions

This evaluation of the SWEN21 decompression table, using bubble formation measured with echocardiography, suggests that the risk of DCS may be higher than the projected 1%.

Make a difference: Choose artificial reefs over natural reefs to compensate for the environmental impacts of dive tourism

In the marine environment, natural reef habitats are amongst the most threatened by human activities. Although reef-based ecotourism can benefit local economies, dive tourism can damage sensitive habitats. One solution to managing conflicts between the economic value of diving and its ecological threats is the deployment of artificial reefs near popular dive sites. We surveyed recreational divers to assess divers' use, preference, and perceptions of diving artificial versus natural sites. We found that more divers prefer to dive in natural than artificial habitats, with associated biodiversity the most popular reason for preferring natural habitats, and appreciating shipwrecks the most popular reason for preferring artificial ones. Despite our sample population being highly educated and experienced, predominantly European divers, only 49 % of them perceived artificial reefs as important or somewhat important for diverting pressure from sensitive natural habitats. Similarly, only 13 % of respondents exhibited preference to avoid coral reefs to protect them. These results highlight the fact that more needs to be done to educate divers about the potential importance of artificial habitats in diverting divers from natural reefs. We suggest encouraging divers to switch out a proportion of their dives in vulnerable natural sites for artificial reefs. This is not only true for coral reefs, but should be applied to other natural reef habitats that are popular with divers such as kelp forests, sponge gardens and serpulid and coralligenous reefs. We hope that this study will provide a platform to stimulate a diver-led discussion and campaign for increased uptake of artificial reef use, resulting in reduced impacts on natural reefs.

The Establishment of a precise intelligent evaluation system for sports events: Diving

The introduction of action quality assessment technology in sports events to achieve precise intelligent evaluation can greatly enhance the objectivity and effectiveness of competition results. Taking diving as the specific application background, this study proposes a novel Multi-granularity Extraction Approach for Temporal-spatial features in judge scoring prediction (MEAT) under the conditions of action quality assessment. On the one hand, it uses dual-modal inflated 3D ConvNet to extract the temporal and spatial features of each modal diving video at the video granularity parallelly and to merge them to form a global feature. On the other hand, the human body pose is modeled, and the simulated athlete's three-dimensional splash state is taken as local characteristics at the object granularity. Finally, the global and local features are concatenated into the fully connected layer, and heuristic method inspired by competition rules using labeled distribution learning are employed to output the probability distribution of the average score of all referees. The maximum probability score is selected and multiplied by the difficulty coefficient to obtain the final diving score. Through comprehensive experiments, comparing the Spearman's rank correlation (SRC) evaluation results of existing methods on the UNIV-Dive dataset, this framework reflects the greater accuracy advantage and further lays the foundation for the actual implementation of the technology.

Dissolved gases from pressure changes in the lungs elicit an immune response in human peripheral blood

Conventional dogma suggests that decompression sickness (DCS) is caused by nitrogen bubble nucleation in the blood vessels and/or tissues; however, the abundance of bubbles does not correlate with DCS severity. Since immune cells respond to chemical and environmental cues, we hypothesized that the elevated partial pressures of dissolved gases drive aberrant immune cell phenotypes in the alveolar vasculature. To test this hypothesis, we measured immune responses within human lung-on-a-chip devices established with primary alveolar cells and microvascular cells. Devices were pressurized to 1.0 or 3.5 atm and surrounded by normal alveolar air or oxygen-reduced air. Phenotyping of neutrophils, monocytes, and dendritic cells as well as multiplexed ELISA revealed that immune responses occur within 1 hour and that normal alveolar air (i.e., hyperbaric oxygen and nitrogen) confer greater immune activation. This work strongly suggests innate immune cell reactions initiated at elevated partial pressures contribute to the etiology of DCS.

Selecting optimal air diving gradient factors for Belgian military divers: more conservative settings are not necessarily safer

Introduction

In 2018, the Belgian Defence introduced a commercial off-the-shelf dive computer (Shearwater Perdix™) for use by its military divers. There were operational constraints when using its default gradient factors (GF). We aimed to provide guidelines for optimal GF selection.

Methods

The Defence and Civil Institute of Environmental Medicine (DCIEM) dive tables and the United States Navy (USN) air decompression tables are considered acceptably safe by the Belgian Navy Diving Unit. The decompression model used in the Shearwater Perdix (Bühlmann ZH-L16C algorithm with GF) was programmed in Python. Using a sequential search of the parameter space, the GF settings were optimised to produce decompression schedules as close as possible to those prescribed by the USN and DCIEM tables.

Results

All reference profiles are approached when GFLO is kept equal to 100 and only GFHI is reduced to a minimum of 75 to prolong shallower stop times. Using the Perdix default settings (GFLO = 30 and GFHI = 70) yields deeper initial stops, leading to increased supersaturation of the 'slower' tissues, which potentially leads to an increased DCS risk. However, Perdix software does not currently allow for the selection of our calculated optimal settings (by convention GFLO < GFHI). A sub-optimal solution would be a symmetrical GF setting between 75/75 and 95/95.

Conclusions

For non-repetitive air dives, the optimal GF setting is GFLO 100, with only the GFHI parameter lowered to increase safety. No evidence was found that using the default GF setting (30/70) would lead to a safer decompression for air dives as deep as 60 metres of seawater; rather the opposite. Belgian Navy divers have been advised against using the default GF settings of the Shearwater Perdix dive computer and instead adopt symmetrical GF settings which is currently the optimal achievable approach considering the software constraints.

The pulmonary oxygen toxicity index

Pulmonary oxygen toxicity (POT) is a major risk in diving while breathing hyperoxic gas and is also considered in clinical hyperbaric oxygen treatment. The POTindex calculated by the power equation K = t² × PO₂^4.57 with the recovery form Ktr = Ke × e ^{- [- 0.42 + 0.384 × (PO}₂⁾_ex^{] × tr} which are based on chemical and physiological principles, have a better prediction power than other suggested approaches. Reduction of vital capacity as well as incidence of POT are well predicted by the POTindex. Both the cumulative pulmonary toxic effect and concomitant recovery were suggested to operate at the lower toxic range of PO₂ used in saturation diving K = t² × PO₂^4.57 × e^{-0.0135 × t}, and further experimental support is supplied. The recovery time constant for the full range of PO₂ is presented. POTindex is suggested to replace the old method of UPTD for safe diving. Many diving clubs and diving institutes already adopted the POTindex.

Dolphin leukocytes exhibit an attenuated cytokine response and increase heme oxygenase activity upon exposure to lipopolysaccharides

Cetaceans exhibit physiological adaptations that allowed the transition to aquatic life, including a robust antioxidant defense system that prevents injury from repeated exposure to ischemia/reperfusion events associated with breath-hold diving. The signaling cascades that characterize ischemic inflammation in humans are well characterized. In contrast, cetaceans' molecular and biochemical mechanisms that confer tolerance to inflammatory events are poorly understood. Heme oxygenase (HO) is a cytoprotective protein with anti-inflammatory properties. HO catalyzes the first step in the oxidative degradation of heme. The inducible HO-1 isoform is regulated by various stimuli, including hypoxia, oxidant stress, and inflammatory cytokines. The objective of this study was to compare the response of HO-1 and cytokines to a proinflammatory challenge in leukocytes isolated from humans and bottlenose dolphins (Tursiops truncatus). We measured changes in HO activity and expression, and abundance and expression of interleukin 1 beta (IL-1β), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and heme oxygenase 1 (HMOX1) in leukocytes treated with lipopolysaccharide (LPS) for 24 and 48 h. HO activity increased (p < 0.05) in dolphin (48 h) but not human cells. TNF-α expression increased in human (24 h, 48 h), but not dolphin cells following LPS stimulation. LPS-induced cytokine expression was lower in dolphin than in human leukocytes, suggesting a blunted cytokine response in bottlenose dolphin leukocytes treated with LPS. Results suggest species-specific regulation of inflammatory cytokines in leukocytes treated with LPS, which may lead to differential responses to a pro-inflammatory challenge between marine and terrestrial mammals.

Intraindividual variability of the Eustachian tube function: a longitudinal study in a pressure chamber

INTRODUCTION

The Eustachian tube (ET) is essential for fast and direct pressure equalisation between middle ear and ambient pressure. It is not yet known to what extent Eustachian tube function in healthy adults changes in a weekly periodicity due to internal and external factors. This question is particularly interesting with regard to scuba divers among whom there is a need to evaluate intraindividual ET function variability.

METHODS

Continuous impedance measurement in a pressure chamber was performed three times at one-week intervals between measurements. Twenty healthy participants (40 ears) were enrolled. Using a monoplace hyperbaric chamber, individual subjects were exposed to a standardised pressure profile consisting of a 20 kPa decompression over 1 min, a 40 kPa compression over 2 min, and a 20 kPa decompression over 1 min. Measurements of Eustachian tube opening pressure (ETOP), opening duration (ETOD), and opening frequency (ETOF) were made. Intraindividual variability was assessed.

RESULTS

Mean ETOD during compression (actively induced pressure equalisation) on the right side was 273.8 (SD 158.8) ms, 259.4 (157.7) ms, and 249.2 (154.1) ms (Chi-square 7.30, P = 0.026) across weeks 1-3. Mean ETOD for both sides was 265.6 (153.3) ms, 256.1 (154.6) ms, and 245.7 (147.8) ms (Chi-square 10.00, P = 0.007) across weeks 1-3. There were no other significant differences in ETOD, ETOP and ETOF across the three weekly measurements.

CONCLUSIONS

This longitudinal study suggests low week-to-week intraindividual variability of Eustachian tube function.

The risk of decompression illness in breath-hold divers: a systematic review

INTRODUCTION

Breath-hold (BH) diving has known risks, for example drowning, pulmonary oedema of immersion and barotrauma. There is also the risk of decompression illness (DCI) from decompression sickness (DCS) and/or arterial gas embolism (AGE). The first report on DCS in repetitive freediving was published in 1958 and from then there have been multiple case reports and a few studies but no prior systematic review or meta-analysis.

METHODS

We undertook a systematic literature review to identify articles available from PubMed and Google Scholar concerning breath-hold diving and DCI up to August 2021.

RESULTS

The present study identified 17 articles (14 case reports, three experimental studies) covering 44 incidences of DCI following BH diving.

CONCLUSIONS

This review found that the literature supports both DCS and AGE as potential mechanisms for DCI in BH divers; both should be considered a risk for this cohort of divers, just as for those breathing compressed gas while underwater.

Generation of forward angular impulse with different initial conditions

Generation of angular impulse during foot contact is regulated by controlling the relative orientation between the total body center of mass (CoM) and the reaction force (RF) applied to the feet. Between-task differences in initial CoM horizontal momentum were hypothesized to alter how forward angular impulse was generated during two forward translating tasks. Five skilled athletes performed standing (SFS) and running (RFS) forward somersaulting dives. Sagittal plane kinematics and RFs were obtained during the take-off phase of both tasks. The initial CoM momentum differences resulted in significant differences in control of the CoM relative to the RF, RF generation mechanisms, and knee and hip net joint moments (NJMs). During the RFS, angular impulse was generated by positioning the feet anterior to the CoM at initial contact so that the RF passed posterior to the CoM throughout the take-off phase. During the SFS, angular impulse was generated by positioning the CoM anterior to the feet prior to the push interval so that the RF passed posterior to the CoM. Task-specific differences in segment kinematics and RF direction contributed to the redistribution of knee and hip NJMs. These results suggest that initial conditions influence strategies the nervous system uses to satisfy task objectives.

Into the Blue: First in Man Data on Diving Physiology in Fontan Patients

Swimming and diving are popular recreational activities. As congenital heart disease, especially patients with univentricular hearts after Fontan palliation are thought to have reduced physiologic capacities for compensation of submersion-associated physiologic demands, current guidelines put restraints on this group of patients. Although these restrictions on doctoral advice place a significant burden on affected patients, it is especially interesting that these guideline recommendations are merely based on physiologic assumptions, i.e., expert consensus. A recent study by Paech et al. presented the first in vivo data on the effects of immersion in Fontan patients, stating no major adverse events in their study group as well as comparable physiologic adaption as reported in the literature for healthy people. Yet, submersion was not reflected in this study, and the current study therefore aimed to conduct a first study for the evaluation of the effects of submersion and apnea diving in Fontan patients. A control group of healthy adults as well as patients recruited from the Heart Center Leipzig, Department of pediatric cardiology underwent a standardized diving protocol including a static as well as dynamic apnea phase. Physiologic data were recorded. This study presents the first structured data on diving physiology in Fontan patients compared to healthy probands. There were no adverse events. The physiologic response to diving seems to be comparable between healthy probands and Fontan patients. Although, healthy probands did reach a much better performance, the basic mechanisms of physiologic adaption seem comparable.

Electric shock leading to acute lung injury in a scuba diver

INTRODUCTION

Electrical injuries are a rarely reported complication of scuba diving.

CASE REPORT

A 33-year-old woman wore a 12-volt heated shirt designed for motorcycling, powered by a canister light battery, while scuba diving. A leak in her drysuit allowed water to make contact with an electrified connector from the heated shirt, and she experienced painful electrical shocks. She was able to disconnect the power source and finish the dive, but she developed progressive fevers and dyspnoea several hours later. She was diagnosed with acute lung injury and treated with bronchodilators. Her symptoms resolved over subsequent weeks.

DISCUSSION

Acute lung injury is rarely reported after low voltage electrical injury. In this case, the use of a heated shirt that was not intended for underwater activities heightened the patient's risk for electric shock that likely resulted in aspiration of sea water and subsequent acute lung injury. To reduce risk of injury, divers should use equipment that is designed for underwater submersion. Medical professionals who treat the diving population should be aware that divers may use modified equipment that increases the risk of diving-related complications.

Oxidative stress, apoptosis, and transcriptional responses in Acropora microphthalma under simulated diving activities

This study simulated the effects of diving activities on the physiology, enzymatic, and transcriptional responses of Acropora microphthalma. Touching had less impact on Fv/Fm, but a few zooxanthellae were decreased and minor MDA was elevated. Caspase 3 was activated to remove damaged cells, and SOD was increased to alleviate oxidative damage. Under double or triple diving stress, we observed mass loss of zooxanthellae and Fv/Fm, a significant increase in MDA, and SOD, CAT was activated in response to oxidative stress. Transcriptome analyses showed that corals activated immune signaling pathways, anti-oxidation pathways, lysosomal, phagosomal, and cellular autophagy pathways to manage oxidation stress. Moreover, it up-regulated carbohydrate metabolisms, as well as lipopolysaccharide metabolism, glycosphingolipid biosynthesis, photorespiration, amino acid metabolism, and fatty acid beta-oxidation, but down-regulated fatty acid biosynthesis to answer energy insufficiency. This research supported that even in a short time, improper diving activities could have a serious impact on coral health.

Lung function changes in divers after a single deep helium-oxygen dive

INTRODUCTION

This study measured pulmonary function in divers after a single helium-oxygen (heliox) dive to 80, 100, or 120 metres of sea water (msw).

METHODS

A total of 26 divers participated, of whom 15, five, and six performed a 80, 100, or 120 msw dive, respectively. While immersed, the divers breathed heliox and air, then oxygen during surface decompression in a hyperbaric chamber. Pulmonary function was measured twice before diving, 30 min after diving, and 24 h after diving.

RESULTS

At 30 min after the 80 msw dive the forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ratio and the maximum expiratory flow at 25% of vital capacity (MEF₂₅) values decreased (89.2% to 87.1% and 2.57 L·s⁻¹ to 2.35 L·s⁻¹, P = 0.04, P = 0.048 respectively) but FEV₁/FVC returned to the baseline values by 24 h post-dive. Other pulmonary indicators exhibited downward trends at 30 min after the dive, but statistical significance was lacking. Interestingly, though several parameters decreased after the 100 msw dive, statistical significance was not reached. After the 120 msw dive, the FEV₁/FVC and MEF₇₅ decreased (90.4% to 85.6% and 8.05 L·s⁻¹ to 7.46 L·s⁻¹, P = 0.01, P = 0.007). The relatively small numbers of subjects who dived to 100 and 120 msw depths may explain the inconsistent results. The subjects diving to 100 and 120 msw were more trained / skilled, but this would not explain the inconsistencies in results between these depths.

CONCLUSIONS

We conclude that single deep heliox dives cause a temporary decrease in FEV₁/FEV and MEF25 or MEF₇₅, but these changes can recover at 24 h after the dive.

Diving ergospirometry with suspended weights: breathing- and fin-swimming style matter

Purpose

Scuba diving is a complex condition including elevated ambient pressure, limited air supply, increased breathing work, and unfamiliar fin-swimming. Earlier approaches to assess diving specific data did not comprehensively address these aspects. We first present an underwater ergospirometry system and then test the hypothesis that both breathing characteristics and fin-swimming style affect the air consumption.

Methods/Participants

A suspended-weights ergospirometry system was mounted inside a hyperbaric chamber. Ergo group: 25 divers (24.6 ± 4.1 years); three set-ups: dry normobaric cycling (75–225 W), dry cycling at 20 m simulated depth (75–225 W), fin-swimming at 20 m (5–8 kg suspended weights). Style group: 20 other divers (24.6 ± 4.1 years): fin-swimming at 20 m (5–8 kg) with regard to ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙E) and fin-swimming style.

Results

Ergo group: linear heart rate and oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂) increases with both 50 W-bicycle steps and suspended-weights ergometry (r = 0.97). During hyperbaric conditions, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙E was less increased versus normobaric conditions. Style group: the more efficient hip/thigh-oriented style shifted towards the knee/calf-oriented style. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙E and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂ were higher in beginners (< 100 dives) versus advanced divers (≥ 100 dives). Significant differences on the 5 kg-step: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙E: 31.5 ± 7.1 l/min vs. 23.7 ± 5.9 l/min and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂: 1.6 ± 0.3 l/min vs. 1.2 ± 0.3 l/min. A comparison is presented, in addition to illustrate the impact of differences in breathing characteristics and fin-swimming style.

Conclusions

Diving ergospirometry with suspended weights in a hyperbaric chamber allows for comprehensive studies. Little diving experience in terms of breathing characteristics and fin-swimming style significantly increases \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙E thereby increasing the risk of running-out-of-air.

Extreme anaerobic exercise causes reduced cytotoxicity and increased cytokine production by peripheral blood lymphocytes

Exercise has many beneficial effects for our body, but can become detrimental at high intensity, especially for our immune system. Little is known about the underlying mechanism of impaired immune functionality under conditions of intense physical strain. Freedivers, people who dive to high depths on a single breath, perform extreme exercise under anaerobic conditions. In this study, we investigated the impact of freediving on the cytotoxic arm of the immune system. At rest, elite freedivers did not display changes in their immunological profile compared to non-diving controls. In contrast, after a freedive, granzyme B and IL-2 production were reduced, whereas IFNγ and TNF secretion were increased by cytotoxic immune cells. Using in vitro models mimicking freedive conditions, we could show that hypoxia in combination with stress hyperglycemia had a negative impact on Granzyme B secretion, whereas IL-2 production was inhibited by stress hormones. Our findings suggest that in response to extreme exercise, cytotoxic immune cells transiently change their functional profile to limit tissue damage.

Effects of a parasympathetic blocker on the heart rate of loggerhead turtles during voluntary diving

Diving bradycardia is a reduction in the heart rate mediated by the parasympathetic system during diving. Although diving bradycardia is pronounced in aquatic mammals and birds, the existence of this response in aquatic reptiles, including sea turtles, remains under debate. Using the parasympathetic blocker atropine, we evaluated the involvement of the parasympathetic nervous system in heart rate reduction of loggerhead sea turtles (Caretta caretta) during voluntary diving in tanks. The heart rate of the control group dropped by 40-60 % from the pre-dive value at the onset of diving; however, administration of atropine significantly inhibited heart rate reduction (P<0.001). Our results indicate that, similar to mammals and birds, the heart rate reduction in sea turtles while diving is primarily mediated by the parasympathetic nervous system. In conclusion, we suggest that diving bradycardia exists not only in aquatic mammals and birds but also in aquatic reptiles.

Health and wellbeing of recently active United States scuba divers

INTRODUCTION

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.

Protein tau concentration in blood increases after SCUBA diving: an observational study

Purpose

It is speculated that diving might be harmful to the nervous system. The aim of this study was to determine if established markers of neuronal injury were increased in the blood after diving.

Methods

Thirty-two divers performed two identical dives, 48 h apart, in a water-filled hyperbaric chamber pressurized to an equivalent of 42 m of sea water for 10 min. After one of the two dives, normobaric oxygen was breathed for 30 min, with air breathed after the other. Blood samples were obtained before and at 30–45 and 120 min after diving. Concentrations of glial fibrillary acidic, neurofilament light, and tau proteins were measured using single molecule array technology. Doppler ultrasound was used to detect venous gas emboli.

Results

Tau was significantly increased at 30–45 min after the second dive (p < 0.0098) and at 120 min after both dives (p < 0.0008/p < 0.0041). Comparison of matching samples showed that oxygen breathing after diving did not influence tau results. There was no correlation between tau concentrations and the presence of venous gas emboli. Glial fibrillary acidic protein was decreased 30–45 min after the first dive but at no other point. Neurofilament light concentrations did not change.

Conclusions

Tau seems to be a promising marker of dive-related neuronal stress, which is independent of the presence of venous gas emboli. Future studies could validate these results and determine if there is a quantitative relationship between dive exposure and change in tau blood concentration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-022-04892-9.

Inner ear barotrauma and inner ear decompression sickness: a systematic review on differential diagnostics

INTRODUCTION

Inner ear barotrauma (IEBt) and inner ear decompression sickness (IEDCS) are the two dysbaric inner ear injuries associated with diving. Both conditions manifest as cochleovestibular symptoms, causing difficulties in differential diagnosis and possibly delaying (or leading to inappropriate) treatment.

METHODS

This was a systematic review of IEBt and IEDCS cases aiming to define diving and clinical variables that help differentiate these conditions. The search strategy consisted of a preliminary search, followed by a systematic search covering three databases (PubMed, Medline, Scopus). Studies were included when published in English and adequately reporting one or more IEBt or IEDCS patients in diving. Concerns regarding missing and duplicate data were minimised by contacting original authors when necessary.

RESULTS

In total, 25 studies with IEBt patients (n = 183) and 18 studies with IEDCS patients (n = 397) were included. Variables most useful in differentiating between IEBt and IEDCS were dive type (free diving versus scuba diving), dive gas (compressed air versus mixed gas), dive profile (mean depth 13 versus 43 metres of seawater), symptom onset (when descending versus when ascending or surfacing), distribution of cochleovestibular symptoms (vestibular versus cochlear) and absence or presence of other DCS symptoms. Symptoms of difficult middle ear equalisation or findings consistent with middle ear barotrauma could not be reliably assessed in this context, being insufficiently reported in the IEDCS literature.

CONCLUSIONS

There are multiple useful variables to help distinguish IEBt from IEDCS. Symptoms of difficult middle ear equalisation or findings consistent with middle ear barotrauma require further study as means of distinguishing IEBt and IEDCS.

Metal content in stranded pelagic vs deep-diving cetaceans in the Canary Islands

The Canary Islands are home to many cetacean species, many of which are resident species. The present work aims to analyze, for the first time to the best of the authors' knowledge, the macronutrients, micronutrients and trace elements and toxic heavy metals in muscle and liver tissue of six species of stranded cetaceans in the Canary Islands. The study species were: Tursiops truncatus, Stenella frontalis, Delphinus delphis, Grampus griseus, Globicephala macrorynchus and Physeter macrocephalus. Statistical analysis studied the significant differences between the concentrations in muscle and liver tissues, with the differences in element content depending on the type of diving and length of the species. The results indicate that there are differences between muscle and liver for Ca, Cd, Co, Cu, K, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn. Deep-diving animals differ in their concentrations of Cr, Cu, Mg, Mn, Mo, and Zn with respect to shallow-diving animals in muscle and in liver in Al, B, Cr, K, Mn and Mo. As for the differences between sex, the males present differences in their concentrations of B, Cd, K and Mg in muscle tissue with respect to the females, while differences in the liver were only detected in the Fe content. The study of the correlations shows that as the size of the animal increases, the concentration of Cd increases while the concentrations of Al, Cu and Zn decrease. The specimens foraging in shallower waters had the highest concentration of the macronutrient.

Physiology of repeated mixed gas 100-m wreck dives using a closed-circuit rebreather: a field bubble study

PURPOSE

Data regarding decompression stress after deep closed-circuit rebreather (CCR) dives are scarce. This study aimed to monitor technical divers during a wreck diving expedition and provide an insight in venous gas emboli (VGE) dynamics.

METHODS

Diving practices of ten technical divers were observed. They performed a series of three consecutive daily dives around 100 m. VGE counts were measured 30 and 60 min after surfacing by both cardiac echography and subclavian Doppler graded according to categorical scores (Eftedal-Brubakk and Spencer scale, respectively) that were converted to simplified bubble grading system (BGS) for the purpose of analysis. Total body weight and fluids shift using bioimpedancemetry were also collected pre- and post-dive.

RESULTS

Depth-time profiles of the 30 recorded man-dives were 97.3 ± 26.4 msw [range: 54-136] with a runtime of 160 ± 65 min [range: 59-270]. No clinical decompression sickness (DCS) was detected. The echographic frame-based bubble count par cardiac cycle was 14 ± 13 at 30 min and 13 ± 13 at 60 min. There is no statistical difference neither between dives, nor between time of measurements (P = 0.07). However, regardless of the level of conservatism used, a high incidence of high-grade VGE was detected. Doppler recordings with the O'dive were highly correlated with echographic recordings (Spearman r of 0.81, P = 0.008).

CONCLUSION

Although preliminary, the present observation related to real CCR deep dives questions the precedence of decompression algorithm over individual risk factors and pleads for an individual approach of decompression.

Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens)

Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce. In the present study, 3 adult female Pacific walruses (Odobenus rosmarus divergens) participated in flow-through respirometry trials to measure metabolic rates while floating inactive at the water surface during a minimum of 5 min, during a 180-second stationary dive, and while swimming horizontally underwater for ∼90 m. Metabolic rates during stationary dives (3.82±0.56 l O2 min-1) were lower than those measured at the water surface (4.64±1.04 l O2 min-1), which did not differ from rates measured during subsurface swimming (4.91±0.77 l O2 min-1). Thus, neither stationary diving nor subsurface swimming resulted in metabolic rates above those exhibited by walruses at the water surface. These results suggest that walruses minimize their energetic investment during underwater behaviours as reported for other marine mammals. Although environmental factors experienced by free-ranging walruses (e.g., winds or currents) likely affect metabolic rates, our results provide important information for understanding how behavioural changes affect energetic costs and can be used to improve bioenergetics models aimed at predicting the metabolic consequences of climate change on walruses.

[Remotely operated underwater vehicles used in water rescue]

BACKGROUND

The search for and rescue of missing persons is always coupled with a high demand on human resources. In cases of suspected drowning it is often necessary to search huge expanses of water. For depths of more than 3-5 m the search and rescue procedure needs to be performed by specialist rescue divers. Due to saturation with nitrogen caused by the higher ambient pressure during the dive, the operating time for each rescue diver is limited. In addition, each dive is linked with an increased risk.

OBJECTIVE

Miniaturization of sensors, higher performance of embedded systems and high energy density of modern accumulators offer the chance to operate with unmanned flying and diving vehicles for search and rescue even with moderate financial investment.

MATERIAL AND METHODS

Based on funding by the Federation of the German Live Saving Association (DLRG) the DLRG national association of Bavaria procured three different models of remotely operated underwater vehicles (ROUV) and two different systems for underwater positioning. These systems will be offered to local associations of the DLRG in Bavaria for intense testing in their waters based on a common implementation strategy to ensure comparability and reproducibility.

RESULTS

Initial tests with different types of ROUV and underwater positioning have been performed in preparation of the survey. As a result, mini-ROUVs found in the lower consumer segment have been identified as insufficient as they are not able to carry the additional payload of the underwater positioning systems whilst maintaining controllability. In contrast, more complex drones are difficult to handle and require longer preparation times before they are ready for use. The ROUVs in the median range, preferably with a streamlined structure, have so far been found to be optimal; however, operating the vehicle without a positioning system is not recommended.

CONCLUSION

In combination with an underwater positioning system, remotely operated underwater vehicles are identified as a reasonable supplement for rescue divers. Fast time to operation enables a preview of the operating area before starting the rescue operation and can therefore support the rescue diver team.

The Fontan and the Sea: First-in-Man Data on Swimming and Diving Physiology in Fontan Patients

While swimming represents a popular recreational activity, the immersion of the human body into the water requires a complex physiologic adaption of the whole cardiopulmonary and circulatory system. While this sport is regarded as beneficial, especially in cardiovascular patients, current guidelines hypothesized a possible hazardous effect of swimming and especially diving in patients with univentricular hearts after Fontan palliation. Yet, actual data to underline or contradict these assumptions are lacking. Therefore, this study aimed to conduct a first feasibility study for the evaluation of these effects on Fontan physiology and elucidate the gap of evidence currently preventing patients after Fontan palliation from being restricted from swimming or diving on doctoral advice. Patients recruited from the Heart Center Leipzig, Department of pediatric cardiology, underwent spiroergometry treadmill testing followed by a spiroergometry swimming stress test in a counter current pool. Physiologic data were recorded. A short apnea diving test was performed. The current study found similar physiologic reactions comparing treadmill and swimming exercise stress testing. Heart rate response and oxygen uptake were comparable on land and in the water. This study presents the first-in-man data on swimming and diving in Fontan patients. In this small study cohort of three Fontan patients, there were no adverse events triggered by swimming and breath-hold diving seen. Basically, the physiologic response to exercise was comparable on land and in the water.

Audit of waist measurement methods during statutory diving medical assessments

BACKGROUND

Measurement of waist circumference is used to assess abdominal fat and risk of heart disease, type 2 diabetes, cancer and stroke. It is performed in several clinical settings for health promotion and medical assessment purposes, including statutory medical assessments where results may influence decisions on fitness to work. Under the Diving at Work Regulations 1997, working divers must have an annual assessment of their fitness to dive performed by an approved medical examiner of divers (AMED), appointed by the Health and Safety Executive (HSE). The assessment includes measurement of height, weight and waist circumference, the latter used as an indicator of central adiposity and associated health risks.

AIMS

To establish the practice of AMEDs in measuring waist circumference of working divers undergoing medical assessment to determine their fitness to dive.

METHODS

Ninety-seven AMEDs were sent a questionnaire and asked to describe their current practice in measuring waist circumference. The response rate was 79%. The audit standard used was the consensus document published by the World Health Organization (WHO).

RESULTS

Of the 77 responses, 76 were completed sufficiently to allow analysis. When the waist was measured, there was consistency in the diver's level of clothing, stage of breathing and posture for the procedure but variability in the site of measurement. Only 7/76 (9%) respondents carried out waist measurement fully in line with WHO guidance.

CONCLUSIONS

The audit has identified that there is a need for guidance for AMEDs on measuring waist circumference in the statutory medical assessment of working divers.

[A case of pulmonary barotrauma complicated with cerebral arterial air embolism in a diver]

Pulmonary barotrauma is a kind of disease caused by the injury of lung tissue or blood vessel when the gas pressure of lung is too high or too lower than the external pressure of the body, which causes the air to enter the blood vessel and adjacent tissue. It could be happened in the escape of the divers with the light diving equipment or the sailors from submarine. Generally, the decompression chamber was used to treating the disease, and the minimum air pressure of 0.5 MPa recompression therapeutic schedule was used to selecting. In November 2019, a patient with pulmonary barotrauma combined with cerebral arterial gas embolism caused by improper underwater escape with light diving equipment was admitted to the General Hospital of Eastern War Zone. He was treated with 0.12 MPa oxygen inhalation recompression scheme in the oxygen chamber pressurized with air. 7 days later, the patient recovered and discharged.

Metabolic trade-offs in tropical and subtropical marine mammals: unique maintenance and locomotion costs in West Indian manatees and Hawaiian monk seals

Unlike the majority of marine mammal species, Hawaiian monk seals (Neomonachus schauinslandi) and West Indian manatees (Trichechus manatus latirostris) reside exclusively in tropical or subtropical waters. Although potentially providing an energetic benefit through reduced maintenance and thermal costs, little is known about the cascading effects that may alter energy expenditure during activity, dive responses and overall energy budgets for these warm-water species. To examine this, we used open-flow respirometry to measure the energy expended during resting and swimming in both species. We found that the average resting metabolic rates (RMRs) for both the adult monk seal (753.8±26.1 kJ h-1, mean±s.e.m.) and manatees (887.7±19.5 kJ h-1) were lower than predicted for cold-water marine mammal species of similar body mass. Despite these relatively low RMRs, both total cost per stroke and total cost of transport (COTTOT) during submerged swimming were similar to predictions for comparably sized marine mammals (adult monk seal: cost per stroke=5.0±0.2 J kg-1 stroke-1, COTTOT=1.7±0.1 J kg-1 m-1; manatees: cost per stroke=2.0±0.4 J kg-1 stroke-1, COTTOT=0.87±0.17 J kg-1 m-1). These lower maintenance costs result in less variability in adjustable metabolic costs that occur during submergence for warm-water species. However, these reduced maintenance costs do not appear to confer an advantage in overall energetic costs during activity, potentially limiting the capacity of warm-water species to respond to anthropogenic or environmental threats that require increased energy expenditure.

Persistent pathology of the patent foramen ovale: a review of the literature

A patent foramen ovale (PFO) is an interatrial shunt, with a prevalence of 20-34% in the general population. While most people do not have secondary manifestations of a PFO, some reported sequelae include ischaemic stroke, migraine, platypnoea-orthodeoxia syndrome and decompression illness. Furthermore, in some cases, PFO closure should be considered for patients before neurosurgery and for patients with concomitant carcinoid syndrome. Recent trials support PFO closure for ischaemic stroke patients with high risk PFOs and absence of other identified stroke mechanisms. While PFOs can be associated with migraine with auras, with some patients reporting symptomatic improvement after closure, the evidence from randomised controlled trials is less clear in supporting the use of PFO closure for migraine treatment. PFO closure for other indications such as platypnoea-orthodeoxia syndrome, decompression illness and paradoxical embolism are based largely on case series with good clinical outcomes. PFO closure can be performed as a day surgical intervention with high procedural success and low risk of complications.

The early life of king penguins: ontogeny of dive capacity and foraging behaviour in an expert diver

The period of emancipation in seabirds, when juveniles change from a terrestrial existence to a life at sea, is associated with many challenges. Apart from finding favourable foraging sites, they have to develop effective prey search patterns and physiological capacities that enable them to capture sufficient prey to meet their energetic needs. Animals that dive to forage, such as king penguins (Aptenodytes patagonicus), need to acquire an adequate breath-hold capacity, allowing them to locate and capture prey at depth. To investigate the ontogeny of their dive capacity and foraging performance, we implanted juvenile king penguins before their first departure to sea and also adult breeders with a data-logger recording pressure and temperature. We found that juvenile king penguins possess a remarkable dive capacity when leaving their natal colony, enabling them to conduct dives in excess of 100 m within their first week at sea. Despite this, juvenile dive/foraging performance, investigated in relation to dive depth, remained below the adult level throughout their first year at sea, probably reflecting physiological limitations as a result of incomplete maturation. A significantly shallower foraging depth of juveniles, particularly during their first 5 months at sea, could also indicate differences in foraging strategy and targeted prey. The initially greater wiggle rate suggests that juveniles fed opportunistically and also targeted different prey from adults and/or that many of the wiggles of juveniles reflect unsuccessful prey-capture attempts, indicating a lower foraging proficiency. After 5 months, this difference disappeared, suggesting sufficient physical maturation and improvement of juvenile foraging skills.

Prospective study on the Eustachian tube function during Frenzel maneuver in a hypobaric/hyperbaric pressure chamber

Introduction

The Frenzel maneuver describes a technique for middle ear equalizing which is frequently used by apnea divers. It offers advantages compared to the most commonly used techniques such as the Valsalva or Toynbee maneuver. Until now, there is insufficient literature about the pressure dynamics and Eustachian tube (ET) function during the Frenzel maneuver. The aim of the present study was to characterize the ET function during the Frenzel maneuver.

Materials and methods

By means of an established standardized profile of compression and decompression in a hypo/hyperbaric pressure chamber, we examined different parameters such as the ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF) in 11 experienced apnea divers and compared them to the parameters during the Valsalva and Toynbee maneuver.

Results

Standard values for ETOP, ETOD, and ETOF could be established for the Frenzel maneuver under standardized conditions in a hypo/hyperbaric pressure chamber. Compared to the Frenzel maneuver, ETOP was higher and ETOD longer (both p < 0.001) during the Valsalva maneuver whereas ETOP was lower and ETOD shorter (both p < 0.001) during the Toynbee maneuver. No difference regarding ETOF was observed between the Frenzel, Valsalva, and Toynbee maneuver.

Discussion

The Frenzel maneuver was shown to be at least as effective as the Valsalva maneuver concerning ET opening. We believe that knowledge of the Frenzel technique might facilitate the pressure equalization during diving and recommend implementation of an appropriate equalization training in apnea and scuba diving education.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-06888-1.

[A case of decompression sickness complicated with multiple organ failure treated by hyperbaric oxygen therapy sequential with continuous renal replacement therapy and extracorporeal membrane oxygenation]

Objective: To discuss the new idea of on-the-spot recompression treatment and multidisciplinary treatment (MDT) for patients with unstable vital signs of type II decompression sickness. To provide reference for the nearby treatment of patients with critical decompression sickness. Methods: The clinical data of a case of a multi-disciplinary collaborative treatment of type II decompression sickness complicated with multiple organ dysfunction syndrome (MODS) admitted to a third-class A hospital in January 2020 were analyzed and summarized. Results: The patient suffered from consciousness disturbance and shock after 3 min of diver's blow-up out of the water. CT examination showed gas accumulation in the systemic multi-organ venous system, and laboratory examination suggested MODS. The oxygen inhalation regimen was given in the session of recompression treatmen by 0.12-0.18 MPa. Intravenous fluid was the total of 8900 ml in the session, and the total recompression treatment time was 9 h 45 min. The patient was still in unconscious when he finished the session. CT re-examination confirmed the elimination of venous bubbles, and laboratory examination indicated multiple organ failure (MOF) . The patient was given comprehensive supporting treatment by mechanical assisted breathing and following by continuons renal replacement therapy (CRRT) and extrocorporeal membrane oxygenation (ECMO) in the intensive care unit, and was discharged after 32 d of hospitalization. Conclusion: Critical decompression sickness patients with unstable vital signs are taken to a local general hospital with hyperbaric oxygen chamber and intensive care unit. The successful treatment can be achieved by organizing diving medicine, hyperbaric oxygen medicine and critical medical personnel for MDT.

Occupational Safety and Health in a Community of Shellfish Divers: A Community-Based Participatory Approach

In artisanal fishing communities in Chile, the access to occupational safety and health (OSH) is limited by factors such as the informality of employment. Our objective was to analyze the working and health conditions of workers in a coastal town in Southern Chile, under a community-based participatory approach. We carried out two independent social dialogue workshops within the community. The first one (N of participants = 25) was aimed to identify the strengths, weaknesses and challenges for preventing decompression sickness among divers. The second workshop (N of participants = 10) was set to identify the work processes and to map the occupational risks during seafood harvesting and processing in the community. Community members' training for handling and preventing decompression sickness among divers, and the collaboration between a local health representative, stakeholders and authorities, were identified as contributing factors in reducing fatalities and sequels among divers in the past. Technology and safety on board the vessels, training of healthcare personnel in OSH, and access to health programs, were identified as remaining challenges. Through risk mapping, the participants identified the relationship between working and health conditions in the community, reinforcing the necessity of improving access to health and social security. The community participation in identifying and analyzing working and health conditions could be the first step for a strategy to address OSH through primary health care in rural communities. Community empowerment and involvement in action plans, training on basic OSH for health care workers, and public policies are required.

Decompression sickness after a highly conservative dive in a diver with known persistent foramen ovale: Case report

A diver returned to diving, 15 months after an episode of neuro-spinal decompression sickness (DCS) with relapse, after which she had been found to have a moderate to large provoked shunt across a persistent (patent) foramen ovale (PFO), which was not closed. She performed a single highly conservative dive in line with the recommendations contained in the 2015 position statement on PFO and diving published jointly by the South Pacific Underwater Medicine Society and the United Kingdom Sports Diving Medical Committee. An accidental Valsalva manoeuvre shortly after surfacing may have provoked initial symptoms which later progressed to DCS. Her symptoms and signs were milder but closely mirrored her previous episode of DCS and she required multiple hyperbaric oxygen treatments over several days, with residua on discharge. Although guidance in the joint statement was mostly followed, the outcome from this case indicates that there may be a subgroup of divers with an unclosed PFO, who have had a previous episode of serious DCS, who may not be safe to dive, even within conservative limits.

An insight to tympanic membrane perforation pressure through morphometry: A cadaver study

INTRODUCTION

A cadaveric experimental investigation aimed to show the rupture pressure of the tympanic membrane (TM) for otologists to evaluate its tensile strength.

METHODS

Twenty adult ears in 10 fresh frozen whole cadaveric heads (four males, six females) mean age 72.8 (SD 13.8) years (range 40-86) were studied. The tensile strength of the TM was evaluated with bursting pressure of the membrane. The dimensions of the membranes and perforations were measured with digital imaging software.

RESULTS

The mean bursting pressure of the TM was 97.71 (SD 36.20) kPa. The mean area, vertical and horizontal diameters of the TM were 57.46 (16.23) mm², 9.54 (1.27) mm, 7.99 (1.08) mm respectively. The mean area, length and width of the perforations were 0.55 (0.25) mm², 1.37 (0.50) mm, and 0.52 (0.22) mm, respectively. Comparisons of TM dimension, bursting pressure, and perforation size by laterality and gender showed no significant differences. The bursting pressure did not correlate (positively or negatively) with the TM or perforation sizes.

CONCLUSIONS

The TM can rupture during activities such as freediving or scuba diving, potentially leading to serious problems including brain injuries. Studying such events via cadaveric studies and data from case studies is of fundamental importance. The minimum experimental bursting pressures might better be taken into consideration rather than average values as the danger threshold for prevention of TM damage (and complications thereof) by barotrauma.

An underappreciated cause of ocean-related fatalities: A systematic review on the epidemiology, risk factors, and treatment of snorkelling-related drowning

Aim

Snorkelling is a popular aquatic activity which may result in fatal and non-fatal drowning. However, little is known about the scale of injury, factors impacting risk and strategies for prevention. This review assesses the current literature on snorkelling-related drowning with the aim of assessing available data, improving safety recommendations and reducing the global mortality burden.

Methods

A systematic review of peer-reviewed literature in English, Spanish and Portuguese language published between 1 January 1980 and 31 October 2020 was conducted using the PRISMA guidelines. CINAHL Complete, Embase, Medline (Ovid), PubMed, SafetyLit, SportDiscus and grey literature were searched to identify studies reporting the incidence of fatal and non-fatal snorkelling-related drowning, or associated risk factors, prevention strategies, treatments or casualty characteristics. Quality was assessed using the NIH Quality Assessment Tool.

Results

Forty-three studies were included (26 reporting population data, 17 case series), of which 27 (62.8%) studies reported data from Australia. Incidence was reported as about 8% of total ocean-related drownings. Case series documented 144 fatalities over 17 years. Frequent casualty characteristics include male (82.6%), pre-existing heart disease (59.4%), tourists (73%) who were inexperienced (71.0%), and lack of a buddy system (89.6%). Two at-risk profiles identified were older adult tourists with pre-existing medical conditions and local, experienced spearfishers. Twenty-two expert recommendations were developed to improve the safety of snorkellers related to individuals, tourism companies, government agencies and diving organisations.

Conclusion

Snorkelling-related drownings are not infrequent, and there are many opportunities to improve the safety of this activity based on available data.

Pathophysiological Responses to a Record-Breaking Multi-hour Underwater Endurance Performance: A Case Study

The "Endless Diving Project-Step 36" took place in the harbor waters of the town of Maratea in Italy in September 2014. The goal of the project was an attempt by an experienced male diver, equipped with a wet 7-mm suit and a normal gas tank, to set the world record-breaking of nonstop underwater performance. We studied inflammatory, hematological, and endocrine responses during the extreme condition of the attempt. Venous blood samples were collected at baseline, the day before the attempt; immediately after the return from underwater; then at Day 1, Day 4, and Day 12; and later at Month 1 and Month 41 of follow-up. We found that there was an increase in the content of blood neutrophils, monocytes, and eosinophils and a decrease in lymphocytes at Day 1 and a late increase in basophils at Day 12 after the dive. Inflammatory markers and hematocrit and hemoglobin increased immediately after the dive, dropped at Day 1, and reverted gradually to the control level from Day 4 to Day 12. Serotonin and dopamine decreased, while adrenaline increased at Day 1, gradually recovering in the days of follow-up. Insulin, luteinizing hormone, growth hormone, and prolactin increased, while testosterone, cortisol, 17β-estradiol, thyroid-stimulating hormone, and adrenocorticotropic hormone decreased at Day 1, with a partial recovery at Day 4. We conclude that the homeostatic response to the extreme, prolonged underwater performance showed signs of psychological and pro-inflammatory stress. The hormonal response reflected an acute testicular insufficiency. These responses resembled those characteristics for ultra-endurance exercise accompanied by vasculitis and dehydration.

[Asthma and scuba diving: Creation and evaluation of a website (For doctors, asthmatics and diving instructors)]

INTRODUCTION

Scuba diving has long been strictly contraindicated for asthmatics; this contraindication has been questioned in recent years. Our objective was to provide a website, evaluated by its users, for doctors, diving instructors and asthmatics.

MATERIALS AND METHODS

Creation of the site Asthme-Plongee.com based on a peer-reviewed literature review, then distribution of a questionnaire in summer 2018 to diving clubs, general practitioner groups, pulmonologists and FFESSM federal offices, and via social networks.

RESULTS

Our sample consisted of 413 assessors, including 264 health professionals (63.9%), 74 asthmatics (17.9%) and 92 diving instructors (22.3%), spread over the entire territory of France. The structure of the website, the clarity of the information written and its relevance were generally appreciated by the entire population with a median score of 8/10. The site was found useful: 72.9% of respondents thought they would visit it later.

CONCLUSION

Faced with a growing number of amateur divers, it seems essential to raise awareness of current recommendations and good diving practices.

Decompression illness treated at the Geneva hyperbaric facility 2010-2016: A retrospective analysis of local cases

INTRODUCTION

The Geneva hyperbaric chamber is the main treatment centre for decompression illness (DCI) in Switzerland. The characteristics, symptomatology, treatment and short-term outcome of divers treated at this chamber have not previously been investigated.

METHODS

This was a retrospective study of patients treated with hyperbaric oxygen (HBO) for DCI from 2010 to 2016. Data were analysed to provide a description of the cases and statistical analysis for possible factors associated with an unfavourable outcome.

RESULTS

One hundred and thirty-five patients were treated for DCI. Ninety-two were included in the study. Sixty-four presented with neurological and 28 with mild DCI. One hundred and thirty-five patients were treated for DCI. Ninety-two were included in the study. Sixty-four presented with neurological and 28 with mild DCI. Patients with mild DCI mainly had musculoskeletal symptoms (79%). Patients with neurological DCI mainly had spinal (55%), followed by vestibular (36%) symptoms. Arterial gas embolism was diagnosed in 30% of cases. Diving depths ranged between 15 and 142 metres, and dive times between two and 241 min. Median time to treatment was 6 h. Patients with neurological DCI had a high rate (25%) of persisting deficits after treatment. Older age was associated with an unfavourable outcome in univariate but not in multivariate analysis. No adverse effects of HBO were observed. For spinal DCI, a high Boussuges score was associated with persisting deficits after treatment.

CONCLUSIONS

Our findings are consistent with other series. Severe DCI was associated with a high rate of persisting deficits. No single factor was associated with a negative outcome. A Boussuges score > 7 had sensitivity of 90% and positive predictive value 53% for predicting an unfavourable outcome in spinal DCI.