Introduction: Oxidating fat as an energy substrate requires more oxygen than utilizing carbohydrates and can be acutely increased by hyperoxia. Therefore, substrate utilization may affect endurance performance and gas consumption in divers, but previous research is limited. This study aimed to evaluate changes in maximal fat oxidation (MFO) in navy divers during training.

Methods: Seven explosive ordnance disposal (EOD) divers (age 20.0±1.4, BMI 23.5±1.6), five combat divers (age 23.6±3.0, BMI 26.2±1.2), and seven amphibious rangers (controls) (age 23.0±2.9, BMI 26.2±1.7) were recruited. MFO was measured with indirect calorimetry using an incremental test before and after diver training of 15 weeks (EOD divers) or 16 weeks spaced over nine months (combat divers and controls). EOD divers performed a treadmill protocol in normoxia and hyperoxia, and combat divers and controls performed a bicycle ergometer protocol in normoxia.

Results: Combat divers increased their MFO with 0.14 g/minute ([95 % CI] 0.04 to 0.23) while no difference was observed in EOD divers (-0.05 g/minute; -0.19 to 0.08) or controls (0.00 g/minute; -0.14 to 0.14).

Discussion: Combat diver training can increase fat oxidation, potentially affecting oxygen consumption and carbon dioxide production. A combination of training stressors, including hyperoxia, training load, and negative energy balance, may cause these changes. 

Introduction: The optimal depth for decompression stops is unclear. We hypothesize that a decompression stop at 1.3 bar, compared with 1.6 bar, decreases post-dive whole-body nitrogen washout volumes and venous gas emboli (VGE).

Methods: In this randomized crossover trial, divers performed wet air dives of 40 minutes at 3.4 bar (340 kPa) with a seven-minute-long decompression stop at either 1.3 bar (Deco 1.3) or 1.6 bar (Deco 1.6) in randomized order. The primary outcome was the difference in post-dive whole body nitrogen washout volume, analyzed using multilevel linear regression.The secondary outcome was the difference in peak VGE detected by cardiac two-dimensional ultrasound, graded using the Eftedal-Brubakk scale, and analyzed with Wilcoxon matched-pairs signed-rank tests.

Results: Sixteen divers completed both Deco 1.3 and Deco 1.6. Post-dive whole body nitrogen washout volumes were measured in eight of the 16 participants and were lower with Deco 1.3 than Deco 1.6 (696 ml [95% confidence interval [CI], 601 to 790] versus 1068 ml [95% CI, 962 to 1174]), mean difference of 373 ml (95% CI, 243 to 502). Deco 1.3 had lower peak bubble grades than Deco 1.6 (interquartile range 2-3 versus 3-4; P=0.005), but the median grade was the same at 3.

Conclusions: Decompression stop at 1.3 bar instead of 1.6 bar decreased post-dive whole body nitrogen washout volume and VGE. These findings may inform the development of future decompression models.

Undersea communication cables (UCCs) are critical for global connectivity but remain vulnerable to physical and cyber threats. This paper presents insights from the NATO Science for Peace and Security Project: Hybrid Space and Submarine Architecture to Ensure Information Security of Telecommunications (HEIST), a system designed to enhance the redundancy and resilience of UCCs. The proposed architecture aims to efficiently reroute data from submarine cables to satellite networks upon detection of threats via enhanced subsea sensing and monitoring. We discuss the components, including secure communication links, real-time situational awareness, and smart contracting for automated routing of compromised UCC communications. We demonstrate the operational capabilities of HEIST in mitigating disruptions through a simulation environment. The architecture indicates improved robustness to accidental or malicious attacks against submarine cables, reinforcing the strategic importance of hybrid multi-domain networks for resilient telecommunications. As such, the HEIST provides a blueprint for a future robust and resilient backbone for the internet. 

Introduction: Divers are reported to have a lower ventilatory response to elevated levels of carbon dioxide (CO2) than non-divers. Hypoventilation with CO2 retention during diving is potentially dangerous. It is unknown if CO2 retention is largely inherited or develops during diving training. We aimed to investigate if a military dive training course would influence the ventilatory response to CO2.

Methods: Novice rebreather Divers with Amphibious Rangers as controls were tested at baseline, after 12 weeks of water exercise training, and after 15 weeks of diving: participants rebreathed in a Douglas bag filled with an initial 100% oxygen, resulting in increasing levels of inspiratory CO2 (iCO(2)).The test was performed until symptom-limitation or an expiratory CO2 of 8.0 kPa. To decrease conscious control of breathing, participants were distracted with a memory game during the test. Differences between groups and over time were analyzed using independent and paired t-tests.

Results: Ten Divers and six Amphibious Rangers completed baseline testing and eight Divers completed all tests. Divers had a statistically significant higher Minute Ventilation (V'E) after dive training, compared to after water exercise training and baseline, at all levels of iCO(2). However, the change in Hypercapnic ventilatory response (HCVR) before and after dive training across pCO(2) values 5.0-7.9, did not reach statistical significance. At baseline, Amphibious Rangers had a non-significant higher V'E compared to Divers at higher levels of iCO(2).

Conclusion: A military rebreather diving program might be associated with increased ventilatory response to CO2.

Introduction: Quantifying inert gas wash-out is crucial to understanding the pathophysiology of decompression sickness. In this study, we developed a portable closed-circuit device for measuring inert gas wash-out and validated its precision and accuracy both with and without human subjects. Methods: We developed an exhalate monitor with sensors for volume, temperature, water vapor and oxygen. Inert gas volume was extrapolated from these inputs using the ideal gas law. The device's ability to detect volume differences while connected to a breathing machine was analysed by injecting a given gas volume eight times. One hundred and seventy-two coupled before-and-after measurements were then compared with a paired t-test. Drift in measured inert gas volume during unlabored breathing was evaluated in three subjects at rest using multilevel linear regression. A quasi-experimental cross-over study with the same subjects was conducted to evaluate the device's ability to detect inert gas changes in relation to diving interventions and simulate power. Results: The difference between the injected volume (1,996 ml) and the device's measured volume (1,986 ml) was -10 ml. The 95% confidence interval (CI) for the measured volume was 1,969 to 2,003 ml. Mean drift during a 43 min period of unlaboured breathing was -19 ml, (95% CI, -37 to -1). Our power simulation, based on a cross-over study design, determined a sample size of two subjects to detect a true mean difference of total inert gas wash-out volume of 100 ml. Conclusions: We present a portable device with acceptable precision and accuracy to measure inert gas wash-out differences that may be physiologically relevant in the pathophysiology of decompression sickness. Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.

The Swedish Armed Forces (SwAF) air dive tables are under revision. Currently, the air dive table from the U.S. Navy (USN) Diving Manual (DM) Rev. 6 is used with an msw-to-fsw conversion. Since 2017, the USN has been diving according to USN DM rev. 7, which incorporates updated air dive tables derived from the Thalmann Exponential Linear Decompression Algorithm (EL-DCM) with VVAL79 parameters. The SwAF decided to replicate and analyze the USN table development methodology before revising their current tables. The ambition was to potentially find a table that correlates with the desired risk of decompression sickness.  New compartmental parameters for the EL-DCM algorithm, called SWEN21B, were developed by applying maximum likelihood methods on 2,953 scientifically controlled direct ascent air dives with known outcomes of decompression sickness (DCS). The targeted probability of DCS for direct ascent air dives was ≤1% overall and ≤1‰ for neurological DCS (CNS-DCS). One hundred fifty-four wet validation dives were performed with air between 18 to 57 msw. Both direct ascent and decompression stop dives were conducted, resulting in incidences of two joint pain DCS (18 msw/59 minutes), one leg numbness CNS-DCS (51 msw/10 minutes with deco-stop), and nine marginal DCS cases, such as rashes and itching. A total of three DCS incidences, including one CNS-DCS, yield a predicted risk level (95% confidence interval) of 0.4-5.6% for DCS and 0.0-3.6% for CNS-DCS. Two out of three divers with DCS had patent foramen ovale. The SWEN21 table is recommended for the SwAF for air diving as it, after results from validation dives, suggests being within the desired risk levels for DCS and CNS-DCS. Copyright© Undersea and Hyperbaric Medical Society.

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

In the transition to a sustainable energy system, there is an urgent need for expansion of offshore renewable energy installations. To ensure sustainable development also with respect to the marine environment, a variety of decision support tools (DSTs) are currently under development, aiming at potentially increased quality and efficiency for environmental risk assessment (EIA) of planned offshore energy installations. However, the savings potential of a DSTs is to a large extent governed by the timing of the DST development, which in turn is directly dependent on the investment rate over time. A set of development scenarios were evaluated, simulating different degrees of strategic implementation and successful utilization of the DST for offshore energy. Using the situation in Sweden as a case study, we demonstrate that a planned investment can lead to considerably lower total costs for the EIA at a national level, at the same time allowing for improved quality of the EIA in line with the ambitions in both marine spatial planning and existing goals within marine environmental management. © 2023 The Author(s)

A new method using burial measurements for risk assessment of subsea cable installations is proposed. Only methods comparing the design boundaries have previously been used to verify subsea cable installments. The disadvantage of utilizing design boundaries is the possibility of not fulfilling the risk requirements since the assumed burial depth of the cable and its measurement data can differ, leading to the challenge of assessing how the difference and its uncertainty affect burial risk. We proposed and tested the method for a scenario using seagoing vessel traffic data and sensor characteristics. The analysis is limited to white measurement noise but shows a deviation in risk estimation between the design-and measurement-based assessments. The presented result enables the approximation of the risk assessment for projects of varying specifications. The proposed statistical method is a less conservative way to assess the correct installment of a cable and possibly to evaluate verification specifications. © 2022 IEEE.