Patent foramen ovale (PFO) is a condition present in 20-25% of the general population and can rarely be associated with clinical conditions such as stroke, decompression sickness, desaturation, and migraine with aura. Screening for PFO for primary prevention is not recommended. Several trials have been published demonstrating the efficacy of percutaneous PFO closure in patients under 60 years of age with embolic stroke of unknown etiology. Such evidence has not been achieved in other patient groups, such as those with migraine with aura or decompression sickness. There is also a subset of patients, such as pregnant women or patients undergoing laparoscopic non-cardiac surgery, in whom an increased risk of paradoxical embolism requires preoperative stratification. In all cases, it is necessary to characterize the PFO based on the size of the shunt and the anatomy (e.g., the presence of a large tunnel, prominent Eustachian valve, atrial septal aneurysm), all factors that can increase the risk of paradoxical embolism. This review summarizes the current view on diagnostic and therapeutic work-up of PFO in light of the most recent international guidelines.

Decompression sickness (DCS) risk limits human undersea operations through tissue inert gas supersaturation and pathological bubble formation. Switching the inert breathing gas prior to decompression to a gas with lower diffusivity could allow faster and safer decompression. This principle was tested in 20 kg swine after a helium-oxygen (He/O2) dive using carbon tetrafluoride. Sedated swine breathed He/O2 79/21 at a pressure equivalent of 200 feet of seawater (714 kPa) in a hyperbaric chamber for 50 min until randomized to continuing He/O2 or switching to carbon tetrafluoride and oxygen (CF4/O2 79/21) for 10 min before decompression. The CF4/O2 group had reduced DCS with lower mortality, hypoxemia, pulmonary edema, venous gas emboli, gait disturbance, rash, and central nervous system hemorrhage. CF4/O2 has the potential to expand human exploration through enabling deeper dives, longer dives, and rapid decompression while maintaining safety.

Marine mammals provide important ecosystem services but are highly vulnerable to anthropogenic noise. Beaked whales (Ziphiidae), among the deepest-diving and least understood marine mammals, remain particularly enigmatic due to their elusive behaviour and limited surface time. Although scientific research efforts have been organized around beaked whales since the 1970s, knowledge of their bioacoustics and responses to anthropogenic sound remains incomplete. Here, we synthesize over two decades of bioacoustic studies to reveal critical gaps in understanding their vulnerability to anthropogenic noise and propose urgent conservation measures in the Anthropocene. Beaked whales produce species-specific frequency-modulated echolocation clicks, with inverse scaling of biosonar frequency relative to body mass, showing evolutionary convergence in biosonar traits. Their specialized auditory anatomy, including unique acoustic pathways and waveguides, supports sensitivity to high-frequency sound, with peak hearing sensitivity between 22 and 64 kHz matching their echolocation spectra. Anthropogenic noise, especially naval sonar, can cause severe behavioural disruption, including foraging cessation, avoidance, abnormal diving, and potentially mass strandings linked to decompression sickness. Species-specific sensitivity thresholds indicate that current noise criteria may not adequately protect beaked whales. Urgent evidence-based conservation measures include expanding global acoustic monitoring, refining hearing assessments, quantifying population-level noise impacts, implementing stricter sonar regulations, and establishing acoustic refugia to safeguard these vulnerable cetaceans in increasingly industrialized oceans.

A 19-month-old patient died suddenly and unexpectedly ~11 months after hematopoietic stem cell transplantation (HSCT) for Hurler syndrome. Post-mortem examination revealed pulmonary air emboli that were attributed to extensive colonic pneumatosis intestinalis, an uncommon but reported complication of HSCT. Gas emboli are not just the result of trauma or decompression sickness but are more commonly iatrogenic in origin, resulting from the procedural-related introduction of air into the vascular system; pneumatosis intestinalis has rarely been associated with air emboli. Pathologists should be cognizant of unusual complications of HSCT and maintain a high index of suspicion for air embolization, even in a medically complex patient, to ensure optimal autopsy examination.

Decompression sickness (DCS) is a low-incidence but potentially severe consequence of hyperbaric exposure. Probabilistic decompression models offer a framework to quantify this risk, yet their calibration is challenged by the scarcity of empirical outcome data. In this study, we propose a gradient-based optimization model to predict DCS probability, trained on 924 dive profiles from the US Navy Experimental Diving Unit XVal-He-9 tables, representing predefined DCS probabilities (2.3% and 4%), and optimized based on actual body tissues grouped in five compartments. The model achieved high predictive accuracy (MAE: 0.535%; RMSE: 0.694%) with consistent performance across training and test sets, indicating limited overfitting. Reduced accuracy was observed in intermediate depth ranges (100-130fsw or 30-39msw). Out-of-sample evaluation on 31 high-risk dives (three DCS cases) showed general agreement between predicted and observed incidence while suggesting a potential contribution of repetitive exposures not accounted for in the model. These results demonstrate that gradient-based optimization, trained based on existing probabilistic tables, seems to be capable of satisfactorily predicting decompression sickness risk for a given dive profile. Additionally, future studies can further adjust the loss function to account for individual or dive-related indicators, leading to a more individualized risk function.

Dysbarism is defined as any adverse medical condition resulting from changes in ambient pressure. These pressure changes must occur at a rate or duration that exceeds physiologic adaptive capacity. Dysbarism encompasses decompression sickness, nitrogen narcosis, high-pressure neurological syndrome, barotrauma, and arterial gas embolism.

The 1987 UHMS Workshop on the Validation of Decompression Tables provided standards for the design, testing, and acceptance of decompression tables. Forty years later, research funding has become scarce, and diving companies no longer receive support from universities and Navy research centers. Companies build on their experience and safety culture to improve existing decompression procedures. We list principles and propose guidelines for these internal developments.

Wildlife exposure is a risk that trained divers are fully aware of. Examples of hazardous wildlife that divers may encounter include, but are not limited to, sharks, coral, sponges, eels, and jellyfish. Encountering wildlife can lead to a diver panicking or being forced to surface rapidly or in an uncontrolled manner due to panic or avoidance of the hazard. This may increase the risk of decompression illness (DCI), mainly pulmonary overinflation syndrome (POIS). Injuries caused by hazardous aquatic wildlife can also be distracting, leading dive supervisors and/or medical personnel to overlook unrelated injuries, such as DCI. If this occurs, the affected diver may suffer a grave outcome that could otherwise have been prevented.

We hereby present a case of abdominal pain resulting from a hemolytic reaction after diving.

Prophylactic recompression treatment (PRT) is an empirical treatment conducted in China for divers who conduct repetitive diving or asymptomatic insufficient decompression to eliminate residual nitrogen and microbubbles and prevent decompression sickness (DCS).

Nitrogen narcosis is a change in consciousness, neuromuscular function, and behavior brought on by breathing compressed inert gasses. It has also been called depth intoxication, “narks,” and rapture of the deep. Traditionally the gas involved in narcosis is nitrogen, and it is associated with dysfunction when breathed by scuba divers from their tanks containing compressed air. Other inert gasses associated with narcosis include neon, argon, krypton, and xenon, with the latter having an anesthetic effect even at sea level. Interestingly, helium does not cause inert gas narcosis and therefore, is used in deep diving as heliox (helium and oxygen mixture).[1][2][3]