Diving & hyperbaric medicine: Overview

Abstract
Decompression illness is a collective term for two maladies (decompression sickness [DCS] and arterial gas embolism [AGE]) that may arise during or after surfacing from compressed gas diving. Bubbles are the presumed primary vector of injury in both disorders, but the respective sources of bubbles are distinct. In DCS bubbles form primarily from inert gas that becomes dissolved in tissues over the course of a compressed gas dive. During and after ascent ('decompression'), if the pressure of this dissolved gas exceeds ambient pressure small bubbles may form in the extravascular space or in tissue blood vessels, thereafter passing into the venous circulation. In AGE, if compressed gas is trapped in the lungs during ascent, pulmonary barotrauma may introduce bubbles directly into the pulmonary veins and thence to the systemic arterial circulation. In both settings, bubbles may provoke ischaemic, inflammatory, and mechanical injury to tissues and their associated microcirculation. While AGE typically presents with stroke-like manifestations referrable to cerebral involvement, DCS can affect many organs including the brain, spinal cord, inner ear, musculoskeletal tissue, cardiopulmonary system and skin, and potential symptoms are protean in both nature and severity. This comprehensive overview addresses the pathophysiology, manifestations, prevention and treatment of both disorders.

Abstract
Background: Even well-planned no-decompression dives can still produce inert gas bubbles that increase decompression sickness risk. A previously proposed formula for predicting post-dive bubble grades integrates individual factors (age, breathing gas consumption) with dive parameters (maximum depth, surface interval). This study aimed to confirm the formula's validity in an independent dataset and to find out whether detailed dive profile data are of further relevance in predicting echocardiography-derived post-dive bubble grades. Additionally, we explored whether machine learning models leveraging detailed dive profile data could enhance predictive accuracy.

Results: A total of 59 divers performed 359 no-decompression open-circuit air dives in freshwater and saltwater. Post-dive transthoracic echocardiography detected bubbles (Eftedal-Brubakk grade ≥ 1) in 29.8% of dives. Maximum depth, total dive time, air consumption, and age correlated significantly with observed bubble grades (rs=0.37, rs=0.16, rs=0.27, rs=0.13, respectively). The original prediction formula remained valid (rs=0.39) and adequately captured higher-grade dives. Spending additional time in shallow water after deep segments reduced bubble formation. Machine learning approaches based on typical dive computer data (e.g. dive profile) provided stronger predictions (rs=0.49).

Conclusions: This study shows that maximum depth, age, surface interval and total breathing gas consumption are sufficient predictors of post-dive bubble load in no-decompression air dives. This allows divers to individually adopt bubble-reducing measures-such as resting, hydrating, and extending surface intervals-once alerted to a higher-risk class. Integrating the formula into dive computers may offer real-time, individualised risk guidance and help prevent decompression sickness despite following computer-derived profiles in recreational diving.

Abstract
Objective: This study aimed to evaluate the effects of acupuncture combined with hyperbaric oxygenation (HBO) compared with HBO alone in improving the disturbance of consciousness (DOC) of people with traumatic brain injury (TBI).

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in this study. In accordance with the preestablished search strategy, all the literature was obtained from eight online databases. Following the stringent application of inclusion and exclusion criteria, two researchers conducted an independent extraction of valid data from eligible randomized controlled trials (RCTs). The risk of bias in each study was assessed using the Cochrane Risk of Bias 2.0 tool. The meta-analysis was conducted utilizing the RevMan software. Adverse events were determined based on data from each study assessing the safety of acupuncture treatment.

Results: A total of 11 RCTs with 896 participants were included in the analysis. Overall, the methodological quality of the RCTs encompassed within this meta-analysis was below standard. The pooled data demonstrated that acupuncture treatment combined with HBO was significantly superior to HBO alone, based on the Glasgow Coma Scale (GCS) scores [mean difference (MD) = 2.13, 95% confidence interval (CI): 1.64-2.62, p < 0.00001]. We also found that electroacupuncture (EA) combined with HBO improved GCS scores more than HBO alone in TBI patients (MD = 2.15, 95% CI: 1.95-2.36). The early intervention (MD = 3.09, 95% CI, 2.66-3.52) demonstrated significantly more significant improvement in GCS scores following combination therapy compared with the late intervention group (MD = 1.86, 95% CI, 1.47-2.25). Furthermore, compared with HBO alone, acupuncture combined with HBO significantly improved patients' consciousness rate (CR) (RR = 2.26, 95% CI: 1.48-3.46). Statistical analysis also revealed that acupuncture combined with HBO improved the effective rate (ER) (RR = 1.47, 95% CI: 1.27-2.69). Additionally, no studies reported any significant adverse events.

Conclusion: Compared with HBO alone, acupuncture combined with HBO has a more substantial positive effect on GCS scores, AR, and ER in patients with TBI. However, given the limited availability of high-quality evidence and the dearth of RCTs in this area, the conclusions drawn herein warrant validation through additional research endeavours.

Abstract
This work describes an innovative simulator for clinical hyperbaric chambers that addresses critical training gaps in hyperbaric medicine. The system provides medical and technical personnel with a risk-free environment to develop essential operational skills without endangering patients or costly equipment. The simulator employs a dual-module architecture with web-based accessibility, intuitive controls for realistic chamber operation, and robust administrative capabilities. To evaluate the effectiveness of the simulator in the training process, we conducted a pilot study with clinical professionals. This study demonstrated significant improvements in procedural proficiency and emergency response capabilities, with participants showing measurable skill enhancement after simulator-based training sessions. The preliminary quantitative assessments revealed high educational value of proposed simulation software. This technological advancement represents a substantial contribution to hyperbaric medicine education, supporting both initial training and ongoing competency maintenance for clinical and technical operators in this specialized medical field.