Hyperbaric Conditions Research Articles

Arterial blood gases in SCUBA divers at depth

BackgroundCurrent diving physiology postulates that SCUBA divers’ arterial blood gas (ABG) levels vary proportionally to environmental pressure, but, to date, ABGs have only been obtained during simulated dives. Also, recent evidence supports the use of the arterial/alveolar (a:A) partial pressures of oxygen (PO2) ratio to predict the arterial PO2 (PaO2) under hyperbaric conditions from measurements obtained at 1 atmosphere absolute (ATA). This work summarizes ABGs obtained in SCUBA divers in real underwater conditions and aims to validate the a:A ratio in predicting PaO2 in this subset of individuals at depth.MethodsThe study was approved by the local ethics committee. After cannulating the radial artery of the non-dominant limb, ABGs were sampled at the surface before the dive (A), at depth (15 meters of freshwater (mfw) or 42 mfw) before (B) and after (C) pedaling on a submersed bicycle for 10 minutes, and back at surface (D). After calculating the surface alveolar PO2 for each subject, the a:A ratio was obtained and used to predict PaO2 at depth. A linear regression between measured and predicted PaO2 was reported, along with the goodness-of-fit F test.ResultsSix subjects performed the dive at 15 mfw, and four others at 42 mfw. The PaO2 proportionally increased at both depths, remaining stable before and after pedaling. The a:A calculated from the baseline ABG obtained at rest, out of the water, adequately predicted the PaO2 at depth (R2 = 0.97, p<0.001), better at 15 mfw but losing accuracy at 42 mfw.ConclusionsThe ABGs confirmed the proportional rise of PaO2 in SCUBA divers underwater. The a:A ratio could be used to predict the magnitude of PaO2 rise at depth to limit exposure to hyperoxia, especially in repetitive recreational dives and professional divers.

Hyperbaric oxygen rapidly produces intracellular bioenergetics dysfunction in human pulmonary cells

Hyperoxic exposure lasting days alters mitochondrial bioenergetic and dynamic functions in pulmonary cells as indices of oxygen toxicity. The aim of this study was to examine effects of short duration hyperbaric and hyperoxic exposures to induce oxygen toxicity similarly. Cultured human lung microvascular endothelial cells, human pulmonary artery endothelial cells and A549 cells were exposed to hyperoxia (∼5 % CO2 equivalent, balance O2) under hyperbaric conditions (4.8 ATA) for 1 and 4 h. Measures of mitochondrial dynamics, inner membrane potential, mitochondrial respiration, the intracellular distribution of bioenergetic capacity and respiration complex protein levels were then quantified. Exposures resulted in altered mitochondrial motility, presence of inhomogeneities in respiration parameters, loss of inner membrane potential, and changes in intracellular partitioning of ATP-linked respiration. Changes in the levels of respiration complex protein levels were also found. The combination of hyperoxic exposure with hyperbaric conditions rapidly produced changes in mitochondrial dynamics and bioenergetics in pulmonary cells. These changes are consistent with the onset of pulmonary oxygen toxicity previously known to result from long duration exposure to hyperoxia alone. These findings suggest health caution is warranted in environmental settings in which both hyperoxic and hyperbaric conditions are present. The synergism of hyperoxia and hyperbaria for rapid induction of oxygen toxicity in cellular models has utility for the study of mechanistic determinants of oxygen toxicity, testing of putative therapeutics, and associated investigations of mitochondrial dysfunction.

Non-Invasive Muscle Metabolism Assessment with Near-Infrared Spectroscopy and Electrical Muscle Stimulation

Background: Muscle biopsy, the gold standard for assessing muscle aerobic capacity, is an invasive procedure. Noninvasive alternatives, such as 31-phosphorus magnetic resonance spectroscopy (31P-MRS) and near-infrared spectroscopy (NIRS), provide valuable insights, with NIRS providing superior time resolution and ease of use compared with 31P-MRS. Objectives: This study aimed to evaluate muscle metabolism using a 6 s muscle contraction phase with electrical muscle stimulation (EMS) and to assess the impact of EMS on exercise performance under hyperbaric conditions with elevated oxygen pressure. Methods: This study included nine male participants (21 ± 2 years) who underwent 5 min of EMS on the forearm flexor muscle group, with muscle oxygen dynamics assessed using NIRS. For statistical analysis, the mean values between groups were assessed using paired t-tests, and associations were evaluated using Pearson’s correlation coefficient. Results: Spontaneous blood flow interruption during EMS-induced muscle activity indicated the potential for assessing muscle metabolism without disrupting external blood flow. A significant negative correlation was observed between oxygen consumption and changes in oxygenated hemoglobin levels during muscle activity under hyperbaric conditions. Conclusions: This study demonstrates that skeletal muscle metabolism can be measured using a brief 6 s quantitative EMS. Furthermore, hyperbaric exercise appears to enhance aerobic capacity by increasing the rate and availability of oxygen consumption during exercise.

Imaging of bones dysbarogenic changes in navy divers

The number of diving descents in the world is steadily growing, as is the complexity of the work performed under conditions of increased environmental pressure. Also, in order to increase efficiency and expand the range of tasks performed, the intensity, depth of dives and the time divers spend in hyperbaric conditions are increasing. These factors contribute to an increase in the number of diving pathologies, including damage to the skeletal bones of dysbarogenic genesis. X-ray diagnostic methods used during annual medical examinations of divers do not always allow the detection of dysbarogenic changes in the bones; in addition, the clinical manifestations of this pathology do not have obvious specificity. In this regard, it can be assumed that the occurrence of this pathology among divers has not been reliably established to date. This article is devoted to a review of the literature on the possibilities of radiodiagnosis of dysbarogenic changes in skeletal bones in specialists whose work involves being in conditions of high environmental pressure. The article highlights the results of a literature review of English-language and Russian-language publications presented in the databases of PubMed and scientific electronic libraries of Russia (eLIBRARY.RU and CYBERLENINKA.RU). In order to determine the optimal methods of radiation diagnostics, the etiological and pathogenetic aspects of the development of dysbarogenic degenerative and necrotic changes in the bones of the skeleton, as well as the experience of scientists in determining the corresponding radiation semiotics, were analyzed. Considering that the worst manifestation of bone pathology of dysbarogenic origin is dysbaric (aseptic) osteonecrosis, we studied the literature on the issues of its clinical and instrumental diagnosis. One of the directions in scientific research was the work of authors exploring the possibilities of early instrumental diagnosis of changes in bone tissue, in particular the possibilities of magnetic resonance imaging in the diagnosis of dysbaric osteonecrosis. In addition, data on modern x-ray methods were analyzed, which may be promising as a screening diagnosis of dysbarogenic degenerative and necrotic changes in the bones of the skeleton.

Advanced high pressure hyperbaric techniques in tunnelling

ABSTRACT Lamont D, Colvin A, Heili A, Ridley T, Slocombe R, Wendling J. Advanced high pressure hyperbaric techniques in tunnelling. Undersea Hyperb Med. 2024 Second Quarter; 51(2):159-171. Work in compressed air and diving are both occupational activities that have been around since the mid- 19th century, and those undertaking their work under elevated pressure. Meeting the demand to go to “higher pressure for longer” in tunneling has lagged in diving, but both activities have found it necessary to adopt mixed gas breathing and saturation exposure techniques. This paper explains how work in hyperbaric conditions at high pressure is undertaken in tunneling and is illustrated by the hyperbaric activity likely to be involved in constructing a large-diameter road tunnel below a body of water such as an estuary. It also explores the practical differences between work in compressed air and diving.

Hyperbaric Oxygenation Maintains Elevated Stromal Oxygen Availability During Corneal Collagen Crosslinking with and Without Epithelial Removal

Purpose Corneal collagen cross-linking (CXL) can halt corneal ectasia. Leaving corneal epithelium intact during treatment may reduce the incidence of complications. However, it is under debate whether this reduces efficacy and if oxygen supplementation may be necessary to optimize the cross-linking effect. This study aimed to investigate the impact of hyperbaric oxygenation (HBO) on intracorneal oxygen concentrations during epi-off and epi-on CXL. Methods CXL was performed using riboflavin and ultraviolet-A (UV-A) irradiance (3 mW/cm2 for 30 min) on porcine corneas under normobaric and hyperbaric conditions, with and without supplemented oxygen, with and without epithelium. Intracorneal oxygen concentrations were continuously monitored before and during irradiation. Biomechanical properties were assessed through tensile strength testing. Results HBO alone did not cause perceivable changes in stromal oxygen concentrations. Oxygen supplementation resulted in higher oxygen concentration in corneal stroma during CXL. HBO may cause a further increase in oxygen levels, although this was not statistically significant in this study. Notably, a tendency of oxygen levels to rise continuously during UV-irradiation was observed using HBO. Biomechanical properties showend no statistically significant differences between any groups. Conclusions In this ex-vivo model, HBO increased stromal oxygen levels during CXL, regardless of the presence of corneal epithelium. The dynamics in oxygen concentrations in corneal stromal tissue during CXL suggest that time is an important factor to consider in modifications of established protocols. Also, we hypothesize that stromal levels of riboflavin and UV-A irradiance may be more critical to the CXL effect when oxygen is supplemented and epithelium is not removed.

Effects of CO₂ on the occurrence of decompression sickness: review of the literature.

Inhalation of high concentrations of carbon dioxide (CO₂) at atmospheric pressure can be toxic with dose-dependent effects on the cardiorespiratory system or the central nervous system. Exposure to both hyperbaric and hypobaric environments can result in decompression sickness (DCS). The effects of CO₂ on DCS are not well documented with conflicting results. The objective was to review the literature to clarify the effects of CO₂ inhalation on DCS in the context of hypobaric or hyperbaric exposure. The systematic review included experimental animal and human studies in hyper- and hypobaric conditions evaluating the effects of CO₂ on bubble formation, denitrogenation or the occurrence of DCS. The search was based on MEDLINE and PubMed articles with no language or date restrictions and also included articles from the underwater and aviation medicine literature. Out of 43 articles, only 11 articles were retained and classified according to the criteria of hypo- or hyperbaric exposure, taking into account the duration of CO₂ inhalation in relation to exposure and distinguishing experimental work from studies conducted in humans. Before or during a stay in hypobaric conditions, exposure to high concentrations of CO₂ favors bubble formation and the occurrence of DCS. In hyperbaric conditions, high CO₂ concentrations increase the occurrence of DCS when exposure occurs during the bottom phase at maximum pressure, whereas beneficial effects are observed when exposure occurs during decompression. These opposite effects depending on the timing of exposure could be related to 1) the physical properties of CO₂, a highly diffusible gas that can influence bubble formation, 2) vasomotor effects (vasodilation), and 3) anti-inflammatory effects (kinase-nuclear factor and heme oxygenase-1 pathways). The use of O₂-CO₂ breathing mixtures on the surface after diving may be an avenue worth exploring to prevent DCS.

Volatile Organic Compounds in Cellular Headspace after Hyperbaric Oxygen Exposure: An In Vitro Pilot Study.

Volatile organic compounds (VOCs) might be associated with pulmonary oxygen toxicity (POT). This pilot study aims to identify VOCs linked to oxidative stress employing an in vitro model of alveolar basal epithelial cells exposed to hyperbaric and hyperoxic conditions. In addition, the feasibility of this in vitro model for POT biomarker research was evaluated. The hyperbaric exposure protocol, similar to the U.S. Navy Treatment Table 6, was conducted on human alveolar basal epithelial cells, and the headspace VOCs were analyzed using gas chromatography-mass spectrometry. Three compounds (nonane [p = 0.005], octanal [p = 0.009], and decane [p = 0.018]), of which nonane and decane were also identified in a previous in vivo study with similar hyperbaric exposure, varied significantly between the intervention group which was exposed to 100% oxygen and the control group which was exposed to compressed air. VOC signal intensities were lower in the intervention group, but cellular stress markers (IL8 and LDH) confirmed increased stress and injury in the intervention group. Despite the observed reductions in compound expression, the model holds promise for POT biomarker exploration, emphasizing the need for further investigation into the complex relationship between VOCs and oxidative stress.

Liquid respiratory desaturation. The first experience of application on large biological objects

Introduction. This article is a continuation of the publication of the experimental studies results of prevention of acute decompression sickness (aDCS) in laboratory animals by the method of liquid respiratory desaturation (LRDS). LRDS is a method of preventing decompression disorders by the excretion of metabolically indifferent gases (in particular nitrogen) from the body during spontaneous respiration with liquid or artificial liquid lung ventilation (ALLV), by dissolved gas concentration gradient "from tissues to respiratory fluid". The method allows to provide rapid desaturation of the body from metabolically indifferent gases in the process of liquid respiration before and/or during decompression, thereby creating conditions for application of ultra-fast decompression profiles without the risk of decompression disorders.
 The aim of the study was to confirm the possibility of LRDS being a method of DCS prevention on large laboratory animals (minipigs).
 Materials and methods. The studies were performed on Wiessenau minipigs (n=8) — male and female, aged 4–5.5 months and weighing 7.1–11.2 kg. Animals of the control (n=4) and experimental (n=4) groups were subjected by compression by keeping in an air environment under high pressure (absolute 0.5 MPa for 60 minutes) to saturate tissues with indifferent gas (nitrogen). After compression experimental group was exposed to 30-minute ALLV with a liquid (perfluorodecalin) saturated with an oxygen under normobaric conditions. Air environment pressure during procedure of artificial lung ventilation was kept at 0.5 MPa. Decompression of the control and experimental groups was carried out in non-stop manner for 80 and 40 seconds respectively. The investigation of severity of clinical manifestations of DCS (changes in hemodynamic and respiratory parameters) including ultrasonic examination of gas bubbles in the heart and large vessels of the liver and as well as survival of animals in groups and pathoanatomical changes was performed.
 Results of the study. Clinical manifestations, ultrasonic scanning of the heart and venous vessels of the liver, as well as morphological examination data indicated the development of severe acute post-decompression disorders (PDD) in animals of the control group, which caused deaths in 100% of cases. Meanwhile all animals in experimental group survived and their state was stable. According to ultrasonic examination, the presence of small number of gas bubbles in the right-side heart chambers and liver's venous vessels being noted, but they disappeared after several hours. Deviations of the respiration's parameters function from background values (shortness of breath of a mixed type with the participation of auxiliary muscles, etc.) observed from the 2nd to the 4th day after ALLV, as well as compensatory reactions from the cardiovascular system (heart rate variability and instability of hemodynamic parameters) were caused by ALLV.
 Conclusions. Compressed air exposure 0.5 MPa for 60 minutes followed by 80 seconds of non-stop decompression allows to provoke the severe acute PDD minipigs model, manifested by pronounced intravascular gas formation, the development of acute respiratory and cardiovascular insufficiency causing the development of adverse outcomes.
 The ultrasound method of visual assessment of intravascular gas formation severity, adapted for minipigs, together with the dynamics of changes in the indicators of respiratory and cardiovascular systems makes possible to assess not only state of animal under anesthesia, but also the effectiveness of PDD prevention measures.
 The usage of ALLV with PFC liquid completely saturated with 100% oxygen under normobaric conditions makes possible partial removal of indifferent gas (nitrogen) dissolved in tissues of experimental animals during exposition in a compressed air environment before decompression and thereby carry out the prevention of DCS by LRDS method. It makes possible to implement successfully ultra-fast decompression profiles, incompatible with life in the control group.
 The state of animals from experimental group after LRDS is characterized by lung impairment caused by ALLV in hyperbaric conditions accompanied by temporary changes of external respiration function and compensatory reactions of cardiovascular system, observed during first 4 days.
 Ethics. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki. The Clinical Study Protocol was approved by local Ethics Committee of The Federal State Budgetary Scientific Institution «Izmerov Research Institute of Occupational Health».

The influence of the mass transport regime on laser chemical vapor deposited carbon fibers

Laser Chemical Vapor Deposition (LCVD) is a process through which fibers are additively deposited by the dissociation and deposition of a precursor gas into the solid phase under a translating laser focal point. In the hyperbaric pressure conditions, LCVD has two identified reaction regimes. The first being limited by surface reaction kinetics (SRK) and the second being limited by mass transport (MT). This article examines the effects of mass transport (MT) limitations on carbon fiber growth using either ethane (C2H6) or ethylene (C2H4). Both hydrocarbon precursors reveal a growth rate reduction when transitioning from SRK-to-MT to meet the no-slip condition in fluid dynamics. This transition correlates to a fiber microstructure change from a core shell morphology with a graphitic structure (SRK) to a nodular morphology with an amorphous structure (MT). The fiber fracture stress is generally found to be higher in the MT than SRK regime because of the reduction of easily cleaved graphitic planes in the MT fibers. Collectively, these results demonstrate the importance of the MT limited growth regime and how fiber characteristics can be manipulated when grown in this regime.

Abstract 6005: Generation of new oncology cell models through long-term acclimation under hypoxic and hyperbaric culture conditions

Abstract Traditional cancer cell lines used as surrogate models in vitro and in vivo have made significant contributions to cancer research and drug discovery. While cell culture and animal studies are critical steps in determining the efficacy, pharmacodynamics, and mechanism of action of novel anti-cancer drugs, it is well-known that cells grown in 2D culture systems have modified growth characteristics and different responses to chemotherapeutic drugs compared to tumors in vivo as a result of differing structural and environmental conditions that fail to replicate in vivo tumor microenvironments. AVATAR bioreactors (Xcell Biosciences, San Francisco, CA) were invented to address these limitations by providing discrete control over oxygen and hyperbaric pressure levels to better mimic the in vivo environment and allow cultured cells to be grown in conditions which mimic the human body. To better serve preclinical research needs, we generated new tumor cell models by long-term acclimating (LTA) existing cancer cells in the AVATAR incubator system using 1% O2 and 2 PSI conditions similar to the conditions expected in the tumor microenvironment (TME). Six different cancer cell lines of diverse origins including pancreas (MIA PaCa-2), breast (BT-474), colon (HCT116), prostate (LNCaP, PC-3) and melanoma (A-375) were adapted for 2-3 months with phenotypic changes recorded. Key marker changes were commonly observed in LTA cells compared to parental lines. For example, in HCT116 colorectal cancer cells, TME culture conditions induced a higher expression level of E-cadherin in both protein and mRNA levels (2.2-fold change), indicating a mesenchymal-epithelial transition of the cell after adaptation. This coincides with the observation that LTA adapted HCT116 cell bodies had a more angular cell morphology as compared to parental cells grown under conventional normoxic culture conditions. In-depth gene-expression analysis using a Nanostring tumor signaling pathway panel identified several common and tissue-specific gene and pathway changes. These included VEGFA, EGF receptor signaling pathway (EGFR, E-Cadherin, GRB7, c-Fos), TGF pathway (IGFBP3, TGFB1, TGFB2, SMAD7), and extracellular matrix signaling (LAMB3, ITGA5, ITGB3, ITGB8, PDGFA, CCND2). Current studies are focusing on drug response testing in 2D and 3D cultures based on above-mentioned gene and signaling pathway changes. Cell proliferation and migration capacity of xenograft LTA cells will be evaluated for the purposes of creating novel murine models for drug screening applications. Citation Format: Yewei Xing, Abriel Czachorowski, James Lim, Scott Wise. Generation of new oncology cell models through long-term acclimation under hypoxic and hyperbaric culture conditions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6005.

Abstract 6334: Metabolic reprogramming enhances expansion and potency of CAR T cells

Abstract Cell therapies, such as Chimeric Antigen Receptor (CAR) T cell therapy, have revolutionized the treatment of hematological malignancies, but their use in solid tumors remains a significant challenge for the field. This is due, in part, to immunosuppressive mechanisms in the tumor microenvironment (TME), which include reduced oxygen tension, high interstitial pressure, and an abundance of immunosuppressive proteins, resulting in mitochondrial dysfunction, exhaustion, and depletion of adoptively transferred cells. Metabolic manipulation of therapeutic cells could overcome these barriers to enable cell therapy success in solid tumors. To this end, we have employed AVATAR technology (Xcellbio, San Francisco, CA), an incubation system that enables precise control of oxygen tension and hyperbaric pressure on cells in culture to improve the manufacture of adoptive T cell therapies. Using a CD19 CAR T model system, we have shown that transduction and expansion of CAR T cells under reduced oxygen and hyperbaric pressure conditions yield greater percentages and total numbers of lentiviral-transduced cells. While cells transduced in a standard CO2 incubator yielded 10-20% CD19 CAR+ cells, transduction in the AVATAR system with increased pressure yielded 15-40% CD19 CAR+ cells. Similarly, T cell cultures performed under pressurized AVATAR conditions generated ~2X more viable cells after 10 days. Furthermore, these metabolically reprogrammed cells exhibit enhanced potency, with improved anti-tumor cytotoxic activity in vitro. We have extended these studies to measure the ability of AVATAR-expanded CD19 CAR T cells to control the growth of CD19-expressing NALM6-Luc tumor cells in vivo compared to CAR T cells grown in a conventional CO2 incubator. Mice (female NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ, Jackson Laboratories, Bar Harbor, ME) dosed with the AVATAR-expanded cells exhibited good tumor control and increased persistence of CAR T cells in relevant organs, along with alterations in cell trafficking to the bone marrow and spleen. The transferred cells maintained a less differentiated phenotype, with central memory and effector memory populations, as measured by expression of the markers CD45RA and CD62L, dominating the T cell compartment. This work showcases the benefits of metabolic reprogramming to improve the yield and functional potency of CAR T cells, which has direct applications to reducing the cost and improving the efficacy of these lifesaving treatments. The AVATAR technology is currently being translated into a closed system bioreactor for use in GMP cell therapy manufacturing. Citation Format: Yewei Xing, Shannon Eaker, Yelena Bronevetsky, Candy Garcia, Hadia Lemar, Evan Massi, Albert Wong, Sheri Barnes, Derrik Germain, Scott Wise, James Lim. Metabolic reprogramming enhances expansion and potency of CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6334.

The effect of pressure on degradation kinetics of polyphenols: Impact of polyphenol structure at hyperbaric storage conditions

Understanding reaction kinetics at elevated pressures is essential for developing efficient pressure-based technologies. It is especially vital for hyperbaric storage (HS), where pressure is applied for long durations. In single and multi-component models, the influence of pressure on the degradation kinetics of different catechins and anthocyanins was studied at accelerated conditions using neutral pH at pressures up to 200 MPa (HS levels) for several hours. In the neutral baroresistant buffer, pressure enhanced the degradation of all tested flavonoids with a negative activation volume. Despite the significant structural variety and major differences in the degradation rates within each tested subgroup, no significant structure-dependent effect of pressure on the activation volume was observed, which is suggestive of a similar mechanism by which pressure accelerates the degradation. The antioxidant capacity of catechins was not affected by pressure compared to control samples when the concentration of the original catechin was similar. Industrial relevanceA better understanding of pressure effects on the degradation reaction kinetics of food components can contribute to the general understanding of mechanisms related to food component degradation under high-pressure treatments. Plant-based foods are rich in polyphenolic compounds and responsible for sensory characteristics and their related health-promoting properties. In conditions similar to HS, that are known to inhibit and even, in some cases, inactivate microorganisms, when food is exposed to high pressures for a long time, it is imperative to investigate the effect of pressure on polyphenol degradation kinetics, which can lead to differences in the polyphenol compositions during the pressurized storage. However, the impact of pressure on polyphenol degradation kinetics is often overlooked. This study provides fundamental information regarding the polyphenol structure-dependent degradation kinetics of catechins and anthocyanins under pressure while taking into account the often overlooked pressure-induced pH shifts. The presented work can promote the development of novel storage and processing technologies based on high pressure that will better preserve oxidation-liable compounds with lower energetic costs.

A novel method for tracking nitrogen kinetics in vivo under hyperbaric conditions using radioactive nitrogen-13 gas and positron emission tomography.

Decompression sickness (DCS) is caused by gaseous nitrogen dissolved in tissues forming bubbles during decompression. To date, no method exists to identify nitrogen within tissues, but with advances in positron-emission tomography (PET) technology, it may be possible to track gaseous radionuclides into tissues. We aimed to develop a method to track nitrogen movement in vivo and under hyperbaric pressure that could then be used to further our understanding of DCS using nitrogen-13 (13N2). A single anesthetized female Sprague-Dawley rat was exposed to 625 kPa, composed of air, isoflurane, and 13N2 for 10 min. The PET scanner recorded 13N2 during the hyperbaric exposure with energy windows of 250-750 keV. The PET showed an increase in 13N2 concentration in the lung, heart, and abdominal regions, which all reached a plateau after ∼4 min. This showed that it is possible to gain noninvasive in vivo measurements of nitrogen kinetics through the body while at hyperbaric pressures. Tissue samples showed radioactivity above background levels in the blood, brain, liver, femur, and thigh muscle when assessed using a γ counter. The method can be used to evaluate an array of challenges to our understanding of decompression physiology by quantifying nitrogen load through γ counts of 13N2, and signal intensity of the PET. Further development of the method will improve the specificity of the measured outcomes, and enable it to be used with larger mammals, including humans.NEW & NOTEWORTHY This article describes a method for the in vivo quantification and tracking of nitrogen through the mammalian body whilst exposed to hyperbaric pressure. The method has the potential to further our understanding of decompression sickness, and quantitatively evaluate the effectiveness of both the treatment and prevention of decompression sickness.

Perbandingan Hipertensi pada Masyarakat Yang Tinggal di Pesisir Pulau Maitara dan Daerah Dataran Tinggi Gurabunga Tidore

Hypertension is a commonly encountered disease in daily clinical practice, but often goes unnoticed by its sufferers. Complications can occur in various organs, with the most significant being complications affecting the heart. The environment plays a role in hypertension, where inhabitants living in coastal areas tend to suffer from hypertension due to high sodium consumption, while in highland areas, hypertension is more influenced by acute hyperbaric hypoxia conditions, although its pathophysiology is not yet precisely known. Various studies have yielded diverse results. North Maluku Province is an archipelagic region with a large coastal area, and no research has been conducted there, prompting this study. An analytical observational study was conducted using a cross-sectional approach, focusing on the population of hypertensive individuals residing in the coastal area of Maitara and the highland area of Gurabunga, Tidore. Samples were consecutively selected until the required sample size was met. Variables examined included gender, age, occupation, salt consumption patterns, body mass index, ancestry, alcohol consumption habits, systolic blood pressure, and diastolic blood pressure. Analysis was performed using an independent t-test when sample homogeneity conditions were met. Significant differences were found in some demographic-clinical variables. There was a significant difference in diastolic blood pressure between the Gurabunga area and the coastal area of Maitara, but no significant difference was observed in systolic blood pressure.
 

A kinetic study on the effect of hyperbaric storage on the development of Maillard reaction in glucose-glycine model systems

The effect of pressure (0.1, 15, 50 and 100 MPa) and temperature (43, 53, 63 °C) on the formation rate (k) of Maillard α-dicarbonyls (absorbance at 294) and melanoidins (absorbance at 420 nm), was studied during hyperbaric storage (HS) of glucose-glycine model solutions (pH 6).While increasing storage temperature increased k values according to the Arrhenius equation (Ea ~ 85 kJ mol−1), increasing pressure decreased reaction rates as predicted by the Eyring model (Va ~ 11 mL mol−1). Pressure did not affect reaction temperature sensitivity, indicating no significant mechanism changes under hyperbaric conditions. A combined model predicting the effect of concomitant changes of temperature and pressure on Maillard reaction rate was implemented and validated within and outside (20–25 °C, 20–200 MPa) its building range.Results indicate HS to limit Maillard browning in food, with possible practical applications, and the potential to develop predictive models based on temperature-accelerated HS trials. Industrial relevanceThe capability of hyperbaric storage to impair Maillard reaction rate extends the scope of this multi-tasking technology to the prevention of color alterations due to non-enzymatic browning. The latter is expected to be of industrial relevance in the case of perishable foods affected by this phenomenon, such as thermally-treated milk. In these matrices, the technology could concomitantly guarantee microbiological safety, protein functionalization, and Maillard browning impairment.

Effects of oxygen-prebreathing on tissue nitrogenation in normobaric and hyperbaric conditions.

Breathing pure oxygen causes nitrogen washout from tissues, a method commonly deployed to prevent decompression sickness from hypobaric exposure. Theoretically prebreathing oxygen increases the capacity for nitrogen uptake and potentially limits supersaturation during dives of short duration. We aimed to use 13N2, a radioactive nitrogen isotope, to quantify tissue nitrogen following normobaric and hyperbaric exposures. Twenty Sprague Dawley rats were divided in 4 conditions; normobaric prebreathe, normobaric control, hyperbaric prebreathe, hyperbaric control. Prebreathed rats breathed oxygen for 1 h prior to the experiment whilst controls breathed air. Normobaric rats breathed air containing 13N2 at 100 kPa for 30 min, whereas hyperbaric rats breathed 13N2 at 700 kPa before being decompressed and sedated using air-isoflurane (without 13N2 for a few minutes). After euthanization, blood, brain, liver, femur and thigh muscle were analyzed by gamma counting. At normobaria prebreathing oxygen resulted in higher absolute nitrogen counts in blood (p = .034), as well as higher normalized counts in both the liver and muscle (p = .034). However, following hyperbaric exposure no differences were observed between conditions for any organ (p>.344). Both bone and muscle showed higher normalized counts after hyperbaria compared to normobaria. Oxygen prebreathing caused nitrogen elimination in normobaria that led to a larger "sink" and uptake of 13N2. The lack of difference between conditions in hyperbaria could be due to the duration and depth of the dive mitigating the effect of prebreathing. In the hyperbaric conditions the lower counts were likely due to off-gassing of nitrogen during the sedation procedure, suggest a few minutes was enough to off-gas in rodents. The higher normalized counts under hyperbaria in bone and muscle likely relate to these tissues being slower to on and off-gas nitrogen. Future experiments could include shorter dives and euthanization while breathing 13N2 to prevent off-gassing.

Critical flicker fusion frequency results during oxygen decompression in standard HBOT session - observational study.

Most hyperbaric medicine reports concentrate on the patient and his morbidities. In addition to the well-known indications for hyperbaric oxygen therapy (HBOT), we cannot discount possible side effects. Among medical staff regularly exposed to hyperbaric conditions the best described so far is decompression sickness. A non-invasive and easily available way to assess cognitive functioning involves the use of the critical flicker fusion frequency (CFFF) test. In the current study, the flicker test was performed several times on 21 subjects, both under normobaric and hyperbaric conditions. The test was conducted using the device that flickering was programmed according to the method of limits. While in the hyperbaric chamber, 15 of the participants breathed oxygen to reduce the risk of decompression sickness. Flicker and fusion frequencies differed from each other in both normo- and hyperbaric conditions (p < 0.01). CFFF results were dependent on oxygen breathing during decompression.

Retinal Layer and Choroidal Changes in Deep and Scuba Divers: Evidence of Pachychoroid Spectrum‐Like Findings

Purpose: Diving is an intense physical activity under hyperbaric and hyperoxic conditions. The aim of this study is to evaluate the long‐term effects of diving on the thicknesses of retinal layers and retinal anatomy in professional deep and scuba divers.Methods: The study included 52 eyes of deep divers who dive to depths of more than 130 feet (ft), 49 eyes of scuba divers who dive up to 130 ft, and 66 eyes of the control group, consisting of nondiving but regularly exercising males. Measurements of macular retinal layer thicknesses, peripapillary nerve fiber layer thickness, subfoveal choroidal thickness, and peripheral retinal examinations with scleral indentation were performed and statistically compared between the groups.Results: The mean diving duration was 455.00 ± 318.88 h in deep divers and 451.67 ± 281.10 h in scuba divers. The retinal pigment epithelium (RPE) was statistically significantly thicker in deep divers than in scuba divers and the control group on the 3 mm ring of the Early Treatment Diabetic Retinopathy Study grid. Subfoveal choroidal thickness was significantly thicker in deep divers than in scuba divers (p &lt; 0.05). RPE abnormalities showed a significant increase in both the deep and scuba diver groups (p = 0.01).Conclusion: An increased thickening of the subfoveal choroid and RPE, resembling pachychoroid pigment epitheliopathy, was detected in deep divers over a long‐term duration.

Нарушения опорно-двигательного аппарата у водолазного состава военно-морского флота

Aim. To study the features of the pathogenesis and clinical picture of musculoskeletal disorders in various categories of military personnel of the Navy (Navy) and pensioners of the Ministry of Defense of the Russian Federation (MOD) based on a set of clinical, instrumental and laboratory data. Design. Prospective observational study. Materials and methods. An examination was carried out and the medical documentation was studied of 98 military personnel of the Navy and pensioners of the Defense Ministry in the following groups: I — military personnel of the Navy without a history of exposure to hyperbaria, II — military personnel belonging to deep-sea divers with moderate work experience, III — military personnel belonging to deep-sea divers with significant work experience, IV — pensioners of the Ministry of Defense, whose professional activity was related to work on deep-sea vehicles (aquanauts), V — pensioners of the Ministry of Defense without a history of exposure to hyperbaria. The patients underwent a detailed laboratory and instrumental study of bone tissue metabolism, including digital radiography, osteodensitometry, magnetic resonance imaging (MRI) and computed tomography. Results. Significant osteo-articular changes of the type of dysbaric osteonecrosis were noted among Navy diving personnel, most pronounced among retired Navy personnel – aquanauts. Conclusion. Osteoarticular changes in Navy diving personnel are of a specific dysbarogenic nature, polyetiological, localized in large joints and diaphyses of adjacent bones and become significant as the length of service, the severity of the work performed and occupational risks in hyperbaric conditions increase. Digital radiography and MRI are recognized as the optimal methods for diagnosing dysbaric osteonecrosis and “dysbarogenic osteoarthropathy”. As a rapid diagnostic method, it is advisable to use innovative urine test strips that allow determining the threshold concentrations of bone resorption markers — β-crosslaps and α-crosslaps. Keywords: diving personnel of the Navy, aquanauts, dysbaric osteonecrosis and "dysbarogenic osteoarthropathy", etiology, pathogenesis, clinical picture, diagnosis.