Blood Gene Expression and Vascular Function Biomarkers in Professional Saturation Diving

Oxy-Inflammation in Humans during Underwater Activities

Underwater activities are characterized by an imbalance between reactive oxygen/nitrogen species (RONS) and antioxidant mechanisms, which can be associated with an inflammatory response, depending on O2 availability. This review explores the oxidative stress mechanisms and related inflammation status (Oxy-Inflammation) in underwater activities such as breath-hold (BH) diving, Self-Contained Underwater Breathing Apparatus (SCUBA) and Closed-Circuit Rebreather (CCR) diving, and saturation diving. Divers are exposed to hypoxic and hyperoxic conditions, amplified by environmental conditions, hyperbaric pressure, cold water, different types of breathing gases, and air/non-air mixtures. The "diving response", including physiological adaptation, cardiovascular stress, increased arterial blood pressure, peripheral vasoconstriction, altered blood gas values, and risk of bubble formation during decompression, are reported.

Extreme environments and human health: From the immune microenvironments to immune cells

Exposure to extreme environments causes specific acute and chronic physiological responses in humans. The adaptation and the physiological processes under extreme environments predominantly affect multiple functional systems of the organism, in particular, the immune system. Dysfunction of the immune system affected by several extreme environments (including hyperbaric environment, hypoxia, blast shock, microgravity, hypergravity, radiation exposure, and magnetic environment) has been observed from clinical macroscopic symptoms to intracorporal immune microenvironments. Therefore, simulated extreme conditions are engineered for verifying the main influenced characteristics and factors in the immune microenvironments. This review summarizes the responses of immune microenvironments to these extreme environments during in vivo or in vitro exposure, and the approaches of engineering simulated extreme environments in recent decades. The related microenvironment engineering, signaling pathways, molecular mechanisms, clinical therapy, and prevention strategies are also discussed.

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.

A Work Environment Under Pressure: Psychosocial Job Demands and Resources Among Saturation Divers

Saturation divers work and live under high physiological and social demands for weeks on end. Even though physiological research has contributed insights to the work conditions of saturation divers, research on the qualities of the divers' psychosocial work environment is lacking. This study aimed to explore which job demands and resources are viewed as characteristic among saturation divers working within an isolated and confined environment. Based on data from 6 in-depth semi-structured interviews, template analysis was applied to map unique characteristics. By using the theoretical framework of the job demands-resources model, we found that the work environment in saturation diving was characterized by shifting demands and big contrasts, requiring adaptability in each individual diver. One major demand described by the informants was an unpredictable future, somewhat due to the changes in the oil and gas industry. Another important demand was the conflict between family and work/leisure when committing to work for extended periods in isolated environments. The monotony that characterizes the work environment is a challenge that must be managed. High wages, periods of leisure, and a prestigious job provide external motivation, while personal resources such as mental endurance and flexibility, a willingness to learn, and keeping up small personal routines, may benefit the divers' mental health. This is also affected by the quality of team climate-with features such as being sociable and considerate, having a dark sense of humor and having trust in one another.

Using Salivary Biomarkers for Stress Assessment in Offshore Saturation Diving: A Pilot Study

Health monitoring during offshore saturation diving is complicated due to restricted access to the divers, the desire to keep invasive procedures to a minimum, and limited opportunity for laboratory work onboard dive support vessels (DSV). In this pilot study, we examined whether measuring salivary biomarkrers in samples collected by the divers themselves might be a feasible approach to environmental stress assessment. Nine saturation divers were trained in the passive drool method for saliva collection and proceeded to collect samples at nine time points before, during, and after an offshore commercial saturation diving campaign. Samples collected within the hyperbaric living chambers were decompressed and stored frozen at −20°C onboard the DSV until they were shipped to land for analysis. Passive drool samples were collected without loss and assayed for a selection of salivary biomarkers: secretory immunoglobulin A (SIgA), C-reactive protein (CRP), tumor necrosis factor (TNF)-α, interleukins IL-6, IL-8, IL-1β, as well as cortisol and alpha-amylase. During the bottom phase of the hyperbaric saturation, SIgA, CRP, TNF-α, IL-8 and IL-1β increased significantly, whereas IL-6, cortisol and alpha-amylase were unchanged. All markers returned to pre-dive levels after the divers were decompressed back to surface pressure. We conclude that salivary biomarker analysis may be a feasible approach to stress assessment in offshore saturation diving. The results of our pilot test are consonant with an activation of the sympathetic nervous system related to systemic inflammation during hyperbaric and hyperoxic saturation.

Functional Profiling Reveals Altered Metabolic Activity in Divers' Oral Microbiota During Commercial Heliox Saturation Diving

Background: The extreme environment in saturation diving affects all life forms, including the bacteria that reside on human skin and mucosa. The oral cavity alone is home to hundreds of different bacteria. In this study, we examined the metabolic activity of oral bacteria from healthy males during commercial heliox saturation diving. We focused on environmentally induced changes that might affect the divers’ health and fitness.

Methods: We performed pathway abundance analysis using PICRUSt2, a bioinformatics software package that uses marker gene data to compute the metabolic activity of microbial communities. The analysis is based on 16S rRNA metagenomic data generated from the oral microbiota of 23 male divers before, during, and after 4weeks of commercial heliox saturation diving. Environmentally induced changes in bacterial metabolism were computed from differences in predicted pathway abundances at baseline before, versus during, and immediately after saturation diving.

Results and Conclusion: The analysis predicted transient changes that were primarily associated with the survival and growth of bacteria in oxygenated environments. There was a relative increase in the abundance of aerobic metabolic pathways and a concomitant decrease in anaerobic metabolic pathways, primarily comprising of energy metabolism, oxidative stress responses, and adenosylcobalamin biosynthesis. Adenosylcobalamin is a bioactive form of vitamin B₁₂ (vitB₁₂), and a reduction in vitB₁₂ biosynthesis may hypothetically affect the divers’ physiology. While host effects of oral bacterial vitamin metabolism are uncertain, this is a finding that concurs with the existing recommendations for vitB₁₂ supplements as part of the divers’ diet, whether to boost antioxidant defenses in bacteria or their host or to improve oxygen transport during saturation diving.

Acute Effects on the Human Peripheral Blood Transcriptome of Decompression Sickness Secondary to Scuba Diving

Decompression sickness (DCS) develops due to inert gas bubble formation in bodily tissues and in the circulation, leading to a wide range of potentially serious clinical manifestations. Its pathophysiology remains incompletely understood. In this study, we aim to explore changes in the human leukocyte transcriptome in divers with DCS compared to closely matched unaffected controls after uneventful diving. Cases (n = 7) were divers developing the typical cutis marmorata rash after diving with a confirmed clinical diagnosis of DCS. Controls (n = 6) were healthy divers who surfaced from a ≥25 msw dive without decompression violation or evidence of DCS. Blood was sampled at two separate time points-within 8 h of dive completion and 40-44 h later. Transcriptome analysis by RNA-Sequencing followed by bioinformatic analysis was carried out to identify differentially expressed genes and relate their function to biological pathways. In DCS cases, we identified enrichment of transcripts involved in acute inflammation, activation of innate immunity and free radical scavenging pathways, with specific upregulation of transcripts related to neutrophil function and degranulation. DCS-induced transcriptomic events were reversed at the second time point following exposure to hyperbaric oxygen. The observed changes are consistent with findings from animal models of DCS and highlight a continuum between the responses elicited by uneventful diving and diving complicated by DCS. This study sheds light on the inflammatory pathophysiology of DCS and the associated immune response. Such data may potentially be valuable in the search for novel treatments targeting this disease.

Change in Oxidative Stress Biomarkers During 30 Days in Saturation Dive: A Pilot Study

Saturation diving allows divers to reduce the risk of decompression sickness while working at depth for prolonged periods but may increase reactive oxygen species (ROS) production. Such modifications can affect endothelial function by exacerbating oxidative stress. This study investigated the effects of saturation diving on oxidative stress damage. Redox status was evaluated through: ROS production; total antioxidant capacity (TAC); nitric oxide metabolites (NOx); nitrotyrosine (3-NT); and lipid peroxidation (8-iso-PGF2α) assessment. Creatinine and neopterin were analyzed as markers of renal function and damage. Measurements were performed on saliva and urine samples obtained at four time points: pre; deep; post; and 24 h post. Four divers were included in the study. After the saturation dive (post), significant (p < 0.05) increases in ROS (0.12 ± 0.03 vs. 0.36 ± 0.06 µmol.min^-1), TAC (1.88 ± 0.03 vs. 2.01 ± 0.08 mM), NOx (207.0 ± 103.3 vs. 441.8 ± 97.3 µM), 3-NT (43.32 ± 18.03 vs. 18.64 ± 7.45 nM·L^-1), and 8-iso-PGF2α (249.7 ± 45.1 vs. 371.9 ± 54.9 pg·mg^-1 creatinine) were detected. Markers of renal damage were increased as well after the end of the saturation dive (creatinine 0.54 ± 0.22 vs. 2.72 ± 1.12 g-L^-1; neopterin 73.3 ± 27.9 vs. 174.3 ± 20.53 μmol·mol^-1 creatinine). These results could ameliorate commercial or military diving protocols or improve the understanding of symptoms caused by oxygen level elevation.

Effects of recreational scuba diving on erythropoiesis-"normobaric oxygen paradox" or "plasma volume regulation" as a trigger for erythropoietin?

PURPOSE

Previous studies have shown an increase in erythrocyte lipid peroxidation and a decrease in red blood cell (RBC) count, hemoglobin, and hematocrit after only one recreational scuba diving session. The aim of this study was to examine the effect of repetitive scuba diving on RBC parameters and erythropoiesis.

METHODS

Divers (N = 14) conducted one dive per week over 5 weeks at a depth of 20-30 m for 30 min. For measuring RBC parameters, erythropoietin, iron, and ferritin, blood samples were collected before and after the first, third, and fifth dive.

RESULTS

Between pre- and post-dive results, a statistically significant increase in RBC count, hemoglobin, hematocrit, mean corpuscular volume (MCV), RBC distribution width (RDW), iron, and ferritin was observed. Analysis of the results between the first, third, and fifth dive showed that the erythropoietin increase at the third (pre-dive p = 0.009; post-dive p = 0.004) and fifth dive (pre-dive p < 0.001; post-dive p = 0.003) was not accompanied by changes in RBC count, hemoglobin, iron, and ferritin. In parallel, a continuous increase in hematocrit, MCV, and RDW was observed, whereas mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) decreased.

CONCLUSIONS

Changes in RBC indices and EPO elevation indicate that the occasional switch from hyperoxia to normoxia or mechanisms for plasma volume regulation may be a step in the maintenance of erythropoiesis.

Hyperoxia Alters Ultrastructure and Induces Apoptosis in Leukemia Cell Lines

Oxygenation conditions are crucial for growth and tumor progression. Recent data suggests a decrease in cancer cell proliferation occurring after exposure to normobaric hyperoxia. Those changes are associated with fractal dimension. The purpose of this research was to study the impact of hyperoxia on apoptosis and morphology of leukemia cell lines. Two hematopoietic lymphoid cancer cell lines (a T-lymphoblastoid line, JURKAT and a B lymphoid line, CCRF-SB) were tested under conditions of normobaric hyperoxia (FiO₂ > 60%, ± 18h) and compared to a standard group (FiO₂ = 21%). We tested for apoptosis using a caspase-3 assay. Cell morphology was evaluated by cytospin, microphotography after coloration, and analysis by a fractal dimension calculation software. Our results showed that exposure of cell cultures to transient normobaric hyperoxia induced apoptosis (elevated caspase-3) as well as significant and precocious modifications in cell complexity, as highlighted by increased fractal dimensions in both cell lines. These features are associated with changes in structure (pycnotic nucleus and apoptosis) recorded by microscopic analysis. Such morphological alterations could be due to several molecular mechanisms and rearrangements in the cancer cell, leading to cell cycle inhibition and apoptosis as shown by caspase-3 activity. T cells seem less resistant to hyperoxia than B cells.

Hemoglobin During and Following a 4-Week Commercial Saturation Dive to 200 m

Commercial saturation divers must acclimatize to hyperbaric hyperoxia in their work environment, and subsequently readjust to breathing normal air when their period in saturation is over. In this study, we measured hemoglobin (Hb) during and following 4 weeks of heliox saturation diving in order to monitor anemia development and the time for Hb to recover post-saturation. Male commercial saturation divers reported their capillary blood Hb daily, before, and during 28 days of heliox saturation to a working depth of circa 200 m (n = 11), and for 12 days at surface post-saturation (n = 9–7), using HemoCue 201+ Hb devices. Hb remained in normal range during the bottom phase, but fell during the decompression; reaching levels of mild anemia (≤13.6 g/dl) the day after the divers’ return to the surface. Hb was significantly lower than the pre-saturation baseline (14.7 ± 1.1 g/dl) on the fifth day post-saturation (12.8 ± 1.8 g/dl, p = 0.028), before reverting to normal after 6–7 days. At the end of the 12-day post-saturation period, Hb was not statistically different from the pre-saturation baseline. The observed Hb changes, although significant, were modest. While we cannot rule out effect of other factors, the presence of mild anemia may partially explain the transient fatigue that commercial saturation divers experience post-saturation.

Pulmonary oxygen toxicity in saturation dives with PO2 close to the lower end of the toxic range - A quantitative approach

Pulmonary oxygen toxicity (POT) has been extensively described at partial pressures of oxygen (PO₂) ≥ 1 bar, but much less so at lower PO₂. We proposed the POT index [K = t² × (PO₂)^4.57] as a means of evaluating the severity of POT, expressed either as reduced lung function or the incidence of POT in a group of divers. In the exponential recovery process (e ^{- [- 0.42 + 0.384 × (PO}₂⁾_ex^{] × tr}), the time constant increases linearly from 0.0024 to 0.54 h^-1 for a PO₂ of 1.1 to 2.5 bar. A linear relationship was demonstrated between the incidence of POT and the POT index, given by the equation: POT incidence % = 1.85 + 0.171 × K. In saturation diving, PO₂ is kept close to the lower end of the toxic limits for POT, which is approximately 0.5 bar. We suggested that at this low range of PO₂, the two processes of cumulative toxicity and recovery operate simultaneously. For one example of saturation diving, we show that a recovery time constant of 0.0135 h^-1 yields the measured incidence of POT. We therefore propose the formula K = t² × PO₂^4.57 × e^{-0.0135 × t} for calculation of the POT index in further analyses of POT in saturation diving.

Commercial Divers' Subjective Evaluation of Saturation

Commercial saturation diving involves divers living and working in an enclosed atmosphere with elevated partial pressure of oxygen (ppO₂) for weeks. The divers must acclimatize to these conditions during compression, and for up to 28 days until decompression is completed. During decompression, the ppO₂ and ambient pressure are gradually decreased; then the divers must acclimatize again to breathing normal air in atmospheric pressure when they arrive at surface. We investigated 51 saturation divers' subjective evaluation of the saturation and post-decompression phase via questionnaires and individual interviews. The questions were about decompression headaches and fatigue; and time before recovering to a pre-saturation state. Twenty-two (44%) of the divers who responded declared having headaches; near surface (44%) or after surfacing (56%). 71% reported post-saturation fatigue after their last saturation, 82% of them described it as typical and systematic after each saturation. Recovery was reported to normally take from 1 to 10 days. The fatigue and headaches observed are compatible with divers' acclimatization to the changes in ppO₂ levels during saturation and decompression. They appear to be reversible post- decompression.

Hemoglobin and Erythropoietin After Commercial Saturation Diving

Saturation divers are exposed to elevated partial pressure of oxygen (ppO₂) in their hyperbaric work environment. Experimental studies indicate that oxygen transport is altered, and we have previously reported a drop in hematocrit and extensive downregulation of genes involved in blood oxygen transport capacity after decompression from professional saturation diving. Here we investigate the initial period of hematological adjustment back to normobaric air after professional saturation diving. Erythropoietin (EPO) and hemoglobin (Hb) were measured in blood from 13 divers at two time-points after saturation assignments lasting up to 4 weeks; first immediately after decompression and again 24 h later. Pre-dive levels defined baselines. The ppO₂ varied from 40 kPa in the saturation chambers during storage, 50 to 80 kPa during bell excursions, and gradually reduced to 21 kPa during decompression to surface pressure. EPO was similar to baseline immediately after saturation diving (P = 0.4), and markedly increased within the next 24 h (99%, P < 0.0002). Hb levels remained slightly reduced at both time-points (4% immediately after; P = 0.02, 8% 24 h after; P < 0.001). The results imply that the hematological acclimatization back to normobaric air was ongoing, but not completed, during the first 24 h after professional saturation diving.