Endothelial Nitric Oxide Production and Antioxidant Response in Breath-Hold Diving: Genetic Predisposition or Environment Related?

IntroductionNitric oxide (NO) is an essential signaling molecule modulating the endothelial adaptation during breath-hold diving (BH-diving). This study aimed to investigate changes in NO derivatives (NOx) and total antioxidant capacity (TAC), searching for correlations with different environmental and hyperbaric exposure.Materials and methodsBlood samples were obtained from 50 breath-hold divers (BH-divers) before, and 30 and 60 min after the end of training sessions performed both in a swimming pool or the sea. Samples were tested for NOx and TAC differences in different groups related to their hyperbaric exposure, experience, and additional genetic polymorphism.ResultsWe found statistically significant differences in NOx plasma concentration during the follow-up (decrease at T30 and increase at T60) compared with the pre-dive values. At T30, we found a significantly lower decrease of NOx in subjects with a higher diving experience, but no difference was detected between the swimming pool and Sea. No significant difference was found in TAC levels, as well as between NOx and TAC levels and the genetic variants.ConclusionThese data showed how NO consumption in BH-diving is significantly lower in the expert group, indicating a possible training-related adaptation process. Data confirm a significant NO use during BH-diving, compatible with the well-known BH-diving related circulatory adaptation suggesting that the reduction in NOx 30 min after diving can be ascribed to the lower NO availability in the first few minutes after the dives. Expert BH-divers suffered higher oxidative stress. A preliminary genetic investigation seems to indicate a less significant influence of genetic predisposition.

Control Study of Short-Term Aftereffect in Diving Exposure Related Pulmonary Ventilation Function

Objective: Ventilation attenuation often happened in professional divers due to long-term cumulative effects in diving exercises. By case-control experiments, we observed the immediate effects of pulmonary ventilation before and after the exposure of 12m-depth underwater for 20 min to discuss the relationships between the short-term and long-time effects caused by diving environment. Methods: Participants were randomly assigned into the Experimental Group (EG) who stayed for 20 min under 12-m water environment or the Control Group (CG) who stayed in hyperbaric chamber under the pressure of 2.2ATA. Pulmonary ventilation function parameters including VC, FVC, MVV and MV were detected respectively before and after hyperbaric exposure by the Spirometer. Immediate effects of pulmonary ventilation before and after diving were compared by paired t test to reveal the different influence caused by environmental pressure. Results: The value of VC appears to rise while the MV, MVV were detected decreased after the exposure of 2.2ATA of environment pressure for 20min in the two groups. VC increased more significantly in the CG (t=-1.26, p=0.23) after hyperbaric exposure, that leads to the FEV1.0%t (=FEV1.0/VC %) increase in EG (t=-0.73, p=0.48) while decrease in CG (t=0.42, p=0.17). The same trend in VC, MV and MVV after high pressure exposure in the two groups mainly due to the effect of common factors –the pressure. In addition to the impact of the pressure itself, EG members also face diving related immersion effect, influence of diving equipment load and water under low temperature. The FVC is detected decreased in EG (t=1.21, P =0.25) while it increased in CG (t=-0.42, P =0.68) , but the differences are not significant and couldn’t affect the measured FEV1.0% (=FEV1.0/FVC %) values showed both increasing in EG (t=-1.48, P =0.16) and in CG (t=-0.23, P =0.82). The expiratory flow rate including PEF, FEF25-75, MEF75, MEF50 increased in EG (t are -0.72, -0.69, -0.87 and -0.36 respectively with P all greater than 0.05) while decreased in CG (t are 1.67, 0.50, 1.53 and 0.71 respectively with P all greater than 0.05). MEF25 is the expiratory flow index of not affected by respiratory muscle force and the measured values of MEF25 increased in the EG (t=-0.68, P =0.51) and in the CG (t=-0.36, P =0.72). Conclusion: Water immersion and water temperature during diving exposure could cause and accelerate hemodynamic changes in pulmonary circulation induced pulmonary interstitial edema and led to the increase of external respiratory work. Instant effects of diving exposure in the study are quite consistent with the long-term cumulative effect of professional divers in previous research, which is FVC reduced because small airway become narrower. The results illustrate even the small depth of short-range diving exercise have definite influences on pulmonary ventilation, which mainly comes from the environmental factor but not the pressure increases.

Spinal cord decompression sickness in an inside attendant after a standard hyperbaric oxygen treatment session

Medical personnel in hyperbaric treatment centres are at occupational risk for decompression sickness (DCS) while attending patients inside the multiplace hyperbaric chamber (MHC). A 51-year-old male hyperbaric physician, also an experienced diver, was working as an inside attendant during a standard hyperbaric oxygen therapy (HBOT) session (70 minutes at 253.3 kPa [2.5 atmospheres absolute, 15 metres’ seawater equivalent]) in a large walk-in MHC. Within 10 minutes after the end of the session, symptoms of spinal DCS occurred. Recompression started within 90 minutes with an infusion of lignocaine and hydration. All neurological symptoms resolved within 10 minutes breathing 100% oxygen at 283.6 kPa (2.8 atmospheres absolute) and a standard US Navy Treatment Table 6 was completed. He returned to regular hyperbaric work after four weeks of avoiding hyperbaric exposures. Transoesophageal echocardiography with a bubble study was performed 18 months after the event without any sign of a persistent (patent) foramen ovale. Any hyperbaric exposure, even within no-decompression limits, is an essential occupational risk for decompression sickness in internal hyperbaric attendants, especially considering the additional risk factors typical for medical personnel (age, dehydration, tiredness, non-optimal physical capabilities and frequent problems with the lower back).

Acclimatization to diving: a systematic review

Multiday hyperbaric exposure has been shown to reduce the incidence of decompression sickness (DCS) of compressed-air workers. This effect, termed acclimatization, has been addressed in a number of studies, but no comprehensive review has been published. This systematic review reports the findings of a literature search. PubMed, Ovid Embase, The Cochrane Library and Rubicon Research Repository were searched for studies reporting DCS incidence, venous gas embolism (VGE) or subjective health reports after multiday hyperbaric exposure in man and experimental animals. Twenty-nine studies fulfilled inclusion criteria. Three epidemiological studies reported statistically significant acclimatization to DCS in compressed- air workers after multiday hyperbaric exposure. One experimental study observed less itching after standardized simulated dives. Two human experimental studies reported lower DCS incidence after multiday immersed diving. Acclimatization to DCS has been observed in six animal species. Multiday diving had less consistent effect on VGE after hyperbaric exposure in man. Four studies observed acclimatization while no statistically significant acclimatization was reported in the remaining eight studies. A questionnaire study did not report any change in self-perceived health after multiday diving. This systematic review has not identified any study suggesting a sensitizing effect of multiday diving, and there is a lack of data supporting benefit of a day off diving after a certain number of consecutive diving days. The results suggest that multiday hyperbaric exposure probably will have an acclimatizing effect and protects from DCS. The mechanisms causing acclimatization, extent of protection and optimal procedure for acclimatization has been insufficiently investigated.

Cecal metabolome fingerprint in a rat model of decompression sickness with neurological disorders

Massive bubble formation after diving can lead to decompression sickness (DCS), which can result in neurological disorders. We demonstrated that hydrogen production from intestinal fermentation could exacerbate DCS in rats fed with a standard diet. The aim of this study is to identify a fecal metabolomic signature that may result from the effects of a provocative hyperbaric exposure. The fecal metabolome was studied in two groups of rats previously fed with maize or soy in order to account for diet effects. 64 animals, weighing 379.0_20.2 g on the day of the dive, were exposed to the hyperbaric protocol. The rats were separated into two groups: 32 fed with maize (Div MAIZE) and 32 fed with soy (Div SOY). Gut fermentation before the dive was estimated by measuring exhaled hydrogen. Following hyperbaric exposure, we assessed for signs of DCS. Blood was analyzed to assay inflammatory cytokines. Conventional and ChemRICH approaches helped the metabolomic interpretation of the cecal content. The effect of the diet is very marked at the metabolomic level, a little less in the blood tests, without this appearing strictly in the clinic status. Nevertheless, 37 of the 184 metabolites analyzed are linked to clinical status. 35 over-expressed compounds let suggest less intestinal absorption, possibly accompanied by an alteration of the gut microbial community, in DCS. The decrease in another metabolite suggests hepatic impairment. This spectral difference of the ceca metabolomes deserves to be studied in order to check if it corresponds to functional microbial particularities.

Biomarkers of neuronal damage in saturation diving—a controlled observational study

Purpose A prospective and controlled observational study was performed to determine if the central nervous system injury markers glial fibrillary acidic protein (GFAp), neurofilament light (NfL) and tau concentrations changed in response to a saturation dive. Methods The intervention group consisted of 14 submariners compressed to 401 kPa in a dry hyperbaric chamber. They remained pressurized for 36 h and were then decompressed over 70 h. A control group of 12 individuals was used. Blood samples were obtained from both groups before, during and after hyperbaric exposure, and from the intervention group after a further 25–26 h. Results There were no statistically significant changes in the concentrations of GFAp, NfL and tau in the intervention group. During hyperbaric exposure, GFAp decreased in the control group (mean/median − 15.1/ − 8.9 pg·mL−1, p < 0.01) and there was a significant difference in absolute change of GFAp and NfL between the groups (17.7 pg·mL−1, p = 0.02 and 2.34 pg·mL−1, p = 0.02, respectively). Albumin decreased in the control group (mean/median − 2.74 g/L/ − 0.95 g/L, p = 0.02), but there was no statistically significant difference in albumin levels between the groups. In the intervention group, haematocrit and mean haemoglobin values were slightly increased after hyperbaric exposure (mean/median 2.3%/1.5%, p = 0.02 and 4.9 g/L, p = 0.06, respectively). Conclusion Hyperbaric exposure to 401 kPa for 36 h was not associated with significant increases in GFAp, NfL or tau concentrations. Albumin levels, changes in hydration or diurnal variation were unlikely to have confounded the results. Saturation exposure to 401 kPa seems to be a procedure not harmful to the central nervous system. Trial registration ClinicalTrials.gov NCT03192930.

Effects of hyperbaric environment on endurance and metabolism are exposure time-dependent in well-trained mice

Hyperbaric exposure (1.3 atmospheres absolute with 20.9% O2) for 1 h a day was shown to improve exercise capacity. The present study was designed to reveal whether the daily exposure time affects exercise performance and metabolism in skeletal and cardiac muscles. Male mice in the training group were housed in a cage with a wheel activity device for 7 weeks from 5 weeks old. Trained mice were then subjected to hybrid training (HT, endurance exercise for 30 min followed by sprint interval exercise for 30 min). Hyperbaric exposure was applied following daily HT for 15 min (15HT), 30 min (30HT), or 60 min (60HT) for 4 weeks (each group, n = 10). In the endurance capacity test, maximal work values were significantly increased by 30HT and 60HT. In the left ventricle (LV), activity levels of 3-hydroxyacyl-CoA-dehydrogenase, citrate synthase, and carnitine palmitoyl transferase (CPT) 2 were significantly increased by 60HT. CPT2 activity levels were markedly increased by 60HT in the plantaris muscle (PL). Pyruvate dehydrogenase complex (PDHc) activity values in PL were enhanced more by 30HT and 60HT than by HT. In both 30HT and 60HT groups, lactate dehydrogenase activity levels were significantly increased and decreased, respectively, in the gastrocnemius muscle and LV. These results indicate that hyperbaric exposure for 30 min or longer has beneficial effects on endurance, and 60-min exposure has the potential to further increase performance by facilitating fatty acid metabolism in skeletal and cardiac muscles in highly-trained mice.

Hyperbaric hyperoxia exposure in suppressing human immunodeficiencyvirus replication: An experimental in vitro in peripheral mononuclear blood cells culture

Cellular immune has an important role in response HIV infection, which is attack the infected cells to activate signaling molecule. Hyperbaric Oxygen (HBO) worked as complementary treatment for HIV infection. The production of ROS and RNS molecules during hyperbaric exposure can affect gene expression which contributes to cellular adaptative response. This study was conducted to explore the mechanisms of cellular adaptive response to HIV infection during hyperbaric exposure. This study was carried on in vitro using healthy volunteers’ PBMCs (Peripheral Blood Mononuclear Cells) cultures infected with HIV-1. The study was conducted as a post- test only group design. The experimental unit was PBMC from venous blood of healthy volunteers which were cultured in vitro and infected by co-culturing with HIV-1 in MT4 cell line. The experimental unit consist of treatment and control group. Each group examined the expression of transcription factor NFκB, Interferon α, reverse transcriptase inhibitors (p21), and the amount of HIV-1 p24 antigen. There were increasingly significant differences in the expression of the trancription factor of NFκB, p21, and HIV-1 p24 antigen,as well as mRNA transcription of interferon α2 between treatment and controlgroup. By decreasing p24 antigen showed that HBO exposure was able to suppress HIV-1 replication. The exposure to hyperbaric oxygen at the pressure of 2.4 ATAand 98% oxygen wasable to produce ROS and RNS molecules, which play a role in cellular adaptive responses through increasing the expression of nfĸb, p21 and mRNA of interferon α2 plays a role in inhibition mechanism of HIV-1 replication in cells.

Analysis of Species Characteristics of Laboratory Animals in Reaction to Hyperbaric Environmental Conditions

The aim of this work is to determine the dynamics of nitrogen saturation in small laboratory animals. Nitrogen was chosen as a model gas in this study because of its availability and characteristics, as it is not metabolised and is subject to passive diffusion. By subjecting different species of animals to hyperbaric exposures of increasing time and pressure, the study aimed to identify how rapid a decompression was possible to achieve an outcome that saw 50% of the animals surviving the ensuing acute decompression sickness. The basic parameters of hyperbaric exposure - pressure and time - made it possible to describe the saturation phenomena on the basis of partial saturation periods and to show whether a small animal organism can be considered as a single compartment model.