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Diving can have significant cardiovascular effects on the human body and increase the risk of developing cardiac health issues. This study aimed to investigate the autonomic nervous system (ANS) responses of healthy individuals during simulated dives in hyperbaric chambers and explore the effects of the humid environment on these responses. Electrocardiographic- and heart-rate-variability (HRV)-derived indices were analyzed, and their statistical ranges were compared at different depths during simulated immersions under dry and humid conditions. The results showed that humidity significantly affected the ANS responses of the subjects, leading to reduced parasympathetic activity and increased sympathetic dominance. The power of the high-frequency band of the HRV after removing the influence of respiration, PHF⊥¯, and the number of pairs of successive normal-to-normal intervals that differ by more than 50 ms divided by the total number of normal-to-normal intervals, pNN50¯, indices were found to be the most informative in distinguishing the ANS responses of subjects between the two datasets. Additionally, the statistical ranges of the HRV indices were calculated, and the classification of subjects as “normal” or “abnormal” was determined based on these ranges. The results showed that the ranges were effective at identifying abnormal ANS responses, indicating the potential use of these ranges as a reference for monitoring the activity of divers and avoiding future immersions if many indices are out of the normal ranges. The bagging method was also used to include some variability in the datasets’ ranges, and the classification results showed that the ranges computed without proper bagging represent reality and its associated variability. Overall, this study provides valuable insights into the ANS responses of healthy individuals during simulated dives in hyperbaric chambers and the effects of humidity on these responses.

This study’s primary objective was to identify individuals whose physiological responses deviated from the rest of the study population by automatically monitoring atmospheric pressure levels to which they are exposed and using parameters derived from their heart rate variability (HRV). To achieve this, 28 volunteers were placed in a dry hyperbaric chamber, where they experienced varying pressures from 1 to 5 atmospheres, with five sequential stops lasting five minutes each at different atmospheric pressures. The HRV was dissected into two components: the respiratory component, which is linked to respiration; and the residual component, which is influenced by factors beyond respiration. Nine parameters were assessed, including the respiratory rate, four classic HRV temporal parameters, and four frequency parameters. A k-nearest neighbors classifier based on cosine distance successfully identified the atmospheric pressures to which the subjects were exposed to. The classifier achieved an 88.5% accuracy rate in distinguishing between the 5 atm and 3 atm stages using only four features: respiratory rate, heart rate, and two frequency parameters associated with the subjects’ sympathetic responses. Furthermore, the study identified 6 out of 28 subjects as having atypical responses across all pressure levels when compared to the majority. Interestingly, two of these subjects stood out in terms of gender and having less prior diving experience, but they still exhibited normal responses to immersion. This suggests the potential for establishing distinct safety protocols for divers based on their previous experience and gender.

The hyperbaric environment, to which many categories of workers are exposed, can provoke injuries that can lead to various types of disorders. A major part of the studies aiming to explore the causes/effects leading to these injuries are conducted in vivo. In the present manuscript, we describe the effects on osteoblast cell cultures stressed in a hyperbaric purpose-built chamber, using an in vitro model to analyze the affected pathways. A hyperbaric chamber for cell cultures was constructed by adapting a pressurized test chamber originally designed for technical use. The MG-63 cell line and human primary osteoblasts were placed into this chamber at different atm and exposure times, at 37 °C. After treatment, the chamber was depressurized by performing controlled decompression stops. Then, the pro-inflammatory cytokines and bone tissue biomarker expression were analyzed. The stress conditions induced the overexpression of pro-inflammatory cytokines, such as IL-6, IL-1β, and TNF-α, along with reactive oxygen species release. Moreover, the alteration of bone tissue marker production was observed. In particular, the increase in Receptor Activator of NF-κB Ligand (RANKL) and the decrease in Osteoprotegerin (OPG) were detected. Further modulation was observed regarding other biomarkers, Alkaline phosphatase, Osteocalcin, Bone Morphogenetic Protein-2, and mainly Collagen type I, all of which were downregulated by treatment. Taken together, these findings account for certain illnesses, such as dysbaric osteonecrosis, diagnosed in workers exposed to a hyperbaric environment. Inflammation induced by this kind of stress affects several factors involved in bone tissue homeostasis, leading to bone injuries, which are among the typical disorders observed in divers.

A film stress measurement system applicable for hyperbaric environment was developed to characterize stress evolution in a physical simulation test of a gas-solid coupling geological disaster. It consists of flexible film pressure sensors, a signal conversion module, and a highly-integrated acquisition box which can perform synchronous and rapid acquisition of 1 kHz test data. Meanwhile, we adopted a feasible sealing technology and protection method to improve the survival rate of the sensors and the success rate of the test, which can ensure the accuracy of the test results. The stress measurement system performed well in a large-scale simulation test of coal and gas outburst that reproduced the outburst in the laboratory. The stress evolution of surrounding rock in front of the heading is completely recorded in a successful simulation of the outburst which is consistent with the previous empirical and theoretical analysis. The experiment verifies the feasibility of the stress measurement system as well as the sealing technology, laying a foundation for the physical simulation test of gas-solid coupled geological disasters.

Purpose The purpose of this paper is to introduce a new method for the design of a pressure sensor in the hyperbaric environment. Design/methodology/approach The new method focuses on two vital parameters that are closely related to the output and sensitivity of the sensor. The rectangular diaphragm structure is adopted, and the piezoresistors are planted on the surface accordingly. To verify the effect of the method, a contrastive sensor chip is fabricated in a conventional way, and two types of sensor chips are tested at the same time. Findings The new method for the design of a pressure sensor is advisable and favorable. The sensor fabricated by the method possesses outstanding high sensitivity and a wide measurement range. Originality/value This paper provides a new idea for increasing the measurement range of the pressure sensor with an acceptable sacrifice of sensitivity.

Il crescente numero di soggetti che pratica attività subacquea in apnea indica la sempre maggiore necessità, da parte del medico, di conoscere le possibili conseguenze di tale attività sportiva svolta in un ambiente così particolare. Tra le possibili conseguenze di tale attività, la sincope in ambiente iperbarico configura una condizione estremamente particolare che esula dalle abituali classificazioni delle sincopi. I meccanismi fisiopatologici coinvolti nella sua genesi sono complessi e comportano la conoscenza di numerosi riflessi che vengono attivati in tali circostanze.La prevenzione della sincope in apnea implica la conoscenza da parte del cardiologo e del cardiologo dello sport dei meccanismi fisiopatologici determinanti la sincope e le metodiche di prevenzione della stessa.

One of the basic pathways to nonhealing of wounds is the interplay between tissue hypoperfusion, resulting hypoxia, and infection. One of the challenges of advanced wound care is identifying the extent to which local hypoxia contributes to the abnormal healing, and then correcting that hypoxia to the extent possible. A large body of research and clinical evidence has shown that intermittent oxygenation of hypoperfused tissue, which can only be achieved by exposure to hyperbaric oxygen, mitigates many of these impediments and sets in motion a cascade of responses that contributes to wound healing. Molecular oxygen is required for hydroxylation of proline during collagen synthesis and cross linking as well as for the production of reactive oxygen species during the respiratory burst occurring within leukocytes that phagocytizes bacteria. Inflammation and oxidative stress are critical components of healing success, and when either under‐ or overexpressed, healing fails.

I report here a theoretical study of the dependence on ambient pressure of heat and mass (water vapour) rate transfer processes between the human body and its gaseous surroundings, for monocomponent gases (N2, O2, He) and/or diatomic gas mixtures (He-O2, N2-O2). Heat and water vapour rate transport are described by the following rate transfer parameters: the convective heat transfer coefficient (hc), the evaporative heat transfer coefficient (he) and the Lewis relationship (LR). It is shown that the thermal stability of the human body under hyperbaric conditions is proportional to the evaporative resistance. It is also shown that in a He atmosphere the change in the thermal state caused by a heat load of 1 W x m(-2) at sea level is equivalent to the effect of a heat flow of 0.186 W x m(-2) at 30 atmospheres absolute. This indicates that the thermal state of the body is more prone to instability at increasing ambient pressures.