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Pavlyuk E, Yungerman I, Bliznyuk A, Moskovitz Y. Studying the Effects of Dissolved Noble Gases and High Hydrostatic Pressure on the Spherical DOPC Bilayer Using Molecular Dynamic Simulations. Membranes (Basel) 2024; 14:89. [PMID: 38668117 PMCID: PMC11052037 DOI: 10.3390/membranes14040089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Revised: 04/04/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024]
Abstract
Fine-grained molecular dynamics simulations have been conducted to depict lipid objects enclosed in water and interacting with a series of noble gases dissolved in the medium. The simple point-charge (SPC) water system, featuring a boundary composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) molecules, maintained stability throughout the simulation under standard conditions. This allowed for the accurate modeling of the effects of hydrostatic pressure at an ambient pressure of 25 bar. The chosen pressure references the 240 m depth of seawater: the horizon frequently used by commercial divers, who comprise the primary patient population of the neurological complication of inert gas narcosis and the consequences of high-pressure neurological syndrome. To quantify and validate the neurological effects of noble gases and discriminate them from high hydrostatic pressure, we reduced the dissolved gas molar concentration to 1.5%, three times smaller than what we previously tested for the planar bilayer (3.5%). The nucleation and growth of xenon, argon and neon nanobubbles proved consistent with the data from the planar bilayer simulations. On the other hand, hyperbaric helium induces only a residual distorting effect on the liposome, with no significant condensed gas fraction observed within the hydrophobic core. The bubbles were distributed over a large volume-both in the bulk solvent and in the lipid phase-thereby causing substantial membrane distortion. This finding serves as evidence of the validity of the multisite distortion hypothesis for the neurological effect of inert gases at high pressure.
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Affiliation(s)
- Eugeny Pavlyuk
- Laboratory of Multi-Scale Mathematical Modeling, Ural Federal University, Ekaterinburg 620002, Russia
| | - Irena Yungerman
- Department of Chemical Engineering, Technion—Israel Technological Institute, Technion City, Haifa 3200003, Israel
| | - Alice Bliznyuk
- Ilse Katz Institute for Nanoscale Science and Technology (IKI), Ben Gurion University of the Negev, Beer Sheva 8410501, Israel
| | - Yevgeny Moskovitz
- Laboratory of Multi-Scale Mathematical Modeling, Ural Federal University, Ekaterinburg 620002, Russia
- Department of Chemical Engineering, Technion—Israel Technological Institute, Technion City, Haifa 3200003, Israel
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Moes MI, Elia A, Gennser M, Keramidas ME. Combined effects of mild hypothermia and nitrous-oxide-induced narcosis on manual and cognitive performance. Am J Physiol Regul Integr Comp Physiol 2024; 326:R197-R209. [PMID: 38189165 DOI: 10.1152/ajpregu.00246.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 12/18/2023] [Accepted: 01/02/2024] [Indexed: 01/09/2024]
Abstract
Divers are at enhanced risk of suffering from acute cognitive deterioration because of the low ambient temperatures and the narcotic action of inert gases inspired at high pressures. Yet, the behavioral effects of cold and inert gas narcosis have commonly been assessed in isolation and during short-term provocations. We therefore evaluated the interactive influence of mild hypothermia and narcosis engendered by a subanesthetic dose of nitrous oxide (N2O; a normobaric intervention analog of hyperbaric nitrogen) on cognitive function during prolonged iterative exposure. Fourteen men partook in two ∼12-h sessions (separated by ≥4 days), wherein they performed sequentially three 120-min cold (20°C) water immersions (CWIs), while inhaling, in a single-blinded manner, either normal air or a normoxic gas mixture containing 30% N2O. CWIs were separated by a 120-min rewarming in room-air breathing conditions. Before the first CWI and during each CWI, subjects performed a finger dexterity test, and the Spaceflight Cognitive Assessment Tool for Windows (WinSCAT) test assessing aspects of attention, memory, learning, and visuospatial ability. Rectal and skin temperatures were, on average, reduced by ∼1.2 °C and ∼8 °C, respectively (P < 0.001). Cooling per se impaired (P ≤ 0.01) only short-term memory (∼37%) and learning (∼18%); the impairments were limited to the first CWI. N2O also attenuated (P ≤ 0.02) short-term memory (∼37%) and learning (∼35%), but the reductions occurred in all CWIs. Furthermore, N2O invariably compromised finger dexterity, attention, concentration, working memory, and spatial processing (P < 0.05). The present results demonstrate that inert gas narcosis aggravates, in a persistent manner, basic and higher-order cognitive abilities during protracted cold exposure.
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Affiliation(s)
- Maaike I Moes
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Antonis Elia
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Mikael Gennser
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Michail E Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
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Moes MI, Elia A, Gennser M, Eiken O, Keramidas ME. Nitrous oxide consistently attenuates thermogenic and thermoperceptual responses to repetitive cold stress in humans. J Appl Physiol (1985) 2023; 135:631-641. [PMID: 37471214 PMCID: PMC10642508 DOI: 10.1152/japplphysiol.00309.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/26/2023] [Accepted: 07/17/2023] [Indexed: 07/22/2023] Open
Abstract
Divers are at enhanced risk of hypothermia, due to the independent action of the inspired inert gases on thermoregulation. Thus, narcosis induced by acute (≤2 h) exposure to either hyperbaric nitrogen or normobaric nitrous oxide (N2O) impairs shivering thermogenesis and accelerates body core cooling. Animal-based studies, however, have indicated that repeated and sustained N2O administration may prevent N2O-evoked hypometabolism. We, therefore, examined the effects of prolonged intermittent exposure to 30% N2O on human thermoeffector plasticity in response to moderate cold. Fourteen men participated in two ∼12-h sessions, during which they performed sequentially three 120-min cold-water immersions (CWIs) in 20°C water, separated by 120-min rewarming. During CWIs, subjects were breathing either normal air or a normoxic gas mixture containing 30% N2O. Rectal and skin temperatures, metabolic heat production (via indirect calorimetry), finger and forearm cutaneous vascular conductance (CVC; laser-Doppler fluxmetry/mean arterial pressure), and thermal sensation and comfort were monitored. N2O aggravated the drop in rectal temperature (P = 0.01), especially during the first (by ∼0.3°C) and third (by ∼0.4°C) CWIs. N2O invariably blunted the cold-induced elevation of metabolic heat production by ∼22%-25% (P < 0.001). During the initial ∼30 min of the first and second CWIs, N2O attenuated the cold-induced drop in finger (P ≤ 0.001), but not in forearm CVC. N2O alleviated the sensation of coldness and thermal discomfort throughout (P < 0.001). Thus, the present results demonstrate that, regardless of the cumulative duration of gas exposure, a subanesthetic dose of N2O depresses human thermoregulatory functions and precipitates the development of hypothermia.NEW & NOTEWORTHY Human thermoeffector plasticity was evaluated in response to prolonged iterative exposure to 30% N2O and moderate cold stress. Regardless of the duration of gas exposure, N2O-induced narcosis impaired in a persistent manner shivering thermogenesis and thermoperception.
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Affiliation(s)
- Maaike I Moes
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Antonis Elia
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Mikael Gennser
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Ola Eiken
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Michail E Keramidas
- Division of Environmental Physiology, Swedish Aerospace Physiology Center, KTH Royal Institute of Technology, Stockholm, Sweden
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Savioli G, Alfano C, Zanza C, Bavestrello Piccini G, Varesi A, Esposito C, Ricevuti G, Ceresa IF. Dysbarism: An Overview of an Unusual Medical Emergency. Medicina (Kaunas) 2022; 58:104. [PMID: 35056412 PMCID: PMC8778177 DOI: 10.3390/medicina58010104] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/27/2021] [Accepted: 12/29/2021] [Indexed: 02/03/2023]
Abstract
Dysbarism is a general term which includes the signs and symptoms that can manifest when the body is subject to an increase or a decrease in the atmospheric pressure which occurs either at a rate or duration exceeding the capacity of the body to adapt safely. In the following review, we take dysbarisms into account for our analysis. Starting from the underlying physical laws, we will deal with the pathologies that can develop in the most frequently affected areas of the body, as the atmospheric pressure varies when acclimatization fails. Manifestations of dysbarism range from itching and minor pain to neurological symptoms, cardiac collapse, and death. Overall, four clinical pictures can occur: decompression illness, barotrauma, inert gas narcosis, and oxygen toxicity. We will then review the clinical manifestations and illustrate some hints of therapy. We will first introduce the two forms of decompression sickness. In the next part, we will review the barotrauma, compression, and decompression. The last three parts will be dedicated to gas embolism, inert gas narcosis, and oxygen toxicity. Such an approach is critical for the effective treatment of patients in a hostile environment, or treatment in the emergency room after exposure to extreme physical or environmental factors.
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Affiliation(s)
- Gabriele Savioli
- Emergency Medicine and Surgery, IRCCS Fondazione Policlinico San Matteo, 27100 Pavia, Italy;
- PhD School in Experimental Medicine, Department of Clinical-Surgical, Diagnostic and Pediatric Sciences, University of Pavia, 27100 Pavia, Italy
| | - Claudia Alfano
- Emergency Medicine and Surgery, IRCCS Fondazione Policlinico San Matteo, 27100 Pavia, Italy;
| | - Christian Zanza
- “Ospedale Alba-Bra Onlus”—Department of Emergency Medicine, Anesthesia and Critical Care Medicine, Michele and Pietro Ferrero Hospital, 12060 Verduno, Italy;
- Research Training Innovation Infrastructure, Research and Innovation Department, Azienda Ospedaliera SS Antonio e Biagio e Cesare Arrigo, 15121 Alessandria, Italy;
| | | | - Angelica Varesi
- Department of Biology and Biotechnology, University of Pavia, 27100 Pavia, Italy;
| | - Ciro Esposito
- Unit of Nephrology and Dialysis, ICS Maugeri, University of Pavia, 27100 Pavia, Italy;
| | - Giovanni Ricevuti
- School of Pharmacy, Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy;
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Affiliation(s)
- C.J. Edge
- Royal Berkshire NHS Foundation Trust, Reading, UK
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Piispanen WW, Lundell RV, Tuominen LJ, Räisänen-Sokolowski AK. Assessment of Alertness and Cognitive Performance of Closed Circuit Rebreather Divers With the Critical Flicker Fusion Frequency Test in Arctic Diving Conditions. Front Physiol 2021; 12:722915. [PMID: 34447319 PMCID: PMC8384076 DOI: 10.3389/fphys.2021.722915] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 07/12/2021] [Indexed: 12/29/2022] Open
Abstract
Introduction: Cold water imposes many risks to the diver. These risks include decompression illness, physical and cognitive impairment, and hypothermia. Cognitive impairment can be estimated using a critical flicker fusion frequency (CFFF) test, but this method has only been used in a few studies conducted in an open water environment. We studied the effect of the cold and a helium-containing mixed breathing gas on the cognition of closed circuit rebreather (CCR) divers. Materials and Methods: Twenty-three divers performed an identical dive with controlled trimix gas with a CCR device in an ice-covered quarry. They assessed their thermal comfort at four time points during the dive. In addition, their skin temperature was measured at 5-min intervals throughout the dive. The divers performed the CFFF test before the dive, at target depth, and after the dive. Results: A statistically significant increase of 111.7% in CFFF values was recorded during the dive compared to the pre-dive values (p < 0.0001). The values returned to the baseline after surfacing. There was a significant drop in the divers’ skin temperature of 0.48°C every 10 min during the dive (p < 0.001). The divers’ subjectively assessed thermal comfort also decreased during the dive (p = 0.01). Conclusion: Our findings showed that neither extreme cold water nor helium-containing mixed breathing gas had any influence on the general CFFF profile described in the previous studies from warmer water and where divers used other breathing gases. We hypothesize that cold-water diving and helium-containing breathing gases do not in these diving conditions cause clinically relevant cerebral impairment. Therefore, we conclude that CCR diving in these conditions is safe from the perspective of alertness and cognitive performance.
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Affiliation(s)
- Wilhelm W Piispanen
- Faculty of Medicine, University of Turku, Turku, Finland.,DAN Europe Research Division, Finnish Branch, Helsinki, Finland
| | - Richard V Lundell
- The Centre for Military Medicine, The Finnish Defense Forces, Helsinki, Finland.,Department of Pathology, Helsinki University, Helsinki, Finland
| | - Laura J Tuominen
- Department of Pathology, Helsinki University, Helsinki, Finland.,Anesthesia and Intensive Care Unit, Tampere University Hospital, Tampere, Finland
| | - Anne K Räisänen-Sokolowski
- DAN Europe Research Division, Finnish Branch, Helsinki, Finland.,The Centre for Military Medicine, The Finnish Defense Forces, Helsinki, Finland.,Department of Pathology, Helsinki University and Helsinki University Hospital, Helsinki, Finland
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Abstract
Moving and acting underwater within recreational or occupational activities require intact executive functions, since they subserve higher cognitive functions such as successful self-regulation, coping with novel situations, and decision making; all of which could be influenced by nitrogen narcosis due to elevated partial pressure under water. However, specific executive functions that could provide a differentiated view on humans' cognitive performance ability have not yet been systematically analyzed in full-water immersion, which is a research gap addressed within this approach to contribute to a better understanding of nitrogen narcosis. In this study, 20 young, healthy, and certified recreational divers participated and performed three different executive-function tests: the Stroop test (Inhibition), the Number/Letter test (Task switching), the 2-back test (Updating/Working memory), and a simple reaction time test (Psychomotor performance). These tests were performed once on land, at 5-meter (m) water depth, and at 20-meter (m) water depth of an indoor diving facility in standardized test conditions (26°C in all water depths). A water-proofed and fully operational tablet computer was used to present visual stimuli and to register reaction times. Performance of the simple reaction time test was not different between underwater and land testing, suggesting that reaction times were not biased by the utilization of the tablet in water immersion. Executive functions were not affected by the shallow water immersion of 5-m water depth. However, performance scores in 20-m water depth revealed a decreased performance in the incongruent test condition (i.e., an index of inhibitory control ability) of the Stroop test, while all other tests were unaffected. Even though only one out of the three tested cognitive domains was affected, the impairment of inhibitory control ability even in relatively shallow water of 20-m is a critical component that should be considered for diver's safety, since inhibition is required in self-control requiring situations where impulsive and automatic behavior must be inhibited. Our interpretation of these selective impairments is based on a discussion suggesting that different neural networks within the central nervous system, which process specific executive functions, are affected differently by nitrogen narcosis.
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Affiliation(s)
- Fabian Steinberg
- Department of Sport Psychology, Institute of Sport Science, Johannes Gutenberg University MainzMainz, Germany
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