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AbstractBreath-hold divers, also known as freedivers, are at risk of specific injuries that are unique from those of surface swimmers and compressed air divers. Using peer-reviewed scientific research and expert opinion, we created a guide for medical providers managing breath-hold diving injuries in the field. Hypoxia induced by prolonged apnea and increased oxygen uptake can result in an impaired mental state that can manifest as involuntary movements or full loss of consciousness. Negative pressure barotrauma secondary to airspace collapse can lead to edema and/or hemorrhage. Positive pressure barotrauma secondary to overexpansion of airspaces can result in gas embolism or air entry into tissues and organs. Inert gas loading into tissues from prolonged deep dives or repetitive shallow dives with short surface intervals can lead to decompression sickness. Inert gas narcosis at depth is commonly described as an altered state similar to that experienced by compressed air divers. Asymptomatic cardiac arrhythmias are common during apnea, normally reversing shortly after normal ventilation resumes. The methods of glossopharyngeal breathing (insufflation and exsufflation) can add to the risk of pulmonary overinflation barotrauma or loss of consciousness from decreased cardiac preload. This guide also includes information for medical providers who are tasked with providing medical support at an organized breath-hold diving event with a list of suggested equipment to facilitate diagnosis and treatment outside of the hospital setting.

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. [ABSTRACT FROM AUTHOR]

Blood alcohol concentrations above defined levels are detrimental to cognitive performance. Empirical and published evidence suggest that nitrogen narcosis is analogous to alcohol intoxication with both impairing prefrontal cortex function. Nitrogen narcosis is also known to have been a factor in fatal accidents. To examine the effects of nitrogen narcosis, a recent publication used the Iowa Gambling Task tool, to simulate dynamic real-life risky decision-making behaviour. If the reported outcomes are corroborated in larger rigorously designed studies it is likely to provide further evidence that divers may well experience the negative effects of a 'narcotic agent', even at relatively shallow depths. These deleterious effects may occur regardless of diving experience, aptitude or professional status. In 1872, English law made it an offence to be 'drunk' whilst in charge of horses, carriages, cattle and steam engines. Understanding the danger was easy, establishing who is 'drunk' in the eyes of the court required a legal definition. Driving above a 'legal limit' for alcohol was made illegal in the United Kingdom in 1967. The limit was set at 80 milligrams of alcohol per 100 millilitres of blood. It took just short of one hundred years to get from first introducing a restriction to specific activities, whilst under the influence of alcohol, to having a clear and well-defined enforceable law. The question surely is whether our modern society will tolerate another century before legally defining safe parameters for nitrogen narcosis? [ABSTRACT FROM AUTHOR]

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.

Blood alcohol concentrations above defined levels are detrimental to cognitive performance. Empirical and published evidence suggest that nitrogen narcosis is analogous to alcohol intoxication with both impairing prefrontal cortex function. Nitrogen narcosis is also known to have been a factor in fatal accidents. To examine the effects of nitrogen narcosis, a recent publication used the Iowa Gambling Task tool, to simulate dynamic real-life risky decision-making behaviour. If the reported outcomes are corroborated in larger rigorously designed studies it is likely to provide further evidence that divers may well experience the negative effects of a 'narcotic agent', even at relatively shallow depths. These deleterious effects may occur regardless of diving experience, aptitude or professional status. In 1872, English law made it an offence to be 'drunk' whilst in charge of horses, carriages, cattle and steam engines. Understanding the danger was easy, establishing who is 'drunk' in the eyes of the court required a legal definition. Driving above a 'legal limit' for alcohol was made illegal in the United Kingdom in 1967. The limit was set at 80 milligrams of alcohol per 100 millilitres of blood. It took just short of one hundred years to get from first introducing a restriction to specific activities, whilst under the influence of alcohol, to having a clear and well-defined enforceable law. The question surely is whether our modern society will tolerate another century before legally defining safe parameters for nitrogen narcosis?, Competing Interests: The authors report no conflicts of interest in this work., (Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.)

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. [ABSTRACT FROM AUTHOR]

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.

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.

Introduction: Critical flicker fusion frequency (CFFF) has been used in various studies to measure the cognitive effects of gas mixtures at depth, sometimes with conflicting or apparently paradoxical results. This study aimed to evaluate a novel automatic CFFF method and investigate whether CFFF can be used to monitor gas-induced narcosis in divers. Methods: Three hyperbaric chamber experiments were performed: 1) Automated and manual CFFF measurements during air breathing at 608 kPa (n = 16 subjects); 2) Manual CFFF measurements during air and heliox breathing at sea level (101.3 kPa) and 608 kPa (n = 12); 3) Manual CFFF measurements during oxygen breathing at sea level, 142 and 284 kPa (n = 10). All results were compared to breathing air at sea level. Results: Only breathing oxygen at sea level, and at 284 kPa, caused a significant decrease in CFFF (2.5% and 2.6% respectively compared to breathing air at sea level. None of the other conditions showed a difference with sea level air breathing. Conclusions: CFFF did not significantly change in our experiments when breathing air at 608 kPa compared to air breathing at sea level pressure using both devices. Based on our results CFFF does not seem to be a sensitive tool for measuring gas narcosis in divers in our laboratory setting. [ABSTRACT FROM AUTHOR]

Introduction: Gas narcosis impairs divers when diving deeper. Pupillometry is sensitive to alcohol intoxication and it has been used in anaesthesia to assess nitrous oxide narcosis. It is a potential novel method to quantify narcosis in diving. The aim of this study was to evaluate pupillometry for objective measurement of narcosis during exposure to hyperbaric air or nitrous oxide. Method: Pupil size in 16 subjects was recorded directly at surface pressure and during air breathing at 608 kPa (equivalent to 50 metres’ seawater depth) in a hyperbaric chamber. Another 12 subjects were exposed to nitrous oxide at end-tidal percentages of 20, 30 and 40% in random order at surface pressure. Pupil size and pupil light reflex were recorded at baseline and at each level of nitrous oxide exposure. Results: Pupil size did not significantly change during exposure to hyperbaric air or nitrous oxide. The pupil light reflex, evaluated using percentage constriction and minimum diameter after exposure to a light stimulus, was affected significantly only during the highest nitrous oxide exposure – an end-tidal level of 40%. Conclusion: Pupillometry is insensitive to the narcotic effect of air at 608 kPa in the dry hyperbaric environment and to the effects of low dose nitrous oxide. Pupillometry is not suitable as a monitoring method for gas narcosis in diving. [ABSTRACT FROM AUTHOR]

Introduction: When humans breathe compressed air or N2-O2 mixtures at three to four atmospheres pressure, they will experience nitrogen narcosis that may possibly lead to a diving accident, but the underlying mechanisms remain unclear. Methods: Mice were exposed to 1.6 MPa breathing a N2-O2 mixture adjusted to deliver an inspired PO2 of 32-42 kPa. The electroencephalogram (EEG) and forced swimming test were used to evaluate the narcotic effect of nitrogen. Neuronal activity was observed via c-Fos expression in cortex and hippocampus tissue after decompressing to the surface. To further investigate underlying molecular mechanisms, we incubated cultured hippocampal neurons with various NMDA concentrations, and measured expression of NMDA receptors and its down-stream signal with or without 1.6 MPa N2-O2 exposure. Results: Both the frequency of the EEG and the drowning time using the forced swimming test were significantly decreased during exposure to 1.6 MPa N2-O2 (P < 0.001). Additionally, in cultured hippocampal neurons, the increased levels of phosphorylated NR2B and cAMP-response element binding protein (CREB) induced by NMDA stimulation were significantly inhibited by exposure to 1.6 MPa N2-O2. Conclusions: Our findings indicated that NR2B-containing NMDA receptors were inhibited during nitrogen narcosis. [ABSTRACT FROM AUTHOR]

Introduction: While gas narcosis is familiar to most divers conducting deep (> 30 metres) dives, its effects are often considered minuscule or subtle at 30 metres. However, previous studies have shown that narcosis may affect divers at depths usually considered safe from its influence, but little knowledge exists on the effects of gas narcosis on higher cognitive functions such as decision-making in relatively shallow water at 30 metres. Impaired decision-making could be a significant safety issue for a multitasking diver., Methods: We conducted a study exploring the effects of gas narcosis on decision-making in divers breathing compressed air underwater. The divers (n = 22) were evenly divided into 5-metre and 30-metre groups. In the water, we used underwater tablets equipped with the Iowa Gambling Task (IGT), a well-known psychological task used to evaluate impairment in decision-making., Results: The divers at 30 metres achieved a lower score (mean 1,584.5, standard deviation 436.7) in the IGT than the divers at 5 metres (mean 2,062.5, standard deviation 584.1). Age, body mass index, gender, or the number of previous dives did not affect performance in the IGT., Conclusions: Our results suggest that gas narcosis may affect decision-making in scuba divers at 30 metres depth. This supports previous studies showing that gas narcosis is present at relatively shallow depths and shows that it may affect higher cognitive functions., (Copyright: This article is the copyright of the authors who grant Diving and Hyperbaric Medicine a non-exclusive licence to publish the article in electronic and other forms.)

Introduction: Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safety and operations at depth that might be reduced by using enriched air nitrox (EANx) mixtures. Using critical flicker fusion frequency (CFFF), a possible early detection of cognitive abilities/cerebral arousal impairment when breathing different oxygen (O2) fractions was investigated. Methods: Eight male volunteers performed, in random order, two dry chamber dives breathing either air or EANx40 (40% O2-60% nitrogen) for 20 minutes (min) at 0.4 MPa. Cognition and arousal were assessed before the dive; upon arrival at 0.4 MPa; after 15 min exposure at 0.4 MPa; on surfacing and 30 min post-dive using behavioural computer-based testing psychology experiment building language (PEBL) and by CFFF while continuously recording brain oxygenation with near-infrared spectroscopy. Results: In both breathing conditions, CFFF and PEBL demonstrated a significant inverse correlation (Pearson r of -0.90, P < 0.0001), improved cognitive abilities/cerebral arousal occurred upon arrival at 0.4 MPa followed by a progressive deterioration. Initial brain activation was associated with a significant increase in oxyhaemoglobin (HbO2) and a simultaneous decrease of deoxyhaemoglobin (HHb). The magnitude of the changes was significantly greater under EANx (P = 0.038). Conclusions: Since changes were not related to haemodynamic variables, HbO2 and HHb values indicate a significant, O2-dependent activation in the prefrontal cortex. Owing to the correlation with some tests from the PEBL, CFFF could be a convenient measure of cognitive performance/ability in extreme environments, likely under the direct influence of oxygen partial pressure, a potent modulator of IGN symptoms. [ABSTRACT FROM AUTHOR]

Nakajo-Nishimura syndrome (NNS) is an inherited inflammatory and wasting disease caused by a distinct homozygous mutation of the PSMB8 gene, which encodes the β5i subunit of the immunoproteasome. Although NNS was originally reported in Japan more than 70 years ago, related diseases with an overlapping entity, namely joint contractures, muscular atrophy, microcytic anemia and panniculitis-associated lipodystrophy (JMP) syndrome and chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature (CANDLE) syndrome, have recently been reported and these three diseases are now collectively referred to as proteasome-associated autoinflammatory syndromes (PRAAS). Although some distinct characteristics can be pointed out in each disease, most patients with these diseases commonly start to show inflammatory attacks in infancy and, after growing-up, clinically resemble progeria with marked emaciation especially in the upper body. Notably, some NNS cases with premature or sudden death have been reported and cardiac failure was considered to be a major cause of death. Here we report a Japanese male case with NNS, who had received no continuous medication and died of CO2 narcosis (respiratory acidosis) triggered by an acute septic infection in the absence of cardiac failure at 47 years of age. Due to a remarkable lipomuscular atrophy and contracture of the chest wall, CO2 narcosis should be noted as an important complication of NNS/PRAAS, which can develop into premature death. [ABSTRACT FROM AUTHOR]

Purpose: Underwater divers face several potential neurological hazards when breathing compressed gas mixtures including nitrogen narcosis which can impact diver's safety. Various human studies have clearly demonstrated brain impairment due to nitrogen narcosis in divers at 4 ATA using critical flicker fusion frequency (CFFF) as a cortical performance indicator. However, recently some authors have proposed a probable adaptive phenomenon during repetitive exposure to high nitrogen pressure in rats, where they found a reversal effect on dopamine release.Methods: Sixty experienced divers breathing Air, Trimix or Heliox, were studied during an open water dive to a depth of 6 ATA with a square profile testing CFFF measurement before (T0), during the dive upon arriving at the bottom (6 ATA) (T1), 20 min of bottom time (T2), and at 5 m (1.5 ATA) (T3).Results: CFFF results showed a slight increase in alertness and arousal during the deep dive regardless of the gas mixture breathed. The percent change in CFFF values at T1 and T2 differed among the three groups being lower in the air group than in the other groups. All CFFF values returned to basal values 5 min before the final ascent at 5 m (T3), but the Trimix measurements were still slightly better than those at T0.Conclusions: Our results highlight that nitrogen and oxygen alone and in combination can produce neuronal excitability or depression in a dose-related response. [ABSTRACT FROM AUTHOR]

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 (N 2 O) impairs shivering thermogenesis and accelerates body core cooling. Animal-based studies, however, have indicated that repeated and sustained N 2 O administration may prevent N 2 O-evoked hypometabolism. We, therefore, examined the effects of prolonged intermittent exposure to 30% N 2 O 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% N 2 O. 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. N 2 O aggravated the drop in rectal temperature ( P = 0.01), especially during the first (by ∼0.3°C) and third (by ∼0.4°C) CWIs. N 2 O 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, N 2 O attenuated the cold-induced drop in finger ( P ≤ 0.001), but not in forearm CVC. N 2 O 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 N 2 O 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% N 2 O and moderate cold stress. Regardless of the duration of gas exposure, N 2 O-induced narcosis impaired in a persistent manner shivering thermogenesis and thermoperception.

Abstract: Although petroleum hydrocarbons released to the environment typically occur as mixtures, petroleum hydrocarbon remediation guidelines often reflect individual substance toxicity. It is well documented that groups of aliphatic petroleum hydrocarbons act via the same mechanism of action (nonpolar narcosis) and, theoretically, concentration addition mixture toxicity principles apply. To assess this theory, 10 standardized acute and chronic soil invertebrate toxicity tests on a range of organisms (Eisenia fetida, Lumbricus terrestris, Enchytraeus crypticus, Folsomia candida, Oppia nitens, and Hypoaspis aculeifer) were conducted with a refined petroleum hydrocarbon binary mixture. Reference models for concentration addition and independent action were applied to the mixture toxicity data with consideration of synergism, antagonism, and dose level toxicity. Both concentration addition and independent action, without further interactions, provided the best fit with observed response to the mixture. Individual fraction effective concentration values were predicted from optimized, fitted reference models. Concentration addition provided a better estimate than independent action of individual fraction effective concentrations based on comparison with available literature and species trends observed in toxic responses to the mixture. Interspecies differences in standardized laboratory soil invertebrate species responses to petroleum hydrocarbon–contaminated soil was reflected in unique traits. Diets that included soil, large body size, permeable cuticle, low lipid content, lack of ability to molt, and no maternal transfer were traits linked to a sensitive survival response to petroleum hydrocarbon–contaminated soil in laboratory tests. Traits linked to sensitive reproduction response in organisms tested were long life span and small clutch size. By deriving single‐fraction toxicity endpoints considerate of mixtures, we can reduce the resources and time required to conduct site‐specific risk assessments for the protection of a soil organism's exposure pathway. Environ Toxicol Chem 2018;37:2222–2234. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Human beings are exposed to compressed air or a nitrogen-oxygen mixture, they will produce signs and symptoms of nitrogen narcosis such as amnesia or even loss of memory, which may be disappeared once back to the normobaric environment. This study was designed to investigate the effect of nitrogen narcosis induced by repetitive hyperbaric nitrogen-oxygen mixture exposure on long-term cognitive function in newborn mice and the underlying mechanisms. The electroencephalogram frequency was decreased while the amplitude was increased in a pressure-dependent manner during 0.6, 1.2, 1.8 MPa (million pascal) nitrogen-oxygen mixture exposures in adult mice. Nitrogen narcosis in postnatal days 7–9 mice but not in adult mice induced by repetitive hyperbaric exposure prolonged the latency to find the platform and decreased the number of platform-site crossovers during Morris water maze tests, and reduced the time in the center during the open field tests. An increase in the expression of cleaved caspase-3 in the hippocampus and cortex were observed immediately on the first day after hyperbaric exposure, and this lasted for seven days. Additionally, nitrogen narcosis induced loss of the dendritic spines but not of the neurons, which may mainly account for the cognitive dysfunction. Nitrogen narcosis induced long-term cognitive and emotional dysfunction in the postnatal mice but not in the adult mice, which may result from neuronal apoptosis and especially reduction of dendritic spines of neurons. [ABSTRACT FROM AUTHOR]

The detrimental effects on breathing pattern during multiple breath inert gas washout (MBW) have been described with different inhaled gases [100% oxygen (O2) and sulfur hexafluoride (SF6)] but detailed comparisons are lacking. N2- and SF6-based tests were performed during spontaneous quiet sleep in 10 healthy infants aged 0.7-1.3 yr using identical hardware. Differences in breathing pattern pre and post 100% O2 and 4% SF6 exposure were investigated, and the results obtained were compared [functional residual capacity (FRC) and lung clearance index (LCI)]. During 100% O2 exposure. mean inspiratory flow ("respiratory drive") decreased transiently by mean (SD) 28 (9)% (P < 0.001), and end-tidal CO2 (carbon dioxide) increased by mean (SD) 0.3 (0.4)% units (P < 0.05) vs. air breathing prephase. During subsequent N2 washin (i.e., recovery phase), the pattern of change reversed. No significant effect on breathing pattern was observed during SF6 testing. In vitro testing confirmed that technical artifacts did not explain these changes. Mean (SD) FRC and LCI in vivo were significantly higher with N2 vs. SF6 washout: 216 (33) vs. 186 (22) ml (P < 0.001) and 8.25 (0.85) vs. 7.55 (0.57) turnovers (P < 0.021). Based on these results, SF6 based MBW is the preferred methodology for tests in this age range. NEW & NOTEWORTHY Inert gas choice for multiple breath inert gas washout (MBW) in infants has important consequences on both breathing pattern during test performance and the functional residual capacity and lung clearance index values obtained. Data suggest the detrimental effect of breathing pattern of 100% O2 and movement of O2 across the alveolar capillary membrane, with direct effects on MBW outcomes. SF6 MBW during infancy avoids this and can be further optimized by addressing the sources of technical artifact identified in this work. [ABSTRACT FROM AUTHOR]

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.

BACKGROUND: Divers try to limit risks associated with their sport, for instance by breathing enriched air nitrox (EANx) instead of air. This double blinded, randomized trial was designed to see if the use of EANx could effectively improve cognitive performance while diving. METHODS: Eight volunteers performed two no-decompression dry dives breathing air or EANx for 20 min at 0.4 MPa. Cognitive functions were assessed with a computerized test battery, including MathProc and Ptrail. Measurements were taken before the dive, upon arrival and after 15 min at depth, upon surfacing, and at 30 min postdive. After each dive subjects were asked to identify the gas they had just breathed. RESULTS: Identification of the breathing gas was not possible on subjective assessment alone, while cognitive assessments showed significantly better performance while breathing EANx. Before the dives, breathing air, mean time to complete the task was 1795 ms for MathProc and 1905 ms for Ptrail. When arriving at depth MathProc took 1616 ms on air and 1523 ms on EANx, and Ptrail took 1318 ms on air and and 1356 ms on EANx, followed 15 min later by significant performance inhibition while breathing air during the ascent and the postdive phase, supporting the concept of late dive/postdive impairment. DISCUSSION: The results suggest that EANx could protect against decreased neuro-cognitive performance induced by inert gas narcosis. It was not possible for blinded divers to identify which gas they were breathing and differences in postdive fatigue between air and EANx diving deserve further investigation. [ABSTRACT FROM AUTHOR]

This paper reports on a study that investigated the aquatic toxicity of new non-ionic surfactants derived from renewable raw materials, polyoxyethylene glycerol ester (PGE), and their binary mixtures with anionic and non-ionic surfactants. Toxicity of pure PGEs was determined using representative organisms from different trophic levels: luminescent bacteria ( Vibrio fischeri), microalgae ( Pseudokirchneriella subcapitata), and freshwater crustaceans ( Daphnia magna). Relationships between toxicity and the structural parameters such as unit of ethylene oxide (EO) and hydrophilic-lipophilic balance (HLB) were evaluated. Critical micellar concentration (CMC) in the conditions of the toxicity test was also determined. It was found that the toxicity of the aqueous solutions of PGE decreased when the number of EO units in the molecule, HLB, and CMC increased. PGEs showed lower CMC in marine medium, and the toxicity to V. ficheri is lower when the CMC was higher. Given their non-polar nature, narcosis was expected to be the primary mode of toxic action of PGEs. For the mixture of surfactants, we observed that the mixtures with PGE that had the higher numbers of EO units were more toxic than the aqueous solutions of pure surfactants. Moreover, we found that concentration addition was the type of action more likely to occur for mixtures of PGE with lower numbers of EO units with non-ionic surfactants (alkylpolyglucoside and fatty alcohol ethoxylate), whereas for the mixture of PGE with lower EO units and anionic surfactant (ether carboxylic derivative), the most common response type was response addition. In case of mixtures involving amphoteric surfactants and PGEs with the higher numbers of EO units, no clear pattern with regard to the mixture toxicity response type could be observed. [ABSTRACT FROM AUTHOR]

Epigenetic modifications, mediated by DNA methylation, are involved in caste differentiation between queen and worker honey bees, Apis mellifera. This study uses methylation sensitive amplified fragment length polymorphism (MS-AFLP) to investigate whether genome-wide DNA methylation is implicated in the regulation of honey bee worker sterility and whether CO2 narcosis, which suppresses ovary activation in queenless workers, influences DNA methylation. Queenless workers were divided into control and experimental (CO2 narcosis) cages. We compared MS-AFLP patterns in CO2-treated and non-treated workers with and without activated ovaries at 4 h, 2 and 7 days after treatment. While there was evidence of DNA methylation in all samples, there was no detectable difference in genome-wide methylation patterns between any treatment comparisons. This suggests that mechanisms that regulate worker sterility in the adult honey bee worker are not related to genome-wide methylation, and that CO2 narcosis does not significantly affect DNA methylation patterns in the worker ovary. However, because DNA methylation is sparse in the honey bee, and because MS-AFLP detects only a proportion of methylated sites, it remains possible that a subset of genes that are responsible for the regulation of worker sterility are differentially methylated, but that we failed to pick these up in our genome-wide scan. [ABSTRACT FROM AUTHOR]

Although many factors contributing to inert gas narcosis onset and severity have been put forward, the available evidence is not particularly strong. Using objective criteria, we have assessed brain impairment associated with narcosis under various environmental diving conditions. 40 volunteers performed a no-decompression dive (33 m for 20 min) either in a dry chamber, a pool or open sea. They were assessed by critical flicker fusion frequency before the dive, upon arriving at depth, 5 min before ascent, on surfacing and 30 min post-dive. Compared to the pre-dive value, the mean value of each measurement was significantly different. An increase of flicker fusion to 105.00 ±0.69% when arriving at depth is followed by a decrease to 94.05 ±0.65%. This impairment persists when surfacing and 30 min post-dive, decreasing further to 96.36±0.73% and 96.24 ±0.73%, respectively. Intragroup comparison failed to demonstrate any statistical difference. When objectively measured narcosis may not be influenced by external factors other than pressure and gas. This might be of importance for training to avoid any over- or underestimation of the severity of narcosis based only on subjective symptoms. [ABSTRACT FROM AUTHOR]

Introduction: Inert gas narcosis (IGN) impairs cognitive performance and some divers are more susceptible to IGN than others. We compared the sensitivity of two reaction time tests to detect changes in performance at pressure and compared these results with critical flicker fusion frequency (CFF) changes at the same ambient pressures. Methods: The study assessed simple reaction time (RT), mean time correct of the discrimination reaction time (MTC) and CFF in 30 professional divers breathing air at 101 kPa and 608 kPa in a hyperbaric chamber. Results: RT and MTC increased at 608 kPa by 5.1 ± 9.4% (P = 0.04) and 7.3 ± 12.3% (P = 0.01) respectively. RT decreased to pre-compression level after decompression and MTC decreased to a level lower than pre-compression (P < 0.001) values. CFF increased by 2.5 ± 2.8% (P < 0.001) at 608 kPa. CFF decreased to pre-compression level after decompression. An increase in CFF was inversely correlated with a decrease in RT (r = 0.38, P = 0.04) and in MTC (r = 0.43, P = 0.02) at 608 kPa. Conclusions: Response speeds of the same subjects were impaired in both reaction time tasks at 608 kPa, whereas CFF increased at depth. An association between changes in response times and changes in CFF suggests that divers susceptible to IGN may also be susceptible to the effects of elevated oxygen partial pressure. If this holds true, the future selection of professional divers could be improved by the use of simple cognitive tests. [ABSTRACT FROM AUTHOR]

"Cutis Marmorata" skin symptoms after diving, most frequently in the form of an itching or painful cutaneous red-bluish discoloration are commonly regarded as a mild form of decompression sickness (DCS), and treated with oxygen inhalation without reverting to hyperbaric recompression treatment. It has been observed that the occurrence of Cutis Marmorata is frequently associated with the presence of a Patent Foramen Ovale (PFO) of the heart, and indeed, with a properly executed contrast echocardiographic technique, these patients have an almost 100% prevalence of PFO. Only occasionally, Cutis Marmorata is accompanied by other symptoms of DCS. These symptoms usually are in the form of visual distortions, vertigo, or mild, vague but generalized cerebral dysfunction (such as abnormal fatigue, clumsiness, concentration problems). The pathogenesis of these other manifestations is clearly emboligenic, and we hypothesize that Cutis Marmorata is also a manifestation of gas bubbles embolizing the brain stem: the site of autonomic nervous system regulation of skin blood vessel dilation and constriction. The consequences of this hypothesis are that Cutis Marmorata skin decompression sickness should no longer be considered a mild, innocuous form but rather a serious, neurological form and treated accordingly. [ABSTRACT FROM AUTHOR]

Breathing hyperbaric air or gas mixtures, for example during diving or when working underwater is known to alter the electrophysiological behavior of neuronal cells, which may lead to restricted cognition. During the last few decades, only very few studies into hyperbaric effects have been published, especially for the most relevant pressure range of up to 10 bar. We designed a pressurized measuring chamber to record pressure effects on the electrical activity of neuronal networks formed by primary cells of the frontal cortex of NMRI mice. Electrical activity was recorded with multi-electrode arrays (MEAs) of glass neuro chips while subjected to a step-by-step pressure increase from atmospheric pressure (1 bar) to 2 and 4 bar, followed by a decompression to 1 bar, in order to record recovery effects. The effects of pressure on the total spike rates (TSRs), which were averaged from at least 45 chips, were detected in two cell culture media with different compositions. In a DMEM medium with 6% horse serum, the TSR was increased by 19% after a pressure increase to 2 bar and remained stable at 4 bar. In NMEM medium with 2% B27, the TSR was not altered by a pressure increase to 2 bar but increased by 9% at 4 bar. After decompression to 1 bar, the activities decreased to 76% and 101% of their respective control levels in the two media. MEA recordings from neuronal networks in miniaturized hyperbaric measuring chambers provide new access for exploring the neuronal effects of hyperbaric breathing gases. [ABSTRACT FROM AUTHOR]

Exposure to increased ambient pressure causes inert gas narcosis of which one symptom is long-term memory (LTM) impairment. Narcosis is posited to impair LTM by disrupting information encoding, retrieval (self-guided search), or both. The effect of narcosis on the encoding and retrieval of LTM was investigated by testing the effect of learning–recall pressure and levels of processing (LoP) on the free-recall of word lists in divers underwater. All participants (n = 60) took part in four conditions in which words were learnt and then recalled at either low pressure (1.4–1.9 atm/4–9 msw) or high pressure (4.4–5.0 atm/34–40 msw), as manipulated by changes in depth underwater: low–low (LL), low–high(LH), high–high (HH), and high–low (HL). In addition, participants were assigned to either a deep or shallow processing condition, using LoP methodology. Free-recall memory ability was significantly impaired only when words were initially learned at high pressure (HH & HL conditions). When words were learned at low pressure and then recalled at low pressure (LL condition) or high pressure (LH condition) free-recall was not impaired. Although numerically superior in several conditions, deeper processing failed to significantly improve free-recall ability in any of the learning–recall conditions. This pattern of results support the hypothesis that narcosis disrupts encoding of information into LTM, while retrieval appears to be unaffected. These findings are discussed in relation to similar effects reported by some memory impairing drugs and the practical implications for workers in pressurised environments. [ABSTRACT FROM AUTHOR]

The ability of a diver to pass the deep diving course is tested through trials that evaluate the tolerance of a diver to hyperbaric respiratory gases. Three of these tests take place in the hyperbaric chamber in order to highlight the effect of oxygen and inert gases over the diver, during pressurization. These are: the Oxygen test, the Narcosis test and HPNS (High Pressure Nervous Syndrome). If the first two tests are frequently executed, HPNS was resumed and improved at Hyperbaric Complex of Diving Center. Hypothermia is another stress factor in the hyperbaric environment that has been studied and was identified by a series of dives at different depths of immersion in wet simulator of Diving Center. The experimental results were consistent with calculated temperature losses previously established by mathematical model. [ABSTRACT FROM AUTHOR]

Ecotoxicological effect data are generally expressed as effective concentrations in the external exposure medium and do thus not account for differences in chemical uptake, bioavailability, and metabolism, which can introduce substantial data variation. The Critical Body Residue (CBR) concept provides clear advantages, because it links effects directly to the internal exposure. Using CBRs instead of external concentrations should therefore reduce variability. For compounds that act via narcosis even a constant CBR has been proposed. Despite the expected uniformity, CBR values for these compounds still show large variability, possibly due to biased and inconsistent experimental testing. In the present study we tested whether variation in CBR data can be substantially reduced when using an improved experimental design and avoiding confounding factors. The aim was to develop and apply a well-defined test protocol for accurately and precisely measuring CBR data, involving improved (passive) dosing, sampling, and processing of organisms. The chemicals 1,2,4-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 2,3,4-trichloroaniline, 2,3,5,6-tetrachloroaniline, 4-chloro-3-methylphenol, pentylbenzene, pyrene, and bromophos-methyl were tested on Lumbriculus variegatus (California blackworm), Hyalella azteca (scud), and Poecilia reticulata (guppy), which yielded a high-quality database of 348 individual CBR values. Medians of CBR values ranged from 2.1 to 16.1 mmol/kg wet weight (ww) within all combinations of chemicals and species, except for the insecticide bromophos-methyl, for which the median was 1.3 mmol/kg ww. The new database thus covers about one log unit, which is considerably less than in existing databases. Medians differed maximally by a factor of 8.4 between the 7 chemicals but within one species, and by a factor of 2.6 between the three species but for individual chemicals. Accounting for the chemicals' internal distribution to different partitioning domains and relating effects to estimated concentrations in the target compartment (i.e., membrane lipids) was expected to but did not decrease the overall variability, likely because the surrogate partition coefficients for membrane lipid, storage lipid, protein, and carbohydrate that were used as input parameters did not sufficiently represent the actual partitioning processes. The results of this study demonstrate that a well-designed test setup can produce CBR data that are highly uniform beyond chemical and biological diversity. [ABSTRACT FROM AUTHOR]

Nile tilapia,Oreochromis niloticus, is one of the most cultivated fish species in Brazil. However, few studies evaluate how the stunning methods affect the meat quality of this fish. This study evaluates how both stunning methods, iced water and CO2narcosis, affect the quality of tilapia meat that was stored refrigerated in ice (4°C) for up to 26 days. Tilapia stunned by CO2narcosis showed less stress compared to iced water, which was evidenced by the higher ATP, and better meat color as well, evidenced by higher lightness (L*) and lower redness (a*) values. After sensorial analysis, fish were classified as extra-fresh during the first 2 days of storage; as fresh from day 3 to day 14, not fresh from day 15 to day 23; and as spoiled from day 23 onwards. Stunning of tilapia by CO2narcosis can be an alternative to the traditional method of desensitization (iced water) used in Brazil. [ABSTRACT FROM AUTHOR]

It was hypothesized that normoxic 30% nitrous oxide (N 2 O) would suppress and hyperthermia would increase exercise ventilation during short duration, high intensity exercise. Thirteen males (24.2 ± 0.8 y; mean ± SE), of normal physique (BMI, 23.8 ± 1.0 kg m −2 ), performed 4 separate 30 s Wingate tests on a cycle ergometer. Exercise ventilation and its components, as well as mean skin and esophageal temperature ( T ES ), were assessed in 2 way experimental design with factors of Thermal State (Normothermia or Hyperthermia) and Gas Type (Air or 30% Normomoxic N 2 O). In the 2 hyperthermic tests T ES was elevated to ∼38.5 °C in a 40 °C bath. The main results indicated a significant interaction ( F = 7.14, P = 0.02) between Gas Type and Thermal state for the exercise-induced increase in ventilation (Δ V ˙ E ). During both the normothermia and hyperthermia conditions with AIR breathing, the exercise Δ V ˙ E was ∼80 L min −1 and it was significantly decreased to 73.1 ± 24.1 L min −1 in the normothermia condition with N 2 O breathing relative to that of 92.0 ± 25.0 L min −1 in the hyperthermia condition with N 2 O breathing. In conclusion, normoxic N 2 O breathing suppressed high intensity exercise ventilation during normothermia relative to that during hyperthermia on account of decreases in the tidal volume and this led CO 2 retention. [ABSTRACT FROM AUTHOR]

We investigated 105 professional divers using a computerized visual discrimination trial (Cognitrone) to measure the effects of ambient pressure on reaction times. The possible improvement in performance due to practice was anticipated, and the trials were carried out four times prior to pressurization in a hyperbaric chamber. The effect of increased ambient pressure was measured at 6.0 and 1.9 atm abs, and the potential for residual effects was tested after decompression. The results of our study indicate that repeated testing had a systematic influence on the measured time values. The effects of learning, which were independent of diver age, may have independently influenced response times. Exposure to 6.0 atm abs modified the systematic pattern of learning and was associated with increased reaction times. There were also age-related differences in response times associated with exposure to increased ambient pressures. Younger divers were more susceptible to elevated ambient pressure, evidenced by increased response times at 6 atm abs relative to their older colleagues. One out of every four of the younger divers could be considered susceptible to inert gas narcosis (IGN) when an increase of one standard deviation/1SD (>19 %) or more in discrimination reaction time is used as an indicator. IGN susceptibility appears independent of body composition and physical fitness. The slowed response speed experienced at 6.0 atm abs was of short duration and returned to baseline immediately with decompression. Our results suggest that IGN is demonstrated by an impaired learning process and decreased response speed and that some younger divers appear more susceptible. [ABSTRACT FROM AUTHOR]

We encountered 14 fish species in Carei Plain natural protected area, from which 10 were native and 4 were non native. Cobitis elongatoides and Misgurnus fossilis registered the highest frequency of occurrence and percentage abundance. Unlike the studies undertaken before in the region, our data emphasize a distinct aspect of the ichthyofauna, due to the fact that we used a net designed for capturing amphibians. This allowed us to investigate some habitats that are difficult to study with other methods. The species from the area are generally characteristic to small plain rivers, with abundant vegetation and sandy or muddy substratum. The presence of Umbra krameri and Carassius carassius is important, they being native species, characteristic to the habitats from the area. The waters from Carei Plain are man-modified or artificial. Thus the fish assemblages, although with many protected, ecologically or zoogeographically important species cannot present the aspect of the initial communities from the region. Due to the anthropic impact and to the drought from the past decade, it is expected that the ichthyofauna from the region will be even more affected in the future. [ABSTRACT FROM AUTHOR]

Background: The interaction of subjective experiences and objective measures of neuropsychological performance during hyperbaric exposure has received less attention in the literature, in part due to the shortage of available and appropriately standardized measures. Objective: This study aimed to describe the psychometric properties of a modified version of the Subjective High Assessment Scale when used in the hyperbaric context, by exploring internal reliability, factor structure, associations with psychological variables and simple cognitive delayed recall, and the effect of task focus on the recall of subjective experience. Method: Seventy qualified divers completed dry hyperbaric chamber dives to 607.95 kPa, and completed ratings of their subjective experiences. Some also completed a delayed recall task and psychological measures prior to their dives. Results: The scale displayed good internal consistency, with four meaningful factors emerging. It showed some significant but small associations with trait anxiety and transient mood states, and a small to moderate correlation with recall performance. There was no significant effect of task focus on self-report of subjective experiences. Conclusion: The modified scale, renamed the Subjective Narcosis Assessment Scale here, has useful psychometric properties, and promising potential for future use. [ABSTRACT FROM AUTHOR]

Objective: The current study tested whether undersea divers are able to accurately judge their level of memory impairment from inert gas narcosis. Background: Inert gas narcosis causes a number of cognitive impairments, including a decrement in memory ability. Undersea divers may be unable to accurately judge their level of impairment, affecting safety and work performance. Method: In two underwater field experiments, performance decrements on tests of memory at 33 to 42 m were compared with self-ratings of impairment and resolution. The effect of depth (shallow [1-11 m] vs. deep [33-42 m]) was measured on free-recall (Experiment 1; n = 41) and cued-recall (Experiment 2; n = 39) performance, a visual-analogue self-assessment rating of narcotic impairment, and the accuracy of judgements-of-learning (JOLs). Results: Both free- and cued-recall were significantly reduced in deep, compared to shallow, conditions. This decrement was accompanied by an increase in self-assessed impairment. In contrast, resolution (based on JOLs) remained unaffected by depth. The dissociation of memory accuracy and resolution, coupled with a shift in a self-assessment of impairment, indicated that divers were able to accurately judge their decrease in memory performance at depth. Conclusion: These findings suggest that impaired self-assessment and resolution may not actually be a symptom of narcosis in the depth range of 33 to 42 m underwater and that the divers in this study were better equipped to manage narcosis than prior literature suggested. The results are discussed in relation to implications for diver safety and work performance. [ABSTRACT FROM AUTHOR]