Cognitive Deterioration in Moderate and Severe Hypobaric Hypoxia Conditions

Beer, Jeremy; Shender, Barry S.; Chauvin, Daren; Dart, Todd S; Fischer, Joseph

doi:10.3357/amhp.4709.2017

Cited by 24 publications

(17 citation statements)

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“…In the remaining studies, an average of 23% fewer correct responses were recorded at altitudes ranging between 2,440 and 5,500 m (Crowley et al, 1992;Legg et al, 2016;Magg, 1957;Paul & Fraser, 1994). Composite scores on a time-sharing task were lower at 4,300 m, 5,486 m, and 7,620 m compared with sea level (Beer, Shender, Chauvin, Dart, & Fischer, 2017;Beidleman et al, 2017). Risk aversion was reduced at 3,000 m with participants accepting a gamble where the potential gain was 1.7 times the potential loss, compared with acceptance at sea level being only when the gain was 2.4 times the potential loss (Pighin, Bonini, Savadori, Hadjichristidis, & Schena, 2014).…”

Section: Altitude Exposurementioning

confidence: 99%

The Impact of Environmental Stress on Cognitive Performance: A Systematic Review

et al. 2019

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Objective: In this review, we detail the impact of environmental stress on cognitive and military task performance and highlight any individual characteristics or interventions which may mitigate any negative effect. Background: Military personnel are often deployed in regions markedly different from their own, experiencing hot days, cold nights, and trips both above and below sea level. In spite of these stressors, high-level cognitive and operational performance must be maintained. Method: A systematic review of the electronic databases Medline (PubMed), EMBASE (Scopus), PsycINFO, and Web of Science was conducted from inception up to September 2018. Eligibility criteria included a healthy human cohort, an outcome of cognition or military task performance and assessment of an environmental condition. Results: The search returned 113,850 records, of which 124 were included in the systematic review. Thirty-one studies examined the impact of heat stress on cognition; 20 of cold stress; 59 of altitude exposure; and 18 of being below sea level. Conclusion: The severity and duration of exposure to the environmental stressor affects the degree to which cognitive performance can be impaired, as does the complexity of the cognitive task and the skill or familiarity of the individual performing the task. Application: Strategies to improve cognitive performance in extreme environmental conditions should focus on reducing the magnitude of the physiological and perceptual disturbance caused by the stressor. Strategies may include acclimatization and habituation, being well skilled on the task, and reducing sensations of thermal stress with approaches such as head and neck cooling.

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Section: Altitude Exposurementioning

confidence: 99%

The Impact of Environmental Stress on Cognitive Performance: A Systematic Review

et al. 2019

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“…Cognitive impairment may persist for several minutes-to-hours following arterial blood reoxygenation (Phillips et al, 2009(Phillips et al, , 2015Beer et al, 2017;Varis et al, 2019). For example, after 10 min normobaric hypoxia (simulated 20,000 ft), reaction times were impaired during a 10-min recovery (normoxic) period, despite resolution of hypoxaemia within ~1 min (Phillips et al, 2009).…”

Section: Recovery Of Brain Function Following Hypoxiamentioning

confidence: 99%

Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives

Shaw

Cabre²

2021

Front. Physiol.

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Acute hypobaric hypoxia (HH) is a major physiological threat during high-altitude flight and operations. In military aviation, although hypoxia-related fatalities are rare, incidences are common and are likely underreported. Hypoxia is a reduction in oxygen availability, which can impair brain function and performance of operational and safety-critical tasks. HH occurs at high altitude, due to the reduction in atmospheric oxygen pressure. This physiological state is also partially simulated in normobaric environments for training and research, by reducing the fraction of inspired oxygen to achieve comparable tissue oxygen saturation [normobaric hypoxia (NH)]. Hypoxia can occur in susceptible individuals below 10,000 ft (3,048 m) in unpressurised aircrafts and at higher altitudes in pressurised environments when life support systems malfunction or due to improper equipment use. Between 10,000 ft and 15,000 ft (4,572 m), brain function is mildly impaired and hypoxic symptoms are common, although both are often difficult to accurately quantify, which may partly be due to the effects of hypocapnia. Above 15,000 ft, brain function exponentially deteriorates with increasing altitude until loss of consciousness. The period of effective and safe performance of operational tasks following exposure to hypoxia is termed the time-of-useful-consciousness (TUC). Recovery of brain function following hypoxia may also lag beyond arterial reoxygenation and could be exacerbated by repeated hypoxic exposures or hyperoxic recovery. This review provides an overview of the basic physiology and implications of hypoxia for military aviation and discusses the utility of hypoxia recognition training.

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“…Failure to acclimatize due to rapid ascent leads to acute altitude illness such as acute mountain sickness (AMS) ( Hackett and Roach, 2001 ; Bartsch and Swenson, 2013 ; Luks et al, 2017 ). The continuous gain in elevation and prolonged exposure to altitude can lead to adverse neurological consequences ( Basnyat et al, 2004 ; Wilson et al, 2009 ; Strapazzon et al, 2014 ; Phillips et al, 2017 ) and possibly impaired cognitive function although this has not been consistently demonstrated ( Latshang et al, 2013 ; Roach et al, 2014 ; Beer et al, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance

et al. 2018

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Aim: High altitude (HA) hypoxia may affect cognitive performance and sleep quality. Further, vigilance is reduced following sleep deprivation. We investigated the effect on vigilance, actigraphic sleep indices, and their relationships with acute mountain sickness (AMS) during very HA exposure, acclimatization, and re-exposure.Methods: A total of 21 healthy altitude-naive individuals (25 ± 4 years; 13 females) completed 2 cycles of altitude exposure separated by 7 days at low altitude (LA, 520 m). Participants slept at 2900 m and spent the day at HA, (5050 m). We report acute altitude exposure on Day 1 (LA vs. HA1) and after 6 days of acclimatization (HA1 vs. HA6). Vigilance was quantified by reaction speed in the 10-min psychomotor vigilance test reaction speed (PVT-RS). AMS was evaluated using the Environmental Symptoms Questionnaire Cerebral Score (AMS-C score). Nocturnal rest/activity was recorded to estimate sleep duration using actigraphy.Results: In Cycle 1, PVT-RS was slower at HA1 compared to LA (4.1 ± 0.8 vs. 4.5 ± 0.6 s-1, respectively, p = 0.029), but not at HA6 (4.6 ± 0.7; p > 0.05). In Cycle 2, PVT-RS at HA1 (4.6 ± 0.7) and HA6 (4.8 ± 0.6) were not different from LA (4.8 ± 0.6, p > 0.05) and significantly greater than corresponding values in Cycle 1. In both cycles, AMS scores were higher at HA1 than at LA and HA6 (p < 0.05). Estimated sleep durations (TST) at LA, 1st and 5th nights were 431.3 ± 28.7, 418.1 ± 48.6, and 379.7 ± 51.4 min, respectively, in Cycle 1 and they were significantly reduced during acclimatization exposures (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.012; and 1st vs. 5th night, p = 0.054). LA, 1st and 5th nights TST in Cycle 2 were 477.5 ± 96.9, 430.9 ± 34, and 341.4 ± 32.2, respectively, and we observed similar deteriorations in TST as in Cycle 1 (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.001; and 1st vs. 5th night, p < 0.0001). At HA1, subjects who reported higher AMS-C scores exhibited slower PVT-RS (r = -0.56; p < 0.01). Subjects with higher AMS-C scores took longer time to react to the stimuli during acute exposure (r = 0.62, p < 0.01) during HA1 of Cycle 1.Conclusion: Acute exposure to HA reduces the PVT-RS. Altitude acclimatization over 6 days recovers the reaction speed and prevents impairments during subsequent altitude re-exposure after 1 week spent near sea level. However, acclimatization does not lead to improvement in total sleep time during acute and subacute exposures.

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Cognitive Deterioration in Moderate and Severe Hypobaric Hypoxia Conditions

Cited by 24 publications

References 0 publications

The Impact of Environmental Stress on Cognitive Performance: A Systematic Review

The Impact of Environmental Stress on Cognitive Performance: A Systematic Review

Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives

Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance

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