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Beer J, Mojica AJ, Blacker KJ, Dart TS, Morse BG, Sherman PM. Relative Severity of Human Performance Decrements Recorded in Rapid vs. Gradual Decompression. Aerosp Med Hum Perform 2024; 95:353-366. [PMID: 38915160 DOI: 10.3357/amhp.6402.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/26/2024]
Abstract
INTRODUCTION: Cabin decompression presents a threat in high-altitude-capable aircraft. A chamber study was performed to compare effects of rapid (RD) vs. gradual decompression and gauge impairment at altitude with and without hypoxia, as well as to assess recovery.METHODS: There were 12 participants who completed RD (1 s) and Gradual (3 min 12 s) ascents from 2743-7620 m (9000-25000 ft) altitude pressures while breathing air or 100% O₂. Physiological indices included oxygen saturation (SPo₂), heart rate (HR), respiration, end tidal O₂ and CO₂ partial pressures, and electroencephalography (EEG). Cognition was evaluated using SYNWIN, which combines memory, arithmetic, visual, and auditory tasks. The study incorporated ascent rate (RD, gradual), breathing gas (air, 100% O₂) and epoch (ground-level, pre-breathe, ascent-altitude, recovery) as factors.RESULTS: Physiological effects in hypoxic "air" ascents included decreased SPo₂ and end tidal O₂ and CO₂ partial pressures (hypocapnia), with elevated HR and minute ventilation (V˙E); SPo₂ and HR effects were greater after RD (-7.3% lower and +10.0 bpm higher, respectively). HR and V˙E decreased during recovery. SYNWIN performance declined during ascent in air, with key metrics, including composite score, falling further (-75% vs. -50%) after RD. Broad cognitive impairment was not recorded on 100% O₂, nor in recovery. EEG signals showed increased slow-wave activity during hypoxia.DISCUSSION: In hypoxic exposures, RD impaired performance more than gradual ascent. Hypobaria did not comprehensively impair performance without hypoxia. Lingering impairment was not observed during recovery, but HR and V˙E metrics suggested compensatory slowing following altitude stress. Participants' cognitive strategy shifted as hypoxia progressed, with efficiency giving way to "satisficing," redistributing effort to easier tasks.Beer J, Mojica AJ, Blacker KJ, Dart TS, Morse BG, Sherman PM. Relative severity of human performance decrements recorded in rapid vs. gradual decompression. Aerosp Med Hum Perform. 2024; 95(7):353-366.
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Chakravartula S, Thrasher B, Mann J, Chaturbedi A, Han X, Dahan A, Florian J, Strauss D, Li Z. Physiologically based modeling reveals different risk of respiratory depression after fentanyl overdose between adults and children. Clin Transl Sci 2024; 17:e13780. [PMID: 38618722 PMCID: PMC11017203 DOI: 10.1111/cts.13780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 03/01/2024] [Accepted: 03/14/2024] [Indexed: 04/16/2024] Open
Abstract
Despite a rapid increase in pediatric mortality rate from prescription and illicit opioids, there is limited research on the dose-dependent impact of opioids on respiratory depression in children, the leading cause of opioid-associated death. In this article, we extend a previously developed translational model to cover pediatric populations by incorporating age-dependent pharmacokinetic, pharmacodynamic, and physiological changes compared to adults. Our model reproduced previous perioperative clinical findings that adults and children have similar risk of respiratory depression at the same plasma fentanyl concentration when specific endpoints (minute ventilation, CO2 tension in the blood) were used. However, our model points to a potential caveat that, in a perioperative setting, routine use of mechanical ventilation and supplemental oxygen maintained the blood and tissue oxygen partial pressures in patients and prevented the use of oxygen-related endpoints to evaluate the consequences of respiratory depression. In a community setting when such oxygenation procedures are not immediately available, our model suggests that the higher oxygen demand and reduced cerebrovascular reactivity could make children more susceptible to severe hypoxemia and brain hypoxia, even with the same plasma fentanyl concentration as adults. Our work indicates that when developing intervention strategies to protect children from opioid overdose in a community setting, these pediatric-specific factors may need to be considered.
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Affiliation(s)
- Shilpa Chakravartula
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - Bradlee Thrasher
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - John Mann
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - Anik Chaturbedi
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - Xiaomei Han
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - Albert Dahan
- Leiden University Medical CenterLeidenThe Netherlands
| | - Jeffry Florian
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - David Strauss
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
| | - Zhihua Li
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational SciencesCenter for Drug Evaluation and Research, Food and Drug AdministrationSilver SpringMarylandUSA
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Shaw DM, Harrell JW. Integrating physiological monitoring systems in military aviation: a brief narrative review of its importance, opportunities, and risks. ERGONOMICS 2023; 66:2242-2254. [PMID: 36946542 DOI: 10.1080/00140139.2023.2194592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 03/18/2023] [Indexed: 06/18/2023]
Abstract
Military pilots risk their lives during training and operations. Advancements in aerospace engineering, flight profiles, and mission demands may require the pilot to test the safe limits of their physiology. Monitoring pilot physiology (e.g. heart rate, oximetry, and respiration) inflight is in consideration by several nations to inform pilots of reduced performance capacity and guide future developments in aircraft and life-support system design. Numerous challenges, however, prevent the immediate operationalisation of physiological monitoring sensors, particularly their unreliability in the aerospace environment and incompatibility with pilot clothing and protective equipment. Human performance and behaviour are also highly variable and measuring these in controlled laboratory settings do not mirror the real-world conditions pilots must endure. Misleading or erroneous predictive models are unacceptable as these could compromise mission success and lose operator trust. This narrative review provides an overview of considerations for integrating physiological monitoring systems within the military aviation environment.Practitioner summary: Advancements in military technology can conflictingly enhance and compromise pilot safety and performance. We summarise some of the opportunities, limitations, and risks of integrating physiological monitoring systems within military aviation. Our intent is to catalyse further research and technological development.Abbreviations: AGS: anti-gravity suit; AGSM: anti-gravity straining manoeuvre; A-LOC: almost loss of consciousness; CBF: cerebral blood flow; ECG: electrocardiogram; EEG: electroencephalogram; fNIRS: functional near-infrared spectroscopy; G-forces: gravitational forces; G-LOC: gravity-induced loss of consciousness; HR: heart rate; HRV: heart rate variability; LSS: life-support system; NATO: North Atlantic Treaty Organisation; PE: Physiological Episode; PCO2: partial pressure of carbon dioxide; PO2: partial pressure of oxygen; OBOGS: on board oxygen generating systems; SpO2: peripheral blood haemoglobin-oxygen saturation; STANAG: North Atlantic Treaty Organisation Standardisation Agreement; UPE: Unexplained Physiological Episode; WBV: whole body vibration.
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Affiliation(s)
- David M Shaw
- Aviation Medicine Unit, Royal New Zealand Air Force Base Auckland, Auckland, New Zealand
- School of Sport, Exercise and Nutrition, Massey University, Auckland, New Zealand
| | - John W Harrell
- 711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, Dayton, OH, USA
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Bloomfield PM, Fisher JP, Shaw DM, Gant N. Cocoa flavanols protect cognitive function, cerebral oxygenation, and mental fatigue during severe hypoxia. J Appl Physiol (1985) 2023; 135:475-484. [PMID: 37471213 DOI: 10.1152/japplphysiol.00219.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 07/06/2023] [Accepted: 07/06/2023] [Indexed: 07/22/2023] Open
Abstract
We tested the hypothesis that ingestion of cocoa flavanols would improve cognition during acute hypoxia equivalent to 5,500 m altitude (partial pressure of end-tidal oxygen = 45 mmHg). Using placebo-controlled double-blind trials, 12 participants ingested 15 mg·kg-1 of cocoa flavanols 90 min before completing cognitive tasks during normoxia and either poikilocapnic or isocapnic hypoxia (partial pressure of end-tidal carbon dioxide uncontrolled or maintained at the baseline value, respectively). Cerebral oxygenation was measured using functional near-infrared spectroscopy. Overall cognition was impaired by poikilocapnic hypoxia (main effect of hypoxia, P = 0.008). Cocoa flavanols improved a measure of overall cognitive performance by 4% compared with placebo (effect of flavanols, P = 0.033) during hypoxia, indicating a change in performance from "low average" to "average." The hypoxia-induced decrease in cerebral oxygenation was two-fold greater with placebo than with cocoa flavanols (effect of flavanols, P = 0.005). Subjective fatigue was increased by 900% with placebo compared with flavanols during poikilocapnic hypoxia (effect of flavanols, P = 0.004). Overall cognition was impaired by isocapnic hypoxia (effect of hypoxia, P = 0.001) but was not improved by cocoa flavanols (mean improvement = 1%; effect of flavanols, P = 0.72). Reaction time was impaired by 8% with flavanols during normoxia and further impaired by 11% during isocapnic hypoxia (effect of flavanols, P = 0.01). Our findings are the first to show that flavanol-mediated improvements in cognition and mood during normoxia persist during severe oxygen deprivation, conferring a neuroprotective effect.NEW & NOTEWORTHY We show for the first time that cocoa flavanols exert a neuroprotective effect during severe hypoxia. Following acute cocoa flavanol ingestion, we observed improvements in cognition, cerebral oxygenation, and subjective fatigue during normoxia and severe poikilocapnic hypoxia. Cocoa flavanols did not improve cognition during severe isocapnic hypoxia, suggesting a possible interaction with carbon dioxide.
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Affiliation(s)
- Peter M Bloomfield
- Exercise Neurometabolism Laboratory, University of Auckland, Auckland, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical & Health Sciences, Manaaki Mānawa - The Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - David M Shaw
- Aviation Medicine Unit, Royal New Zealand Air Force Base Auckland, Whenuapai, Auckland, New Zealand
| | - Nicholas Gant
- Exercise Neurometabolism Laboratory, University of Auckland, Auckland, New Zealand
- Centre for Brain Research, University of Auckland, Auckland, New Zealand
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Bloomfield PM, Green H, Fisher JP, Gant N. Carbon dioxide protects simulated driving performance during severe hypoxia. Eur J Appl Physiol 2023:10.1007/s00421-023-05151-1. [PMID: 36952086 DOI: 10.1007/s00421-023-05151-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 01/31/2023] [Indexed: 03/24/2023]
Abstract
PURPOSE We sought to determine the effect of acute severe hypoxia, with and without concurrent manipulation of carbon dioxide (CO2), on complex real-world psychomotor task performance. METHODS Twenty-one participants completed a 10-min simulated driving task while breathing room air (normoxia) or hypoxic air (PETO2 = 45 mmHg) under poikilocapnic, isocapnic, and hypercapnic conditions (PETCO2 = not manipulated, clamped at baseline, and clamped at baseline + 10 mmHg, respectively). Driving performance was assessed using a fixed-base motor vehicle simulator. Oxygenation in the frontal cortex was measured using functional near-infrared spectroscopy. RESULTS Speed limit exceedances were greater during the poikilocapnic than normoxic, hypercapnic, and isocapnic conditions (mean exceedances: 8, 4, 5, and 7, respectively; all p ≤ 0.05 vs poikilocapnic hypoxia). Vehicle speed was greater in the poikilocapnic than normoxic and hypercapnic conditions (mean difference: 0.35 km h-1 and 0.67 km h-1, respectively). All hypoxic conditions similarly decreased cerebral oxyhaemoglobin and increased deoxyhaemoglobin, compared to normoxic baseline, while total hemoglobin remained unchanged. CONCLUSIONS These findings demonstrate that supplemental CO2 can confer a neuroprotective effect by offsetting impairments in complex psychomotor task performance evoked by severe poikilocapnic hypoxia; however, differences in performance are unlikely to be linked to measurable differences in cerebral oxygenation.
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Affiliation(s)
- Peter Michael Bloomfield
- Exercise Neurometabolism Laboratory, University of Auckland, Building 907, 368 Khyber Pass Road, Newmarket, Auckland, 1023, New Zealand
| | - Hayden Green
- Exercise Neurometabolism Laboratory, University of Auckland, Building 907, 368 Khyber Pass Road, Newmarket, Auckland, 1023, New Zealand
| | - James P Fisher
- Department of Physiology, Faculty of Medical and Health Sciences, Manaaki Mānawa-The Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Nicholas Gant
- Exercise Neurometabolism Laboratory, University of Auckland, Building 907, 368 Khyber Pass Road, Newmarket, Auckland, 1023, New Zealand.
- Centre for Brain Research, University of Auckland, Auckland, New Zealand.
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Beer J, Morse B, Dart T, Adler S, Sherman P. Lingering Altitude Effects During Piloting and Navigation in a Synthetic Cockpit. Aerosp Med Hum Perform 2023; 94:135-141. [PMID: 36829284 DOI: 10.3357/amhp.6149.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
INTRODUCTION: A study was performed to evaluate a cockpit flight simulation suite for measuring moderate altitude effects in a limited subject group. Objectives were to determine whether the apparatus can detect subtle deterioration, record physiological processes throughout hypobaric exposure, and assess recovery.METHODS: Eight subjects trained to perform precision instrument control (PICT) flight and unusual attitude recovery (UAR) and completed chamber flights dedicated to the PICT and UAR, respectively. Each flight comprised five epochs, including ground level pressure (GLP), ascent through altitude plateaus at 10,000, 14,000, and 17,500 ft (3050, 4270, and 5338 m), then postexposure recovery. PICT performance was assessed using control error (FSE) and time-out-of-bounds (TOOB) when pilots exited the flight corridor. UARs were assessed using response times needed to initiate correction and to achieve wings-level attitude. Physiological indices included Spo₂, heart rate (HR), end tidal O₂ and CO₂ pressures, and respiration metrics.RESULTS: Seven subjects completed both flights. PICT performance deteriorated at altitude: FSE increased 33% at 17,513 ft and 21% in Recovery vs. GLP. Mean TOOB increased from 11 s at GLP to 60 s in Recovery. UAR effects were less clear, with some evidence of accelerated responses during and after ascent.CONCLUSIONS: The test paradigm was shown to be effective; piloting impairment was detected during and after exposure. Physiological channels recorded a combination of hypoxia, elevated ventilation, and hypocapnia during ascent, followed by respiratory slowing in recovery. Findings indicate precision piloting and respiration are subject to changes during moderate altitude exposure and may remain altered after Spo₂ recovers, and changes may be linked to hypocapnia.Beer J, Morse B, Dart T, Adler S, Sherman P. Lingering altitude effects during piloting and navigation in a synthetic cockpit. Aerosp Med Hum Perform. 2023; 94(3):135-141.
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Fujimoto T, Dobashi K, Fujii N, Matsutake R, Nishiyasu T. Hypocapnia attenuates local skin thermal perception to innocuous warm and cool stimuli in normothermic resting humans. Am J Physiol Regul Integr Comp Physiol 2023; 324:R120-R127. [PMID: 36534588 DOI: 10.1152/ajpregu.00126.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
When one is exposed to a stressful situation in their daily life, a common response is hyperventilation. Although the physiological significance of stress-induced hyperventilation remains uncertain, this response may blunt perception of the stress-inducing stimulus. This study examined the effects of voluntary hyperventilation and resultant hypocapnia on the local skin thermal detection threshold in normothermic resting humans. Local skin thermal detection thresholds were measured in 15 young adults (three females) under three breathing conditions: 1) spontaneous breathing (Control trial), 2) voluntary hypocapnic hyperventilation (HH trial), and 3) voluntary normocapnic hyperventilation (NH trial). Local skin thermal detection thresholds were measured using thermostimulators containing a Peltier element that were attached to the forearm and forehead. The temperature of the probe was initially equilibrated to the skin temperature, then gradually increased or decreased at a constant rate (±0.1 °C/s) until the participants felt warmth or coolness. The difference between the initial skin temperature and the local skin temperature at which the participant noticed warmth/coolness was assessed as an index of the local skin warm/cool detection threshold. Local detection of warm and cool stimuli did not differ between the Control and NH trials, but it was blunted in the HH trial as compared with the Control and NH trials, except for detection of warm stimuli on the forearm. These findings suggest that hyperventilation-induced hypocapnia, not hyperventilation per se, attenuates local skin thermal perception, though changes in responses to warm stimuli may not be clearly perceived at some skin areas (e.g., forearm).
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Affiliation(s)
- Tomomi Fujimoto
- Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan.,Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan
| | - Kohei Dobashi
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.,Faculty of Education, Hokkaido University of Education, Asahikawa, Japan
| | - Naoto Fujii
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.,Advanced Research Initiative for Human High Performance (ARIHHP), University of Tsukuba, Tsukuba, Japan
| | - Ryoko Matsutake
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan
| | - Takeshi Nishiyasu
- Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.,Advanced Research Initiative for Human High Performance (ARIHHP), University of Tsukuba, Tsukuba, Japan
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Fabries P, Gomez-Merino D, Sauvet F, Malgoyre A, Koulmann N, Chennaoui M. Sleep loss effects on physiological and cognitive responses to systemic environmental hypoxia. Front Physiol 2022; 13:1046166. [PMID: 36579023 PMCID: PMC9792101 DOI: 10.3389/fphys.2022.1046166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/29/2022] [Indexed: 12/15/2022] Open
Abstract
In the course of their missions or training, alpinists, but also mountain combat forces and mountain security services, professional miners, aircrew, aircraft and glider pilots and helicopter crews are regularly exposed to altitude without oxygen supplementation. At altitude, humans are exposed to systemic environmental hypoxia induced by the decrease in barometric pressure (<1,013 hPa) which decreases the inspired partial pressure of oxygen (PIO2), while the oxygen fraction is constant (equal to approximately 20.9%). Effects of altitude on humans occur gradually and depend on the duration of exposure and the altitude level. From 1,500 m altitude (response threshold), several adaptive responses offset the effects of hypoxia, involving the respiratory and the cardiovascular systems, and the oxygen transport capacity of the blood. Fatigue and cognitive and sensory disorders are usually observed from 2,500 m (threshold of prolonged hypoxia). Above 3,500 m (the threshold for disorders), the effects are not completely compensated and maladaptive responses occur and individuals develop altitude headache or acute altitude illness [Acute Mountain Sickness (AMS)]. The magnitude of effects varies considerably between different physiological systems and exhibits significant inter-individual variability. In addition to comorbidities, the factors of vulnerability are still little known. They can be constitutive (genetic) or circumstantial (sleep deprivation, fatigue, speed of ascent.). In particular, sleep loss, a condition that is often encountered in real-life settings, could have an impact on the physiological and cognitive responses to hypoxia. In this review, we report the current state of knowledge on the impact of sleep loss on responses to environmental hypoxia in humans, with the aim of identifying possible consequences for AMS risk and cognition, as well as the value of behavioral and non-pharmacological countermeasures.
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Affiliation(s)
- Pierre Fabries
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France,*Correspondence: Pierre Fabries,
| | - Danielle Gomez-Merino
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
| | - Fabien Sauvet
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
| | - Alexandra Malgoyre
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France
| | - Nathalie Koulmann
- Laboratoire de Biologie de l’Exercice pour la Performance et la Santé (LBEPS), UMR, Université Paris-Saclay, IRBA, Evry-Courcouronnes, France,French Military Health Academy—Ecole du Val-de-Grâce, Place Alphonse Laveran, Paris, France
| | - Mounir Chennaoui
- REF-Aero Department, French Armed Forces Biomedical Research Institute—IRBA, Brétigny-sur-Orge, France,Vigilance Fatigue Sommeil et Santé Publique (VIFASOM) URP 7330, Université de Paris Cité, Paris, France
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Rogan M, Friend AT, Rossetti GM, Edden R, Mikkelsen M, Oliver SJ, Macdonald JH, Mullins PG. Hypoxia alters posterior cingulate cortex metabolism during a memory task: A 1H fMRS study. Neuroimage 2022; 260:119397. [PMID: 35752413 PMCID: PMC9513808 DOI: 10.1016/j.neuroimage.2022.119397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 06/16/2022] [Indexed: 11/16/2022] Open
Abstract
Environmental hypoxia (fraction of inspired oxygen (FIO2) ∼ 0.120) is known to trigger a global increase in cerebral blood flow (CBF). However, regionally, a heterogeneous response is reported, particularly within the posterior cingulate cortex (PCC) where decreased CBF is found after two hours of hypoxic exposure. Furthermore, hypoxia reverses task-evoked BOLD signals within the PCC, and other regions of the default mode network, suggesting a reversal of neurovascular coupling. An alternative explanation is that the neural architecture supporting cognitive tasks is reorganised. Therefore, to confirm if this previous result is neural or vascular in origin, a measure of neural activity that is not haemodynamic-dependant is required. To achieve this, we utilised functional magnetic resonance spectroscopy to probe the glutamate response to memory recall in the PCC during normoxia (FIO2 = 0.209) and after two hours of poikilocapnic hypoxia (FIO2 = 0.120). We also acquired ASL-based measures of CBF to confirm previous findings of reduced CBF within the PCC in hypoxia. Consistent with previous findings, hypoxia induced a reduction in CBF within the PCC and other regions of the default mode network. Under normoxic conditions, memory recall was associated with an 8% increase in PCC glutamate compared to rest (P = 0.019); a change which was not observed during hypoxia. However, exploratory analysis of other neurometabolites showed that PCC glucose was reduced during hypoxia compared to normoxia both at rest (P = 0.039) and during the task (P = 0.046). We conclude that hypoxia alters the activity-induced increase in glutamate, which may reflect a reduction in oxidative metabolism within the PCC. The reduction in glucose in hypoxia reflects continued metabolism, presumably by non-oxidative means, without replacement of glucose due to reduced CBF.
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Affiliation(s)
- Matthew Rogan
- School of Human and Behavioural Sciences, Bangor University, Bangor, United Kingdom; The Bangor Imaging Unit, Bangor University, Bangor, United Kingdom; Institute for Applied Human Physiology, Bangor University, Bangor, United Kingdom
| | - Alexander T Friend
- School of Human and Behavioural Sciences, Bangor University, Bangor, United Kingdom; Institute for Applied Human Physiology, Bangor University, Bangor, United Kingdom
| | - Gabriella Mk Rossetti
- Centre for Integrative Neuroscience and Neurodynamics, University of Reading, Reading, United Kingdom
| | - Richard Edden
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States; F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States
| | - Mark Mikkelsen
- Department of Radiology, Weill Cornell Medicine, New York, NY, United States
| | - Samuel J Oliver
- School of Human and Behavioural Sciences, Bangor University, Bangor, United Kingdom; Institute for Applied Human Physiology, Bangor University, Bangor, United Kingdom
| | - Jamie H Macdonald
- School of Human and Behavioural Sciences, Bangor University, Bangor, United Kingdom; Institute for Applied Human Physiology, Bangor University, Bangor, United Kingdom
| | - Paul G Mullins
- School of Human and Behavioural Sciences, Bangor University, Bangor, United Kingdom; The Bangor Imaging Unit, Bangor University, Bangor, United Kingdom; Institute for Applied Human Physiology, Bangor University, Bangor, United Kingdom.
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Varis N, Leinonen A, Parkkola K, Leino TK. Hyperventilation and Hypoxia Hangover During Normobaric Hypoxia Training in Hawk Simulator. Front Physiol 2022; 13:942249. [PMID: 35910556 PMCID: PMC9326353 DOI: 10.3389/fphys.2022.942249] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 06/24/2022] [Indexed: 11/25/2022] Open
Abstract
Introduction: In military aviation during high-altitude operations, an oxygen or cabin pressure emergency can impair brain function and performance. There are variations in individuals’ physiological responses to low partial pressure of oxygen and hypoxia symptoms can vary from one exposure to another. The aim of this study was to evaluate how normobaric hypoxia (NH) affects pilots’ minute ventilation and 10 min afterwards on Instrument Landing System (ILS) flight performance in Hawk simulator during a tactical flight sortie. Methods: Fifteen volunteer fighter pilots from the Finnish Air Force participated in this double blinded, placebo controlled and randomized study. The subjects performed three flights in a tactical Hawk simulator in a randomized order with full flight gear, regulators and masks on. In the middle of the flight without the subjects’ knowledge, 21% (control), 8% or 6% oxygen in nitrogen was turned on. Minute ventilation (VE) was measured before, during NH and after NH. Forehead peripheral oxygen saturation (SpO2), wireless ECG and subjective symptoms were documented. The flights were conducted so that both subjects and flight instructors were blinded to the gas mixture. The pilots performed tactical maneuvers at simulated altitude of 20,000 ft or 26,000 ft until they recognized the symptoms of hypoxia. Thereafter they performed hypoxia emergency procedures with 100% oxygen and returned to base (RTB). During the ILS approach, flight performance was evaluated. Results: The mean VE increased during NH from 12.9 L/min (21% O2 on the control flight) to 17.8 L/min with 8% oxygen (p < 0.01), and to 21.0 L/min with 6% oxygen (p < 0.01). Ten minutes after combined hyperventilation and hypoxia, the ILS flight performance decreased from 4.4 (control flight) to 4.0 with 8% oxygen (p = 0.16) and to 3.2 with 6% oxygen (p < 0.01). A significant correlation (r = -0.472) was found between the subjects’ VE during 6% oxygen exposure and the ILS flight performance. Discussion: Hyperventilation during NH has a long-lasting and dose-dependent effect on the pilot’s ILS flight performance, even though the hypoxia emergency procedures are executed 10 min earlier. Hyperventilation leads to body loss of carbon dioxide and hypocapnia which may even worsen the hypoxia hangover.
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Affiliation(s)
- Nikke Varis
- Faculty of Medicine and Health Technology Tampere University, Tampere, Finland
- *Correspondence: Nikke Varis,
| | - Antti Leinonen
- School of Medicine University of Eastern Finland, Kuopio, Finland
| | - Kai Parkkola
- Faculty of Medicine and Health Technology Tampere University, Tampere, Finland
- National Defense University, Helsinki, Finland
| | - Tuomo K. Leino
- National Defense University, Helsinki, Finland
- Aeromedical Centre Centre for Military Medicine, Helsinki, Finland
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Marine Survival in the Mediterranean: A Pilot Study on the Cognitive and Cardiorespiratory Response to Sudden Cool Water Immersion. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19031601. [PMID: 35162622 PMCID: PMC8834950 DOI: 10.3390/ijerph19031601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 01/11/2022] [Accepted: 01/19/2022] [Indexed: 02/05/2023]
Abstract
Background and Aim: The Mediterranean is one of the major gateways of human migratory fluxes from Northern Africa, the Middle East, and Central Asia to Europe. Sea accidents have become an urgent humanitarian crisis due to the high number of migrants on the move, but data on the physiological effects to sudden cool water immersion are not as extensive as cold-water studies. We wanted to evaluate to what extent cool water immersion (~18 °C) may detrimentally affect cognitive ability and cardiorespiratory strain compared to the more prevalent cold-water (<10–15 °C) studies. Methods: In this case, 10 active, healthy men participated in this study which consisted of completing one familiarization trial, and then a control (CON) or experimental (EXP) trial in a randomized, repeated-measures, cross-over fashion, separated by at least 7-days. Cognitive function was assessed via the Symbol Digit Modalities Test (SDMT), a code substitution test, performed at baseline, then repeated in either a thermoneutral (~25 °C room air) dry environment, or when immersed to the neck in 18 °C water. Testing consisted of six “Step” time-blocks 45-s each, with a 5-s pause between each Step. Cardiorespiratory measures, continuously recorded, included heart rate (beats per minute), minute ventilation (V˙E, L∙min−1), oxygen consumption (V˙O2, L∙min−1), and respiratory frequency (fR, count∙min−1). Results: Initial responses to cool water (<2 min) found that participants performed ~11% worse on the code substitution test (p = 0.025), consumed 149% greater amounts of oxygen (CI: 5.1 to 9.1 L∙min−1, p < 0.0001) and experienced higher cardiovascular strain (HR CI: 13 to 38 beats per minute, p = 0.001) than during the control trial. Physiological strain was in-line to those observed in much colder water temperature. Conclusion: Sudden, cool water immersion also negatively affects cognitive function and cardiorespiratory strain, especially during the first two minutes of exposure. The magnitude increase in heart rate is strongly associated with poorer cognitive function, even in (relatively) warmer water consistent with temperatures found in the Mediterranean Sea environment.
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Schultz Martins R, Wallace PJ, Steele SW, Scott JS, Taber MJ, Hartley GL, Cheung SS. The Clamping of End-Tidal Carbon Dioxide Does Not Influence Cognitive Function Performance During Moderate Hyperthermia With or Without Skin Temperature Manipulation. Front Psychol 2021; 12:788027. [PMID: 35002880 PMCID: PMC8730541 DOI: 10.3389/fpsyg.2021.788027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/26/2021] [Indexed: 11/13/2022] Open
Abstract
Increases in body temperature from heat stress (i.e., hyperthermia) generally impairs cognitive function across a range of domains and complexities, but the relative contribution from skin versus core temperature changes remains unclear. Hyperthermia also elicits a hyperventilatory response that decreases the partial pressure of end-tidal carbon dioxide (PetCO2) and subsequently cerebral blood flow that may influence cognitive function. We studied the role of skin and core temperature along with PetCO2 on cognitive function across a range of domains. Eleven males completed a randomized, single-blinded protocol consisting of poikilocapnia (POIKI, no PetCO2 control) or isocapnia (ISO, PetCO2 maintained at baseline levels) during passive heating using a water-perfused suit (water temperature ~ 49°C) while middle cerebral artery velocity (MCAv) was measured continuously as an index of cerebral blood flow. Cognitive testing was completed at baseline, neutral core-hot skin (37.0 ± 0.2°C-37.4 ± 0.3°C), hot core-hot skin (38.6 ± 0.3°C-38.7 ± 0.2°C), and hot core-cooled skin (38.5 ± 0.3°C-34.7 ± 0.6°C). The cognitive test battery consisted of a detection task (psychomotor processing), 2-back task (working memory), set-shifting and Groton Maze Learning Task (executive function). At hot core-hot skin, poikilocapnia led to significant (both p < 0.05) decreases in PetCO2 (∆−21%) and MCAv (∆−26%) from baseline, while isocapnia clamped PetCO2 (∆ + 4% from baseline) leading to a significantly (p = 0.023) higher MCAv (∆−18% from baseline) compared to poikilocapnia. There were no significant differences in errors made on any task (all p > 0.05) irrespective of skin temperature or PetCO2 manipulation. We conclude that neither skin temperature nor PetCO2 maintenance significantly alter cognitive function during passive hyperthermia.
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Affiliation(s)
- Ricardo Schultz Martins
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Phillip J. Wallace
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Scott W. Steele
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Jake S. Scott
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Michael J. Taber
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
- NM Consulting Inc., St. Catharines, ON, Canada
| | - Geoffrey L. Hartley
- Department of Physical and Health Education, Nipissing University, North Bay, ON, Canada
| | - Stephen S. Cheung
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
- *Correspondence: Stephen S. Cheung,
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Johnson MA, Sharpe GR, Needham RS, Williams NC. Effects of Prior Voluntary Hyperventilation on the 3-min All-Out Cycling Test in Men. Med Sci Sports Exerc 2021; 53:1482-1494. [PMID: 33481485 DOI: 10.1249/mss.0000000000002608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
INTRODUCTION The ergogenic effects of respiratory alkalosis induced by prior voluntary hyperventilation (VH) are controversial. This study examined the effects of prior VH on derived parameters from the 3-min all-out cycling test (3MT). METHODS Eleven men ( = 46 ± 8 mL·kg-1·min-1) performed a 3MT preceded by 15 min of rest (CONT) or VH ( = 38 ± 5 L·min-1) with PETCO2 reduced to 21 ± 1 mm Hg (HYP). End-test power (EP; synonymous with critical power) was calculated as the mean power output over the last 30 s of the 3MT, and the work done above EP (WEP; synonymous with W') was calculated as the power-time integral above EP. RESULTS At the start of the 3MT, capillary blood PCO2 and [H+] were lower in HYP (25.2 ± 3.0 mm Hg, 27.1 ± 2.6 nmol·L-1) than CONT (43.2 ± 2.0 mm Hg, 40.0 ± 1.5 nmol·L-1) (P < 0.001). At the end of the 3MT, blood PCO2 was still lower in HYP (35.7 ± 5.4 mm Hg) than CONT (40.6 ± 5.0 mm Hg) (P < 0.001). WEP was 10% higher in HYP (19.4 ± 7.0 kJ) than CONT (17.6 ± 6.4 kJ) (P = 0.006), whereas EP was 5% lower in HYP (246 ± 69 W) than CONT (260 ± 74 W) (P = 0.007). The ΔWEP (J·kg-1) between CONT and HYP correlated positively with the PCO2 immediately before the 3MT in HYP (r = 0.77, P = 0.006). CONCLUSION These findings suggest that acid-base changes elicited by prior VH increase WEP but decrease EP during the all-out 3MT.
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Affiliation(s)
- Michael A Johnson
- Exercise and Health Research Group, Sport, Health and Performance Enhancement (SHAPE) Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, UNITED KINGDOM
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14
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Shaw DM, Cabre G, Gant N. Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives. Front Physiol 2021; 12:665821. [PMID: 34093227 PMCID: PMC8171399 DOI: 10.3389/fphys.2021.665821] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 04/22/2021] [Indexed: 01/04/2023] Open
Abstract
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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Affiliation(s)
- David M Shaw
- Aviation Medicine Unit, Royal New Zealand Air Force Base Auckland, Auckland, New Zealand.,School of Sport, Exercise and Nutrition, Massey University, Auckland, New Zealand
| | - Gus Cabre
- Aviation Medicine Unit, Royal New Zealand Air Force Base Auckland, Auckland, New Zealand
| | - Nicholas Gant
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand
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Friend AT, Rogan M, Rossetti GMK, Lawley JS, Mullins PG, Sandoo A, Macdonald JH, Oliver SJ. Bilateral regional extracranial blood flow regulation to hypoxia and unilateral duplex ultrasound measurement error. Exp Physiol 2021; 106:1535-1548. [PMID: 33866627 DOI: 10.1113/ep089196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 04/14/2021] [Indexed: 02/05/2023]
Abstract
NEW FINDINGS What is the central question of this study? Is blood flow regulation to hypoxia different between the internal carotid arteries (ICAs) and vertebral arteries (VAs), and what is the measurement error in unilateral extracranial artery assessments compared to bilateral? What is the main finding and its importance? ICA and VA blood flow regulation to hypoxia is comparable when factoring for vessel type and vessel side. Compared to bilateral assessment, vessels assessed unilaterally had individual measurement errors of up to 37%. Assessing the vessel with the larger resting blood flow, not the left or right vessel, reduces unilateral measurement error. ABSTRACT Whether blood flow regulation to hypoxia is similar between left and right internal carotid arteries (ICAs) and vertebral arteries (VAs) is unclear. Extracranial blood flow is regularly calculated by doubling a unilateral assessment; however, lateral artery differences may lead to measurement error. This study aimed to determine extracranial blood flow regulation to hypoxia when factoring for vessel type (ICAs or VAs) and vessel side (left or right) effects, and to investigate unilateral assessment measurement error compared to bilateral assessment. In a repeated-measures crossover design, extracranial arteries of 44 participants were assessed bilaterally by duplex ultrasound during 90 min of normoxic and poikilocapnic hypoxic (12.0% fraction of inspired oxygen) conditions. Linear mixed model analyses revealed no Condition × Vessel Type × Vessel Side interaction for blood flow, vessel diameter and flow velocity (all P > 0.05) indicating left and right ICA and VA blood flow regulation to hypoxia was similar. Bilateral hypoxic reactivity was comparable (ICAs, 1.4 (1.0) vs. VAs, 1.7 (1.1) Δ%·Δ S p O 2 -1 ; P = 0.12). Compared to bilateral assessment, unilateral mean measurement error of the relative blood flow response to hypoxia was up to 5%, but individual errors reached 37% and were greatest in ICAs and VAs with the smaller resting blood flow due to a ratio-scaling problem. In conclusion, left and right ICA and VA regulation to hypoxia is comparable when factoring for vessel type and vessel side. Assessing the ICA and VA vessels with the larger resting blood flow, not the left or right vessel, reduces unilateral measurement error.
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Affiliation(s)
- Alexander T Friend
- Extremes Research Group, School of Sport, Health and Exercise Sciences, College of Human Sciences, Bangor University, Bangor, UK
| | - Matthew Rogan
- Bangor Imaging Unit, School of Psychology, College of Human Sciences, Bangor University, Bangor, UK
| | - Gabriella M K Rossetti
- Extremes Research Group, School of Sport, Health and Exercise Sciences, College of Human Sciences, Bangor University, Bangor, UK.,Centre for Integrative Neuroscience and Neurodynamics, School of Psychology and Clinical Language Sciences, University of Reading, Reading, UK
| | - Justin S Lawley
- Department of Sport Science, Division of Physiology, University of Innsbruck, Innsbruck, Austria
| | - Paul G Mullins
- Bangor Imaging Unit, School of Psychology, College of Human Sciences, Bangor University, Bangor, UK
| | - Aamer Sandoo
- Extremes Research Group, School of Sport, Health and Exercise Sciences, College of Human Sciences, Bangor University, Bangor, UK
| | - Jamie H Macdonald
- Extremes Research Group, School of Sport, Health and Exercise Sciences, College of Human Sciences, Bangor University, Bangor, UK
| | - Samuel J Oliver
- Extremes Research Group, School of Sport, Health and Exercise Sciences, College of Human Sciences, Bangor University, Bangor, UK
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Connolly DM, Lee VM, McGown AS, Green NDC. Hypoxia-Like Events in UK Typhoon Aircraft from 2008 to 2017. Aerosp Med Hum Perform 2021; 92:257-264. [PMID: 33752789 DOI: 10.3357/amhp.5719.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
INTRODUCTION: Recent reports of in-flight, hypoxia-like events have prompted concern that aircraft life support systems (LSS) may not always provide effective altitude protection. An analysis was undertaken of hypoxia-like incidents reported in a UK front-line combat aircraft.METHODS: A search of the UK Aviation Safety Information Management System database identified all Typhoon Defense Air Safety Occurrence Reports (DASORs) notifying in-flight symptoms over the decade 20082017. Qualitative analysis focused on the event narrative, altitude profile, timeline, symptom description, sortie characteristics, LSS function, postflight engineering investigation, and training implications. The plausibility and likelihood of hypobaric hypoxia were assessed, and the probable cause of symptoms ascribed.RESULTS: There were 18 DASORs with notified symptoms of suspected in-flight hypoxia, 13 in solo pilots and 5 reports of symptoms affecting 7 of 10 aircrew in 2-seat aircraft. Two cases of probable hypoxia comprised one oxygen bottle failure and one mask-off cabin depressurization. In one report, hypoxia was assessed as plausible but unlikely, following birdstrike with failure of cabin pressurization during climb. Symptoms were explained by hyperventilation in 13 cases (65%) and twice by minor constitutional upset. Suspected hypoxia was managed by immediate selection of emergency oxygen and expedited descent in 10 of 18 occurrences (56%).CONCLUSIONS: Only 2 cases of probable hypoxia have been reported in over 150,000 Typhoon flying hours. The Typhoon LSS has provided effective altitude protection including during cases of cabin depressurization. Symptom occurrences in Typhoon are idiosyncratic and unrelated; hyperventilation probably accounts for two-thirds of reports.Connolly DM, Lee VM, McGown AS, Green NDC. Hypoxia-like events in UK Typhoon aircraft from 2008 to 2017. Aerosp Med Hum Perform. 2021; 92(4):257264.
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Duffin J, Hare GM, Fisher JA. A mathematical model of cerebral blood flow control in anaemia and hypoxia. J Physiol 2020; 598:717-730. [DOI: 10.1113/jp279237] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 12/02/2019] [Indexed: 12/21/2022] Open
Affiliation(s)
- James Duffin
- Departments of Anaesthesia and PhysiologyUniversity of Toronto Toronto Ontario Canada
- Thornhill Research Inc. Toronto Ontario Canada
| | - Gregory M.T Hare
- Departments of Anaesthesia and PhysiologyUniversity of Toronto Toronto Ontario Canada
- Department of AnesthesiaKeenan Research Centre for Biomedical Science and Li Ka Shing Knowledge Institute of St Michael's HospitalUnity Health Toronto Toronto Ontario Canada
| | - Joseph A. Fisher
- Departments of Anaesthesia and PhysiologyUniversity of Toronto Toronto Ontario Canada
- Thornhill Research Inc. Toronto Ontario Canada
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Leacy JK, Day TA, O'Halloran KD. Is alkalosis the dominant factor in hypoxia-induced cognitive dysfunction? Exp Physiol 2019; 104:1443-1444. [PMID: 31340075 DOI: 10.1113/ep087967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 07/22/2019] [Indexed: 11/08/2022]
Affiliation(s)
- Jack K Leacy
- Department of Physiology, School of Medicine, College of Medicine & Health, University College Cork, Cork, Ireland
| | - Trevor A Day
- Department of Biology, Mount Royal University, Calgary, Alberta, Canada
| | - Ken D O'Halloran
- Department of Physiology, School of Medicine, College of Medicine & Health, University College Cork, Cork, Ireland
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