G-induced Loss Of Consciousness Research Articles

+Gz Standards for the Indian Air Force.

INTRODUCTION: +Gz tolerance is an important aspect for the success of fighter aircrew as it reflects the ability of the neuro-cardiovascular response to compensate and prevent adverse manifestations such as gray-out, black-out, and G-induced loss of consciousness (G-LOC) under high-G stress.METHODS: The data for aircrew taking the Operational Training in Aerospace Medicine for Fighters course at the Institute of Aerospace Medicine Indian Air Force (IAF) from January 2017 to December 2020 were analyzed to assess the effectiveness of the existing training goal to recommend a G-tolerance standard for fighter aircrew.RESULTS: During the study period, 334 aircrew took the Operational Training in Aerospace Medicine for Fighter course. Only three aircrew failed to achieve the training goal of the course (failure rate <1%). There was a significant difference in the relaxed gradual onset rate tolerance of aircrew experiencing G-LOC and not experiencing G-LOC during the training. The odds of experiencing G-LOC at 9 G after clearing the 7-G and 8-G profiles were 4.4 and 4.7, respectively.DISCUSSION: It is generally accepted that aircrew having higher G tolerance have less chance of G-LOC in the air. There is a need to have an operational definition of G tolerance for fighter aircrew that aligns with the operational training goal of the organization. The G tolerance of IAF aircrew is as per the institutional definition of the IAF Institute of Aerospace Medicine. The high-G training has stood the test of time and has served well for the IAF.Kumar A. +Gz standards for the Indian Air Force. Aerosp Med Hum Perform. 2023; 94(10):780-785.

In-flight loss of consciousness in a fighter aircrew – G-LOC or No G-LOC conundrum

The differential diagnosis for inflight loss of consciousness in a fighter pilot is G-induced Loss of Consciousness (G-LOC) as it is physiological and 10–20% of fighter pilots may experience it during their career. However, it is very difficult to establish the diagnosis in many cases. Three cases of in-flight episodes of loss of consciousness (LOC) have been discussed in the paper highlighting how to investigate such cases to establish the diagnosis of G-LOC. Three cases have been discussed in the paper where two cases were considered as a case of G-LOC based on the circumstantial evidence and data from the flight data recorder. However, one case was diagnosed to be of LOC (Inv). One case did not benefit from the high-G training as he repeatedly experienced “GLOC” at very low G levels while wearing Anti-G Suit and performing an Anti-G Straining Maneuver (AGSM). He was recommended unfit for fighter flying. Another aircrew was experiencing G-LOC due to incorrect technique of AGSM as he had not undergone “high-G training.” After correction of technique, he could successfully meet the qualifying requirements of 9G for high G training. The third case was considered as a case of inflight LOC, not due to G exposure. Subsequently, he was diagnosed to have Focal Cortical Dysplasia. The paper describes the approach and aeromedical disposition of in-flight LOC among fighter aircrew. The paper also discusses the need for “G tolerance standard” at entry and high G training for fighter aircrew. The first case highlights that not all case of in-flight LOC among aircrew is G-LOC, even if it occurs in conjunction with high-G exposure. Ruling out the presence of any potential cause for inflight LOC is extremely important before labeling a recurrent case of inflight LOC as G-LOC. The second case re-iterates the fact that there are a set of people who will not be able to endure high G exposures due to inherent individual characteristics. These people need to be identified and screened at initial entry into fighter flying itself. The cause for the recurrent episodes of inflight G-LOC in the third case was identified as improper AGSM. The problem could be identified and corrected in the Dynamic Flight Simulator. This highlights the significance of high-G training using High Performance Human Centrifuge before the commencement of operational flying and high-G sorties and also establishes it as a diagnostic tool for such cases. In-flight LOC in a fighter pilot poses a challenge in diagnosis and differentiation from G-LOC. The paper discusses an approach to such a case in detail.

Cerebral Blood Flow Based Computer Modeling of Gz-Induced Effects

BACKGROUND: There is continued interest in acceleration (G) effects in civil aviation, as G-induced loss of consciousness (G-LOC), impaired consciousness, and visual effects play a role in aerobatic, agricultural, and military aviation accidents.METHODS: A software model [the Civil Aerospace Medical Institute G-Effects Model (CGEM)] based on physical and physiological variables related to in-flight tissue resupply and using oxygen flow as a proxy for supply availability, was developed to evaluate risk of G-LOC and related phenomena in aeronauts. Aeronauts were modeled using several parameters, including sex, cardiovascular fitness, and other common modifiers such as G-suits, positive pressure breathing gear, anti-G straining, and other muscle tensing. The software was validated by comparison with experimental data from the peer-reviewed literature.RESULTS: CGEM predicted physiological effects of Gz exposure accurately, particularly for rapid onset rates. Predicted times to G-LOC and absolute incapacitation periods were consistently within 1 SD of pooled results obtained during centrifuge experiments using U.S. Navy (USN) and U.S. Air Force (USAF) pilots. Predictions of G tolerance based on visual effects onset also compared well with published data, as did evaluation of symptoms expected during a difficult aerobatic maneuver.DISCUSSION: CGEM is a new tool for civil and military aviation. Rather than providing a simple G tolerance number, flight surgeons, pilots, and accident investigators can gain insight into changes in risk-from factors such fatigue, medications, dehydration, and anti-G countermeasures used-through proper selection of parameters.Copeland K, Whinnery JE. Cerebral blood flow based computer modeling of Gz-induced effects. Aerosp Med Hum Perform. 2023; 94(5):409-414.

Physiological Effects of Centrifuge-Simulated Suborbital Spaceflight

BACKGROUND: High-G acceleration experienced during launch and re-entry of suborbital spaceflights may present challenges for older or medically susceptible participants. A detailed understanding of the associated physiological responses would support the development of an evidence-based medical approach to commercial suborbital spaceflight.METHODS: There were 24 healthy subjects recruited into 'younger' (18-44 yr), 'intermediate' (45-64 yr) and 'older' (65-80 yr) age groups. Cardiovascular and respiratory variables were measured continuously during dynamic combinations of +Gx (chest-to-back) and +Gz (head-to-foot) acceleration that simulated suborbital G profiles for spaceplane and rocket/capsule platforms. Measurements were conducted breathing air and breathing 15% oxygen to simulate a cabin pressure altitude of 8000 ft.RESULTS: Suborbital G profiles generated highly dynamic changes in heart rate, blood pressure, and cardiac output. G-induced hypoxemia was observed, with minimum arterial oxygen saturation < 80% in a quarter of subjects. Increased age was associated with greater hypoxemia and reduced cardiac output responses but did not have detrimental cardiovascular effects. ECG changes included recurrent G-induced trigeminy in one individual. Respiratory and visual symptoms were common, with 88% of subjects reporting greyout and 29% reporting blackout. There was one episode of G-induced loss of consciousness (G-LOC).DISCUSSION: Suborbital acceleration profiles are generally well tolerated but are not physiologically inconsequential. Marked hemodynamic effects and transient respiratory compromise could interact with predisposing factors to precipitate adverse cardiopulmonary effects in a minority of participants. Medically susceptible individuals may benefit from expanded preflight centrifuge familiarization that includes targeted physiological evaluation in the form of a 'G challenge test'.Smith TG, Pollock RD, Britton JK, Green NDC, Hodkinson PD, Mitchell SJ, Stevenson AT. Physiological effects of centrifuge-simulated suborbital spaceflight. Aerosp Med Hum Perform. 2022; 93(12):830-839.

Noninvasive mechanical auxiliary circulation (NMAC): A general concept and the technological trends

A series of noninvasive mechanical auxiliary circulation (NMAC) technologies, such as intermittent pneumatic compression (IPC), external counterpulsation (ECP), and anti-G suit, had been widely used to realize noninvasive intervention of human cardiovascular system for different purposes, such as treatments of cardiovascular diseases and protecting pilot from G-induced loss of consciousness (G-LOC) during exposure to sustained accelerations. There are lots of similarities among these NMAC technologies, especially on aspects of hardware constitutions and their physiological effects. However, these technologies were almost independently developed in the past few decades. The similarities and differences were summarized on aspects of hardware constitutions and physiological effects of IPC, ECP and anti-G suit in this paper, and a general concept for NMAC technologies was proposed. This concept did not include a restrict definition, but generally focused on the physiological benefits, while any non-invasive mechanical methods that can achieve such benefits are welcomed. Trends for these typical NMAC technologies, especially about the strategies to realize personalized therapy or to meet new challenges, are discussed. This paper provided a unified perspective for non-invasive mechanical technologies aiming at cardiovascular benefits, and might inspire new technologies to be introduced in.

Effect of aeromedical training on anxiety levels of ab initio pilots

PurposeAeromedical training is meant to train aircrew in combating physiological problems that they might face in flight. Given the importance of the training, there are limited studies in the literature investigating the anxiety levels during aeromedical training along with training outcomes. This study aims to assess the untrained participants’ anxiety levels before and after aeromedical training, investigate the differences in anxiety levels across different physiological training devices and determine whether participants’ anxiety levels affect their G tolerances.Design/methodology/approachThis study was carried out on 61 healthy male subjects (n = 61) who had applied for initial aeromedical training. Anxiety surveys and visual analog scales were administered before and after the practical aeromedical training. In addition, blood pressure and heart rate measurements were carried out.FindingsParticipants had significantly higher anxiety levels before human centrifuge training (pre-Glab) than before the altitude chamber training (pre-hypobaric). Participants who experienced G-induced loss of consciousness (G-LOC) had slightly more anxiety reported than the non-G-LOC group. There was a significant decrease between pre-Glab and post-Glab (after the human centrifuge training) and between pre-hypobaric and post-hypobaric (after the altitude chamber training) anxiety levels. The incidence of G-LOC was lower in participants having higher pre-G-Lab blood pressure. However, the difference in anxiety levels between the G-LOC group and the non-G-LOC group was not statistically significant.Research limitations/implicationsIn this study, state anxiety inventory was not performed after human centrifuge training as centrifuge training lasted for around 5 min only, and it is not advisable to repeat state anxiety inventory in such short periods. Blood pressure was not measured after G-Lab training because human centrifuge training is hard training and has an impact on blood pressure. Hence, it would have been difficult to distinguish whether the blood pressure change was due to anxiety or hard physical activity. These limitations, especially for the G-Lab, caused us to evaluate state anxiety only with VAS. It would be worthwhile to repeat similar studies with objective measurements before and after the training.Practical implicationsThis information suggests that instructors who train the applicants on aerospace medicine be ready for the possible consequences of anxiety.Originality/valueThere are only a few centers in the world that include all the physiological training devices (practical aeromedical training laboratories) together. To the best of authors’ knowledge, there are no studies in the literature investigating the differences in anxiety levels across various physiological training devices. The studies about the effect of anxiety levels on aeromedical training outcomes and anxiety levels before and after the training are scant.

Appendix A

BACKGROUND: High-G acceleration experienced during launch and re-entry of suborbital spaceflights may present challenges for older or medically susceptible participants. A detailed understanding of the associated physiological responses would support the development of an evidence-based medical approach to commercial suborbital spaceflight.METHODS: There were 24 healthy subjects recruited into ‘younger’ (18-44 yr), ‘intermediate’ (45-64 yr) and ‘older’ (65-80 yr) age groups. Cardiovascular and respiratory variables were measured continuously during dynamic combinations of +Gx (chest-to-back) and +Gz (head-to-foot) acceleration that simulated suborbital G profiles for spaceplane and rocket/capsule platforms. Measurements were conducted breathing air and breathing 15% oxygen to simulate a cabin pressure altitude of 8000 ft.RESULTS: Suborbital G profiles generated highly dynamic changes in heart rate, blood pressure, and cardiac output. G-induced hypoxemia was observed, with minimum arterial oxygen saturation &lt; 80% in a quarter of subjects. Increased age was associated with greater hypoxemia and reduced cardiac output responses but did not have detrimental cardiovascular effects. ECG changes included recurrent G-induced trigeminy in one individual. Respiratory and visual symptoms were common, with 88% of subjects reporting greyout and 29% reporting blackout. There was one episode of G-induced loss of consciousness (G-LOC).DISCUSSION: Suborbital acceleration profiles are generally well tolerated but are not physiologically inconsequential. Marked hemodynamic effects and transient respiratory compromise could interact with predisposing factors to precipitate adverse cardiopulmonary effects in a minority of participants. Medically susceptible individuals may benefit from expanded preflight centrifuge familiarization that includes targeted physiological evaluation in the form of a ‘G challenge test’.Smith TG, Pollock RD, Britton JK, Green NDC, Hodkinson PD, Mitchell SJ, Stevenson AT. Physiological effects of centrifuge-simulated suborbital spaceflight. Aerosp Med Hum Perform. 2022; 93(12):830–839.

Analysis of incapacitation during +Gz induced loss of consciousness

Introduction: Occurrence of G induced loss of consciousness (G-LOC) during centrifuge training is a known entity. The Indian Air Force is currently undertaking high G training of its fighter pilots in High Performance Human Centrifuge (HPHC) which has significantly higher operational capabilities. The study aimed to analyse the incapacitation periods and myoclonic jerks associated with G-LOC occurring during HPHC training. Material and Methods: Records of episodes of 161 G-LOC during closed loop Rapid Onset Rates (ROR) runs over a period of 7 years from 2011 to 2017 were analyzed. The video recordings of these G-LOC episodes were assessed in terms of the participant demographics, +Gz onset rates, incapacitation periods, and presence or absence of myoclonic jerks during the G-LOC episodes. Descriptive statistics was applied to analyze the incapacitation periods and the duration of the myoclonic flail movements. Single tailed t-test was used to analyze the difference between the incapacitation periods of the aircrew who suffered myoclonic flail movements and those who did not. One-way ANOVA was carried out to assess the differences in incapacitation periods, if any, between aircrew of different age groups. Significance was set at P &lt; 0.05. Results: Of these 161 episodes of G-LOC, 43.5% were seen in trainee aircrew. The mean Absolute Incapacitation Period (AIP), Relative Incapacitation Period (RIP) and Total Incapacitation Period (TIP) was 6.9 ± 2.3 s, 12.2 ± 4.7 s, and 19.1 ± 5.5 respectively. Age and flying experience did not show any significant effect with any of the incapacitation periods (p&gt;0.05). The TIP correlated better with the RIP than with the AIP (Pearson’s correlation values of 0.9 and 0.52 respectively). Myoclonic flail movements were witnessed in 25.5% of G-LOC episodes with an average duration of 5.3 s and more than 50% occurring at ≥8Gz. The mean duration of RIP was significantly higher (P=0.03) when G-LOC was associated with myoclonic flail movements, whereas, the duration of AIP did not show any significant difference. Conclusion: The shorter incapacitation periods observed in the study compared to that reported in most of the previous studies could be attributed to the faster Gz offset rates of the present HPHC. Episodes of G-LOC having myoclonic movements were found to have higher relative incapacitation periods. Even though these movements were associated with G-LOC occurring at higher Gz levels, the durations were independent of the Gz levels.

Describing the continuum from ALOC to G-LOC

Introduction: G-induced loss of consciousness (G-LOC) has been extensively investigated and pathophysiology of the same has been well elucidated in the literature. The syndrome of almost loss of consciousness or ALOC has also been described which is a loose collection of signs and symptoms of a physiological, emotional, and cognitive nature. This is believed to occur under +Gz stress which is insufficient to cause G-LOC. Institute of Aerospace Medicine IAF regularly conducts high-G training for its fighter pilots in the High Performance Human Centrifuge. Episodes of G-LOC and ALOC are unintended outcomes of such training. A study was conducted to understand the nature of these episodes in the Department of Acceleration Physiology and Spatial Orientation. Material and Methods: A G-LOC/ALOC proforma was designed in the Department of Acceleration Physiology and Spatial Orientation to understand the nature and causes of the G-LOC/ALOC and was filled up by the aircrew on a voluntary basis. The data were analyzed using Microsoft Excel and SPSS 20 with significance set at 95% confidence interval and alpha at 0.05. Results: Forty-seven aircrew experiencing G-LOC/ALOC agreed to be part of the study and filled up the proforma after the episodes. However, only 42 proforma (31 G-LOC and 11 ALOC) was found suitable for the analysis. There was no statistical difference in heart rate (HR) measured during the rate of onset and G-level at which G-LOC and ALOC resulted. There was no difference in psycho-somatic manifestations of G-LOC and ALOC episodes. Conclusion: ALOC and G-LOC have similar manifestations and operational implications. There is ample evidence to suggest that ALOC is a manifestation of G-LOC syndrome rather than a separate entity.

Analysis of G-induced Loss of Consciousness (G-LOC) and Almost Loss of Consciousness (A-LOC) incidences in high-performance human centrifuge at Institute of Aerospace Medicine Indian Air Force

Introduction: Institute of Aerospace Medicine (IAM) Indian Air Force (IAF) conducts operational training in Aerospace Medicine for IAF fighter aircrew since 2009. This includes high-G training with qualifying criteria of demonstrating ability of the aircrew to sustain 9G for 5 s in closed-loop run (pilot-in-control) wearing anti-G suit while performing anti-G straining maneuver (AGSM). Incidences of inadvertent almost loss of consciousness (A-LOC)/G-induced loss of consciousness (G-LOC) are an unavoidable unintended consequence of such training. The aim of the paper is to study the incidence of G-LOC and A-LOC and its nature in the high-performance human centrifuge (HPHC) and compare it with our previous experiences. Material and Methods: A G-LOC/A-LOC proforma was designed at the Department of Acceleration Physiology and Spatial Orientation at IAM IAF to understand the nature and cause of the G-LOC/A-LOC. This was to be filled up by the aircrew on a voluntary basis. The data were analyzed using Microsoft Excel with a significance level set at 95% confidence interval and alpha ≤0.05. Results: Fifty-two aircrew (19.92%) experienced inadvertent G-LOC/A-LOC in 83 such episodes (54 G-LOC and 29 A-LOC) during the period January 2018–December 2018. Forty-seven aircrew experiencing G-LOC/ALOC agreed to be part of the study and filled up the proforma after the episodes. The incidence of G-LOC in the institute has reduced significantly over the past two decades, perhaps due to change in the HPHC used for training of aircrew. The incidence of G-LOC found in this study is comparable to the global incidence. Rise in heart rate was higher during A-LOC than G-LOC and was found to be statistically significant (t statistic = 2.33; P = 0.01). Relative incapacitation period was lesser than absolute incapacitation period during G-LOC and was found to be statistically significant (t statistic = 3.29, P = 0.001). G-level at which Type II G-LOC occurred was significantly higher than the Type I G-LOC. Conclusion: The incidence of A-LOC/G-LOC has reduced over the past two decades of high G training in IAF and is comparable to global incidence.

AGSM Proficiency and Depression Are Associated With Success of High-G Training in Trainee Pilots.

INTRODUCTION: High-gravity (G) training is used to educate trainee pilots about anti-G straining maneuvers (AGSM) in an environment similar to that of a real fighter aircraft, and to enhance their G tolerance. The success or failure of high-G training could be multifactorial, but most previous studies have only focused on the effect of pilots' physical condition.METHODS: A total of 138 male trainee pilots participated in this study. All trainee pilots had received AGSM training from experienced instructors and then underwent centrifuge high-G training. Participants completed questionnaire surveys about body size, lifestyle, self-reported AGSM proficiency, resilience (Connor-Davidson Resilience Scale, CD-RISC), and depression level (Center for Epidemiologic Studies Depression Scale, CES-D).RESULTS: Of the 138 subjects, 100 (72.5%) successfully completed high-G training without experiencing G-induced loss of consciousness (G-LOC) within two trials; these were allocated to the success group. The remaining 38 (27.5%) subjects who completed the training after three or more attempts, or who failed to complete the training at all, were allocated to the failure group. Multivariate analyses revealed that the success of centrifuge training was positively associated with age and self-reported AGSM proficiency, and negatively associated with depression level.DISCUSSION: The success of high-G training was significantly associated with self-reported AGSM proficiency and depression level. Instructors should emphasize the importance of AGSM proficiency and offer practice-based learning to trainee pilots. In addition, they should pay attention to not only trainee pilots' physical condition, but also their psychological status.Yun C, Oh S, Shin YH. AGSM proficiency and depression are associated with success of high-G training in trainee pilots. Aerosp Med Hum Perform. 2019; 90(7):613-617.

G-LOC Warning Algorithms Based on EMG Features of the Gastrocnemius Muscle.

G-induced loss of consciousness (G-LOC) is mainly caused by failure to sustain an oxygenated blood supply to the pilot's brain because of the sudden acceleration in the direction of the +Gz axis, and is considered a critical safety issue. The purpose of this study was to develop G-LOC warning algorithms based on monitoring electromyograms (EMG) of the gastrocnemius muscle on the calf. EMG data was retrieved from a total of 67 pilots and pilot trainees of the Korean Air Force during high-G training on a human centrifugal simulator. Seven EMG features were obtained from root mean square (RMS), integrated absolute value (IAV), and mean absolute value (MAV) for muscle contraction, slope sign changes (SSC), waveform length (WL), zero crossing (ZC), and median frequency (MF) for muscle contraction and fatigue. Out of seven EMG features, IAV and WL showed a rapid decay before G-LOC. Based on these findings, this study developed two algorithms which can detect G-LOC during flight and provide warning signals to the pilots. The probability of G-LOC occurrence was detected through monitoring the decay trend for representing muscle endurance and climb rate of the IAV and WL value during sudden acceleration above 6 G, representing muscle power. The sensitivity of the algorithms using IAV and WL features was 100% and the specificity was 66.7%. This study suggests that a G-LOC detecting and warning system may be a customized, real-time countermeasure by improving the accuracy of detecting G-LOC.Kim S, Cho T, Lee Y, Koo H, Choi B, Kim D. G-LOC warning algorithms based on EMG features of the gastrocnemius muscle. Aerosp Med Hum Perform. 2017; 88(8):737-742.

Incidence of G-Induced Loss of Consciousness and Almost Loss of Consciousness in the Royal Air Force.

Exposure to sustained +Gz acceleration with inadequate G protection can result in G-induced loss of consciousness (G-LOC) or almost loss of consciousness (A-LOC). The UK Royal Air Force (RAF) last conducted a survey of G-LOC within their military aircrew in 2005 with interventions subsequently introduced. The aim of this study was to repeat the 2005 survey in order to evaluate the impact of those interventions. An anonymous questionnaire requesting details of G-LOC and A-LOC events was mailed to all RAF pilots (N = 1878) and weapons systems operators (WSOs) (N = 473), irrespective of aircraft currently flown. The questionnaire was returned by 809 aircrew (34.4% response rate). There were 120 (14.8%) aircrew who reported at least one episode of G-LOC and 260 (32.2%) reported at least one episode of A-LOC. The reported prevalence of G-LOC in the previous 2005 survey was 20.1% (N = 454). There was an increased reporting of G-LOC in the Hawk, Tucano, and Grob Tutor aircraft, with 5 G-LOC and 19 A-LOC events reported in the Grob Tutor compared to none in 2005. The prevalence of reported G-LOC has decreased in the surveyed populations, which may be due to the introduction of centrifuge training, but also may be influenced by patterns of G exposure and other factors. Scope for further reduction remains through correct execution of the anti-G straining maneuver (AGSM) with centrifuge training early in flying training and use of a structured conditioning program to increase the general strength of muscles involved in the AGSM.Slungaard E, McLeod J, Green NDC, Kiran A, Newham DJ, Harridge SDR. Incidence of G-induced loss of consciousness and almost loss of consciousness in the Royal Air Force. Aerosp Med Hum Perform. 2017; 88(6):550-555.

G-induced Loss of Consciousness(G-LOC) 예측을 위한 신체 부위별 Electromyogram(EMG) 신호 분석

G-induced Loss of Consciousness(G-LOC) 예측을 위한 신체 부위별 Electromyogram(EMG) 신호 분석

A review of high G-stress induced problems and their solutions

G stress can debilitate pilots of modern fighter aircraft and consequence accidents due to G-induced loss of consciousness (G-LOC). The physiological effects of high G stress include reduction in head level blood pressure and cardiac output that subsequently results loss of vision and G-LOC. The body's natural resistance system helps the pilot to fight against the effects of G stress to some level. To understand the medical and physiological consequences of high G forces on humans, research around the world is conducted using centrifuges, tilt tables, lower body negative pressure (LBNP) devices, etc. Physiological effects due to G-stress are experienced by the pilot on the cardiovascular, respiratory, musculoskeletal and central nervous systems. Many physiological, environmental and habitual conditions are found responsible for decreasing the G-tolerance. Mechanical, physiological and educational countermeasures are suggested to protect the pilots of high performance aircraft against the extreme acceleration. Expected inventions of more manoeuvrable aircrafts will possibly demand the use of advanced countermeasures to protect the pilots from the effect of high G forces.

Detection of G-Induced Loss of Consciousness (G-LOC) prognosis through EMG monitoring on gastrocnemius muscle in flight.

G-Induced Loss of Consciousness (G-LOC) is mainly caused by the sudden acceleration in the direction of +Gz axis from the fighter pilots, and is considered as an emergent situation of which fighter pilots are constantly aware. In order to resist against G-LOC, fighter pilots are subject to run Anti-G straining maneuver (AGSM), which includes L-1 respiration maneuvering and muscular contraction of the whole body. The purpose of this study is to create a G-LOC warning alarm prior to G-LOC by monitoring the Electromyogram (EMG) of the gastrocnemius muscle on the calf, which goes under constant muscular contraction during the AGSM process. EMG data was retrieved from pilots and pilot trainees of the Korean Air Force, during when subjects were under high G-trainings on a human centrifugal simulator. Out of the EMG features, integrated absolute value (IAV), reflecting muscle contraction, and waveform length (WL), reflecting muscle contraction and fatigue, have shown a rapid decay during the alarm phase, 3 seconds before G-LOC, compared to that of a normal phase withstanding G-force. Such results showed consistency amongst pilots and pilot trainees who were under G-LOC. Based on these findings, this study developed an algorithm which can detect G-LOC prognosis during flight, and at the same time, generate warning signals. The probability of G-LOC occurrence is detected through monitoring the decay trend and degree of the IVA and WL value of when the pilot initiates AGSM during sudden acceleration above 6G. Conclusively, this G-LOC prognosis detecting and warning system is a customized, real-time countermeasure which enhanced the accuracy of detecting G-LOC.

Visual Symptoms and G-Induced Loss of Consciousness in 594 Chinese Air Force Aircrew—A Questionnaire Survey

A questionnaire survey was performed for the first time to assess the prevalence of visual symptoms and G-induced loss of consciousness (G-LOC) due to +Gz exposure in the Chinese Air Force (CAF) to determine the effectiveness of current G tolerance training. Responses were received from 594 individuals. Among them, 302 reported at least one episode of some sort of symptoms related to +Gz, including 110 (18.5%) with visual blurring, 231 (38.9%) with greyout, 111 (18.7%) with blackout, and 49 (8.2%) with G-LOC. Incidences were most common in aircrew with 250-1,000 flying hours (53.6%) and were more prevalent in those with fewer on type flying hours (p < 0.001). The most common situation was reported between +5 and 5.9 Gz. The results indicate a fairly high prevalence of visual symptoms and G-LOC among Chinese Air Force aircrew. There remains considerable scope for +Gz education, particularly in the early centrifuge training and selection of rational physical exercises.

Online acquisition and wireless transmission of carotid pulse waveforms to analyse posture related changes

The physiological parameters of the fighter plane pilot undergo drastic changes leading to G stress accumulation. Heart rate is considered primary mechanism which plays a great role in acceleration protection research especially for G-LOC (G-induced loss of consciousness). Various methods based on various principles have been developed to study heart rate so far. Carotid pulse waveforms obtained from the human subject with the help of piezoelectric transducer may be used to analyse the cardiac activity. Change in heart rate due to change in the posture may be used to explain G stress effect on humans. Carotid signal is acquired by placing piezoelectric sensor based system on the subject’s carotid artery. The piezoelectric sensor has a transducing element which is efficient and effective to sense movement due to carotid pulse and produce piezoelectric signal data in response thereto. The real time data of carotid pulse waveforms of 12 human subjects are acquired and filtered using MATLAB software in various body postures. RR period and pulse amplitudes are quantified from real time recorded carotid signal by visual inspection. Further Statistical analysis is done to calculate the heart rate. The filtered stored data is transmitted wirelessly from one PC to another PC using Teamviewer software.

Severe Hypotension During the Decreasing Phase of G&lt;SUB&gt;z&lt;/SUB&gt; Stress in Anesthetized Rats Wearing an Anti-G Suit

Physiological responses to +Gz stress have been reported in several studies. However, no reports exist on differences in arterial pressure responses between increasing and decreasing G phases. We hypothesized that +Gz stress and/or an anti-G support might disturb the circulation system and cause potential brain hypoperfusion, even if the anti-G support protects against G-induced loss of consciousness. Dependency of +Gz magnitude, hemodynamic changes, renal sympathetic nerve activity (RSNA), and aortic blood flow (AoBF) were estimated in anesthetized rats to analyze the effects of +Gz stress and/or an anti-G support on arterial pressure at a level of the brain (APLB). The rats were exposed to +Gz using a centrifuge for small animals while wearing an anti-G suit. APLB remained at the control level while the anti-G suit was inflated. However, a decrease in APLB was observed twice during increasing and decreasing G phases using the anti-G suit. Hypotension in the decreasing C phase at +5 Gz was significantly deeper than that in the increasing G phase (47.5 +/- 7.7 vs. 29.6 +/- 3.0 mmHg). RSNA responses to Gz loads were greater in the decreasing G than in the increasing G phase (129.7 +/- 8.6 vs. 147.3 +/- 10.4%). Both AoBF and calculated vascular resistance were suppressed more significantly in the decreasing G than in the increasing G phase (38.3 +/- 4.4 vs. 34.4 +/- 3.4 ml x min(-1), 1.44 +/- 0.22 vs. 1.09 +/- 0.14 mmHg x min(-1) x ml(-1)). We conclude that transient excessive decreasing G hypotension may occur during the decreasing G phase, which may be due to anti-G suit functioning.

Subjective stress factors in centrifuge training for military aircrews

This study investigates stress-influence factors perceived by military aircrews undergoing centrifuge training, which lowers the incidence of G-induced loss of consciousness (G-LOC) for the crews of high-performance combat aircrafts. We used questionnaires to assess the subjective stress-influence factors of crews undergoing centrifuge training. Professionals in aviation physiology identified attributes measuring the perceived stress induced by centrifuge training, which were segmented into three constructs by factor analysis, theory lecture, centrifuge equipment, and physical fitness. Considerable interpenetration was discernible between these factors and military rank, age, length of service, flight hours accrued, and type of aircraft piloted. Identifying and quantifying the perceived stressors experienced in human-use centrifuge training enables aviators, astronauts, and air forces of the world to determine which constructs perceptibly increase or alleviate the perceived stress undergone by trainees when partaking in centrifuge training.