Gz Acceleration Research Articles

The effect of acceleration on color vision

Background/Aim. Over 80% of all information a pilot receives during the flight is visual with color perception being one of the most important visual functions for managing an aircraft. The reception of color is of high significance in aviation due to the importance of signal tracking on instrument panels as well as the importance of visual stimulus and environment signs. There is no sufficient number of papers and studies that deal with this issue, although recent studies have shown that the connection between acceleration and color perception exists. The aim of this study was to demonstrate the correlation between pilot exposure to +Gz acceleration in human centrifuge and color perception before and after acceleration exposure. Methods. Subjects of the study were 40 military pilots, aged 35?45, with 10 and 20 years of flying experience. Pilots were exposed to +Gz acceleration (inertial force acts from head to feet) in the human centrifuge for pilot training with accelerations of +2Gz, +5.5Gz up to +7Gz. The tests focused on color perception before and after the exposure to the acceleration. Results. Out of 40 pilots examined for color vision, in 35 (87.50%) had normal results in color identification before and after +Gz; 5.00% (2 subjects) had two mistakes ? reading number 5 instead of number 3, which falls within the normal trichomes, and reading number 16 instead of number 26. Three subjects (7.50%) gave their answers slower than the accepted response time. After the +7Gz exposure, 34 (85%) persons had normal results in color identification, 2 (5%) subjects made three mistakes ? at numbers 5, 74 and 26; one (2.50%) pilot made four mistakes on numbers 5, 7, 74 and 26; 7.50% (3 pilots) of the subjects identified colors slower. Conclusion. Color perception in pilots is unstable on high +Gz accelerations. Exposure to +5.5Gz acceleration does not lead to significant changes in color perception, while exposure to +7Gz acceleration showed a significant percentage of reversible disturbance in color perception which lasted for 10 minutes.

Тhe Impact Of Positive Acceleration (+Gz) on Antioxidant Capacity and Histopathological Alterations in Different Organs and Tissues in Rats

Abstract Since the early 1940s, a significant amount of research has been conducted to describe the impact of the high-G acceleration on the cardiovascular system. The objective of the present study was to examine the role of the antioxidant enzyme system under biodynamic stress in the liver, heart and gastric mucosa in response to high-magnitude +Gz exposure in a rat model. Twenty adult male Wistar albino rats (10 rats per group; 9-11 weeks old, 200-250 g b.w.) were divided into the following two groups: control and G (exposed to a biodynamic stress model under positive (+7 Gz) acceleration for 40 s). The influence of acute biodynamic stress on pro-oxidative parameters in the rat liver (xanthine oxidase (XOD), catalase (CAT), peroxidase (Px), glutathione peroxidase (GSH-Px), total content of glutathione (GSH), lipid peroxidation (LPx)) and on histopathological alterations in the liver, cardiac muscle and gastric mucosa was examined. Biodynamic stress resulting from positive (+7 Gz) acceleration resulted in a highly statistically signifi cant increase of CAT GSH-Px activity compared to the control group. The LPx levels were significantly decreased, but the GSH contents and the activities of other enzymes were not significantly changed. Significant microscopic changes in the liver, heart and gastric mucosa were observed in the G group. These results clearly indicate that +Gz acceleration alters biochemical systems. These alterations in cellular processes may be mediated by influences of hypoxia or ischaemia via changes in the antioxidant capacity.

A study of the application of Brain Atlas with and without +Gz acceleration conditions.

The purposes of this study were to utilize Brain Atlas to investigate the fluctuations in the characteristics of human EEG, with and without +Gz acceleration produced by human centrifuge, and also to examine the G load endurance of human body. The Brain Atlas of the EEG signal with and without +Gz acceleration in a static state were compared in order to reveal the correlation and differences. When compared with those in a static state, it was found that for the EEG readings of the subjects undergoing +Gz acceleration conditions, the energy and gray scale values of the low-frequency component-delta rhythm showed significant increases, while the energy and gray scale values of the high-frequency component-beta rhythm showed significant decreases. Among these, the beta2 rhythm was determined to be significantly inhibited. These fluctuations suggested that the ischemia conditions of brain had been improved. Also, the recoveries in the energy and gray-scale values were determined to be faster, which suggested that the G load endurance of human body had been enhanced. The Brain Atlas was found to show observable changes in color. The experimental results indicated that the Brain Atlas was able to provide assistance during the exploration of the fluctuations in the characteristics of EEG, and provided a criterion to assist in the observations of the function state fluctuations of human brain with +Gz acceleration. It also assisted in the evaluations of the G load endurance of human body.

The first sign of loss of consciousness

The first clinically observable sign of an unconsciousness episode (UNCE) serves as the temporal sequence (kinetics) onset point for neurological events occurring during the loss of consciousness, unconsciousness and recovery of consciousness phases of the UNCE. The initial neurologic signs of 212 individuals exposed to gradual (N=114) and rapid (N=98) onset +Gz acceleration stress, inducing the ischemic LOC phase in 83.3±18.6s and 8.89±1.52s; p<0.001 respectively, were determined. The duration of the unconscious phase (considered absolute incapacitation) was 10.42±5.3s and 9.36±3.99s; p>0.1 for gradual and rapid onset +Gz-stress, respectively. Cerebral autoregulation may play a role in determination of ischemic UNCE induction and recovery. Five signs: loss of muscle control, eyelid closure, eye fixation, upward eye deviation, and muscular twitching occurred at LOC phase onset. The most frequent initial sign of LOC phase onset was loss of muscle control (84% of the episodes), followed by eye fixation (8.5%), and upward eye deviation (6.1%). Signs play a key role in differential diagnosis of syncopal, epileptic, psychogenic and other causes of UNCEs. Sign kinetics may provide insight into localization of the essential components and networks within the cephalic nervous system associated with UNCEs.

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.

The Comparison and Study of WVD, PWVD, SPWVD Time Frequency Analysis Technologies Based on Observed Dynamic EEG Data

For the observed EEG data under +Gz acceleration, the traditional Fourier transformation can not express the change regularity of EEG frequency spectrum characteristic with time, so it is tried to make data treatment with the help of analysis tool of WVD. Through the theory comparison on WVD, PWVD and SPWVD-this three analysis methods and the comparison analysis on the application results of the actually measured EEG data under centrifuge +Gz acceleration, the respective advantage and disadvantage of the three methods is studied, and SPWVD is found to be relatively a better analysis method. It can eliminate effectively crossing term interference which is innate for quadratic form distribution and has better focusing characteristic, and can better reflect the state of EEG under different G acceleration and frequency spectrum change characteristic.

Effects of Flight Aptitude Tests and +Gz Acceleration Stress on Trace Mineral Levels in Human Serum and Urine

Effects of Flight Aptitude Tests and +Gz Acceleration Stress on Trace Mineral Levels in Human Serum and Urine

近赤外分光法を用いた非侵襲的測定による加速度(+Gz)負荷中の脳内ヘモグロビン濃度変化に関する研究

近赤外分光法を用いた非侵襲的測定による加速度(+Gz)負荷中の脳内ヘモグロビン濃度変化に関する研究

Effects of Flight Aptitude Tests and +Gz Acceleration Stress on Trace Mineral Levels in Human Serum and Urine

Effects of Flight Aptitude Tests and +Gz Acceleration Stress on Trace Mineral Levels in Human Serum and Urine

Lipid peroxidation and the antioxidant protection system in humans exposed to hypergravity of varying intensity

The effects of +Gz acceleration (head–pelvis) of 3, 5, and 7g (rate of increase, 0.03 g/s) on the intensity of lipid peroxidation (LPO) and the state of the antioxidant protection system were assessed in 14 subjects 25–45 years of age. The content of lipid peroxidation products (diene conjugates, malonic dialdehyde, and Schiff bases) in the blood of the subjects was quantitated, and the status of the water-soluble (catalase and glutathione peroxidase activities and total antioxidant activity) and lipid (tocopherol concentration) components of the antioxidant protection system was assessed. Exposure to hypergravity of 3g was accompanied by a slight activation of LPO, and further increase in the load to 5g resulted in inhibition of LPO, whereas no statistically significant changes in any of the parameters investigated were recorded at a load of 7g. Induction of the passive mechanisms of biomembrane protection associated with changes in the phase status of the membrane appears to be the most plausible explanation for the phenomenon observed. Further research on the mechanisms of compensation and control of the intensity of free radical-mediated processes upon the impact of hypergravity seems necessary.

Effects and biological limitations of +Gz acceleration on the autonomic functions-related circulation in rats.

The effects of gravitational loading (G load) on humans have been studied ever since the early 20th century. After the dangers of G load in the vertical head-to-leg direction (+Gz load) became evident, many animal experiments were performed between 1920 and 1945 in an effort to identify the origins of high G-force-induced loss of consciousness (G-LOC), which led to development of the anti-G suit. The establishment of norms and training for G-LOC prevention resulted in a gradual decline in reports of animal experiments on G load, a decline that steepened with the establishment of anti-G techniques in humans, such as special breathing methods and skeletal muscle contraction, called an anti-G straining maneuver, which are voluntary physiological functions. Because the issue involves humans during flight, the effects on humans themselves are clearly of great importance, but ethical considerations largely preclude any research on the human body that probes to any depth the endogenous physiological states and functions. The decline in reports on animal experiments may therefore signify a general decline in research into the changes seen in the various involuntary, autonomic functions. The declining number of related reports on investigations of physiological autonomic systems other than the circulatory system seems to bear this out. In this review, we therefore describe our findings on the effects of G load on the autonomic nervous system, cardiac function, cerebral blood flow, tissue oxygen level, and other physiological autonomic functions as measured in animal experiments, including denervation or pharmacological blocking, in an effort to present the limits and the mechanisms of G-load response extending physiologically. We demonstrate previously unrecognized risks due to G load, and also describe fundamental research aimed at countering these effects and development of a scientific training measure devised for actively enhancing +Gz tolerance in involuntary, autonomic system functions. The research described here is rough and incomplete, but it is offered as a beginning, in the hope that researchers may find it of reference and carry the effort toward completion. The advances described here include (1) a finding that cerebral arterial perfusion pressure decreases to nearly zero under +5.0 Gz loads, (2) indications that G load may cause myocardial microinjuries, (3) detection of differences between cerebral regions in tissue-oxygen level under +3.0 Gz load, (4) discovery that hypotension is deeper under decreasing +Gz loads than increasing +Gz loads with use of an anti-G system, due in part to suppression of baroreceptor reflex, and (5) revelations and efforts investigating new measures to reduce cerebral hypotension, namely the “teeth-clenching pressor response” and preconditioning with slight but repeated G loads.

Research of EEG change feature under +Gz acceleration

High G protection is an important theoretical and practical issue which needs to be solved urgently in the aviation medicine field. Due to the particularity of equipment used in the centrifuge experiment, and the high risk of experiment for human body, EEG research under +Gz acceleration is rare. The research on preventing and early warning human syncope induced by +Gz by means of EEG signal is therefore much less. In this study, the EEG change feature under +Gz Acceleration is studied with the human experiment by use of a new type human centrifuge. The valuable feature parameters changes are extracted by using the analysis method based on periodogram parameters, after data filtering and other pretreatment. The results show that, the features of some typical EEG levels are significant for aviation medicine. Particularly, the comprehensive parameter R change of alpha and beta frequency bands early shown is applicable and significant for early warning syncope induced by +Gz acceleration.

Visual Attention Distribution and Rate of Visual Information Acquisition in Human Centrifuge under +Gz Acceleration

Visual Attention Distribution and Rate of Visual Information Acquisition in Human Centrifuge under +Gz Acceleration

Reaction time in pilots during intervals of high sustained g.

An important problem for pilots is visual disturbances occurring under +Gz acceleration. Assessment of the degree of intensification of these disturbances is generally accepted as the acceleration tolerance level (ATL) criterion determined in human centrifuges. The aim of this research was to evaluate the visual-motor responses of pilots during rapidly increasing acceleration contained in cyclic intervals of +6 Gz to the maximum ATL. The study involved 40 male pilots ages 32-41 yr. The task was a quick and faultless response to the light stimuli presented on a light bar during exposure to acceleration until reaching the ATL. Simple response time (SRT) measurements were performed using a visual-motor analysis system throughout the exposures which allowed assessment of a pilot's ATL. There were 29 pilots who tolerated the initial phase of interval acceleration and achieved +6 Gz, completing the test at ATL. Relative to the control measurements, the obtained results indicate a significant effect of the applied acceleration on response time. SRT during +6 Gz exposure was not significantly longer compared with the reaction time between each of the intervals. SRT and erroneous reactions indicated no statistically significant differences between the "lower" and "higher" ATL groups. SRT measurements over the +6-Gz exposure intervals did not vary between "lower" and "higher" ATL groups and, therefore, are not useful in predicting pilot performance. The gradual exposure to the maximum value of +6 Gz with exposure to the first three intervals on the +6-Gz plateau effectively differentiated pilots.

First-time imaging of effects of inspired oxygen concentration on regional lung volumes and breathing pattern during hypergravity.

Aeroatelectasis can develop in aircrew flying the latest generation high-performance aircraft. Causes alleged are relative hyperoxia, increased gravity in the head-to-foot direction (+Gz), and compression of legs and stomach by anti-G trousers (AGT). We aimed to assess, in real time, the effects of hyperoxia, +Gz accelerations and AGT inflation on changes in regional lung volumes and breathing pattern evaluated in an axial plane by electrical impedance tomography (EIT). The protocol mimicked a routine peacetime flight in combat aircraft. Eight subjects wearing AGT were studied in a human centrifuge during 1 h 15 min exposure of +1 to +3.5Gz. They performed this sequence three times, breathing AIR, 44.5 % O2 or 100 % O2. Continuous recording of functional EIT enabled uninterrupted assessment of regional lung volumes at the 5th intercostal level. Breathing pattern was also monitored. EIT data showed that +3.5Gz, compared with any moment without hypergravity, caused an abrupt decrease in regional tidal volume (VT) and regional end-expiratory lung volume (EELV) measured in the EIT slice, independently of inspired oxygen concentration. Breathing AIR or 44.5 % O2, sub-regional EELV measured in the EIT slice decreased similarly in dorsal and ventral regions, but sub-regional VT measured in the EIT slice decreased significantly more dorsally than ventrally. Breathing 100 % O2, EELV and VT decreased similarly in both regions. Inspired tidal volume increased in hyperoxia, whereas breathing frequency increased in hypergravity and hyperoxia. Our findings suggest that hypergravity and AGT inflation cause airway closure and air trapping in gravity-dependent lung regions, facilitating absorption atelectasis formation, in particular during hyperoxia.

Emergency Medical Support for a Manned Stratospheric Balloon Test Program

Red Bull Stratos was a commercial program that brought a test parachutist, protected by a full-pressure suit, in a stratospheric balloon with pressurized capsule to over 127,582 ft (38,969 m), from which he free fell and subsequently parachuted to the ground. Given that the major risks to the parachutist included ebullism, negative Gz (toe-to-head) acceleration exposure from an uncontrolled flat spin, and trauma, a comprehensive plan was developed to recover the parachutist under nominal conditions and to respond to any medical contingencies that might have arisen. In this report, the project medical team describes the experience of providing emergency medical support and crew recovery for the manned balloon flights of the program. The phases of flight, associated risks, and available resources were systematically evaluated. Six distinct phases of flight from an Emergency Medical Services (EMS) standpoint were identified. A Medical Support Plan was developed to address the risks associated with each phase, encompassing personnel, equipment, procedures, and communications. Despite geographical, communications, and resource limitations, the medical team was able to implement the Medical Support Plan, enabling multiple successful manned balloon flights to 71,615 ft (21,828 m), 97,221 ft (29,610 m), and 127,582 ft (38,969 m). The experience allowed refinement of the EMS and crew recovery procedures for each successive flight and could be applied to other high altitude or commercial space ventures.

Blood pressure, vascular resistance, and +Gz tolerance during repeated +Gz exposures.

Cardiovascular reflexes that regulate blood pressure (BP) adapt during repeated exposure to +Gz acceleration separated by short (< 20 s) breaks, but whether this effect is preserved with longer intervals remains unknown. There were 17 subjects who completed 5 repeated gradual onset (0.1 G x s(-1)) runs (GOR1-5) to 60 degrees peripheral light loss (PLL) on a human centrifuge, separated by 2 min. Heart rate (HR) and BP were measured before and during each GOR and noninvasive estimation of cardiac output (CO) was used to calculate total peripheral resistance (TPR). Mean resting (+/- SE) systolic BP (138 +/- 4 vs. 128 +/- 3 mmHg) and TPR (13.9 +/- 1.2 vs. 12.7 +/- 1.0 mmHg x L(-1) x min(-1)) were elevated after GOR1 and remained elevated thereafter. Compared with that before GOR1, resting HR was decreased (5-6 bpm) before GOR2-5. Resting CO decreased from 8.3 +/- 0.6 L x min(-1) before GOR1 to a nadir of 7.2 +/- 0.5 L x min(-1) before GOR4 and GOR5. The change in HR under increased +Gz decreased from +39 +/- 3 bpm during GOR1 to +31 +/- 3 bpm during GOR4 and GOR5, but the decrease in eye level BP under +Gz was unaffected. RGT did not change across the five GORs. Increased resting BP and TPR following a single +Gz exposure suggest alterations in the cardiovascular system expected to confer improved tolerance during subsequent exposures. However, these changes were insufficient to improve +Gz tolerance measured during repeated GORs separated by 2 min.

+Gz tolerance, with and without muscle tensing, following loss of anti-G trouser pressure.

Fast jet aircrew are heavily reliant on anti-G trousers (AGT) and failure of the garment or its pressure supply would expose them to high levels of +Gz acceleration without protection. A previous study demonstrated the severity of this event at high +Gz, but no data exists as to the maximum +Gz level which could be tolerated. : While relaxed and with lower body muscle tensing, 10 experienced centrifuge subjects had their AGT deflated after 5 and 30 s of +Gz exposure. Discrete +Gz exposures of increasing intensity were performed until deflation resulted in central light loss (CLL). Visual symptoms, eye-level systolic BP (SBPeye), and mean blood flow velocity in the middle cerebral artery (MCAVmean) were recorded. The mean +Gz level at CLL following AGT deflation was comparable to that without AGT inflation (+4.07 Gz) and increased by muscle tensing (+0.53 G) independent of exposure duration. Initial visual symptoms occurred more rapidly in the shorter +Gz exposures, while progression to CLL was quicker with muscle tensing compared with relaxed, but never less than 6.7 s. At CLL, the nadir in SBPeye was higher (+17 mmHg) with muscle tensing compared with relaxed, while MCAVmean was decreased by about 50% in all conditions. +Gz tolerance following AGT deflation is comparable to that without inflation and only modestly increased by muscle tensing. Although vision is maintained for several seconds following AGT deflation, progression of light loss symptoms can be rapid, possibly resulting in insufficient time to respond before G-induced loss of conciousness (G-LOC) ensues.

+Gz ubrzanje i oksidativni stres

+Gz ubrzanje i oksidativni stres

Flat Spin and Negative G&lt;SUB&gt;z&lt;/SUB&gt; in High-Altitude Free Fall: Pathophysiology, Prevention, and Treatment

Red Bull Stratos was a commercial program that brought a test parachutist protected by a full pressure suit to 127,852 ft (38,964 m), via a stratospheric balloon with a pressurized capsule, from which he free fell and subsequently parachuted to the ground. In light of the uniqueness of the operation and the medical threats faced, medical protocols specific to distinctive injury patterns were developed. One unique threat was that of a flat spin during free fall with resultant exposure to -Gz (toe-to-head) acceleration. In preparation for stratospheric free fall, the medical team conducted a review of the literature on the spectrum of human and animal injury patterns attributable to -Gz exposures. Based on the findings, an emergency medical field response protocol was developed for the rapid assessment, diagnosis, and treatment of individuals suspected of -Gz injury. A systematic review was conducted on available literature on human and animal studies involving significant -Gz exposure, with subsequent development of an applicable field treatment protocol. The literature review identified pathophysiologic processes and mitigation strategies that were used to develop a prevention and treatment protocol, outlining appropriate interventions using current best medical practices. A medical field treatment protocol was successfully established for the high-altitude balloon program. Available literature provided insight into best medical practices for the prevention and treatment of significant -Gz exposures during high-altitude parachute activity. Using the protocol developed for the field medical response, injuries from sustained -Gz exposure can be effectively managed in similar high-altitude and space operations.