Gravity induced loss of consciousness

The Gravitational Acceleration Test (G-test) is a demanding, and sophisticated high-intensity physical activity, greatly influenced by individual body composition and physical strength. This study analyzed the general nutrition knowledge questionnaire (GNKQ) responses of Air Force cadets to identify the relationship between nutrition knowledge, body composition, physical activity, physical strength, and gravity-induced loss of consciousness. Based on the G-test results, 105 fourth-year Air Force cadets were divided into two groups: GP (G-test pass group) and GF (G-test fail group)...

INTRODUCTION: There is no consensus on whether cardiopulmonary reserve affects the risk of gravity-induced loss of consciousness (G-LOC) or almost loss of consciousness (A-LOC). Few previous studies have used cardiopulmonary exercise testing (CPET) to assess cardiopulmonary reserve function (CPRF) of fighter aviators. We compared CPET-related parameters in G-LOC/A-LOC and non-G-LOC/A-LOC fighter aviators to explore the effect of cardiopulmonary reserve function on G tolerance. METHODS: A total of 264 male fighter aviators with more than 500 h of flight experience participated in the study, all of whom underwent CPET and human centrifuge testing...

INTRODUCTION: Gravity-induced loss of consciousness (G-LOC) is a major threat to fighter pilots and may result in fatal accidents. The brain has a period of 5-6 s from the onset of high +Gz exposure, called the functional buffer period, during which transient ischemia is tolerated without loss of consciousness. We tried to establish a method for predicting G-LOC within the functional buffer period by using machine learning. We used a support vector machine (SVM), which is a popular classification algorithm in machine learning...

Introduction: Orthostatic dysregulation occurs during exposure to an increased gravitational vector and is especially common upon re-entering standard Earth gravity (1 g) after an extended period in microgravity (0 g). External peripheral skin cooling (PSC) has recently been described as a potent countermeasure against orthostatic dysregulation during heat stress and in lower body negative pressure (LBNP) studies. We therefore hypothesized that PSC may also be an effective countermeasure during hyper-gravity exposure (+Gz)...

INTRODUCTION: Several previous studies have reported that hypoxia accidents of fighter pilots are rarer than gravity-induced loss of consciousness and spatial disorientation; however, the risk is greater. Therefore, this study aimed to investigate the relationship between physical fitness and body composition on time of useful consciousness (TUC) in hypobaric hypoxia. MATERIALS AND METHODS: Body composition and physical fitness testing on human participants were performed; subsequently, they were exposed to hypobaric hypoxia at a simulated altitude of 25,000 ft...

Exposure to acute transition from negative (-Gz) to positive (+ Gz) gravity significantly impairs cerebral perfusion in pilots of high-performance aircraft during push-pull maneuver. This push-pull effect may raise the risk for loss of vision or consciousness. The aim of the present study was to explore effective countermeasures against cerebral hypoperfusion induced by the push-pull effect. Twenty healthy young volunteers (male, 21 ± 1 year old) were tested during the simulated push-pull maneuver by tilting...

OBJECTIVE: Anti-gravity straining maneuver (AGSM) helps to reduce the occurrence of gravity-induced visual disturbances and loss of consciousness. An objective assessment of the AGSM is still missing during ground training. This study evaluated the feasibility of using electrical impedance tomography (EIT) to assess the performance of AGSM. METHODS: Eight undergraduates and eight teachers majoring in aerospace medicine were included in the study. An experienced professor from the department of aerospace medicine reviewed the key points of AGSM with each subject...

Gravity in the head-to-toe direction, known as +Gz (G force), forces blood to pool in the lower body. Fighter pilots experience decreases in blood pressure when exposed to hypergravity in flight. Human centrifuge has been used to examine the G tolerance and anti-G straining maneuver (AGSM) techniques of military pilots. Some factors that may affect G tolerance have been reported but are still debated. The aim of this study was to investigate the physiological responses and anthropometric factors correlated with G tolerance...

KEY POINTS: Rapid alterations of gravitational stress during high-performance aircraft push-pull manoeuvres induce dramatic shifts in volume and pressure within the circulation system, which may result in loss of consciousness due to the rapid and significant reduction in cerebral perfusion. There are still no specific and effective countermeasures so far. We found that lower body negative pressure (LBNP), applied prior to and during -Gz and released at the subsequent transition to +Gz, could effectively counteract gravitational haemodynamic stress induced by a simulated push-pull manoeuvre and improve cerebral diastolic perfusion in human subjects...

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...

Orthostatic instability is one of the main consequences of weightlessness or gravity challenge and plays as well a crucial role in public health, being one of the most frequent disease of aging. Therefore, the assessment of effective countermeasures, or even the possibility to predict, and thus prevent orthostatic instability is of great importance. Heat stress affects orthostatic stability and may lead to impaired consciousness and decrease in cerebral perfusion, specifically during the exposure to G-forces...

Purpose: The purpose of this study was to evaluate the effect of gravity acceleration on choroidal and retinal nerve fiber layer (RNFL) thickness using swept-source optical coherence tomography (SS-OCT). Methods: Thirteen healthy volunteers who planned to participate in human centrifuge training as part of the flight surgeon selection process enrolled this study. During centrifuge training, gravity was gradually increased up to six times that of sea level. All subjects underwent complete ophthalmologic examination and three-dimensional wide-scanning SS-OCT imaging (DRI OCT-1 Atlantis; Topcon, Tokyo, Japan)...

Pilots are required to have the ability to evaluate their own physical and psychological status to operate high performance aircrafts effectively. Existing studies have lacked consideration of applying bio signal of pilots in real time flight situation. The purpose of this study is to develop a wearable bio signal monitoring system that can measure the condition of pilots under an extreme flight environment to ensure flight safety. The wearable bio signal monitoring system consists of an algorithm for evaluating pilots' physiological stability, algorithms for detecting Gravity-induced Loss of Consciousness (G-LOC) prognosis, pilots' interaction module, and pilots' context awareness platform...

BACKGROUND: Consensus on whether physical condition affects the risk of gravity-induced loss of consciousness (G-LOC) has not been reached, and most previous studies about the issue did not include well-experienced aviators. We compared the physical conditions of well-experienced young aviators according to the occurrence of G-LOC during human centrifuge training. METHODS: Among 361 young male aviators on active flight duty with experience in high performance aircrafts for at least 2 years, 350 had full data available and were reviewed in this study...

INTRODUCTION: +G(z) exposure above the tolerance threshold typically induces a sequence of symptoms/signs, with loss of: peripheral vision, central vision (black out), and consciousness (G-LOC). The aims of this study were to investigate: 1) whether G history influences latent time to, or sequence of, symptoms/signs upon G exposures exceeding the tolerance threshold; and 2) how pilots respond to a sudden loss of pressure in the anti-G garment (AGG) in flight-like scenarios. METHODS: There were 14 subjects who were exposed to rapid onset rate +G(z)-time profiles, with plateaus 1 and 2 G above the relaxed tolerance level, without initial pressurization of the AGG (NoAGG) and when losing AGG pressure after 10 (AGG_10) and 120 (AGG_120) s at the plateau...

INTRODUCTION: Blast injuries are psychologically and physically devastating. Notably, primary blast injury occurs as a direct effect of changes in atmospheric pressure caused by a blast wave. The combat-related traumatic brain injuries (TBI) resulting from exposure to explosions is highly prevalent among military personnel who have served in current wars. Traumatic brain injury is a common cause of neurological damage and disability among civilians and servicemen. Most patients with TBI suffer a mild traumatic brain injury with transient loss of consciousness...

INTRODUCTION: 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. METHODS: 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 Push-Pull Effect (PPE) is a physiological phenomenon defined as a reduction of +Gz tolerance induced by a previous exposure to a -Gz acceleration, that may lead to loss of consciousness. Aim of this study was to evaluate, for the first time, the cardiac rhythm changes associated with PPE during real flights. Data were collected in 3 pilots during flights on the Aermacchi MB- 339-CD aircraft. In each flight, lasting about 60 minutes, ECG, respiration and 3D accelerations were recorded by a new smart garment (the MagIC System)...

OBJECTIVE: The aim of this study was to track the course of cerebral tissue oxygen saturation (rSO2) and pilot performance during an episode of gravity-induced loss of consciousness (GLOC). BACKGROUND: GLOC, a major problem facing pilots of high-performance aircraft, is brought about by a sudden reduction in rSO2 as a result of increased +Gz force. It consists of 24 s of complete functional impairment followed by a prolonged period of performance recovery. This study tested the hypothesis that delayed recovery in GLOC is caused by a slow return of rSO2 following removal of the g-force that induced the episode...

Gravity-induced loss of consciousness (G-LOC) is caused by loss of cerebral blood flow during high +Gz (head-to-foot inertial forces). The resistance of the jugular vein is a significant factor in decrease in cerebral blood flow. Ultrasonography of thoracic inlet veins, including internal jugular vein, is feasible to visualize the internal jugular vein and hemodynamic information. Anti-gravity straining maneuver (AGSM) was widely recognized as one of the important factors in preventing G-LOC. The purpose of this study was to evaluate the relationship between the ultrasonographic shape and size of internal jugular vein during AGSM and G-LOC...