Initial Investigation of a Grating Stimulus as a Visual Endpoint for Human Centrifuge Research.

G tolerance has been widely assessed using Peripheral Light Loss (PLL), but this approach has several limitations and may lack sensitivity. The aim of this study was to investigate the use of a foveal visual endpoint for centrifuge research (Grating Loss; GL) and assess its repeatability, reliability, and usability with PLL as a reference. A total of 11 subjects undertook centrifuge assessment.

Physiological Effects of Centrifuge-Simulated Suborbital Spaceflight.

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. There were 24 healthy subjects recruited into 'younger' (18-44 yr), 'intermediate' (45-64 yr) and 'older' (65-80 yr) age groups.

Indirect Measurements of Acceleration Atelectasis and the Role of Inspired Oxygen Concentrations.

A growing number of symptom reports suggestive of acceleration atelectasis in fast jet aircrew have raised the question as to whether traditional guidelines on inspired gas composition remain valid. The aim of this study was to assess the effects of inspired O₂ concentration on the development of acceleration atelectasis when wearing modern anti-G garments. There were 14 nonaircrew subjects who completed 5 centrifuge exposures to +5 G lasting 90 s.

Pulmonary Effects of Sustained Periods of High-G Acceleration Relevant to Suborbital Spaceflight.

Members of the public will soon be taking commercial suborbital spaceflights with significant G (chest-to-back) acceleration potentially reaching up to 6 G. Pulmonary physiology is gravity-dependent and is likely to be affected, which may have clinical implications for medically susceptible individuals. During 2-min centrifuge exposures ranging up to 6 G, 11 healthy subjects were studied using advanced respiratory techniques.

Dynamic lung behavior under high G acceleration monitored with electrical impedance tomography.

. During launch and atmospheric re-entry in suborbital space flights, astronauts are exposed to high G-acceleration. These acceleration levels influence gas exchange inside the lung and can potentially lead to hypoxaemia.

Indices of acceleration atelectasis and the effect of hypergravity duration on its development.

New Findings: What is the central question of the study? The aim was to determine the effects of duration of acceleration in the cranial-caudal direction (+Gz) on acceleration atelectasis and identify measurement techniques that can be used to assess it. What is the main finding and its importance? Non-invasive measurement of acceleration atelectasis using electrical impedance tomography and estimates of pulmonary shunt provide more detailed assessment of acceleration atelectasis than traditional forced vital capacity measures. Using these techniques, it was found that as little as 30 s of exposure to +Gz acceleration can cause acceleration atelectasis.

Hemodynamic Responses and G Protection Afforded by Three Different Anti-G Systems.

UK Royal Air Force fast jet aircrew use three different anti-G systems, however, little objective comparison of the G protection they provide exists. The G-protection afforded by each system and associated hemodynamic responses were investigated. Ten subjects performed centrifuge acceleration exposures using Mk-10 (S1) and Mk-4 (S2) five-bladder anti-G trousers (AGT) and full coverage AGT plus pressure breathing for G-protection (PBG; S3).

Aircrew Conditioning Programme Impact on +Gz Tolerance.

Physical conditioning may improve aircrew performance during exposure to high +G acceleration, although few studies have directly assessed this. The present study investigated the effects of a 12-wk Aircrew Conditioning Programme (ACP) on markers of G tolerance. The ACP comprises aerobic and muscle strengthening exercise performed twice weekly and targets improved fitness and reduced injury risk.

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

Background: 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.

Methods: 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.

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

Background: 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.

Methods: : While relaxed and with lower body muscle tensing, 10 experienced centrifuge subjects had their AGT deflated after 5 and 30 s of +Gz exposure.

Subjective and objective measures of relaxed +Gz tolerance following repeated +Gz exposure.

Background: Repeated exposure to +Gz acceleration provokes cardiovascular adaptations of potential benefit to pilots' +Gz tolerance, but whether such changes actually improve human tolerance to +Gz acceleration is uncertain. This study assessed +Gz tolerance before and after repeated exposure to +Gz at two different intensities as the role of frequency of +Gz exposure in adaptation also remains unknown.

Methods: In a cross-over design, 10 experienced male centrifuge volunteers completed two experimental conditions separated by at least 3 wk.

Garment fit and protection from sustained +Gz acceleration with 'full-coverage' anti-G trousers.

Introduction: Garment fit may influence the effectiveness with which Full-Coverage Anti-G Trousers (FCAGT) transmit pressure to the skin surface, and hence provide protection from sustained +Gz acceleration. A search of the available literature, however, did not reveal any prior work quantifying this effect.

Methods: Three related studies were performed.