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Biomedical subjects

K K Gillingham

Publications and source records attributed to K K Gillingham.

At least 19 recordsLinked to original sources
PubMed1994

United States Air Force head-up display control and performance symbology evaluations.

The United States Air Force has conducted an extensive research effort to determine the most effective way to present aircraft control, performance, and navigation information on the head-up display (HUD). The primary objective of the research was to develop a standard HUD symbology set to be used as a primary flight reference for fighter-type aircraft during instrument meteorological conditions. This paper summarizes the research conducted by scientists in the Visual Orientation Laboratory at the Flight Motion Effects Branch of the Human Systems Center's Armstrong Laboratory. Five experiments that examined various control and performance symbology elements are reviewed. Suggested standardization guidelines based on experimental findings are discussed, including the following: the use of counter-pointers for airspeed and altitude indicators, vertical and horizontal asymmetry for climb/dive ladder configurations, a ghost horizon, analog vertical-velocity information, energy management symbology, and quickening for climb/dive markers.

Aerospace Medicine↗
PubMed1994

Classification problems of U.S. Air Force spatial disorientation accidents, 1989-91.

Spatial disorientation (SD) continues to contribute to a fairly constant proportion of military aircraft accidents. The U.S. Air Force (USAF) fielded a new accident investigation reporting form in July 1989, which for the first time specified Type I SD, Type II SD, and Type III SD as possible causes of aircraft accidents. Of a total of 91 major accidents that occurred over the 2-year period beginning in October 1989, SD was rated as contributing significantly to 13 (14%). Coding for SD on accident investigation reporting forms was not consistent, however. Individual flight surgeons differed in their approaches to coding accidents as SD-related; other differences were noted between flight surgeons and pilots, and additional procedural differences resulted in inconsistent reporting over time. There is a consensus that SD represents a major problem in military aviation, but a scientific approach to this important problem would be facilitated if agreement could be reached on definitional and semantic issues.

Accidents, Aviation↗
PubMed1992

The spatial disorientation problem in the United States Air Force.

Spatial disorientation (SD) in flight wastes hundreds of millions of dollars worth of defense capability annually and continues to kill air-crew. SD results primarily from inadequacies of human visual and vestibular sensory systems in the flying environment; but other factors, such as task saturation and distraction, precipitate it. The United States Air Force is conducting a three-pronged research and development effort to solve the SD problem. We are attempting 1) to elucidate further the mechanisms of visual and vestibular orientation and disorientation, 2) to develop ground-based and inflight training methods for demonstrating to pilots the potential for SD and the means of coping with it, and 3) to conceive and evaluate new ways to display flight control and performance information so that pilots can maintain accurate spatial orientation.

Aerospace Medicine↗
PubMed1992

Visual scene effects on the somatogravic illusion.

This study attempted to determine which visual scene cues are most effective in overcoming the somatogravic illusion (SGI), a form of spatial disorientation that occurs when a shift in the resultant gravitoinertial force vector created by a sustained linear acceleration is misinterpreted as a change in pitch or bank attitude. Nine subjects were exposed to a gravitoinertial force shift of -30 degrees in the pitch plane, both with their eyes closed and while viewing computer-generated visual scenes through a wide field-of-view head-mounted display. The scenes depicted acceleration over a shoreline by means of horizon, texture, perspective, and color cues that were presented both in isolation and in various combinations. None of the scenes significantly reduced the magnitude of the SGI relative to the eyes-closed (baseline) pitch illusion, even though the textured scenes produced some linear vection. It remains to be established whether low-cost head-mounted visual displays can reliably reduce the magnitude of the SGI and other spatially disorienting illusions.

Acceleration↗
PubMed1991

A test of thumb and index finger control in overcoming a visual analogue of the giant hand illusion.

Anecdotal evidence suggests that a thumb and index finger grip might facilitate recovery from the manifestation of spatial disorientation known as the giant hand phenomenon. Sixteen pilots volunteered as subjects in an experiment that compared the effectiveness of the thumb and index finger versus the whole hand technique to overcome a visually-induced analogue of the giant hand phenomenon. Thumb and index finger control produced greater stability overall, but did not overcome the specific tracking bias induced by a background visual roll stimulus. Various hypotheses are discussed as to why the thumb and index finger technique was ineffective in the present instance.

Adult↗
PubMed1990

Rigid gas-permeable contact lens wear during + Gz acceleration.

This study was designed to determine how well rigid gas-permeable contact lenses maintain position on the cornea under high G forces, and the effect on visual acuity. One hyperopic and five myopic subjects were fitted with lenses made from Pasifocon C material (specific gravity = 1.07). Two lens diameters (8.8-9.4 mm and 9.6-10.0 mm) were compared upon the myopic subjects for centering on the cornea. Visual acuity was measured at + 1 Gz (baseline), +3 Gz, +4 Gz, +6 Gz, and +8 Gz in the straight-ahead, lateral, and up-gaze positions from three acuity charts mounted in the gondola. All lenses, as estimated from the videotape, decentered down the z axis 2-3 mm at high + Gz. Visual acuity was reduced at the higher +Gz levels to similar measurements in most subjects for both the contact lens and spectacle control rides. No lens displaced from the cornea or dislodged from the eye during any of the 25 centrifuge runs.

Aerospace Medicine↗
PubMed1990

A case of left hypoglossal neurapraxia following G exposure in a centrifuge.

Isolated hypoglossal (XIIth cranial nerve) neurapraxia is a rare clinical presentation. We present a case of an isolated hypoglossal neurapraxia following exposure to +7.2 Gz in a human centrifuge. Although a variety of cervical spine injuries have been reported as a result of G exposure in an aircraft, no cranial nerve injuries have been reported. A review of the literature of isolated hypoglossal neurapraxia is presented with discussion of the probable cause of this nerve injury.

Adult↗
PubMed1990

The effects of acoustic orientation cues on instrument flight performance in a flight simulator.

An initial version of an acoustic orientation instrument (AOI), in which airspeed was displayed as sound frequency, vertical velocity as amplitude modulation rate, and bank angle as right-left lateralization, was evaluated in a T-40 (Link GAT-3) motion-based simulator. In this study, 15 pilots and 3 non-pilots were taught to use the AOI and flew simulated flight profiles under conditions of neither visual nor auditory instrumentation (NO INPUT), AOI signals only (AOI), T-40 simulator instrumentation only (VISUAL), and T-40 simulator instrumentation with AOI signals (BOTH). Bank control under AOI conditions was significantly better than under the NO INPUT condition for all flying tasks. Bank control under VISUAL conditions was significantly better than under the AOI condition only during turning and when performing certain complex secondary tasks. The pilots' ability to use the AOI to control vertical velocity and airspeed was less apparent. However, during straight-and-level flight, turns, and descents the AOI provided the pilots with sufficient information to maintain controlled flight. Factors of potential importance in using sound to convey aircraft attitude and motion information are discussed.

Acoustic Stimulation↗
PubMed1988

High-G stress and orientational stress: physiologic effects of aerial maneuvering.

G stress can readily incapacitate pilots of modern fighter aircraft and result in mishaps due to G-induced loss of consciousness (GLC). The physiologic effects of high-G stress, including decreased head-level blood pressure due to hydrostatic pressure drop and decreased cardiac output due to inadequate venous return, result in the symptoms of visual loss and GLC. The body's primary natural defenses against the effects of G stress in flight, i.e., the neural tissue energy reserve and the cardiovascular baroceptor reflexes, determine the characteristic shape of the G-time tolerance curve, which is presented. Means of raising G tolerance fall into three categories: mechanical, physiological, and educational. Mechanical means include anti-G suits and valves, assisted positive-pressure breathing (APPB) systems, and special seats in which the seatback is reclined and/or the pilot's legs are elevated. Physiological means include frequent exposure to G stress, physical conditioning (weight training and moderate aerobic conditioning), selection of pilots for high natural tolerance, and performance of a vigorous and efficient anti-G straining maneuver. Educational means include briefings on methods of enhancing tolerance, and high-G training in a centrifuge to allow the pilot to perfect his anti-G straining maneuver. An improved anti-G valve, physical conditioning, high-G awareness briefings, and centrifuge training are now being applied in efforts to prevent GLC in current fighter aircraft. Future generations of even more maneuverable aircraft will probably necessitate the use of APPB, pilot selection, and high-G seats for protection of pilots from the effect of sustained high G forces.

Aerospace Medicine↗
PubMed1988

High-G training for fighter aircrew.

From 8 Jan 85 through 12 Feb 86, 741 USAF fighter aircrew from Tactical Air Command underwent high-G training at the USAF School of Aerospace Medicine, the major objectives of the training being to increase their understanding of G stress and G protection and to raise their G tolerance. The didactics centered on discussion of the G-time tolerance curve and demonstration of an effective anti-G straining maneuver (AGSM). Exposure to G stress on the USAFSAM centrifuge allowed the trainees to determine their G tolerances and to perfect and practice their AGSM. The trainees' mean relaxed and straining G tolerances on the gradual-onset run (GOR) without anti-G suit inflation were 5.2 and 8.3 G, respectively; and 41% of the trainees reached the 9.0-G run limit. All but two of the trainees completed the 8-G, 15-s rapid-onset run (ROR) with anti-G suit inflated; 94% completed the 9-G, 15-s ROR; and 93% were able to tolerate the 9-G, 10-s ROR while looking back over their left shoulder. G-induced loss of consciousness (G-LOC) occurred in 9% of the trainees, most commonly on the GOR, less often on the 9-G RORs. Motion sickness was a significant problem in less than 1% of the trainees. Critiques provided by 382 trainees revealed 73% enthusiastic or positive assessments of the training, as opposed to only 2% negative or hostile responses. We conclude that high-G training is well-tolerated by fighter aircrew and is a highly appropriate method for minimizing the potential for aircraft mishaps due to G-LOC in flight.

Cognition Disorders↗
PubMed1987

Induction and prevention of acceleration atelectasis.

Acceleration atelectasis is the absorptional collapse of alveoli in the dependent lung due to increased accelerative forces. It is exacerbated by breathing 100% oxygen and, during +Gz exposure, by the use of an anti-G suit. Experiments were conducted on 12 subjects using simulated aerial combat maneuvers (SACM) with G profiles having peak exposures of either 4.5 G or 9 G. Decreases in vital capacity (VC) measurements were used as quantification of atelectasis, two types of reduction being identified and described. Labile reductions in VC were readily restored by a deep breath or cough. Such reduction approximated 28% following the 4.5-G SACM and 25% following the 9-G SACM. More persistent (so called) stable reductions were of lesser degree, values of -20% being seen following both 9 G and 4.5 G maneuvers. Acceleration atelectasis causes symptoms of chest pain, coughing, and shortness of breath. Subjective ratings of the severity of these symptoms were obtained from the subjects, and these were much greater following the 4.5-G SACM exposures than after the 9-G runs. Acceleration atelectasis was reduced by dilution of the inspired oxygen concentration by argon and nitrogen (evaluated at 95, 82.5, 70, 50, and 20% oxygen); the addition of unassisted positive pressure at 30 mm Hg (4 kPa) to the breathing mask; or the performance of the anti-G straining maneuver (AGSM).

Acceleration↗
PubMed1987

G-tolerance standards for aircrew training and selection.

G tolerance widely among individuals. It stands to reason that aircrew with higher G tolerance are less likely to experience symptoms of G stress in flight than are those with lower G tolerance, and that they can fly highly maneuverable aircraft with greater safety and effectiveness. To assure that aircrew with abnormally low G tolerance are not assigned to aircraft that operate in the high-G environment, a G-tolerance standard and the means to implement that standard are necessary. Since 1977, for human centrifuge operations, the USAF School of Aerospace Medicine has used an informal G-tolerance standard for selecting experimental subjects, evaluating medically disqualified aircrew, and ensuring efficacy of high-G training for aircrew. That standard consists of the subject's being able to sustain a rapidly applied +7-Gz load for 15 s, without totally losing peripheral vision or losing consciousness, while wearing a functioning anti-G suit, performing an anti-G straining maneuver, and sitting in a conventionally configured fighter aircraft seal. Inability to tolerate a 7-G, 15-s, rapid-onset G profile in a centrifuge is also the basis of internationally recognized (NATO, ASCC) definitions of low G tolerance. The rationale for choosing the 7-G, 15-s standard is discussed. Experience with use of this standard, and the equivalent standard of 8 G for 15 s when the F-16-configured seat is used, reveals that fewer than 1% of actively flying aircrew are unable to meet the standard. Eventually a formal, more stringent, G-tolerance standard may become a valuable component of the means of selecting and training aircrew for high-performance fighter aircraft.

Aerospace Medicine↗
PubMed1986

Women's G tolerance.

G tolerances of 102 women and 139 men subjected to Standard Medical Evaluation (Medeval) G Profiles were compared. Unpaired t-tests revealed no significant difference between the women and men in either relaxed or straining G tolerance. Covariance analysis controlling for differences in tolerance due to age, height, weight, and activity status revealed the women to have marginally lower tolerance; the analysis also identified height as a factor having a strong negative influence on G tolerance, and weight as having a positive influence. When the women were matched only by height to the men in the comparison group, the women's mean G tolerances were significantly lower than the men's. On Standard Training G Profiles 88% of 24 women and 80% of 213 men completed the runs, but this difference was not significant. G tolerances of 47 women were measured on the Medeval Profiles both during and between menses, but no significant differences related to menstruation were found. No important differences between women and men in signs or symptoms of G stress were observed, except for two instances of urinary stress incontinence in women during the Training Profiles. We conclude that women should not categorically be excluded from aircrew duties for reasons of G intolerance.

Adult↗
PubMed1983

Medical standards for experimental human use in acceleration stress research.

Acceleration research is necessary to ensure optimum protection for individuals flying high performance fighter aircraft. Human volunteers exposed to high sustained +Gz stress must be carefully screened to assure that no one is at increased risk for G-induced trauma. Rigorous medical standards for qualifying research subjects must be established and followed. Careful documentation of G-related symptoms and physiologic disturbances enhances the safety aspects of human experimentation. No severe or life-threatening incidents have occurred. A number of symptoms resulting from +Gz exposure have been documented with loss of consciousness being the most frequently documented symptom. The most frequent medical reason for disqualifying an individual volunteer from participation in the acceleration program was because of irregularities noted on spinal x-rays. The current medical standards and clinical diagnostic testing used to screen volunteer subjects at the USAF School of Aerospace Medicine are reviewed along with the symptoms which have resulted over a three year period of high sustained +Gz stress exposures.

Acceleration↗
PubMed1982

G stress on A-10 pilots during JAWS II exercises.

Gz loads in A-10 aircraft were recorded on nine sorties during JAWS II exercises, and the pilots completed questionnaires on the effects of G stress in the A-10. Analysis of the recordings provided, among other statistics, the following means: maneuvering time, 28 min; peak +Gz load, +6.2; peak -Gz load, -0.1; G-time integral above 4 G, 85 G.s; G onsets greater than or equal to 6 G/s, 13. The questionnaires and follow-up interviews generated little evidence of G intolerance; the pilots did report significant task saturation, however. To compare the physiologic effects of G stress in the A-10 with those of G stress in the F-4, eight volunteer subjects were exposed to simulated A-10 and F-4 missions on the USAFSAM centrifuge. Although the two G-stress profiles were equally difficult and fatiguing, the subjects experienced less visual loss and had lower maximum heart rates during the A-10 profile.

Aerospace Medicine↗
PubMed1978

Calibration of a new ear oximeter in humans during exposure to centrifugation.

An optoelectronic ear oximeter (Hewlett-Packard, model 47201A) was evaluated as a noninvasive method for determining arterial oxygen saturation (SaO2) in human subjects during exposure to various levels of accelerative forces. This physiological calibration involved exposing five subjects, while breathing air and wearing the ear oximeter for 60 s to each of three levels of accelerative forces (3, 5, and 7 G); arterial blood samples were withdrawn concurrently. SaO2 was calculated indirectly from the oxygen tensions (PaO2) measured from the sampled arterial blood with a blood gas analyzer and corrected for pH and base excess. These data were compared, as were similar data taken from the same subjects breathing three different hypoxic gas mixtures while resitng at earth's gravity (1 G). Regression analyses of these data for both experimental groups (a, G exposure, or b, hypoxic exposure), comparing the ear-oximeter SaO2 with the calculated SaO2, showed the ear oximeter to be accurate with correlation coefficients of 0.95 and 0.98, respectively.

Adaptation, Physiological↗
PubMed1978

Relaxed +GZ tolerance in healthy men: effect of age.

Fifty-three healthy US Air Force aircrewmen, 26-55 yr old, volunteered for a centrifuge study designed to determine the effect of age on relaxed +GZ tolerance. Each was subjected to G forces of gradual and rapid onset, with G tolerance determined by standardized contraction of peripheral visual fields. Of the subject characteristics studied, only age was positively correlated with rapid-onset G tolerance; both age and weight were positively correlated with gradual-onset G tolerance. A combination of age and weight gave a stronger positive correlation with G tolerance (rapid- and gradual-onset) than did either characteristic alone. No significant negative correlations were observed. We conclude that aging may offer some protection from G stress; there is no evidence that aging leads to a decrement in G tolerance.

Adaptation, Physiological↗