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Biomedical subjects

A H Rupert

Publications and source records attributed to A H Rupert.

9 recordsLinked to original sources
PubMed1995

Visually triggered migraine headaches affect spatial orientation and balance in a helicopter pilot.

The authors present a case of an attack helicopter pilot with recurrent spatial disorientation (SD) flying with night vision goggles (NVG's), diagnosed as having visually triggered migraine headaches. Serial Dynamic Platform Posturography testing during an acute migraine attack demonstrated balance dysfunction under visual and somatosensory deficient conditions, correlating with headache intensity. Vestibular symptoms are associated with migraine, and may be triggered by visual stimuli. NVG scintillations in susceptible individuals may act as a visual trigger for migraine. Migraine phenomenon may be a contributing factor to SD, especially during NVG operations. The association of visual and vestibular dysfunction with migraine and aeromedical disposition of migraine in aviators is discussed.

Adult↗
PubMed1994

The "push-pull effect".

The purpose of this study was to prove or refute previous authors' suggestions that tolerance to +Gz is reduced when preceded by 0 Gz or -Gz. Six men and six women were subjected to one session of acceleration stresses that varied between -2 and +2.25 Gz on the NAMRL Coriolis Acceleration Platform (CAP). At the beginning and end of each session, we exposed the relaxed subjects to identical control segments that were comprised of +1 Gz for 30 s, followed by +2.25 Gz for 15 s, and then return to +1 Gz. Subjects were also exposed to three experimental segments that were comprised of 0, -1, or -2 Gz for 10 s, followed by +2.25 Gz for 15 s, and then return to +1 Gz. Subjects verbally reported any decrements in peripheral vision during exposure to +2.25 Gz. Blood pressure (BP) was reduced during each 15-s period at +2.25 Gz. The minimum BP was progressively lower during the 15-s period as the preexposure experimental conditions became more negative (+1, 0, -1, and -2 Gz). Episodes of peripheral vision loss increased as the preceding -Gz became more negative. BP during exposure to +Gz was significantly affected by the preceding 10-s exposure to -Gz, and is indicative of reduced +Gz tolerance. As this "push-pull effect" may result in unexpected incapacitation, it has important implications for aviation safety.

Acceleration↗
PubMed1992

The dynamics of spatial orientation during complex and changing linear and angular acceleration.

The dynamics of spatial orientation perception were examined in a series of experiments in which a total of 43 subjects were passively exposed to various combinations of linear and angular acceleration during centrifuge runs. Perceptual effects during deceleration were much stronger than effects during acceleration. The dynamics of spatial orientation perception differed substantially from changes in the vestibulo-ocular reflex (VOR). VOR was fairly well predicted by a current model, but our experiments revealed perceived change in attitude (roll, pitch, yaw tilt position in space) and perceived angular velocity in space that was not reflected by parallel changes in the plane or magnitude of the VOR. This series of experiments establishes several facts concerning spatial orientation perception beyond the predictive domain of any current model. New concepts are needed and several are suggested to deal with changing reactions to complex combinations of linear and angular accelerations.

Acceleration↗
PubMed1992

Spatial disorientation and dysfunction of orientation/equilibrium reflexes: aeromedical evaluation and considerations.

Loss of spatial awareness has been implicated as a direct causal factor in 4-10% of serious aircraft mishaps and 10-20% of fatal aircraft mishaps (7). Spatial disorientation in flight usually results from misperception of visual, vestibular, or proprioceptive cues. Pathologic causes have rarely been implicated. A student naval aviator with recurrent loss of spatial awareness due to a defective vestibulo-ocular reflex (VOR), presumably from vestibular neuronitis in adolescence, is reported. His chief complaint, an inability to focus on the instrument panel during turbulent instrument meteorological conditions (IMC), resulted in spatial disorientation and adverse flight attitude. A simple test of visual-vestibular interaction, the dynamic visual acuity test, could identify a defective vestibulo-ocular reflex in aviation personnel. An absent or defective vestibulo-ocular reflex has potential for disorientation in instrument flight. A comprehensive vestibular function test battery is indicated in individuals with recurrent or overwhelming spatial disorientation who fail a screening dynamic visual acuity test. The aeromedical disposition of vertigo and dysequilibrium is discussed.

Adult↗
PubMed1991

Steady state and transient G-excess effects.

Acceleration forces of flight are associated with a number of spatial orientation illusory effects. This note focuses on two effects, both called the "G-excess effect." A distinction between steady-state and transient G-excess effects is important because prescriptions for preventive management of effects in flight will differ.

Acceleration↗
PubMed1990

B virus (Herpesvirus simiae) infection in humans: epidemiologic investigation of a cluster.

A cluster of four cases of symptomatic B virus infection in humans occurred in Pensacola, Florida, in March 1987. Three cases occurred in persons who worked with monkeys at a research facility, and the fourth resulted from apparent autoinoculation through use of a nonprescription skin cream. Contact tracing identified 159 persons who may have been exposed to B virus (21 had been exposed to monkeys at the facility and 138 had been exposed to one or more of the case-patients), but no further cases were identified. Comparisons of restriction endonuclease patterns from B virus isolates linked two of the three cases in monkey handlers to one clinically ill monkey and the other to a second, healthy monkey. Three risk factors for human infection were identified: nonuse of mechanical or chemical restraints for monkeys before handling, nonuse of available protective gear, and direct viral inoculation through the application of a topical medication.

Acute Disease↗
PubMedDate not supplied

Vestibulo-ocular response of human subjects seated in a pivoting support system during 3 Gz centrifuge stimulation.

The vestibulo-ocular reflex (VOR) and spatial orientation perceptions were recorded in 15 subjects during 3 Gz centrifuge runs. These data were obtained to study two issues: (1) to gain insight into reports of asymmetrical disorientation and disturbance during acceleration and deceleration of centrifuge runs like those used to train pilots on the procedures to counteract G-induced loss of consciousness (G-LOC); (2) to study the effects of sustained vertical linear acceleration on the vestibular system. The centrifuge angular velocity profile consisted of a 19 s angular acceleration to 3 Gz that was sustained for 5 min during a period of constant angular velocity, and a 19 s deceleration to 1 Gz. The runs were repeated three times with the subject facing the motion and three times with the subject's back to the motion. The VOR and spatial orientation perceptions from the eight subjects who completed all six runs were analyzed. The total VOR response during acceleration and deceleration was composed of interacting angular (AVOR) and linear components (LVOR). Asymmetries in pitch orientation perception between centrifuge acceleration and decleration were not matched by asymmetries in the total VOR slow phase velocity. During the constant velocity high-G phase of the run, sustained up-beating LVOR (Lz nystagmus) was present in 14 of the 15 subjects. Significant individual differences in Lz nystagmus were found, but the maximum Lz response in our 15 subjects was probably of insufficient magnitude to degrade visual scan of cockpit instruments. Mean magnitudes ranged from 0 to 10 deg/s at 90 s from onset of centrifuge run.

Adult↗