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Biomedical subjects

H W Mertens

Publications and source records attributed to H W Mertens.

At least 19 recordsLinked to original sources
PubMed1988

Age, alcohol, and simulated altitude: effects on performance and breathalyzer scores.

Trained men in two age groups, 30-39 (n = 12) and 60-69 (n = 13), each performed at the Multiple Task Performance Battery in four separate full-day sessions with and without alcohol (2.2 ml of 100-proof vodka per kilogram of body weight) at ground level and at a simulated altitude of 12,500 ft (3,810 m). Subjects breathed appropriate gas mixtures through oxygen masks at both ground level and altitude. Mean breathalyzer readings peaked near 88 mg% and did not differ between age groups or altitude conditions. Younger subjects performed better than older subjects; performance of both age groups was significantly impaired by alcohol but these adverse effects were greater for the older subjects. No significant effects on performance were obtained due to altitude or to the interaction of altitude with alcohol. These results and those from several other studies suggest that prevalent views regarding the nature of the combined effects of alcohol and altitude on blood alcohol levels and on performance need to be redefined.

Adult↗
PubMed1987

Some effects of alcohol and simulated altitude on complex performance scores and breathalyzer readings.

Each of 17 men was trained on 7 tasks in the Multiple Task Performance Battery and then performed over a 2-week period in four experimental sessions: ground level with and without alcohol, and simulated altitude (12,500 ft), with and without alcohol. Subjects breathed appropriate gas mixtures through oxygen masks at both ground level and altitude. Alcohol doses of 100-proof vodka mixed with juice 2.2 ml X kg-1 of body weight. Results showed no differential effect of simulated altitude on breathalyzer readings (peaks averaged 78 mg % at 12,500 ft and 77 mg % at ground level). The best performance occurred at ground level under placebo conditions; the 12,500-ft simulated altitude produced some decrement for placebo scores. Alcohol at ground level resulted in significantly impaired performance during the morning sessions; the addition of altitude to the alcohol condition further depressed performance scores, but to about the same extent that placebo scores were depressed by altitude. Thus, there was no synergistic interactive effect of alcohol and altitude on either breathalyzer readings or performance scores.

Adult↗
PubMed1983

Effects of approach lighting and variation in visible runway length on perception of approach angle in simulated night landings.

Previous experiments in this laboratory have demonstrated illusions due to variations in both length and width of runways in nighttime "black hole" approaches. Even though approach lighting is not designed to provide vertical guidance, it is possible that cues from approach lights could interact with cues from runway lighting to reduce illusions due to variation in runway size. Two experiments were conducted to evaluate the effect of approach lighting on perception of approach angle in simulated night approaches. In the first experiment, 40 pilots made simulated visual approaches to a 150- by 6,000-ft runway (45.7-1829 m) with and without a 3,000-ft approach (914 m) light system (ALSF-2). Pilots controlled a moving runway model to produce a constant "normal" angle of approach over the distance range of 23,000 ft (7010 m) to 8,000 ft (2438 m) from threshold. In the second experiment, 24 pilots made simulated approaches to a 150- by 6,000-ft runway which was either fully visible or which had lights of the upwind half occluded. In addition, a 1,400-ft (427 m) abbreviated approach light system (SSALS) was used at three intensities. Decreasing the visible length of the runway by occulting lights of the far half increased mean generated approach angles from 2.2 degrees to 2.7 degrees in agreement with results of a previous experiment involving similar lengths of runways. Neither the presence of equal intensity approach lights nor uncomfortable glare from approach lights 20 times brighter than runway lights had an effect of practical significance on responses. These findings reinforce previous experimental demonstrations of the importance of runway size cues related to varying runway length, and also show that potential size cues provided by approach lights do not prevent illusions due to variations in runway size.

Adult↗
PubMed1979

Pilot performance during simulated approaches and landings made with various computer-generated visual glidepath indicators.

Two simulator experiments were conducted to quantify the effectiveness, in terms of pilot performance, of four different visual glidepath indicator systems (the 2-bar VASI, 3-bar VASI, T-VASIS, and PAPI) in the severely reduced nighttime visual environment often referred to as the "black hole." Performance in Experiment I was best with the T-VASIS and decreased with the 3-bar BASI, PAPI, and 2-bar VASI, in that order; but differences between the T-VASIS, 3-bar VASI, and Papi were not statistically significant. Approaches flown withou the ground-vased glidepath indicators tended to be low and extremely variable. Observing behavior was compared in approaches with the T-VASIS and 2-bar VASI. Observing response frequency increased as distance from runway threshold decreased and was significantly higher with the T-VASIS. Differences in performanange provided by a given system and to the rate of observing the indicator during approaches.

Aerospace Medicine↗
PubMed1978

Comparison of the visual perception of a runway model in pilots and nonpilots during simulated night landing approaches.

Relative motion parallax, a cue that can contribute to visual judgments of glide path angle, was studied for its effect on simulated nighttime approaches in two experiments: 1) 16 pilots and 16 nonpilots adjusted the slant of a model runway to make it appear horizontal under nighttime conditions on both dynamic trials, as the model approached them, and on static trials, with the model stationary; 2) 12 pilots and 12 nonpilots performed the same task in dynamic trials while viewing the model in a dark field as before, and while viewing the model within a window which provided a stable visual frame of reference. Neither flying experience nor the visual frame of reference enhanced sensitivity to relative motion parallax. However, some errors were smaller in pilots, indicating that flying experience enhances other runway images cues. Direct judgments of approach angle magnitude indicated overestimation by an approximate factor of 2. These findings indicate large visual illusions in the nighttime situation and suggest that the ineffectiveness of relative motion parallax may be an important part of night approach problems.

Adolescent↗
PubMed1977

Laboratory apparatus for studying visual space perception of the pilot in simulated night approaches to landing.

The device provides a relatively inexpensive means of assessing a number of perceptual and human factors parameters in the night approach to landing situation. A technique for modeling airport runway lighting is described along with electromechanical and optical systems for precise control of simulated approach speed, model slant, and direction in the visual field of the simulated radial approach axis. The realism of this display is enhanced by preservation of the natural relations of size and brightness of simulated runway lights to distance.

Aerospace Medicine↗
PubMed1976

Some behavioral effects of pesticides: The interaction of mevinphos and atropine in pigeons.

The interaction of the organophosphate mevinphos and atropine was examined in two pigeons performing in a variable interval schedule of reinforcement. When administered separately, both atropine and mevinphos produced a dose-related decrement in responding. The combined exposure to these drugs produced a performance decrement greater than that caused by exposure to each component drug alone. These findings suggest that prophylactic use of atropine may increase the detrimental behavioral effects of organophosphate exposure and that the atropine exposure alone may produce serious behavioral deficits.

Animals↗
PubMed1976

Interaction between marihuana and altitude on a complex behavioral task in baboons.

Marihuana, or its principal active ingredient, delta-9-tetra-hydrocannabinal (delta9-THC), impairs performance on complex behavioral tasks in animals and man. Although there exists some evidence that altitude-induced hypoxia potentiates the physiological effects of marihuana, the interaction between altitude and marihuana on behavioral tasks has not been established. In the absence of evidence that use of marihuana is less frequent among members of the aviation community than among the general population, it was necessary to evaluate the effects on performance of any interaction between hypoxia and marihuana. Two baboons were trained to perform on a delayed matching-to-sample task at ground level and altitudes of 2438 and 3658 m (8000 and 12000 ft). The animals were orally administered doses of delta9-THC, ranging from 0.25 to 2.0 mg/kg, 2 h prior to experimental sessions at each altitude. No effects on accuracy of matching performance were observed for any of the drug doses or altitudes used. Amount of work output, as measured by number of trials completed and speed of responding, was not affected by delta9-THC at ground level but was markedly reduced by the higher drug doses at the 2438- and 3658-m altitudes. This interaction suggests that the behavioral impairment produced by marihuana can be potentiated by hypoxia.

Aerospace Medicine↗
PubMed1975

The effects of mevinphos on appetitive operant behavior in the gerbil.

The need for study of the effects on performance of non-lethal organophosphate insecticide exposure is founded on many reports of behavioral difficulties in aerial applicators following exposure. In this study, a different pair of gerbils served in each of the following schedules of reinforcement: FR 25, FR 75, DRL 12-sec, DRL 20-sec, and VI 1-min. Baseline performance in these tasks tended to be comparable to that of more common laboratory species, but was more variable in the case of the VI 1-min task. Mevinphos doses of 0.20 mg/kg and above produced observable somatic signs of poisoning and also produced dose-related decrements in performance in FR and VI tasks. Performance in the DRL schedule was affected only at a dose of 0.30 mg/kg. No performance deficits or overt somatic signs of poisoning were present at mevinphos doses of 0.10 mg/kg or lower. These results do not agree with those of an earlier study which decrements in VI performance of pigeons and squirrel monkeys appeared at low mevinphos doses which did not produce overt somatic signs of poisoning. The possibility of variations in mevinphos effect as a function of species and task was discussed.

Animals↗