Effects of Visually Induced Motion Sickness on Emergency Braking Reaction Times in a Driving Simulator.

OBJECTIVE: The study explores associations of visually induced motion sickness (VIMS) with emergency braking reaction times (RTs) in driving simulator studies. It examines the effects over the progression of multiple simulated drives. BACKGROUND: Driving simulator usage has many advantages for RT studies; however, if it induces VIMS, the observed driving behavior might deviate from real-world driving, potentially masking or skewing results. Possible effects of VIMS on RT have long been entertained, but the progression of VIMS across simulated drives has so far not been sufficiently considered. METHOD: Twenty-eight adults completed six drives on 2 days in a fixed-base driving simulator. At five points during each drive, pedestrians entered the road, necessitating emergency braking maneuvers. VIMS severity was assessed every minute using the 20-point Fast Motion Sickness Scale. The progression of VIMS was considered in mixed model analyses. RESULTS: RT predictions were improved by considering VIMS development over time. Here, the relationship of VIMS and RT differed across days and drives. Increases in VIMS symptom severity predicted more prolonged RT after repeated drives on a given day and earlier within each drive. CONCLUSION: The assessment of VIMS in RT studies can be beneficial. In this context, VIMS measurements in close temporal proximity to the behaviors under study are promising and offer insights into VIMS and its consequences, which are not readily obtainable through questionnaires. APPLICATION: Driving simulator-based RT studies should consider cumulative effects of VIMS on performance. Measurement and analysis strategies that consider the time-varying nature of VIMS are recommended.

Pressure pain thresholds: Subject factors and the meaning of peak pressures.

BACKGROUND: The assessment of pressure pain has become an integral part in pain research. The distribution of pressure under a plunger can be uneven. However, measurements based on conventional devices show the applied force or mean pressure, failing to take local pressure peaks into account. Our main question was whether peak pressures under the probe are responsible for pain onset. METHODS: A force-controlled algometer was fitted with a newly developed pressure-indicating film. Pressure pain thresholds (PPTs) of 100 healthy subjects (57 men, age 18-66 years) were assessed at 29 sites across the body. Each site was measured three times, nonconsecutively and presented in randomized order. Forty subjects were manual labourers. RESULTS: Pressure distributions on hard tissue (bone) were more heterogeneous and showed more prominent peaks beneath the probe when reaching the PPT. Soft tissue (e.g. muscle) created a distinct distribution, with higher pressure especially around the corners of the probe. A high variability of PPTs between subjects and different measurement sites was observed. Men as well as manual labourers had comparatively higher adjusted pressure pain thresholds (force and pressure). CONCLUSIONS: Peak pressures could be relevant for pain onset and should be accounted for in mechanical pain studies. The probe, indentation depth and tissue properties have a major impact on pressure distributions and may therefore affect the perception of pressure pain. Due to higher intra-individual differences regarding peak pressures at the spinous processes, breastbone, forehead and abdomen caution are needed when interpreting those sites. SIGNIFICANCE: This study adds some important considerations for the use of pressure algometers. It was found that during pressure pain thresholds readings distinct peak pressure profiles could arise, which may influence the perception of pain. Peak pressure could be another contributing factor, which may explain some of the high variability in pressure pain readings.

Measuring mechanical pain: the refinement and standardization of pressure pain threshold measurements.

Pain thresholds are widely used in behavioral research, but unlike other pain modalities, a standardized assessment of pressure pain remains a challenge. In this research, we describe the application of an automatic pressure algometer with a linear increase in force. Ergonomically designed fixation devices were developed to increase the accuracy and to shorten the time of each measurement. Ten healthy volunteers were included in a pilot study to test the algometry method. Pressure pain thresholds (PPTs) were investigated over 2 experimental days in three nonconsecutive runs at 29 measurement sites. During the experiment, subjects reported their subjective sleepiness, level of state-anxiety, psychological status and the perceived pain intensity of each measurement. Pain intensity ratings indicate that instructions were followed. State-anxiety and subjective sleepiness levels were low throughout the experiment. The method has proven to be suitable for standardized PPT measurements across the body in an ergonomic, safe, and user-friendly fashion.

Further development of a commercial driving simulation for research in occupational medicine.

OBJECTIVES: The purpose of this study was to refine a commercial car driving simulation for occupational research. As the effects of ethanol on driving behavior are well established, we choose alcohol as a test compound to investigate the performance of subjects during simulation. MATERIALS AND METHODS: We programmed a night driving scenario consisting of monotonous highway and a rural road on a Foerst F10-P driving simulator. Twenty healthy men, 19-30 years, participated in a pilot study. Subjects were screened for simulator sickness, followed by training on the simulator one hour in total. Experiments were performed in the morning on a separate day. Participants were randomized into either an alcoholized or a control group. All subjects drove two courses consisting of highway and rural road and were sober for the first course. During a 1 h break the ethanol group drank an alcoholic beverage to yield 0.06% blood alcohol concentration (BAC). Generalized linear mixed models were used to analyze the influence of alcohol on driving performance. Among others, independent variables were Simulator Sickness Questionnaire scores and subjective sleepiness. RESULTS: Subjects did not experience simulator sickness during the experiments. Mean BAC before the second test drive was 0.065% in the mildly intoxicated group. There was no clear-cut difference in the number of crashes between 2 groups. BAC of 0.1% would deteriorate mean braking reaction time by 237 ms (SE = 112, p < 0.05). Ethanol slightly impaired the tracking in the right-hand curves (p = 0.058). Braking reaction time improved by 86 ms (SE = 36, p < 0.05) for the second test drive, indicating a learning effect. CONCLUSIONS: In sum, a clear ethanol effect was observed in the driving simulation. This simulation seems suitable for occupational research and produces little simulator sickness. Controlling for possible learning effects is recommended in driving simulation studies.