Kai-Uwe Schmitt

N km : a proposal for a neck protection criterion for low-speed rear-end impacts

Soft tissue neck injuries sustained in low speed rear-end collisions are of continued concern in road traffic. To assess the risk of sustaining such injuries, various neck injury criteria have been proposed. In this study a new candidate for such an injury predictor called N km was developed. It is based on a linear combination of shear forces acting in the sagittal direction and extension/flexion bending moments, both measured at the occipital condyles. Results from a total of 40 sled tests, all performed using the same test procedure, with various car front seat models, and using a Hybrid III/TRID as well as a BioRID dummy, were evaluated in order to validate the new criterion. Additionally, a mathematical model was set up to determine the behavior of the N km at a higher crash pulse than the one used in the sled tests. It was shown that the new criterion offers the additional possibility to assess the kinematic phase of forward motion. Furthermore, the influence of the seat design on its protective potential could be related to the N km values obtained and thus, the new criterion is eligible to be part of a standard seat test procedure.

Comparing eye movements recorded by search coil and infrared eye tracking

ObjectiveThe performance of a new video-based infrared eye tracker (IR) was compared to the magnetic search coil technique (SC). Since the IR offers interesting possibilities as a diagnostic tool in neuro-ophthalmology, it was investigated whether the new device has overcome shortcomings that were reported from former IR systems.MethodsHorizontal saccades were recorded using the IR and the SC. The IR allowed eye movement recordings at different sampling rates ranging from 250xa0Hz to 1000xa0Hz while the SC recorded at 1000xa0Hz.Results/ConclusionsThe results show that the IR and the SC were in good agreement and produced similar results. In contrast to other studies, the influence of the sampling rate of the IR was small. The saccade main-sequences did not show significant differences. The latency times observed for both systems were mainly in the short-latency range.

Cognitive performance in high-altitude climbers: a comparative study of saccadic eye movements and neuropsychological tests

Impairment of cognitive performance during and after high-altitude climbing has been described in numerous studies and has mostly been attributed to cerebral hypoxia and resulting functional and structural cerebral alterations. To investigate the hypothesis that high-altitude climbing leads to cognitive impairment, we used of neuropsychological tests and measurements of eye movement (EM) performance during different stimulus conditions. The study was conducted in 32 mountaineers participating in an expedition to Muztagh Ata (7,546xa0m). Neuropsychological tests comprised figural fluency, line bisection, letter and number cancellation, and a modified pegboard task. Saccadic performance was evaluated under three stimulus conditions with varying degrees of cortical involvement: visually guided pro- and anti-saccades, and visuo-visual interaction. Typical saccade parameters (latency, mean sequence, post-saccadic stability, and error rate) were computed off-line. Measurements were taken at a baseline level of 440xa0m and at altitudes of 4,497, 5,533, 6,265, and again at 440xa0m. All subjects reached 5,533xa0m, and 28 reached 6,265xa0m. The neuropsychological test results did not reveal any cognitive impairment. Complete eye movement recordings for all stimulus conditions were obtained in 24 subjects at baseline and at least two altitudes and in 10 subjects at baseline and all altitudes. Measurements of saccade performances showed no dependence on any altitude-related parameter and were well within normal limits. Our data indicates that acclimatized climbers do not seem to suffer from significant cognitive deficits during or after climbs to altitudes above 7,500xa0m. We demonstrated that investigation of EMs is feasible during high-altitude expeditions.