Postural Instability and Simulator Seasickness.

BACKGROUND: Motion sickness is a serious issue for many individuals, but the problem is particularly important among military personnel who may regularly experience unusual or extreme motion profiles as a part of their duties. As such, it is important to understand the underlying mechanisms that contribute to motion sickness, which in turn can lead to new and more effective countermeasures. The current study investigated causal etiology by examining the predictions of postural instability theory. Subjects experienced multiple motion profiles while reporting their sickness symptoms. METHODS: Postural instability was directly manipulated by including both an active and passive condition. In the active condition, subjects could actively adapt their posture to the motion profile. In the passive condition, subjects had their feet affixed in place and could not effectively adapt their posture to the motion profiles. Subjects completed both conditions to control for individual differences in motion sickness susceptibility. RESULTS: Active condition subjects had greater postural stability as measured by sample entropy (M = 0.179 Active, M = 0.136 Passive), and sickness symptoms increased with time. Both results provide a methodological check against our manipulation. However, there were no differences in symptoms between active or passive conditions as measured by the simulator sickness questionnaire (M = 16.56 and M = 18.25, respectively), and no relationship between our measure of postural instability and symptomology. DISCUSSION: These results do not support postural instability as the primary causal factor in motion sickness; however, more research is needed to elucidate the mechanisms of motion sickness etiology.Pettijohn KA, Geyer D, Gomez J, Becker WJ, Biggs AT. Postural instability and simulator seasickness. Aerosp Med Hum Perform. 2018; 89(7):634-641.

The Persistent Issue of Simulator Sickness in Naval Aviation Training.

INTRODUCTION: Virtual simulations offer nearly unlimited training potential for naval aviation due to the wide array of scenarios that can be simulated in a safe, reliable, and cost-effective environment. This versatility has created substantial interest in using existing and emerging virtual technology to enhance training scenarios. However, the virtual simulations themselves may hinder training initiatives by inducing simulator sickness among the trainees, which is a series of symptoms similar to motion sickness that can arise from simulator use. Simulator sickness has been a problem for military aviation since the first simulators were introduced. The problem has also persisted despite the increasing fidelity and sense of immersion offered by new generations of simulators. As such, it is essential to understand the various problems so that trainers can ensure the best possible use of the simulators. This review will examine simulator sickness as it pertains to naval aviation training. Topics include: the prevailing theories on why symptoms develop, methods of measurement, contributing factors, effects on training, effects when used shipboard, aftereffects, countermeasures, and recommendations for future research involving virtual simulations in an aviation training environment.Geyer DJ, Biggs AT. The persistent issue of simulator sickness in naval aviation training. Aerosp Med Hum Perform. 2018; 89(4):396-405.

Closed reduction of prosthetic hip dislocation by emergency physicians.

OBJECTIVE: The purpose of this study was to determine the frequency of successful closed reduction (CR) of dislocated prosthetic hips performed by emergency physicians (EPs) as well as the incidence of acute complications. METHODS: The study design was an explicit chart review set at an academic ED with an annual census of 55,000. The study was performed on March 1, 1999 to February 28, 2004. Patients were identified using coded ED diagnoses, and data were obtained by a trained abstractor. RESULTS: One hundred twelve dislocations in 66 patients had attempted CR in the ED. Eighty-one had CR attempted solely by an EP with 91% success. Twenty-eight of the remaining 31 (90%) had successful CR performed by either an orthopedic surgeon or both an EP and an orthopedic surgeon. Overall, 10 patients (9%) failed ED CR. No postreduction complications were identified in any patient. CONCLUSIONS: EPs can safely and successfully perform CR on patients with dislocated total hip arthroplasties.