The Neurophysiology and Treatment of Motion Sickness.

BACKGROUND: Seasickness and travel sickness are classic types of motion illness. Modern simulation systems and virtual reality representations can also induce comparable symptoms. Such manifestations can be alleviated or prevented by various measures. METHODS: This review is based on pertinent publications retrieved by a PubMed search, with special attention to clinical trials and review articles. RESULTS: Individuals vary in their susceptibility to autonomic symptoms, ranging from fatigue to massive vomiting, induced by passive movement at relatively low frequencies (0.2 to 0.4 Hz) in situations without any visual reference to the horizontal plane. Younger persons and women are considered more susceptible, and twin studies have revealed a genetic component as well. The various types of motion sickness are adequately explained by the intersensory conflict model, incorporating the vestibular, visual, and proprioceptive systems and extended to include consideration of postural instability and asymmetry of the otolith organs. Scopolamine and H1-antihistamines, such as dimenhydrinate and cinnarizine, can be used as pharmacotherapy. The symptoms can also be alleviated by habituation through long exposure or by the diminution of vestibular stimuli. CONCLUSION: The various types of motion sickness can be treated with general measures to lessen the intersensory conflict, behavioral changes, and drugs.

Reassessing Diagrams of Cardiac Mechanics: From Otto Frank and Ernest Starling to Hiroyuki Suga.

This article explores the importance of diagrams in the history of the understanding of cardiac function, by comparing Ernest Starling's famous "Law of the Heart" (1918) with the mathematically based view of cardiac mechanics put forward by Otto Frank (1897). Whereas Frank's diagrams gained influence in German cardio-physiological publications, they were widely unknown abroad until 1969, when Hiroyuki Suga began to present similar approaches for warm-blooded animals as Frank had done for the frog. Suga succeeded in correlating the pressure volume area (PVA)-a composite of Frank's work loop plus the area of remaining potential energy-with the oxygen consumption of the beating heart. With the concept of time-varying elastance as an index of cardiac contractility, Suga's approach became attractive for clinical applications, and Daniel Burkhoff and colleagues were able to use these insights for real-time, interactive simulations of the cardiovascular system. Such tools can be used for exploring basic hemodynamic principles and, thanks to technical developments of miniature pumps within the same time frame (Καιρός, the "right moment," or "the opportune"), to test the effects of device-based treatment for heart failure. These outcomes confirm that old analyses of the heart's activity may still be useful today.