Vagal response in heart rate variability under motion sickness stimulation

An attempt was made to attain a better understanding of the autonomic effects involved in the motion sickness stimulation of the heart. An attempt was made to monitor the vagal activity in ten NASA volunteers undergoing motion stimulation. The heart rate spectrum was adopted as the technique which noninvasively allows the quantitative measurements of vagal tone by assessing the amount of heart rate variability occurring at the respiratory frequency. Power in the frequency band of the heart rate spectrum corresponding to the nominal respiration frequency has been shown to be purely vagal in origin, and this measure is referred to as vagal power. The initial hypothesis was that vagal tone would drop as a sign of increasing stress when subjects reported increasing motion sickness, as indicated by a standardized diagnostic malaise scale.