Effect on cerebral blood flow of using a power assist robot for standing

This study investigated the effect on cerebral blood flow of using a power assist robot for standing. Subjects were 10 young adults and 22 elderly adults, and the power assist robot used was a hybrid assistive limb (HAL). The experiment involved two standing conditions: active standing and HAL-assisted standing. Cerebral blood flow, blood pressure, and electrocardiographic measurements were recorded over 3 min before and 3 min after standing. Cerebral blood flow was significantly lower during HAL-assisted standing in both groups (p < 0.05), while blood pressure was significantly lower during HAL-assisted standing in the elderly group (p < 0.01). There was little variation in autonomic nervous system activity, as calculated from heart rate variability (fast Fourier transform), in the elderly group. In addition, there tended to be less variation in HF and LF/HF during HAL-assisted standing. These results suggest that using a power assist robot to stand up reduced the capability of feed forward mechanisms to limit orthostatic hypotension, leading to insufficient circulatory regulation.