According to the theory of wave transmission, the speed of wave transmission is dependent on the nature of the transmission medium, which is the vessel wall for pulse wave transmission. Then, the pulse wave velocity is related to the mechanical property of the vessel wall. The mechanical property of the vessel wall is determined by the texture of the vessel wall and the contraction status of the smooth muscle within the vessel wall. Because the texture of the vessel wall could not be changed in a short duration, the sympathetic nerve activity, which controls the contractibility of the smooth muscle, becomes the only determinant factor of pulse wave velocity. So, pulse wave velocity may reflect the status of sympathetic nerve activity. The purpose of this project is to use the pulse wave velocity to measure the sympathetic activity of stroke and spinal cord patients. The present project plans to measure the pulse wave simultaneously at four limbs by pressure receptors, and use the electrocardiogram as the reference to synchronize the recorded pulse wave at different vessels, using the corrected data to calculate the pulse wave velocity. With the pulse wave velocity of different vessels, we, the investigators at National Taiwan University Hospital, can understand the local sympathetic nerve activity in different diseases and different sites.

The first year, we will set up the equipment for measuring the pulse wave velocity, and then apply it to 20 healthy subjects to adjust the measurement error and ascertain the reproducibility of the machine. The second year, we will apply the measurement to 15 complete cervical cord injury individuals and 15 healthy subjects in different erected angles by a tilting table. This procedure will make us understand the response of sympathetic nerve activity to different postures in normal subjects and cervical cord injury patients. The third year, we will apply the measurement to 30 cerebrovascular accident patients to understand the change of sympathetic nerve activity after having a stroke. By comparing the clinical information, we hope to clear up the relationship between sympathetic nerve activity and pulse wave velocity.