The photoplethysmographic (PPG) signal, which is a measure of the systolic oscillations in the tissue blood volume, spontaneously fluctuates in the respiration rate and in lower frequencies similar to the heart rate fluctuations. In the current study, the low frequency fluctuations, which are attributed to the sympathetic nervous system activity, were obtained from PPG examinations simultaneously performed on the right and the left hands of healthy subjects and hemiplegic patients. For normal subjects, the fluctuations in the two hands were found to be correlated, demonstrating their central origin. For some of the hemiplegic patients, the coefficient of correlation between the right and the left hands was significantly lower than the normal range. The simultaneous measurement of the PPG signal fluctuations in both hands provides information on the adequate function of the autonomic nervous system.
- Autonomic nervous system
- Hemiplegic patients
- Tissue blood volume variability