Wavelet analysis for quantification of mental stress stage by finger-tip photo-plethysmography.

Wavelet analysis of the finger-tip photo-plethysmogram (PTG) was performed in order to quantify the stress stage. From the result of the wavelet transform of the PTG, we proposed stress index, with which quantification of the mental stress level was easy. In order to confirm the validity of this index, we compared the stress indexes between the stress and resting stages. The relationship between the stress index and the heart rate variability (HRV) was also investigated. The obtained results indicated that using the wavelet transform in analysis showed a remarkable change in the stress index from the resting stage to the stress stage. This change appears in the tidal wave area of the PTG.