Data from: Measurement of stress-induced sympathetic nervous activity using multi-wavelength photoplethysmography

The onset of stress triggers sympathetic arousal (SA), which causes
detectable changes to physiological parameters such as heart rate, blood
pressure, dilation of the pupils and sweat release. The objective
quantification of SA has tremendous potential to prevent and manage
psychological disorders. Photoplethysmography (PPG), a non-invasive method
to measure skin blood flow changes, has been used to estimate SA
indirectly. However, the impact of various wavelengths of the PPG signal
has not been investigated for estimating SA. In this study, we explore the
feasibility of using various statistical and nonlinear features derived
from peak-to-peak (AC) values of PPG signals of different wavelengths
(green, blue, infrared and red) to estimate stress-induced changes in SA
and compare their performances. The impact of two physical stressors, Cold
Pressor and Hand Grip, is studied on 32 healthy individuals. The results
show that the nonlinear features are the most promising in detecting
stress-induced sympathetic activity. TotalSampEn feature was capable of
detecting stress-induced changes in SA for all wavelengths, whereas other
features (Petrosian, AvgSampEn) are significant (AUC≥0.8$) only for IR and
Red wavelengths. The outcomes of this study can be used to make device
design decisions as well as develop stress detection algorithms.