Fig. 4.
Response of PPG components (IT: foot and peak of the DC component of PPG, IS: amplitude of the AC component of PPG) to intravenous infusion and injection of cardiac stimulants. PPG were continuously measured by a non-invasive method, and normalized in order to compare the results of all the subjects under the same conditions. Points represent average values over a 30 sec period. Data shown as mean and SD. *p < 0.05, **p < 0.01: significant increase / decrease. PPG, photoplethysmograph; DC, direct current; AC, alternating current.