Photoplethysmography (PPG) has proved to be valuable signal carrier information from many biomedical sources. Especially, sauna studies have shown that heart pulse inter beat intervals, heart rate variability (HRV), shape and morphology of PPG can provide much interesting information about arterial elasticity during and after a sauna exposure. These parameters are pulse amplitude, pulse width, and pulse to pulse beat intervals changes caused by the sauna exposure. In our preliminary study there is searched on heart pulse variability information and other hemodynamic parameters. However, there is not yet standard detailed calculation algorithms for these parameters. Merged Poincaré plots, or so called return maps, could give valuable information which is here at the first time noticed.