## 3 Results  
A set of two-dimensional BPA distributions in the selected area of the face of each subject was calculated every 21-34 s (depending on the subject's heart rate) during the entire measurement according to the protocol described above. Examples of such distributions overlaid with respective images of the subject's face are shown in Figure 3A-C. In this particular experiment, the first BPA map (Figure 3A) was calculated at the end of the first minute of the experiment (baseline), the second (Figure 3B) at the sixth minute (with the heated compress) and the third (Figure 3C) at the fifteenth minute when the compress was removed. The red color in the BPA maps shows the points with a higher amplitude of pulsations, while the blue color corresponds to the lower BPA. The color scale of BPA (common for all three maps) is shown on the right of Figure 3C. One can see that the amplitude of blood pulsations significantly increases in the forehead under the warm compress, whereas it remains unchanged in other areas. It is worth noting the difference in BPA maps before and 4 min after applying the compress (Figure 3A vs. Figure 3C); despite the absence of the compress, blood pulsations in the forehead remained doubled, whereas no changes were observed in other areas. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Subject** & **Age, Years** & **Gender** & \begin{tabular}{c} **Height,** \\ **cm** \\ \end{tabular} & \
\begin{tabular}{c} **Weight, kg** \\ **Pressure, mmHg** \\ \end{tabular} &
\begin{tabular}{c} **Arterial Blood** \\ **Pulse, ppm** \\ \end{tabular} \\ \hline ZDV & 20 & M & 171 & 67 & 123/77 & 82 \\ BVE & 22 & M & 184 & 75 & 138/86 & 81 \\ CMA & 23 & M & 170 & 65 & 132/79 & 81 \\ VMA & 31 & M & 175 & 75 & 130/90 & 75 \\ KVO & 19 & M & 164 & 48 & 97/68 & 60 \\ EIA & 19 & M & 175 & 65 & 107/52 & 53 \\ RDI & 19 & M & 165 & 74 & 132/75 & 82 \\ GRD & 20 & M & 168 & 93 & 121/79 & 79 \\ FDA & 18 & F & 170 & 56 & 122/80 & 67 \\ KGA & 18 & M & 185 & 70 & 119/70 & 67 \\ SVS & 20 & F & 170 & 60 & 113/76 & 58 \\ MNB & 48 & M & 175 & 90 & 124/88 & 76 \\ GLU & 24 & F & 168 & 60 & 121/94 & 70 \\ KVS & 22 & M & 178 & 80 & 128/81 & 73 \\ AME & 20 & M & 185 & 75 & 125/78 & 72 \\ SAA & 19 & M & 180 & 71 & 135/72 & 86 \\ SKP & 22 & M & 178 & 80 & 128/81 & 73 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Subjects who participated in the study. To monitor BPA changes in different facial areas, we chose four larger ROIs measuring \(35\times 35\) pixels in the image that corresponds to \(7.5\) mm \(\times 7.5\) mm in the subject's face. Two of them were chosen in the forehead in the middle of the compress application, and two others (reference regions) in the nose and on the cheek. These ROIs are shown in Figure 3A-C by squares of different colors: red and blue in the forehead, black on the bridge of the nose and magenta on the cheek. The evolution of the BPA averaged within four large ROIs is shown in Figure 3D. The color of the curves corresponds to the color of the ROIs in Figure 3A-C. The dashed green line in this graph shows the dynamics of the skin temperature measured in the area of the compress application. For a particular subject shown in Figure 3, the compress was applied on the fifth minute of the experiment and removed on the eleventh one. It is seen that BPA increases sharply after applying the compress, and then it diminishes with the tendency to reach a steady state. Typically, it remains at a level significantly higher than the baseline  
Figure 3: Spatial distribution of amplitude of blood pulsations (BPA) overlaid with an image of the subject’s face before (**A**), during (**B**), and after (**C**) applying the warm compress. BPA maps are shown in pseudocolors with the common color scale in percent on the right of the panel (**C**). Panel (**D**) shows evolution of BPA (solid color lines with the scale on the left) along with skin temperature (dashed green line with the scale on the right).