## 3 Results  
### Characteristics of the Study Group  
The final study group consisted of 70 healthy volunteers, of which 30 were a young group of volunteers with a median age of 23 (20-30) years and 40 were an older group of volunteers with a median age of 70 (60-79) years. Analysis of body composition parameters showed significantly higher median values of body mass index (BMI), percentage of body fat (%/PBF) and fat mass (FM) (\(p\) = 0.01) in the older group compared to the younger group. With regard to tissue oxygen saturation parameters, the median SPO\({}_{2}\) value was 97.5% (92-100%) in the whole group and was significantly higher for the young participants compared to the older ones (\(p\) = 0.01). The median HR value for the entire group was 74 and, similarly, it was slightly higher for the younger group compared to the older group (\(p\) = 0.62). No intergroup differences were found in the ABI (\(p\) = 0.05). All of the analyzed spirometric parameters, except VT (VCmax, VCin, VCex, IC, IRV, ERV), were characterized by higher values in the young group compared to the older group (\(p\) = 0.01). The detailed values of the analyzed parameters, including the division into younger and older groups, are shown in Table 1.  
A comparison of the rSO\({}_{2}\) values read from the corresponding ROIs on the right and left sides showed no significant asymmetry in all analyzed ROIs, except for the older group's carpal tunnel area (\(p\) < 0.01) (Table 2). For this reason, the mean rSO\({}_{2}\) value calculated from the ROI on the right and left sides of the body was taken into account in analyses. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \multicolumn{2}{c}{} & \multicolumn{2}{c}{**Study Group**} & \multicolumn{2}{c}{**Young Group**} & \multicolumn{2}{c}{**Older Group**} & \multicolumn{2}{c}{**Mann–Whitney U Test**} \\ \multicolumn{2}{c}{} & \multicolumn{1}{c}{**n = 70** (\(\lx@math@degree\) = **51**, \(\lx@math@degree\) = **19**)} & \multicolumn{1}{c}{**n = 30** (\(\lx@math@degree\) = **18**, \(\lx@math@degree\) = **12**)} & \multicolumn{1}{c}{**n = 40** (\(\lx@math@degree\) = **33**, \(\lx@math@degree\) = **7**)} & \multicolumn{1}{c}{**Mann–Whitney U Test**} \\ \cline{2-10} \multicolumn{2}{c}{} & **Median** & **Min–Max** & **Median** & **Min–Max** & **Median** & **Min–Max** & **z** & **_p_** \\ \hline Age [years] & 64 & 20–79 & 23 & 20–30 & 70 & 60–79 & \(-\)7.16 & 0.000 \\ Weight [kg] & 71 & 46–115 & 66.50 & 46–115 & 72.5 & 49–94 & \(-\)1.61 & 0.079 \\ Height [cm] & 165.00 & 150.5–196 & 169.25 & 163–196 & 163 & 150.5–185 & 4.38 & 0.000 \\ BMI [kg/m\({}^{2}\)] & 26.24 & 16.2–38.7 & 22.42 & 16.21–38.88 & 27.74 & 20.13–37.8 & \(-\)4.38 & 0.000 \\ \hline FM [kg] & 26.29 & 10.20–55.85 & 20.50 & 10.21–53.93 & 28.14 & 12.76–55.85 & \(-\)3.94 & 0.000 \\ PBF [\%] & 36.3 & 17.02–49.33 & 31.48 & 17.03–49.34 & 39.79 & 20.77–47.17 & \(-\)4.12 & 0.000 \\ WBSAT [kg] & 1.40 & 0.24–3.45 & 0.93 & 0.24–3.08 & 1.52 & 0.66–3.45 & \(-\)4.30 & 0.000 \\ \hline SPO\({}_{2}\) & 97.5 & 92–100 & 98 & 94–100 & 97 & 92–99 & 3.79 & 0.000 \\ HR & 74.5 & 53–116 & 74.5 & 53–100 & 74 & 57–116 & \(-\)0.49 & 0.622 \\ \hline ABI & L & 1.17 & 0.9–1.36 & 1.17 & 1.07–1.31 & 1.16 & 0.9–1.36 & \(-\)0.15 & 0.884 \\ P & 1.19 & 0.9–1.39 & 1.19 & 1.05–1.39 & 1.18 & 0.9–1.36 & 0.51 & 0.610 \\ \hline VC\({}_{\rm max}\) & 3.52 & 1.6–7.31 & 4.45 & 2.57–7.31 & 3.03 & 1.6–5.18 & 5.25 & 0.000 \\ VC\({}_{\rm in}\) & 3.52 & 1.38–7.31 & 4.45 & 1.91–7.31 & 2.99 & 1.38–4.97 & 4.82 & 0.000 \\ VC\({}_{\rm ex}\) & 2.77 & 0.77–7.01 & 3.72 & 1.51–7.01 & 2.09 & 0.77–5.18 & 4.45 & 0.000 \\ IC & 2.59 & 1.23–8.91 & 3.17 & 1.42–5.54 & 2.44 & 1.23–8.92 & 3.57 & 0.000 \\ IRV & 1.67 & 0.2–4.22 & 2.07 & 0.25–4.22 & 1.39 & 0.2–2.72 & 3.50 & 0.000 \\ VT & 1.00 & 0.4–8.04 & 1.02 & 0.4–3.08 & 0.93 & 0.44–8.04 & 1.12 & 0.263 \\ ERV & 0.88 & 0.11–6.98 & 1.33 & 0.33–2.39 & 0.65 & 0.11–6.98 & 4.82 & 0.000 \\ \hline \end{tabular}
\end{table}