## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Condition** & **Mean \(\pm\) SD** & **F** & \(p\) & **Factor 1** & **Factor 2** &
\begin{tabular}{c} **Mean Difference \(\pm\) SE** \\ **(Factor 1-Factor 2)** \\ \end{tabular} & **t** & \(p_{\text{Tukey}}\) \\ \hline \#1 & 97.78 \(\pm\) 0.94 & & & \#1 & \#3 & \(-\)0.69 \(\pm\) 0.19 & \(-\)3.74 & 0.004 \({}^{*}\) \\ \#2 & 98.64 \(\pm\) 0.54 & & & \#4 & \(-\)0.93 \(\pm\) 0.25 & \(-\)3.77 & 0.004 \({}^{*}\) \\ \#3 & 98.47 \(\pm\) 0.63 & & & \#3 & 0.17 \(\pm\) 0.07 & 2.43 & 0.094 \\ \#4 & 98.71 \(\pm\) 0.76 & & & \#2 & \#4 & \(-\)0.07 \(\pm\) 0.15 & \(-\)0.48 & 0.962 \\ \cline{3-8}  & & & & \#3 & \#4 & \(-\)0.24 \(\pm\) 0.14 & \(-\)1.66 & 0.363 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of SpO\({}_{2}\) using RM ANOVA. tended to increase under high concentrations of both O\({}_{2}\) and CO\({}_{2}\) (C2 vs. C3), with the greatest changes observed with high concentrations of O\({}_{2}\) and CO\({}_{2}\). This resulted from the increase in HbO surpassing the decrease in HbR. The excessive supply of O\({}_{2}\) via increased blood flow compared with O\({}_{2}\) consumption in the brain is a mechanism that prioritizes the protection of the O\({}_{2}\)-dependent brain during crisis situations [19]. This finding is consistent with previous studies examining changes in cerebral blood flow during stress and tension states using fMRI and positron emission tomography (PET) [37; 38] and underscores the utility of fNIRS for cerebral blood flow studies. HR decreased in C2 compared to C1 but increased in C3 and more so in C4. All conditions showed significant differences, except for C3 vs. C4. The decrease in HR in C2 was attributed to the stable O\({}_{2}\) supply achieved by elevated blood O\({}_{2}\) concentrations, while the increases in HR and blood flow during high CO\({}_{2}\) concentration ensured sufficient O\({}_{2}\) delivery. As C3 and C4 shared the same high CO\({}_{2}\) concentration, no significant difference was observed [39; 40]. SpO\({}_{2}\) increased in the order of C3, C2, and C4, compared with C1. Significant increases were noted for C1 vs. C2 and C1 vs. C3, but no significant differences were observed for C3 vs. C3, C2 vs. C4, or C3 vs. C4. Therefore, an increase in SpO\({}_{2}\) due to an elevated blood O\({}_{2}\) concentration from a high O\({}_{2}\) supply, coupled with increased HR and physiological effects, promotes blood flow during high CO\({}_{2}\) conditions, thereby maintaining O\({}_{2}\) levels [41]. The results of this study address cerebral hemodynamics, emphasizing how the brain maintains a steady supply of O\({}_{2}\) and removes CO\({}_{2}\), both essential for its function. Changes in O\({}_{2}\) and CO\({}_{2}\) concentrations significantly influence cerebral blood flow [34]. Chemoreceptors detect shifts in blood gas levels, prompting physiological adjustments such as vasodilation, increased blood flow velocity, and altered HR to stabilize the O\({}_{2}\) supply [30]. High CO\({}_{2}\) concentrations are particularly impactful, triggering stronger responses compared to high O\({}_{2}\) concentrations, as evidenced by fNIRS studies showing enhanced COS and Hb concentrations under elevated CO\({}_{2}\) conditions. Inhaled air can induce physiological changes in the human body and may enhance blood flow to the brain. This approach has the potential to improve cerebrovascular circulation and brain function through quantitative stimulation using appropriate gas concentrations, thereby contributing to cerebrovascular health and disease prevention. Additionally, fNIRS offers significant advantages over earlier oxygen saturation measurement methods, particularly in its ability to measure localized blood flow and oxygenation levels in specific regions of the brain [26]. Unlike traditional methods, which are primarily used to measure SpO\({}_{2}\) in peripheral areas, such as the fingers or earlobes [22; 23; 24], fNIRS provides detailed insights into changes in HbO and HbR in targeted cortical regions [27; 28].