## 3 Results  
The measurements of \(R_{\text{rs}}\) in our experiment are summarized in Figure 2 and Table 1. Measurements 1-3 correspond to no added resistor and measurements 4-6 correspond to the phase of the experiment with the added resistor Rp. Three demijohns representing different compliances (37, 24, and 17 mL/cmH\({}_{2}\)O) were used in both phases of the experiment. The resistance \(R_{\text{rs}}\) substantially increased by more than 100 cmH\({}_{2}\)O\(\cdot\)s/L (over 220% increase) after the addition of the resistor to the model of the respiratory system (the change between Sections 3 and 4). The change in the compliance value did not have a substantial effect on the measured \(R_{\text{rs}}\) values as the mean \(R_{\text{rs}}\) did not differ for more than 4 cmH\({}_{2}\)O\(\cdot\)s/L (less than 10%) when Rp remained unchanged.  
Figure 1: Setup of in vitro experiment [24].  
Figure 3: The course of computed \(R_{\rm rs}\) during ventilation of the respiratory system model without an added resistor (three 40 s long measurements correspond to measurement sections 1, 2, and 3 in Figure 2). Three glass demijohns with different compliance (37, 24, and 17 mL/cmH\({}_{2}\)O) were ventilated to investigate the effect of compliance on the measured resistance of the respiratory system.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \(\mathbf{C}\) & \(\mathbf{R_{\rm rs}}\) **with No Resistor** & \multicolumn{2}{c}{\(\mathbf{R_{\rm rs}}\) **with Resistor Rp5**} \\ \hline \hline (mL/cmH\({}_{2}\)O) & **Mean** & **SD 1** & **Mean** & **SD 1** \\ \hline
37 & 41.5 & 0.2 & 147.8 & 0.5 \\
24 & 44.7 & 0.2 & 146.6 & 0.3 \\
17 & 44.3 & 0.1 & 144.7 & 0.3 \\ \hline \hline \end{tabular} \({}^{1}\) SD stands for standard deviation.  
\end{table}
Table 1: Values of computed \(R_{\rm rs}\) (cmH\({}_{2}\)O\(\cdot\)s/L) in both phases of the experiment (without/with the resistor) for glass demijohns of three different compliances \(\mathbf{C}\).  
Figure 2: The computed \(R_{\rm rs}\) during ventilation of the respiratory system model without an added resistor (measurement sections 1, 2, and 3) and with added resistor Rp (measurement sections 4, 5, and 6). To investigate the effect of compliance on the measured resistance of the respiratory system, three glass demijohns with different compliance (37, 24, and 17 mL/cmH\({}_{2}\)O) were ventilated. Negligible change in \(R_{\rm rs}\) signal amplitude during measurement and a small change in \(R_{\rm rs}\) when compliance changed contrast with a large change in \(R_{\rm rs}\) when the resistance increased.  
It can also be seen from Figures 3 and 4 in detail that change of the compliance of the respiratory system model does not affect substantially measured \(R_{\rm rs}\). For a measurement without an added resistor (Figure 3), a small increase in \(R_{\rm rs}\) of 3.2 cmH\({}_{2}\)O-s/L (7.7%) was observed with the change of compliance from 37 to 24 mL/cmH\({}_{2}\)O and a very small change in \(R_{\rm rs}\) of about 0.4 cmH\({}_{2}\)O-s/L (1.0%) was observed with the change of compliance from 24 to 17 mL/cmH\({}_{2}\)O. A decrease in \(R_{\rm rs}\) about 1.2 cmH\({}_{2}\)O-s/L and 1.8 cmH\({}_{2}\)O-s/L (0.8% and 1.3%, respectively) was observed for measurements with the resistor.