## 2 Materials and Methods
Discarded features are marked in light other yellow in Table 1. This is a consequence of preliminary experiments, from which we concluded that the accuracy of the proposed meta-model was slightly higher when we choose features expressed in relative values. In order to have a complete insight into the feature engineering process, we retained the complete initial set of 35 features in Table 1.

Postoperative FEV1 was measured on the first, the fourth, and the seventh day after the surgery. These variables were selected for output variable \(y\) in the model (1), see Table 2 and Figure 2. From these data, we can observe the typical dynamics of lung function recovery. Immediately after surgery, patients experience a decrease in lung function due to factors such as lung volume loss, anesthesia, pain, limited mobility, and the surgical trauma itself. By the fourth day, lung function tends to improve. By the seventh day post-surgery, the measured FEV1[%] should continue to improve. Pain management, early mobilization, and breathing exercises have a significant impact on helping patients regain lung function. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **Feature** & **Description** & **Type** & **Mean \(\pm\) std** \\  & **Label** & & **Mobility of the right** & **Float** \\
26 & **EK** & **hemidiaphrag measured by** & **[47.9, 94.2]** & 68.25 \(\pm\) 10.28 \\  & & **ultrasound (mm)** & & **[47.9, 94.2]** & 68.25 \(\pm\) 11.10 \\ \hline
27 & **EL** & **Mobility of the left hemidiaphrag measured by ultrasound (mm)** & **Float** & **[36.5, 95.0]** & 62.58 \(\pm\) 11.10 \\ \hline
28 & **FK** & **Preoperative PImax** & **Integer** & **83.38 \(\pm\) 28.08** \\  & & **(cmH20)**—Preoperative maximum inspiratory pressure (cmH2O)** & **Float** & **[26, 154]** & \\ \hline
29 & **FL** & **Prooperative PImax** & **Float** & **109.63 \(\pm\) 35.76** \\  & & **respiratory pressure in [\%]** & **Float** & **[35.75, 201.60]** & 109.63 \(\pm\) 35.76 \\ \hline
30 & **FS** & **Preoperative PEmax** & **Integer** & **102.22 \(\pm\) 25.16** \\  & & **respiratory pressure** & **[43, 155]** & 102.22 \(\pm\) 25.16 \\ \hline
31 & **FT** & **Preoperative PEmax** & **Float** & **92.19 \(\pm\) 18.04** \\  & & **respiratory pressure in [\%]** & **Float** & **[46.16, 129.84]** & 92.19 \(\pm\) 18.04 \\ \hline
32 & **GA** & **Preoperative Snip** & **Inter** & **86.53 \(\pm\) 25.09** \\  & & **respiratory pressure (cmH20)** & **Float** & **91.83 \(\pm\) 23.26** \\ \hline
33 & **GB** & **The number of functional segments** & **Integer** & **3.41 \(\pm\) 2.02** \\  & & **removed by the operation** & **[1, 9]** & **3.41 \(\pm\) 2.02** \\ \hline
35 & **LV** & **The number of total functional segments in the lungs** & **Integer** & **17.23 \(\pm\) 1.07** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._ \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **1 st Postoperative Day** & **4 th Postoperative Day** & **7 th Postoperative Day** \\ \hline mean & 44.68 & 50.95 & 58.01 \\ std & 14.07 & 15.80 & 14.78 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean values and variances of measured postoperative FEV1 in [%] at the 1 st, 4 th, and 7 th day after surgery. ### Selection of Existing Methods for Comparison

In order to assess the accuracy of our model we compared it with existing methods of calculating predicted and postoperative FEV1 in [%], based on preoperative measurements.