## 4 Limitations  
Among the presented results, the primary source of error stems from the heterogeneity of the group selected for waveform analysis. The assumption of minimum hemodynamic stress during surgery preparation could be violated in the absence of other additional information. The procedure of anesthetic drug administration, which involves changes in vasomotor activity, could be overlapped with other surgery-related factors that affect the biomechanics of the arterial tree.  
Another source of limitation is represented by the large spectrum of waveform morphology variation for ECG, ABP and PPG signals. Even though the medical experts could eliminate corrupted or unreal waveforms, they could not discard small morphology deviations, which are better characterized via numerical means. Due to broad hemodynamic states among the population, various combinations are present between the tidal and dicrotic wave components. Also, during daily activity, users' body movements affect the hemodynamic behavior of the arterial tree, and hence, the morphology of the recorded waveform.  
A state-of-the-art automated algorithm could numerically evaluate the obtained morphologies in order to sort between real data and artifacts. The determination of LVET detection is primary affected by prolonged or attenuated fiducial points as a result of [PERSON]'s effect. This leads to deviations of the waveform gradients from the initially defined path that challenge the algorithm's ability to approximate the true location. Another source of error, observed while running the investigation, implies an additional false change in gradient behavior. This could originate from the compliance property of the  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**ABP Interval** & **80-89** & **90-99** & **100–109** & **110–119** & **120–129** & **130–139** & **140–149** & **150–169** & **160–169** & **170+** \\ \hline TDW\_PK & \(-55\pm 21\) & \(-57\pm 32\) & \(-52\pm 30\) & \(-56\pm 33\) & \(-59\pm 33\) & \(-57\pm 27\) & \(-56\pm 30\) & \(-54\pm 31\) & \(-54\pm 29\) & \(-49\pm 23\) \\ TDW\_LV & \(-3\pm 24\) & \(15\pm 28\) & \(18\pm 29\) & \(24\pm 26\) & \(23\pm 28\) & \(28\pm 26\) & \(33\pm 23\) & \(37\pm 26\) & \(38\pm 18\) & \(42\pm 17\) \\ TDW\_COMP & \(-29\pm 19\) & \(-21\pm 24\) & \(-17\pm 25\) & \(-16\pm 23\) & \(-18\pm 25\) & \(-14\pm 23\) & \(-11\pm 23\) & \(-8\pm 25\) & \(-8\pm 21\) & \(-3\pm 18\) \\ NOTCH & \(61\pm 32\) & \(94\pm 34\) & \(94\pm 38\) & \(96\pm 33\) & \(90\pm 38\) & \(90\pm 34\) & \(100\pm 35\) & \(103\pm 34\) & \(98\pm 23\) & \(99\pm 17\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Error values for selected fiducial points in ABP waveform. All results are in milliseconds.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**ABP Interval** & **80-89** & **90-99** & **100–109** & **110–119** & **120–129** & **130–139** & **140–149** & **150–169** & **160–169** & **170+** \\ \hline TDW\_PK & \(50\pm 32\) & \(51\pm 28\) & \(46\pm 33\) & \(43\pm 31\) & \(41\pm 33\) & \(41\pm 34\) & \(42\pm 38\) & \(30\pm 33\) & \(36\pm 31\) & \(31\pm 26\) \\ TDW\_LV & \(-13\pm 32\) & \(-2\pm 31\) & \(-7\pm 35\) & \(-9\pm 38\) & \(-11\pm 38\) & \(-14\pm 33\) & \(-14\pm 37\) & \(-23\pm 36\) & \(-9\pm 34\) & \(-15\pm 21\) \\ TDW\_COMP & \(18\pm 31\) & \(25\pm 28\) & \(19\pm 32\) & \(17\pm 32\) & \(15\pm 33\) & \(14\pm 32\) & \(14\pm 36\) & \(4\pm 33\) & \(13\pm 31\) & \(8\pm 22\) \\ NOTCH & \(154\pm 36\) & \(166\pm 41\) & \(176\pm 52\) & \(186\pm 69\) & \(188\pm 70\) & \(188\pm 54\) & \(195\pm 60\) & \(189\pm 58\) & \(193\pm 62\) & \(167\pm 52\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Error values for selected fiducial points in PPG waveform. All results are in milliseconds.  
vessel, which induces blood flow oscillation. Since no universal protocol exists for tidal or dicrotic wave components, cardiovascular information extraction cannot be evaluated from a truly objective point of view.