“…Signal quality estimation of conventional contact ECG has been investigated more extensively than for ccECG. These ECG quality metrics include the use of features such as match between different beat detection algorithms [ 13 , 14 ], multi-lead signal comparison [ 13 , 14 , 15 ], higher order moments such as Kurtosis [ 13 , 14 , 16 ], amplitude characteristics [ 16 , 17 , 18 ], spectral characteristics [ 13 , 14 , 15 , 19 ], HR characteristics [ 15 , 20 ], QRST area [ 21 ], QRST morphology [ 20 ], electrode-tissue impedance (ETI), and motion [ 22 ]; in some cases combined with additional processing such as Kalman Filtering [ 13 ], multi-layer perceptron neural networks (MLP) [ 14 ], support vector machines (SVM) [ 14 ], Least-Mean-Squares (LMS) adaptive filters, and PCA [ 22 ]. The high amount of research on ECG SQIs compared to the one on ccECG SQIs demonstrates the need for additional efforts to further validate these metrics in the contactless signals, due to the special characteristics of ccECG artefacts [ 23 ], which are not always the same as in their contact counterpart, and present a higher challenge.…”