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Application of the FILT (a), ENVL (b), and INTR (c) methods to the respective signals of interest. On the first column, input signals and main features are: (a) PPG signal (light blue); (b) derivative of the PPG signal (grey) and relative superior envelope (black); (c) PPG signal (light blue) and points of maximum slope (red). Second column: breath signals obtained with each method.
