643563.fig.007a
(a)
643563.fig.007b
(b)
643563.fig.007c
(c)
Figure 7: Spectral analysis of the ECG-derived respiration signal: (a)equidistantly repositioned QRS maxima samples with frequency axis scaled according to the mean heart period, (b) spline interpolated unevenly sampled QRS maxima, (c) the Lomb-Scargle periodogram of unevenly sampled QRS maxima.