Fig. 2
From: Heart rate variability parameters indicate altered autonomic tone in subjects with COVID-19
Linear and nonlinear HRV parameters for a sample RR series from each group. The rows in panels (a), (b), and (c) represent the HRV parameters extracted from the RR series of subjects from the groups: healthy control, CVD control, and COVID-19 patients, respectively. The first column displays the time-series of NN intervals (in seconds), the second column presents the power spectral density (PSD) analysis, and the third column shows the Poincaré plots depicting the relationship between successive NN intervals (NN_n vs. NN_n + 1). The healthy volunteers typically exhibited higher variability compared to the CVD and COVID-19 groups.
