Relationship between heart rate variability using Lorenz plot and sleep level

In the present study, we propose a new technique for estimating depth of sleep over the whole night using electrocardiogram (ECG) RR intervals (RRIs). We produced a Lorenz plot (LP) using the RRIs recorded during all-night sleep and confirmed that changes in distribution on the LP occur based on changes in sleep stage. To evaluate the changes in these distributions, RRIs are projected a LP on a y = x axis, y = -x axis, and analyzed the shifting...