Fig. 1.

(color online) Examples of approximately four minutes of continuous RR (interbeat) intervals from four different NICU patients. (a) RR interval series for a healthy NICU patient;(b) RR interval series for a NICU patient showing reduced heart rate variability prior to diagnosis of sepsis (bloodstream infection); (c) RR interval series for a NICU patient showing decelerations; (d) RR interval series showing part of a long cluster of periodic decelerations. Each peaked structure in (c) and (d) is termed a “deceleration.” (d) shows striking periodicity (period ~45 beats, or about 15 s), which lasted well beyond the duration of the shown excerpt; the periodic decelerations lasted over 48 hours. (This infant suffered intracranial hemorrhage with concomitant sepsis.)