High frequency band limits in spectral analysis of heart rate variability in preterm infants.

Objectives: The current study aims to assess different high-frequency (HF) band power calculations based on different frequency bandwidth values, and compare them with the time domain the root mean square of successive RR differences (RMSSD) value in preterm infants.

Methods: At week 32, electrocardiogram (ECG) and breathing rate (BR) were recorded for 24 h on 30 preterm infants born between 28 and 32 weeks. The recording held in the neonatal intensive care unit without any interruption of routine.

Results: The median 24 h BR was 40-78 breaths per minute. The RMSSD was highly and positively correlated with frequency bands that were based on each preterms BR range, or on a constant frequency with band limits of 0.4-2 Hz.

Conclusions: At week 32, HF band Hz limits should be calculated based on each child's breathing rate, generally between 0.4 and 2 Hz.