Spectral analysis of heart rate variability and respiration during sleep in cocaine-exposed neonates

This study's objective was to examine the autonomic control of heart rate and respiration during the neonatal period in human infants with prenatal exposure to cocaine. Four-hour daytime recordings of the electrocardiogram (ECG) were obtained from 15 cocaine-exposed and 13 non-exposed full-term neonates at 2 weeks of age during quiet sleep (QS) and active sleep (AS). For each 1-min epoch of sleep, the power spectrum of the R-R intervals was computed from the ECG to obtain the total power (0-2 Hz), and spectral power in the high-frequency (HFP, 0.3-2 Hz), mid-frequency (MFP, 0.1-0.2 Hz), and low-frequency (LFP, 0.03-0.1 Hz) bands. Respiration was also monitored and processed using similar spectral analysis procedures. Cocaine-exposed neonates showed enhanced heart rate variability reflected by an increase in spectral power across all frequency bands. Spectral power in LFP and MFP was higher in cocaine-exposed neonates during both sleep states, but only in HFP during QS. There were no respiratory patterning differences between the groups to account for these findings. The index of sympathovagal balance (LFP + MFP)/HFP, showed no differences between the groups. We conclude that infants exposed to cocaine in utero show differences in the modulation of heart rate reflecting an increase in both vagal and sympathetic influences.