Table 3.

Correlation coefficients between spectral power values, postmenstrual age and low-frequency transfer gain

	PMA	LF transfer gain
R–R interval series:
R–R interval	+0.61*	+0.66*
LF-RR	+0.53*	+0.76*
HF-RR	+0.62*	+0.75*
Total-RR	+0.62*	+0.81*
SBP series:
SBP	+0.42†	+0.39†
LF-SBP	−0.21	−0.15
HF-SBP	−0.05	−0.25
Total-SBP	−0.16	−0.16

The left column shows Spearman's rho correlation coefficients between postmenstrual age (PMA) and spectral power values of R–R interval and SBP series, respectively. The right column shows Spearman's rho correlation coefficients between LF transfer gain and spectral power values of R–R interval and SBP series, respectively. The total power was computed for the frequency band between 0.04 and 1.5 Hz. The low-frequency (LF) band was defined between 0.04 and 0.15 Hz. The high-frequency (HF) band was defined as the frequency range between the p-10 and p-90 centile of the individual respiratory frequency.

^*P < 0.01;

^†P < 0.05.