C. Vanravenswaaijarts et al., SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY IN SPONTANEOUSLY BREATHING VERY PRETERM INFANTS, Acta paediatrica, 83(5), 1994, pp. 473-480
The influence of maturation, sleep state and respiration on heart rate
variability was studied in 16 spontaneously breathing preterm infants
(<33 weeks). ECG, respiratory impedance curve and movements were reco
rded four times a day, during the first three days of life. The power
content of selected frequency bands of the R-R interval power spectrum
, as well as respiratory frequency and breath amplitude oscillation fr
equency, were calculated for 3-min periods. An increase in low frequen
cy heart rate variability with gestational age was found. High-frequen
cy variability increased during early postnatal life. Sleep state infl
uenced very low-frequency heart rate variability. The amount of respir
atory sinus arrhythmia and breath amplitude sinus arrhythmia was deter
mined mainly by respiratory rate and breath amplitude oscillation freq
uency, respectively. The influences of gestational and postnatal age o
n heart rate variability might be due to an increase in sympathetic to
ne before birth and a change in parasympathetic-sympathetic balance af
ter birth. Respiration has an important influence on heart rate variab
ility, even in very preterm infants.