DYNAMICS OF VASOMOTOR THERMOREGULATION OF THE SKIN IN TERM AND PRETERM NEONATES

Eighteen fullterm infants and 17 preterm infants were studied on their 3rd day of life to investigate the reactivity of skin blood flow to t hermal stimulation. The infants were studied during quiet sleep. After a 10-min control period a constant air current was used to synchronis e the external cutaneous stimulus to the distal lower extremity of eac h infant: the heating element of an air blower was automatically switc hed on and off to generate successive warm and cool periods of equal d uration (5 cycles/min). Heart rate (HR), skin blood flow (SBF) and res piratory waveform signals were recorded and their variability was anal ysed using the fast Fourier transform and spectral analysis. Fullterm infants showed a clear response to external thermal stimulation: both HR and SBF were synchronised to the stimulation frequency. A response of preterm infants was present but it was markedly attenuated in compa rison to term infants. The effect of stimulation did not seem to be de pendent on postnatal age. The results suggest that the vasomotor contr ol is immature in preterm infants.