Skin blood flow changes, measured by laser Doppler flowmetry, in the first week after birth

Changes in forehead skin blood flow were determined in 17 healthy, term newborns, using a fiberless diode laser Doppler flow meter (Diodopp). Measurements were carried out three times on each infant, at postnatal ages of 16.8 +/- 7.4 h, 58.9 +/- 6.2 h and 121.5 +/- 14.2 h (mean +/- S.D.), respectively. Skin blood flow, respiration, heart rate and skin temperature were recorded simultaneously, while the newborns were asleep. During the recordings, the behavioural state of the newborns was observed and environmental temperature and humidity were kept constant. Postocclusive hyperaemia of the skin blood flow was obtained by pressing the laser Doppler probe against the skull for 30 or 60 s. The following parameters changed significantly between the first and third measurements (t-test for paired samples): the basal skin blood flow during active and quiet sleep decreased, the average decrease being 29.4% (P = 0.002) and 25.9% (P = 0.01), respectively; skin blood flow during postocclusive hyperaemia also changed: the time taken to reach maximum hyperaemia increased from 17.3 to 22.7 s (P = 0.01), while the halftime recovery increased from 46.1 to 57.1 s (P = 0.02). The changes in skin blood flow between the first and second measurements and between the second and third measurements did not reach the level of statistical significance.