Apnea associated with hypoxia in preterm infants: impact on cerebral blood volume

The present study analyzed changes in cerebral blood volume (CBV) during apnea associated with hypoxia compared to apnea without hypoxia. Hypoxia was defined as pulsoxymetric oxygen saturation <80%>10 s. The employed technique was near infrared spectroscopy combined with electrocardiogram, electroocologram, pulsoxymetry, sidestream capnography and two respiratory effort sensors. In 24 preterm infants 44 incidences of apnea were analyzed. Two main patterns were observed: a significant decrease or a significant increase of CBV. In the 'CBV decrease' group deltaCBV was -55 microl/100 g brain in hypoxic apnea, and -62 microl/100 g brain in non-hypoxic apnea. In the 'CBV increase' group the rise of CBV above preapneic values was +50 microl/100 g brain in hypoxic apnea, and +47 microl/100 g brain in non-hypoxic apnea. Heart rate showed a significant decrease only in the 'CBV decrease' group. Endexpiratory CO(2) increased significantly 1 min after apnea. In conclusion, this study observed significant changes of CBV during apnea in preterm infants, but no difference in CBV behavior regarding whether incidents of apnea were associated with hypoxia or not. It remains unclear which regulatory mechanisms are responsible for the two observed patterns of deltaCBV during apnea.