In this randomized crossover trial, preterm infants with intermittent hypoxemia and need for supplemental oxygen will be randomized to either Sequence of two different oxygen target ranges (low: 85-89%; high: 91-95%) for a total duration of 19 hours. Cerebral oxygenation, cardiac output, arterial oxygenation and heart rate will be measured continuously. Primary outcome is time with arterial oxygen saturation < 80%.