Cerebral oxygenation and oxygen extraction during and after intermittent hypoxia in preterm infants

Background Intermittent hypoxia (IH) is frequently observed in preterm infants; however, its effect on cerebral oxygenation (rSO2-C%) and fractional oxygen extraction (FOE-C%) remains unclear. This study aimed to characterize changes in rSO2-C% and FOE-C% during and after the IH episodes, while accounting for vital signs and clinical factors. Methods 17 infants, aged 14–20 days and born at 24–28 weeks' gestational age (GA), were studied. We linked rSO2-C% recorded by near-infrared spectroscopy (NIRS) with oxygen saturation (SaO2%), heart rate (HR), and respiratory rate (RR). IH was defined as a SaO2% reading of at least 80% for 20 seconds or more. Paired t-test, absolute percent change (APC%), and regression models were used to identify variations in rSO2-C% and FOE-C% before IH (T0), during IH (T1), and after IH (T2). Results Four hours of NIRS monitoring in each of the 17 infants yielded 44 episodes of IH. During the IH episodes from T1 to T0, the APC% in rSO2-C% was not associated with changes in GA and hematocrit (Hct%). After the IH, from T2 to T1, the APC% in rSO2-C% was directly associated with both GA and Hct%. GA alone directly predicted APC% in FOE-C% during (T1 to T0) and indirectly after the IH (T2 to T1). Changes in rSO2-C% and FOE-C% were not linked to the HR or RR at any measurement points. Conclusion Recovery from the reduction in rSO2-C% during IH episodes is influenced by both gestational age and hematocrit levels. Since this is an exploratory study, the findings, expressed as effect sizes and confidence intervals, should be interpreted with caution, particularly given the imprecision introduced by the small sample size.