Oxygen saturation/FIO2 ratio at 36 weeks’ PMA in 1005 preterm infants: Effect of gestational age and early respiratory disease patterns

Objective: To assess oxygen diffusion at 36 weeks’ post-menstrual age in preterm infants by means of the non-invasive oxygen saturation/fraction of inspired oxygen ratio (36w-SFR) and to identify factors associated with 36w-SFR − ie, gestational age (GA) and early respiratory disease patterns (ERP). Methods: Retrospective analysis of prospectively collected data. Setting: Neonatal Intensive Care Unit. Patients: 1005 preterm infants born below 32 weeks’ GA. Interventions: 36w-SFR was the mean of SFR values over 24 h on the day infants reached 36 weeks’ PMA. Main outcome measures: 36w-SFR. Statistics: descriptive statistics, univariate, and multivariate analysis to study associations of 36w-SFR, including GA and ERP. Results: 36w-SFR was significantly different between infants with and without bronchopulmonary dysplasia (BPD) (371 vs 467, P < 0.001), and according to ERP (LowFIO2 466, pulmonary improvement-PI 460, pulmonary deterioration-PD 405, early persistent pulmonary deterioration-EPPD 344, P < 0.001). Significant differences were found either in BPD and in non-BPD patients according to ERP (P < 0.001). Patients without BPD had significant differences in 36w-SFR according to GA (P < 0.001), while infants with BPD and increasing GA at birth had a non-significant trend for increased 36w-SFR (P = 0.621). Factors associated with 36w-SFR were GA, being small for GA, sepsis, human milk feeding, and ERP. Conclusions: Preterm infants without BPD had a spectrum of oxygen diffusion impairment that was inversely associated with GA at birth. Infants with different patterns of ERP had significant differences in 36w-SFR.