Lung Disease, Oxidative Stress, and Oxygen Requirements in Preterm Infants

Background: The role of oxidative stress remains unclear in the multifactorial pathophysiologic mechanism of lung disease in preterm infants. Aims: The aim of this study was to examine the associations among chronic lung disease (CLD), oxidative stress, and oxygen requirements in preterm infants. Design: Prospective, longitudinal, and correlational design. Subjects: Preterm infants born at <32 weeks' gestation (N = 31), median gestation of 29.0 weeks (range 24.9-31.7). Measurements: The diagnosis of CLD was obtained from the medical record. Oxidative stress was measured using 8-hydroxydeoxyguanosine (8-OHdG) in the cord blood at birth and urine on Days 1 and 7. Oxygen requirements were measured using fraction of inspired oxygen (FIO2) recorded in the first hour after birth/admission and the average FIO2 during the first 12 hr and 7 days after birth. Descriptive statistics are presented. Comparison analyses were performed using Kruskal-Wallis and Fisher's exact tests. Results: Infants with CLD (n = 12) had lower gestational age (p = .04) and weight (p = .04) at birth, more days on the ventilator (p = .004), and longer neonatal intensive care unit stay (p = .04) compared to infants without CLD (n = 19). CLD was associated with lower oxidative stress levels (p = .03) and higher oxygen requirements during the first 12 hr (p = .025) and on Day 7 (p = .001). Lower oxidative stress levels on Day 7 were associated with higher oxygen requirements in the first 12 hr (p = .01) and on Day 7 (p = .03). Conclusion: Our results linking CLD and higher oxygen requirements with low oxidative stress contradict previous reports. Findings identify a gap in knowledge for postresuscitation oxygen therapy in preterm infants and expose the role of oxidative stress from inflammation and intermittent hypoxia in the etiology of CLD.