Abstract
Background: Emerging evidence indicates that hyperoxia is a risk factor for bronchopulmonary dysplasia, a common multifactorial long-term complication of prematurity. To date, the equivalence between set and delivered oxygen (O2) in ventilated preterm infants has not been rigorously studied. Objectives: To test the hypothesis of systematic underestimation of O2 delivery in extremely low birth weight (ELBW) infants during long-term ventilation. Methods: Actually achieved O2 concentrations were measured and compared to the set inspired oxygen fraction (FiO2). A total of 108 O2 measurements were carried out during the ventilation of 54 ELBW infants: O2-Δ error (i.e., the difference between O2 concentrations achieved by the ventilator and set FiO2) was the main study outcome measure. Results: Systematic O2-Δ errors were found, with mean values of +9.52% (FiO2 0.21–0.40), +2.10 (FiO2 0.41–0.60), +2.86% (FiO2 0.61–0.80), and +0.016% (FiO2 0.81–1.0; p < 0.0001). Theoretical simulations from the observed data indicate that, if not corrected, systematic O2-Δ errors would lead to a non-intentional total O2 load of 1,202.9 (FiO2 0.21–0.40), 252.46 (FiO2 0.41–0.60), 342.85 (FiO2 0.61–0.80), and 2 (FiO2 0.81–1.0) extra liters/kg body weight/100 ventilation hours. Conclusions: Systematic underestimation of the O2 delivered by infant ventilators can potentially lead to surprisingly large increases in total O2 load during long-term ventilation of ELBW infants, especially in the lower FiO2 range (i.e., 0.21–0.40). Underestimation of true O2 delivery can potentially lead to unrecognized high O2 loads, and more pronounced and prolonged hyperoxia.