Systematic underestimation of oxygen delivery in ventilated preterm infants

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 (O(2)) in ventilated preterm infants has not been rigorously studied.

Objectives: To test the hypothesis of systematic underestimation of O(2) delivery in extremely low birth weight (ELBW) infants during long-term ventilation.

Methods: Actually achieved O(2) concentrations were measured and compared to the set inspired oxygen fraction (FiO(2)). A total of 108 O(2) measurements were carried out during the ventilation of 54 ELBW infants: O(2)-Delta error (i.e., the difference between O(2) concentrations achieved by the ventilator and set FiO(2)) was the main study outcome measure.

Results: Systematic O(2)-Delta errors were found, with mean values of +9.52% (FiO(2) 0.21-0.40), +2.10 (FiO(2) 0.41-0.60), +2.86% (FiO(2) 0.61-0.80), and +0.016% (FiO(2) 0.81-1.0; p < 0.0001). Theoretical simulations from the observed data indicate that, if not corrected, systematic O2-Delta errors would lead to a non-intentional total O(2) load of 1,202.9 (FiO(2) 0.21-0.40), 252.46 (FiO(2) 0.41-0.60), 342.85 (FiO(2) 0.61-0.80), and 2 (FiO(2) 0.81-1.0) extra liters/kg body weight/100 ventilation hours.

Conclusions: Systematic underestimation of the O(2) delivered by infant ventilators can potentially lead to surprisingly large increases in total O(2) load during long-term ventilation of ELBW infants, especially in the lower FiO(2) range (i.e., 0.21-0.40). Underestimation of true O(2) delivery can potentially lead to unrecognized high O(2) loads, and more pronounced and prolonged hyperoxia.