Assistant Professor UAB Birmingham, Alabama, United States
Background: The severity of pulmonary hypertension can be characterized by the relationship between the magnitude of oxygen administration and achieved oxygen saturation, such as by the oxygen saturation index (OSI = (MAP × FiO2 × 100)/SpO2) defined using the mean airway pressure (MAP), fraction of inspired oxygen (FiO2), and SpO2. Objective: We hypothesized that infants with bronchopulmonary dysplasia associated hypertension (BPD-PH), as compared to infants with BPD alone, would have a higher OSI. Design/Methods: We conducted a case-control single center study of extremely preterm infants with grade 2 to 3 BPD and born between 2018 and 2023 at the University of Alabama at Birmingham. The predictive utility of the OSI was first assessed in the week preceding echocardiographic diagnosis of BPD-PH within a discovery cohort using receiver operator curve (ROC) analysis. Subsequent validation of OSI discrimination was then performed in a validation cohort using a ROC derived cut-point. Lastly, OSI values were assessed over the course of hospitalization to identify the postnatal age at OSI separation between comparison groups. Results: There were 84 infants with grade 2 to 3 BPD during the study period of whom 55 infants had BPD-PH and 29 infants had BPD alone. Infants who developed BPD-PH had a higher OSI compared to infants with BPD alone in the discovery cohort (4.3 vs 2.6; p=0.03; AUC 0.70; Figure 1). In the validation cohort (n=87), test sensitivity was 92% (95 CI 75%-99%), specificity 46% (95% CI 19%-75%), with a positive predictive value of 77% and negative predictive value of 75%. In longitudinal OSI comparisons, there was increasing discriminatory utility and separation in OSI values between infants with BPD alone and BPD-PH beyond 36 weeks’ PMA (Figure 2).
Conclusion(s): The OSI may provide a noninvasive predictor for BPD-PH in preterm infants, especially close to term corrected age.
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