B105-01 Predicting Chronic Phase Ventilation in Bronchopulmonary Dysplasia: The Time (Constant) Has Come!

Abstract Background Despite improved survival among extremely low birth weight infants, the incidence of BPD is unchanged. Up to 40% of infants 28 weeks’ (w) gestational age (GA) and 80% of those 24w develop BPD, with ∼30% progressing to severe (sBPD). The sBPD infants exhibit increased airway resistance with relatively preserved compliance. The timing of this physiological shift is variable, complicating identification of the optimal time to adopt a chronic-phase ventilation (CPV) strategy, a concept based on the change in the time constant of these infants. Objective To characterize the natural evolution of the respiratory time constant (TC = compliance × resistance) in preterm infants with evolving BPD, correlate with chest x-ray (CXR) signs of chronic changes, and to estimate when TC changes indicate the optimal time to transition toward CPV. Methods We prospectively collected de-identified ventilator and clinical data from infants 30w GA (starting September 2024) to date. Exclusion criteria were major congenital lung or heart disease. Weekly assessments to document ventilator and patient data since the last assessment (including CXR findings of hyper expansion and cystic lung changes by 5mm cyst in 0-4 quadrants) continued until 36w postmenstrual age (PMA). Data were managed in REDCap. Descriptive statistics were used for demographics. Associations between TC and PMA or day-of-life (DOL) were tested by linear regression, and differences across cystic change quadrants were assessed using one-way ANOVA with Sidak post-hoc testing. Results Twenty infants contributed 56 weekly assessments and 35 TC values. Mean GA was 26.2w (range 23-30) and mean birth weight 828 g (range 480-1490); all received surfactant. Antenatal steroids were given to 95%, and 10% of mothers had diabetes. Our analysis showed that TC increased significantly with PMA and with DOL (Figure 1a and 1b). Infants with CXRs in the highest cystic-change quartile had significantly higher TC values compared with all other groups (p ≤ 0.04) (Figure 2). Comments In preterm infants with evolving BPD, TC rises progressively with both postnatal age and PMA, and with lung cystic changes, suggesting increasing airway resistance over time. These trends may signal the onset of chronic-phase lung physiology and help define when to shift to CPV strategies. Ongoing data collection will help identify PMA or other clinical variables at which the ventilator settings need to be changed to CPV. This abstract is funded by: UH Rainbow Babies & Children’s Hospital