(40) Time-resolved Changes in Dynamic Lung Compliance to Assess Response to Systemic Steroids in Intubated Infants <32 Weeks Gestation

Background: Prolonged assisted ventilation is a major cause of Bronchopulmonary Dysplasia (BPD). Corticosteroids prevent BPD by improving lung compliance and facilitating extubation.There exists significant heterogeneity in response to systemic corticosteroids. Current guidelines used to wean infants from ventilators rely on highly variable operator-dependent assessments. There is a clear need to develop an objective functional tool to assess changes in pulmonary compliance and thereby facilitate extubation.We hypothesize that temporal trends in dynamic compliance can predict responsiveness to systemic dexamethasone.

Objectives: 1. Derive novel profiles of continuous time-resolved dynamic compliance in intubated preterm infants and determine correlation with other measures of pulmonary function like Respiratory severity score (RSS).
2.To determine whether changes in dynamic compliance can predict responsiveness to systemic steroids and extubation success.

Design/Methods: This is a prospective cohort study of 19 intubated infants < 32 weeks gestation receiving systemic steroids to facilitate extubation in our level 4 NICU. Granular minute-level compliance data was extracted from mechanical ventilator of each infant 12 to 24 hours before starting steroids and continued until they were extubated or for 3 days post steroid therapy whichever came first. Change in dynamic compliance from baseline (6 hours prior to start of steroids) to 12, 24 and 48 hours post steroid were studied. Change is respiratory severity score after systemic steroids were also calculated.

Results: Of the 19 recruited, 2 were excluded. Analysis was performed using a linear mixed-effects model to account for repeated measures of same patient across timepoints. The mean dynamic compliance increased by 26.55% (SD 39.47) at 24 hours post-steroid, 47.62% (SD 52.08) at 48 hours and by 27.96% (SD 27.78) at 72 hours post steroid respectively. The mean decrease of RSS at 24 hours, 48 hours and 72 hours post steroid was -17.32(SD 29.85), -18.15 (SD 34.81) and – 20.73(SD 35.30) respectively. The p value was significant for changes at the 24, 48 and 72 hr post systemic steroid therapy in both models.

Conclusions: Changes in the dynamic lung compliance after dexamethasone is evident by 24 hours and peaks at 48 hours after the second dose of steroid. Based on the results of this novel pilot study, changes in the dynamic compliance could be used as an objective measure to monitor response to systemic steroid therapy.