(14) Respiratory Severity Score Patterns by Birth Gestational Age among a Cohort of Extremely Preterm Infants

Background: Extremely preterm infants often develop respiratory distress syndrome and require respiratory support to manage respiratory failure. Respiratory severity score (RSS) is the product of the mean airway pressure (MAP) and fraction of inspired oxygen (FiO2) delivered by the respiratory device. Among preterm infants, RSS has been used to predict mortality and the development of bronchopulmonary dysplasia. Little is known about the typical progression of RSS over time in this population.

Objectives: To characterize the RSS over time stratified by birth gestational age, in extremely preterm infants.

Design/Methods: Observational study using data from the Prematurity and Respiratory Outcomes Program (PROP) cohort. Data regarding the mode of ventilation, level of respiratory support, and FiO2 were recorded daily. Each patient’s daily RSS was calculated or estimated as shown in Table 1. Gestational age (GA) cohorts were defined by completed weeks of GA. Daily RSS for each neonate was averaged over the number of days within a completed post menstrual age (PMA) week. Linear quantile mixed models were used to estimate longitudinal profiles of the median weekly RSS for completed PMA out to a maximum of 36 weeks. Models were fit separately for each of six GA cohorts (23–28 weeks completed GA).

Results: The analysis included data from 831 infants born between 23 0/7 and 28 6/7 weeks of gestation. Figure 1 shows profiles for the median of the weekly average RSS over time (for 23-36 weeks completed PMA) colored according to their completed GA at time of birth. Figure 2 has each birth GA profile drawn separately with estimated 95% CIs for the median weekly RSS at each PMA.

Conclusion: RSS's both at birth and at corrected PMA are inversely related to birth GA; higher scores are observed among the more preterm infants. Among infants with a birth GA between 23-25 weeks, there is an increase in RSS within the first 2 weeks of life, followed by a gradual decrease over time. In contrast, RSS was highest in the first week of life for infants born at 26-28 weeks. These data can assist with parental counseling, and for determining timing for clinical interventions and patient selection for interventional studies. RSS trends can be used for future studies to predict short and long-term outcomes.