P2C180: A Study to Characterize Continuous Positive Airway Pressure Belly Syndrome in Preterm Infants in the Neonatal Intensive Care Unit

Background: CPAP Belly Syndrome (CBS) describes gaseous enteric distension caused by noninvasive respiratory support in preterm infants. CBS may mimic early necrotizing enterocolitis (NEC), leading to abdominal radiographs, pauses in enteral feeds, and changes in respiratory support. Current management strategies for CBS are heterogeneous and ineffective, in part because CBS remains poorly characterized. This study aims to reproducibly define CBS in a cohort of preterm infants and describe demographic characteristics, mechanical factors, and outcomes associated with CBS.

Methods: A retrospective chart review was conducted of infants < 32 weeks gestation admitted to the Stanford NICU from January 1, 2020 to December 31, 2021. Abdominal radiographs from the first 28 days of life (DOL) were assessed by a pediatric radiologist in accordance with the classification system shown in Figure 1 to determine a diagnosis of CPAP Belly Syndrome. Demographic information, mechanical characteristics, and outcomes data were collected for all infants. Key characteristics were compared using Fischer’s Exact tests for categorical variables and Mann-Whitney U tests for continuous variables. Regression analysis was completed using SPSS Statistical Software.

Results: One hundred and thirty four preterm infants were admitted to the Stanford NICU meeting inclusion criteria. Sixty nine were classified as having no CPAP Belly Syndrome (either no abdominal radiographs or only normal abdominal radiographs) and 41 were classified as having CPAP Belly Syndrome (18 mild, 14 classic, 9 plus). Infants with CBS were delivered at younger gestational ages (median 27.7 vs 30.0 weeks, p< 0.001) and lower birthweights (median 1.00 vs 1.31kg, p< 0.001) compared to infants without CBS. Median time of CBS diagnosis was on day 4 of non-invasive support and day 5 of life. Compared to infants without CBS on day 4 of non-invasive respiratory support, infants with CBS at time of CBS diagnosis were more likely to receive bilevel non-synchronized noninvasive positive pressure ventilation (NIPPV, 14.6% vs 0%, p=0.003) than CPAP and more likely to be receiving higher positive end expiratory pressure (PEEP, p=0.004). Infants with CBS took statistically longer to reach full enteral feeds (median 10 vs 7 days, p=0.003). Infants with CBS also had significantly more non-diagnostic abdominal radiographs [i.e. those that did not diagnose, or follow up a diagnosis of, NEC than infants without CBS (median 3 vs 0 radiographs, p< 0.001)]; CBS was associated with 3.4 more non-diagnostic abdominal radiographs in the first 28 DOL (Table 1).

Conclusion: Infants with CBS are younger, smaller, and more likely to receive bilevel support and higher PEEP despite similar stooling patterns and glycerin use. This suggests that developing an effective therapy for CBS should focus on preventing pressurized air entry from above rather than improved motility from below. This therapy could prevent unnecessary diagnostic testing and protect vulnerable patients from unnecessary radiation.