Which ELGANs are most at risk of low lung function?

In extremely low gestational age newborns (ELGANs), certain demographic factors and less-than-optimal respiratory support in or beyond the neonatal intensive care unit (NICU) can increase the risk of abnormal lung function at 1 year of age. Those are the major findings of a study in 135 ELGANS born at 6 hospitals across the United States.

Following the newborns’ discharge from the NICU, investigators collected quarterly data about the infants’ respiratory symptoms; emergency department (ED) or hospital admissions for respiratory indications; cardiopulmonary medications; and use of supplemental oxygen or ventilatory support. Investigators also collected perinatal demographic data and performed infant pulmonary function tests (iPFTs) when the babies were 1 year of age.

Compared with normative values, infant z scores for all iPFT values were significantly lower except lung function and respiratory system resistance, with the latter significantly higher. Of 6 adverse events, just 1 was deemed serious, and the infant recovered immediately after testing.

With regard to correlations between NICU and post-NICU clinical factors and iPFTs, for each week’s decrease in gestational age, forced expiratory flow (FEF) at 75% of forced vital capacity (FVC) decreased 9.5%. Other neonatal factors associated with significantly lower or abnormal iPFTs included intubation at delivery, need for invasive ventilation at more than 30 weeks’ postmenstrual age (PMA) or noninvasive ventilation at more than 36 weeks’ PMA, treatment with diuretics or systemic steroids, and weight below or equal to the 10th percentile at 36 weeks’ PMA.

Prenatal and family factors generally had no effect on iPFTs, but ED or hospital admissions for respiratory indications, cardiopulmonary medication, and use of supplemental oxygen or ventilatory support were significantly associated with lower iPFTs. Among demographic factors, being male and Black increased the likelihood of a significant decrease in forced expiratory volume 0.5 or FEF at 75% of FVC. Just 7% of the infants had reversible airflow obstruction.

Thoughts from Dr. Farber

I sometimes squeeze infant’s chests (gently) to elicit a wheeze, but it appears it can now be done in a standardized fashion. Prior to this, iPFTs were a pipe dream, but technology marches on. I also note that bronchodilators usually do not help these children, just as they are not of benefit with viral wheezing.

Reference

Voynow JA, Feng R, Ren CL, et al. Pulmonary function tests in extremely low gestational age infants at one year of age. Pediatr Pulmonol. 2022;57(2):435-447. doi:10.1002/ppul.25757