Down syndrome is associated with significant respiratory morbidity. The available pulmonary function testing data in school aged children and adults with Down show evidence of restrictive lung disease. We aimed to evaluated infant pulmonary function tests (iPFTs) in individuals with Down.

An observational case-control study evaluating iPFTs results from a registry of patients assessed at the Hadassah Hebrew University Medical Center between 2008 and 2018. iPFTs results in Infants with Down were compared to a spirometry control group of infants with normal expiratory airflows, using the Mann–Whitney U and Fisher's exact tests.

iPFT data from 66 infants (20 Down and 46 control) were evaluated in the study. Most infants with Down showed abnormalities of an obstructive lung disease with mildly increased lung volumes and significantly decreased expiratory flows, mostly unresponsive to bronchodilators. Airflow limitations were most prominent at low lung volumes (median (IQR); maximal expiratory flow at functional residual capacity,   FRC = 48 (26–78) %predicted in Down Vs.   FRC = 100 (93–114) %predicted in controls, p < 0.001). We further observed an alteration in breathing mechanics with significantly decreased respiratory system compliance and increased airway resistance associated with decreased tidal volumes but similar minute ventilation.

Our study shows that infants with have a fixed airflow obstruction phenotype. These results add comprehensive data to allow better understanding of the lung disease present early in life of infants with Down syndrome. Further studies are required to improve management of respiratory disease in individuals with Down.