Background It is unclear whether increased pulmonary arterial (PA) reactivity to hypoxia observed in preterm infants who develop chronic lung disease of prematurity (CLD) persists into childhood.

Aim We assessed and compared PA pulse wave velocity (PWV) in air and after 12% hypoxia using velocity-encoded MRI between children who had CLD in infancy and preterm-born and term-born controls.

Methods From 67 recruited children, 59 (13 CLD, 21 preterm, 25 term), 9–12-year-old children successfully completed the study. Velocity-encoded phase-contrast MR PA images were acquired breathing air and during breathing 12% hypoxia. PA PWV was derived as the ratio of flow to area changes during early systole.

Results There were no differences in mean (SD) PA PWV between the groups breathing air (CLD=1.3 (0.4) m/s, preterm control=1.3 (0.4) m/s, term control=1.3 (0.3) m/s)) but increased following hypoxia to 1.9 (0.7) m/s, 1.6 (0.6) m/s and 1.5 (0.5) m/s in CLD, preterm and term groups, respectively. The mean differences (95% CI) for PA PWV between CLD and the preterm and control groups were 0.37 (0.08 to 0.70) and 0.34 (0.05 to 0.70), respectively. There was no difference for change in PA PWV with hypoxia between the two control groups, mean difference 0.23 (−0.2 to 0.3).

Conclusions Children who had CLD in infancy had increased pulmonary arterial reactivity during hypoxia, thus long-term follow-up is warranted in this population.