Development of lung diffusion to adulthood following extremely preterm birth.

Background: Gas exchange in extremely preterm (EP) infants must take place in fetal lungs. Childhood lung diffusing capacity of the lung for carbon monoxide ( ) is reduced; however, longitudinal development has not been investigated. We describe the growth of and its subcomponents to adulthood in EP compared with term-born subjects.

Methods: Two area-based cohorts born at gestational age ≤28 weeks or birthweight ≤1000 g in 1982-1985 (n=48) and 1991-1992 (n=35) were examined twice, at ages 18 and 25 years and 10 and 18 years, respectively, and compared with matched term-born controls. Single-breath was measured at two oxygen pressures, with subcomponents (membrane diffusion ( ) and pulmonary capillary blood volume ( )) calculated using the Roughton-Forster equation.

Results: Age-, sex- and height-standardised transfer coefficients for carbon monoxide ( ) and were reduced in EP compared with term-born subjects, and remained so during puberty and early adulthood (p-values for all time-points and both cohorts ≤0.04), whereas alveolar volume ( ) was similar. Development occurred in parallel to term-born controls, with no signs of pubertal catch-up growth nor decline at age 25 years (p-values for lack of parallelism within cohorts 0.99, 0.65, 0.71, 0.94 and 0.44 for z- , z- , z- , and , respectively). Split by membrane and blood volume components, findings were less clear; however, membrane diffusion seemed most affected.

Conclusions: Pulmonary diffusing capacity was reduced in EP compared with term-born subjects, and development from childhood to adulthood tracked in parallel to term-born subjects, with no signs of catch-up growth nor decline at age 25 years.