Longitudinal assessment of lung function in extremely prematurely born children

Objectives: To assess longitudinally small airway function in children born extremely prematurely and whether there was a correlation between airway function in infancy and at 11-14 years.

Working hypotheses: There would be tracking of airways obstruction and small airway function would deteriorate during childhood in those born extremely prematurely.

Study design: A longitudinal study.

Patient-subject selection: Thirty-five children with a mean gestational age of 26 weeks had lung function assessed at 1 year corrected and 11-14 years of age.

Methodology: Lung volumes were measured by helium gas dilution (FRC_He ) and plethysmography (FRC_pleth ) and small airway function assessed by calculating the FRC_He :FRC_pleth ratio. Airway function was assessed at 1 year corrected by measurement of airway resistance (R_aw ) and at 11-14 years by assessment of R_aw , forced expiratory flow from 75% of vital capacity (FEF₇₅ ), and forced expiratory volume at one second (FEV₁ ).

Results: At the first assessment, the children had a mean (SD) FRC_He :FRC_pleth of 0.90 (0.13) and at the second, 0.83 (0.12) (P = 0.035). There was a significant 0.54% decrease (95%CI: -1.02%, -0.06%) in FRC_He :FRC_pleth for increased age per year after adjusting for birth weight, gestational age, sex, and bronchopulmonary dysplasia (P = 0.027). There were significant correlations between R_aw at the first assessment and R_aw (P = 0.012), FEF₇₅ (P = 0.034), and FEV₁ (P = 0.04) at 11-14 years.

Conclusions: These results demonstrate in those born extremely prematurely there is tracking of airway function during childhood.