LONGITUDINAL FOLLOW-UP OF LUNG-FUNCTION FROM CHILDHOOD TO ADOLESCENCEIN PREMATURELY BORN PATIENTS WITH NEONATAL CHRONIC LUNG-DISEASE

We investigated whether early lung function abnormalities in premature ly born children with a history of chronic lung disease improve in lat e childhood and adolescence. We performed a prospective, longitudinal evaluations of pulmonary function over an a year period. In seventeen patients from the age (mean +/- SD) of 8.2 +/- 1.2 years to the age of 15.1 +/- 1.6 years. They had been born at 29.1 +/- 1.9 weeks of gesta tion, with a birthweight of 1120 +/- 190 g, and they had received supp lemental oxygen, with or without mechanical ventilation, for 40.4 +/- 23.8 days during the neonatal period. They all had radiographic eviden ce of chronic lung disease at 4 weeks of age. Annual measurements of l ung volumes using the helium dilution technique, and of airway functio n with spirometry and maximal expiratory flow-volume curves over a 5 t o 8 year period, were obtained. The results indicated that total lung capacity (TLC) and vital capacity (VC) were within the predicted norma l range in all patients and increased over time. In contrast, the init ially abnormal residual volume (RV) and RV/TLC ratio decreased over ti me, suggesting gradual resolution of air-trapping. The peak expiratory flow rate (PEFR), forced expiratory volume in I second (FEV(1)), and the ratio FEV(1)/FVC remained at or above the predicted normal range i n all patients. FEF(25-75) FEF(50), and FEF(75) were within normal lim its in eight patients and abnormally low (more than 2 SD below the pre dicted normal value) in the remaining nine patients, indicating small airway obstruction. Eight of the nine patients with lower airway obstr uction showed significant response to inhaled bronchodilator, and four responded to a histamine challenge. None of the eight patients with n ormal airway function responded to histamine, but four responded to br onchodilators. The perinatal history, family history of asthma, and ex posure to smoking were similar in patients with and without airway obs truction. The height and weight were and remained within the normal ra nge. We conclude that gradual normalization of air-trapping continues well into adolescence in virtually all patients with a history of prem aturity and chronic lung disease. In contrast, airflow obstruction may persist but does not get worse later in life. Although chronic airflo w obstruction probably is the consequence of injury to the small airwa ys during the neonatal period, it is present in only some of the child ren, and it does not appear to be directly related to the perinatal hi story. Finally, there is evidence that airway hyperresponsiveness may be a contributing factor to the development and/or persistence of airf low obstruction in chronic lung disease of prematurity. (C) 1996 Wiley -Liss, Inc.