title: Lung function at 6 and 18 months after preterm birth in relation to severity of bronchopulmonary dysplasia.
abstract: Many preterm infants with bronchopulmonary dysplasia (BPD) demonstrate impaired lung function and respiratory symptoms during infancy. The relationships between initial BPD severity, lung function and respiratory morbidity are not fully understood. We aimed to investigate the association between BPD severity and subsequent lung function and whether lung function impairment is related to respiratory morbidity.
  
  
  METHODS
  In this longitudinal cohort study, 55 infants born preterm (23-30 weeks of gestation) with mild or moderate/severe BPD, based on oxygen requirement at 36 gestational weeks, were followed up at 6 and 18 months postnatal age. Respiratory symptoms, such as recurrent or chronic chough and wheeze, were noted and patient records were scrutinized. Lung function was assessed by passive lung mechanics, whole body plethysmography, and tidal and raised volume rapid thoraco-abdominal compression techniques. Results were related to published normative values.
  
  
  RESULTS
  Besides residual functional capacity (FRC) and respiratory system compliance (Cso ) assessed at 18 months, all measures of lung function were significantly below normative values. Moderate/severe BPD differed significantly from mild BPD only with respect to reduced Cso . At follow-up at 6 and 18 months, participants with respiratory symptoms showed lower; maximal forced expiratory flow at FRC (V'maxFRC) (P = 0.006, P = 0.001), forced mid-expiratory flows (MEF50 ) (P = 0.006, P = 0.048), and Cso (P = 0.004, P = 0.015) as compared to participants without symptoms.
  
  
  CONCLUSIONS
  In the present study BPD severity did not predict lung function, but may be associated with impaired alveolarization, indicated by reduced Cso . Respiratory morbidity was associated with reduced airway function and respiratory compliance in infancy after preterm birth.
authors.affiliation: Sachs' Children's Hospital, Department of Pediatrics, Södersjukhuset, 118 83, Stockholm, Sweden.|Karolinska Institute, Department of Clinical Science and Education, 171 77, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Thunqvist
authors.affiliation: The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.|Central Hospital, Department of Pediatrics, Skövde, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Gustafsson
authors.affiliation: Karolinska Institute, Department of Clinical Science, Intervention and Technology, 141 86, Stockholm, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Norman
authors.affiliation: Sachs' Children's Hospital, Department of Pediatrics, Södersjukhuset, 118 83, Stockholm, Sweden.|Karolinska Institute, Institute of Environmental Medicine, 171 77, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Wickman
authors.affiliation: Sachs' Children's Hospital, Department of Pediatrics, Södersjukhuset, 118 83, Stockholm, Sweden.|Karolinska Institute, Institute of Environmental Medicine, 171 77, Stockholm, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Hallberg
mesh_terms: D001997:Bronchopulmonary Dysplasia / Q000503:physiopathology*; D015331:Cohort Studies; D005260:Female; D005540:Forced Expiratory Flow Rates / Q000502:physiology*; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000502:physiology*; D008137:Longitudinal Studies; D008297:Male; D047928:Premature Birth; D012720:Severity of Illness Index
keywords: infant pulmonary function; longitudinal survey; neonatal prematurity