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Longitudinal changes in lung function during the first three years of premature infants with moderate to severe
G B Mallory1, H Chaney, R L Mutich
1Department of Pediatrics, Washington University School of Medicine, St. Louis Children's Hospital, Missouri 63110.
Insights
This study shows that while lung capacity improves in infants with bronchopulmonary dysplasia (BPD), severe airway obstruction and hyperreactivity persist. Long-term ventilation worsens these pulmonary function deficits in children with BPD.
Area of Science:
- Pediatric Pulmonology
- Neonatal Medicine
- Respiratory Physiology
Background:
- Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants, often requiring mechanical ventilation and oxygen therapy.
- Longitudinal studies on pulmonary function development in infants with BPD are challenging.
- Understanding long-term respiratory outcomes is crucial for managing BPD.
Purpose of the Study:
- To longitudinally assess pulmonary function development in infants with moderate to severe BPD.
- To compare respiratory outcomes based on the duration of mechanical ventilation.
- To investigate the persistence of airway obstruction and hyperreactivity in young children with BPD.
Main Methods:
- Longitudinal study of 11 infants with moderate to severe BPD and prior tracheostomy.
- Measurement of maximal expiratory flow-volume curves using the forced deflation technique.
- Classification of patients into two groups based on mechanical ventilation duration (<5 months vs. ≥10 months).
Main Results:
- Forced vital capacity (FVC) was significantly reduced at 6 months in both groups but normalized by 12 months in the shorter ventilation group.
- Maximum expiratory flow at 25% FVC (MEF25) showed persistent severe obstruction, especially in the longer ventilation group, with minimal improvement by 36 months.
- Over 75% of patients exhibited airway hyperreactivity throughout the study period.
Conclusions:
- Vital capacity in BPD patients may normalize by age 3, but severe lower airway obstruction persists, particularly with prolonged ventilation.
- Airway obstruction in smaller intrathoracic airways and bronchial hyperreactivity do not resolve within the first three years of life in BPD.
- These findings highlight the chronic nature of respiratory impairment in BPD, emphasizing the need for ongoing respiratory support and management.
Abstract:
Bronchopulmonary dysplasia (BPD) is a chronic obstructive pulmonary disease of prematurely born infants following prolonged mechanical ventilation and oxygen therapy. Developmental changes in pulmonary function of children with BPD during their early years have been difficult to study. We longitudinally studied maximal expiratory flow-volume curves by the forced deflation technique in 11 infants who had previous tracheostomy with moderate to severe BPD. Patients were classified into: those who were mechanically ventilated for less than 5 months (Group A), and those who were ventilated for 10 or more months (Group B). At 6 months of age, forced vital capacity (FVC) was 28.1 and 25.5 mL/kg in Group A and B, respectively, significantly less than normal (41.8 mL/kg). The maximum expiratory flow at 25% FVC (MEF25) at 6 months of age was 6.9 and 8.1 mL.kg-1.s-1 in Group A and B, respectively, (predicted value, 39.2 mL.kg-1.s-1). FVC reached the normal range by 12 months of age in Group A, but remained lower until 36 months of age in Group B. MEF25 gradually increased in Group A, reaching 18.0 mL.kg-1.s-1 at 36 months of age, whereas in Group B it was severely decreased at the same age (3.5 mL.kg-1.s-1). More than 75% of the patients had airway hyperreactivity at all ages. We have demonstrated that in patients with moderate to severe BPD, vital capacity is moderately decreased, but catches up to normal levels by 36 months of age. In contrast, severe lower airway obstruction persists in all infants, although in those with moderate BPD gradual improvement is seen. These findings suggest that in BPD neither obstruction of the smaller intrathoracic airways nor bronchial hyperreactivity resolves during the first 3 years of life.