Bronchopulmonary Dysplasia
Bronchopulmonary dysplasia (BPD; formerly chronic lung disease of infancy) is a chronic lung disease in which premature infants, usually those who were treated with supplemental oxygen, require long-term oxygen. The alveoli that are present tend to not be mature enough to function normally. It is more common in infants with low birth weight (LBW) and those who receive prolonged mechanical ventilation to treat respiratory distress syndrome (RDS). It results in significant morbidity and mortality. The definition of BPD has continued to evolve primarily due to changes in the population, such as more survivors at earlier gestational ages, and improved neonatal management including surfactant, antenatal glucocorticoid therapy, and less aggressive mechanical ventilation.
Currently the description of BPD includes the grading of its severity into mild, moderate and severe. This correlates with the infant's maturity, growth and overall severity of illness. The new system offers a better description of underlying pulmonary disease and its severity.
Presentation
Complications
Feeding problems are common in infants with BPD, often due to prolonged intubation. Such infants often display oral-tactile hypersensitivity (also known as oral aversion). Physical findings:
- hypoxemia;
- hypercapnia;
- crackles, wheezing, & decreased breath sounds;
- increased bronchial secretions;
- hyperinflation;
- frequent lower respiratory infections;
- delayed growth & development;
- cor pulmonale;
- CXR shows with hyperinflation, low diaphragm, atelectasis, cystic changes.
Cause
Prolonged high oxygen delivery in premature infants causes necrotizing bronchiolitis and alveolar septal injury, with inflammation and scarring. This results in hypoxemia. Today, with the advent of surfactant therapy and high frequency ventilation and oxygen supplementation, infants with BPD experience much milder injury without necrotizing bronchiolitis or alveolar septal fibrosis. Instead, there are usually uniformly dilated acini with thin alveolar septa and little or no interstitial fibrosis. It develops most commonly in the first 4 weeks after birth.
Diagnosis
Earlier criteria
The classic diagnosis of BPD may be assigned at 28 days of life if the following criteria are met:
- Positive pressure ventilation during the first 2 weeks of life for a minimum of 3 days.
- Clinical signs of abnormal respiratory function.
- Requirements for supplemental oxygen for longer than 28 days of age to maintain PaO2 above 50 mm Hg.
- Chest radiograph with diffuse abnormal findings characteristic of BPD.
Newer criteria
The newer National Institute of Health (US) criteria for BPD (for neonates treated with more than 21% oxygen for at least 28 days) is as follows:,
- Mild
- Breathing room air at 36 weeks' post-menstrual age or discharge (whichever comes first) for babies born before 32 weeks, or
- breathing room air by 56 days' postnatal age, or discharge (whichever comes first) for babies born after 32 weeks' gestation.
- Moderate
- Need for <30% oxygen at 36 weeks' postmenstrual age, or discharge (whichever comes first) for babies born before 32 weeks, or
- need for <30% oxygen to 56 days' postnatal age, or discharge (whichever comes first) for babies born after 32 weeks' gestation.
- Severe
- Need for >30% oxygen, with or without positive pressure ventilation or continuous positive pressure at 36 weeks' postmenstrual age, or discharge (whichever comes first) for babies born before 32 weeks, or
- need for >30% oxygen with or without positive pressure ventilation or continuous positive pressure at 56 days' postnatal age, or discharge (whichever comes first) for babies born after 32 weeks' gestation.
Management
Infants with bronchopulmonary dysplasia are often treated with diuretics that decrease fluid in the alveoli where gas exchange occurs and bronchodilators that relax the airway muscles to facilitate breathing. Viral immunization is also important for these children who have a higher risk of infections in the respiratory tract.
There is evidence to show that steroids given to babies less than 8 days old can prevent bronchopulmonary dysplasia. However, the risks of neurodevelopmental sequelae may outweigh the benefits. It is unclear if starting steroids more than 7 days after birth is harmful or beneficial. It is thus recommended that they only be used in those who cannot be taken off of a ventilator. Evidence suggests that vitamin A in LBW babies is associated with a reduction in mortality and bronchopulmonary dysplasia.Oxygen therapy at home is recommended in those with significant low oxygen levels.
Epidemiology
The rate of BPD varies among institutions, which may reflect neonatal risk factors, care practices (e.g., target levels for acceptable oxygen saturation), and differences in the clinical definitions of BPD.
See also
- Respiratory distress syndrome
- Wilson–Mikity syndrome