Bronchopulmonary dysplasia (BPD) is a chronic lung condition that primarily affects infants born prematurely, typically those who are very low birth weight. It leads to ongoing respiratory problems in the newborn period and beyond. BPD is one of the most common complications of extreme prematurity, impacting thousands of infants each year. The condition’s severity can vary widely, influencing the length of the hospital stay and the required medical interventions.
Defining Bronchopulmonary Dysplasia and Risk Factors
Bronchopulmonary dysplasia develops from a combination of lung immaturity and injury that occurs after birth. The lungs of extremely premature infants are fragile and still developing, especially the alveoli and surrounding blood vessels. When these infants experience respiratory distress, they often require mechanical ventilation and supplemental oxygen to survive.
The pressure from the ventilator and the high concentration of oxygen can cause inflammation and damage to the delicate lung tissue. This injury disrupts the normal development of the lungs, resulting in fewer and larger alveoli, which reduces the surface area available for gas exchange. Extreme prematurity, particularly birth before 32 weeks of gestation, is the main risk factor, as the lungs are significantly underdeveloped at that time. Other contributing factors include infection, such as chorioamnionitis, and a lack of antenatal steroids given to the mother before birth.
Criteria for Staging Severity
The severity of BPD is determined by a standard system established by the National Institute of Child Health and Human Development (NICHD). This classification is based on the infant’s need for respiratory support and supplemental oxygen at a specific benchmark age. The assessment is typically made when the infant reaches 36 weeks of postmenstrual age (PMA), which is the gestational age plus the postnatal age.
The NICHD classification divides the condition into three distinct stages to guide treatment and predict outcomes. The determination of Mild, Moderate, or Severe BPD hinges on the infant’s respiratory status at the 36-week PMA mark.
Mild Bronchopulmonary Dysplasia
An infant is diagnosed with Mild BPD if they are able to breathe room air without any supplemental oxygen at the 36-week PMA assessment. This indicates that the lung injury and developmental disruption are minimal enough to allow for sufficient independent oxygen saturation. While these infants met the initial BPD diagnostic criteria, their lungs have recovered substantially by the classification time point.
Moderate Bronchopulmonary Dysplasia
Moderate BPD is diagnosed in an infant who requires supplemental oxygen at 36 weeks PMA, but at a relatively low concentration. Specifically, the infant needs a fraction of inspired oxygen (FiO2) that is less than 30 percent to maintain adequate oxygen levels. This requirement suggests a greater degree of ongoing lung impairment compared to the mild stage, necessitating continued respiratory assistance.
Severe Bronchopulmonary Dysplasia
Severe BPD represents the most significant level of lung injury and is diagnosed under two scenarios at 36 weeks PMA. Diagnosis requires a high concentration of supplemental oxygen, defined as 30 percent or greater FiO2. Alternatively, the infant may need positive pressure respiratory support, such as continuous positive airway pressure (CPAP), non-invasive ventilation, or invasive mechanical ventilation. This level of support signifies extensive damage and arrested development of the alveoli and pulmonary vasculature, often leading to a prolonged hospital stay.
Medical Management Based on Classification
The staging of BPD directly informs the immediate medical management plan, as treatment is tailored to the degree of respiratory compromise. For all stages, optimizing nutrition is a primary focus, as infants with BPD have increased caloric needs due to the higher work of breathing and the demand for lung growth and repair. Specialized, calorie-dense formulas or human milk fortifiers are often used to ensure adequate energy and protein intake for somatic growth.
Infants with Moderate and Severe BPD often require fluid restriction to manage pulmonary edema, which can worsen breathing mechanics. Diuretics, such as furosemide, are frequently administered to decrease fluid buildup around the alveoli, improving gas exchange. Bronchodilator medications are sometimes used to relax the muscles around the airways, helping to widen the passages and make breathing easier.
In cases of Severe BPD, where the infant remains dependent on a ventilator, corticosteroids may be used cautiously to reduce inflammation and facilitate weaning from the ventilator. However, these medications are reserved for the most severe cases due to potential concerns regarding long-term neurodevelopmental outcomes. A small number of infants with Severe BPD may require prolonged invasive support, eventually necessitating a tracheostomy tube to provide long-term access for mechanical ventilation.
Long-Term Health Outlook
While the symptoms of BPD often improve as a child grows and new lung tissue develops, the condition can lead to persistent health challenges. The severity of the initial BPD diagnosis is strongly linked to the likelihood and degree of long-term complications. Children who had Severe BPD are at a higher risk for reduced lung function, exercise intolerance, and the development of asthma-like symptoms that persist into adolescence and adulthood.
Children who had BPD face an increased susceptibility to severe respiratory infections, such as those caused by respiratory syncytial virus (RSV). Preventive measures, like monthly injections of an RSV-specific antibody during the winter season, are recommended for infants with Moderate or Severe BPD. Specialized follow-up care is necessary, often involving pediatric pulmonologists and multidisciplinary clinics to monitor lung function and neurodevelopmental progress.