Residency · Residency · Pediatrics
Bronchopulmonary Dysplasia
Overview
Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy, primarily affecting premature infants born at less than 32 weeks gestational age. Its incidence reaches 40-60% in infants born before 28 weeks and is inversely proportional to gestational age. The contemporary form of BPD, termed "new BPD," reflects alveolar simplification and dysmorphic pulmonary vasculature rather than the fibrotic airway injury originally described by Northway in 1967. BPD is a major contributor to long-term respiratory morbidity, neurodevelopmental impairment, and healthcare utilization in survivors of extreme prematurity.
Definition and Classification
Historical Definitions
The definition of BPD has evolved considerably. Northway's original 1967 description defined it as oxygen dependence at 28 days of life with characteristic chest radiograph changes. Shennan refined this in 1988 by using oxygen requirement at 36 weeks postmenstrual age (PMA), which proved to be a better predictor of long-term pulmonary outcomes. The 2001 NICHD Workshop introduced severity grading based on the level of oxygen and respiratory support at 36 weeks PMA: mild BPD (breathing room air), moderate BPD (requiring less than 30% FiO2), and severe BPD (requiring 30% or greater FiO2 or positive pressure ventilation).
Jensen 2019 Criteria (Current Standard)
| BPD Grade | Respiratory Support at 36 Weeks PMA | Predicted Outcome |
|---|---|---|
| No BPD | Room air | Low morbidity |
| Grade 1 | Nasal cannula ≤2 L/min | Mild respiratory morbidity |
| Grade 2 | Nasal cannula >2 L/min or noninvasive positive pressure (CPAP/NIPPV) | Moderate respiratory morbidity |
| Grade 3 | Invasive mechanical ventilation | High risk of death, tracheostomy, respiratory morbidity |
The most current classification, published by Jensen in 2019, grades BPD based on the mode of respiratory support at 36 weeks PMA regardless of the specific FiO2. Grade 1 is defined as requiring nasal cannula at 2 L/min or less. Grade 2 requires nasal cannula above 2 L/min or noninvasive positive pressure (CPAP or NIPPV). Grade 3 requires invasive mechanical ventilation. This system better predicts death, tracheostomy, and respiratory morbidity at 18-26 months than prior definitions and eliminates the variability introduced by oxygen reduction tests.
Pathophysiology of "New BPD"
The pathophysiology of new BPD centers on disruption of normal alveolarization during the saccular and alveolar stages of lung development. The key histological features include alveolar simplification (fewer, larger alveoli with decreased surface area for gas exchange), dysmorphic pulmonary vasculature (reduced capillary density with abnormal muscularization of pulmonary arteries), and variable airway disease with less fibrosis and smooth muscle hypertrophy compared to the "old BPD" phenotype.
The etiology is multifactorial, described by the "multiple hit hypothesis." Prematurity itself causes developmental arrest of alveolarization. Oxygen toxicity produces free radical injury to immature lung tissue. Ventilator-induced lung injury (VILI) includes volutrauma, barotrauma, and atelectrauma. Inflammation from chorioamnionitis, postnatal sepsis, and ventilation-induced cytokine release compounds the injury. Nutritional deficits impair compensatory lung growth. Genetic susceptibility is substantial, with twin studies suggesting 50-80% heritability of BPD risk.
<image>Diagram comparing the histopathology of "old BPD" (fibrosis, airway smooth muscle hypertrophy, epithelial metaplasia) versus "new BPD" (alveolar simplification with fewer and larger alveoli, dysmorphic pulmonary vasculature with reduced capillary density) in premature infant lungs</image>
Risk Factors
The strongest risk factors for BPD are lower gestational age and lower birth weight. Mechanical ventilation duration functions as a dose-dependent risk, as does cumulative oxygen exposure. Both early-onset and late-onset sepsis increase BPD risk, with fungal sepsis carrying a particularly strong association. Patent ductus arteriosus, postnatal growth restriction, male sex, and white race (paradoxically, compared to Black infants) are additional risk factors. The role of chorioamnionitis remains controversial, as it may be protective through accelerated lung maturation or harmful through inflammatory injury. Fluid overload, especially during the first postnatal week, also contributes to BPD development.
Prevention Strategies
Antenatal Interventions
A single course of antenatal corticosteroids (betamethasone or dexamethasone) administered at 23-34 weeks gestation reduces RDS severity and BPD risk. Optimal obstetric management to safely prolong gestation when possible also contributes to prevention.
Respiratory Management
Early CPAP with avoidance of intubation when possible represents a cornerstone of BPD prevention, as demonstrated by the COIN, SUPPORT, and VON trials. Volume-targeted ventilation reduces volutrauma compared to pressure-limited modes. Permissive hypercapnia targeting PaCO2 of 45-55 mmHg minimizes ventilator settings. Oxygen saturation targets of 91-95% avoid both hyperoxia and severe hypoxia. Early extubation to noninvasive support should be pursued as soon as feasible. Caffeine citrate is one of the most impactful interventions, reducing BPD with a number needed to treat of approximately 10 as demonstrated in the CAP trial. It should be initiated within the first 10 days of life and works through central respiratory stimulation, anti-inflammatory effects, and improved diaphragmatic function.
Surfactant Strategies
Less Invasive Surfactant Administration (LISA) and the INSURE technique deliver surfactant while avoiding prolonged intubation. The goal is to provide surfactant replacement while maintaining spontaneous breathing on CPAP.
Nutritional Optimization
Aggressive early parenteral nutrition and rapid advancement of enteral feeds support lung growth. Human milk reduces the incidence of NEC and potentially BPD. Vitamin A supplementation provides a modest BPD reduction in very low birth weight infants based on the Tyson meta-analysis, though its adoption has been limited by the burden of intramuscular injections.
<image>Flowchart illustrating a BPD prevention bundle in the NICU including antenatal steroids, early CPAP, caffeine initiation, volume-targeted ventilation, targeted oxygen saturation ranges, early nutrition optimization, and infection prevention strategies</image>
Postnatal Corticosteroids
| Agent | Timing | Dose/Regimen | Benefits | Risks |
|---|---|---|---|---|
| Dexamethasone (early) | <7 days | Variable | Reduces BPD, facilitates extubation | Cerebral palsy, GI perforation, hyperglycemia |
| Dexamethasone (late/DART) | >7 days | 0.15 mg/kg/day tapered over 10 days | Facilitates extubation, lower NDD risk | Consider when BPD risk >50% |
| Hydrocortisone (PREMILOC) | Early | 0.5 mg/kg BID x 7 days + taper | Improved survival without BPD | GI perforation if combined with indomethacin |
| Inhaled budesonide | Variable | Nebulized or with surfactant | Reduced BPD (NEUROSIS) | Trend toward increased mortality |
Dexamethasone
Dexamethasone is the most studied systemic corticosteroid for BPD prevention. Early use (before 7 days of life) reduces BPD and facilitates extubation but increases the risk of cerebral palsy, gastrointestinal perforation, and hyperglycemia, and is generally avoided in current practice. Late use (after 7 days) facilitates extubation in ventilator-dependent infants with a lower neurodevelopmental risk profile. The DART regimen uses a starting dose of 0.15 mg/kg/day tapered over 10 days. The decision to use dexamethasone should incorporate the infant's baseline BPD risk: Doyle's meta-regression analysis demonstrated that when BPD risk exceeds approximately 50%, the benefits of corticosteroid treatment likely outweigh the harms.
Hydrocortisone
Hydrocortisone offers a lower-potency alternative. The PREMILOC trial demonstrated that early low-dose hydrocortisone (0.5 mg/kg twice daily for 7 days followed by a taper) improved survival without BPD in infants less than 28 weeks gestation. Available follow-up data show no increase in cerebral palsy. However, gastrointestinal perforation risk increases when hydrocortisone is combined with indomethacin, and concurrent use should be avoided.
Inhaled Corticosteroids
Nebulized or intratracheal budesonide delivered with surfactant was studied in the NEUROSIS trial, which showed reduced BPD but a concerning trend toward increased mortality. Inhaled corticosteroids are not routinely recommended pending further safety data.
Acute Management of Established BPD
Respiratory support must be optimized for the unique physiology of BPD, which includes obstructive components requiring longer inspiratory times and heterogeneous lung compliance requiring higher PEEP for alveolar recruitment. Transition to chronic ventilator settings is appropriate when weaning is not achievable. Diuretics provide short-term improvement in compliance: furosemide is used acutely but carries risks of ototoxicity, nephrocalcinosis, and electrolyte derangement; chlorothiazide combined with spironolactone is preferred for chronic use. Inhaled albuterol is reasonable for acute bronchospasm episodes but has limited evidence supporting routine use. Fluid restriction to 130-150 mL/kg/day helps manage pulmonary edema while maintaining adequate caloric intake. Nutritional targets of 120-150 kcal/kg/day support catch-up growth and ongoing lung development, achieved by increasing caloric density of feeds to 24-30 kcal/oz.
Pulmonary Hypertension in BPD
Pulmonary hypertension occurs in 15-25% of infants with moderate-to-severe BPD and should be screened for with echocardiography at 36 weeks PMA. Clinical signs include persistent oxygen requirement, recurrent desaturations, and right heart failure. Management begins with optimizing lung recruitment and ventilation, then targeting SpO2 of 92-95% to avoid hypoxic pulmonary vasoconstriction. Sildenafil is the first-line pulmonary vasodilator. Inhaled nitric oxide is reserved for acute pulmonary hypertensive crises. Bosentan and milrinone are options for refractory cases, and cardiac catheterization may be required for diagnosis and vasoreactivity testing in severe disease.
<image>Echocardiographic findings in BPD-associated pulmonary hypertension showing right ventricular hypertrophy, septal flattening, and tricuspid regurgitation jet used to estimate pulmonary artery systolic pressure</image>
Long-Term Outcomes
Respiratory consequences include recurrent wheezing in 50% of infants during the first 2 years, persistent airway hyperreactivity, exercise intolerance, and reduced FEV1 that persists into adolescence and adulthood. Neurodevelopmental outcomes include increased risk of cerebral palsy, cognitive delay, and behavioral difficulties independent of IVH. Growth catch-up often occurs by 2-3 years but may remain below average. Emerging evidence suggests increased cardiovascular risk in BPD survivors, including systemic hypertension and early atherosclerosis. Rehospitalization rates are high in the first 2 years, particularly during RSV season, and RSV prophylaxis with palivizumab or nirsevimab is indicated.
Discharge Planning
Discharge planning for infants with BPD includes home oxygen for those with SpO2 below 92% in room air, home cardiorespiratory monitoring based on institutional practice, pulmonology follow-up, neurodevelopmental follow-up through NICU graduate clinics, RSV prophylaxis, nutrition optimization with high-calorie formula or fortified breast milk, and updated immunizations including influenza vaccine beginning at 6 months of age.
Clinical Pearls
BPD is fundamentally a disease of development in which the lung never completed normal alveolarization, rather than a lung that was damaged and subsequently scarred. Caffeine is one of the most impactful and cost-effective interventions in neonatology and should be started early without premature discontinuation. The decision to use postnatal steroids should be individualized based on each infant's baseline BPD risk rather than applied as a blanket policy. Pulmonary hypertension screening should be routine in moderate-to-severe BPD because it is both underdiagnosed and undertreated. BPD is not merely a lung disease but a systemic disease of prematurity with lifelong implications across multiple organ systems.
<image>Chest radiograph comparison showing the progression from early diffuse haziness of RDS to the heterogeneous pattern of established BPD with areas of hyperinflation, atelectasis, and cystic changes in a premature infant</image>
Key Controversy: Postnatal Dexamethasone
Dexamethasone clearly reduces BPD and facilitates extubation, yet its use remains controversial. Early studies demonstrated increased cerebral palsy risk, creating lasting reluctance among neonatologists. Doyle's meta-regression analysis showed that when baseline BPD risk exceeds approximately 50%, the reduction in BPD-associated neurodevelopmental impairment outweighs the steroid-related cerebral palsy risk. The current approach at many centers involves shared decision-making with families for ventilator-dependent infants at high BPD risk, using low-dose regimens such as the DART protocol. Hydrocortisone (as studied in PREMILOC) may offer a safer alternative, but head-to-head comparisons with dexamethasone are lacking.
References
- Jensen EA, et al. The Diagnosis of Bronchopulmonary Dysplasia in Very Preterm Infants: An Evidence-Based Approach. Am J Respir Crit Care Med. 2019;200(6):751-759.
- Doyle LW, et al. Early (<8 days) systemic postnatal corticosteroids for prevention of BPD in preterm infants. Cochrane Database Syst Rev. 2021.
- Schmidt B, et al. Caffeine therapy for apnea of prematurity (CAP Trial). N Engl J Med. 2006;354:2112-2121.
- Baud O, et al. Effect of early low-dose hydrocortisone on survival without BPD (PREMILOC). JAMA. 2016;315(21):2292-2305.
- Thebaud B, et al. Bronchopulmonary dysplasia. Nat Rev Dis Primers. 2019;5(1):78.
- Abman SH, et al. Interdisciplinary Care of Children with Severe BPD. J Pediatr. 2017;181:12-28.
