Overview
Definition:
Bronchopulmonary dysplasia (BPD), also known as chronic lung disease of infancy, is a common complication in preterm infants requiring prolonged mechanical ventilation and oxygen therapy
It is characterized by persistent respiratory difficulties, impaired lung growth, and inflammation.
Epidemiology:
The incidence of BPD is inversely proportional to gestational age
Infants born before 28 weeks gestation have the highest risk, with incidence rates approaching 50-80% in very low birth weight infants
It affects approximately 10,000-15,000 infants annually in the US.
Clinical Significance:
BPD leads to significant short-term and long-term morbidity, including increased susceptibility to respiratory infections, impaired neurodevelopmental outcomes, and prolonged hospitalization
Effective prevention strategies are crucial for improving outcomes and reducing healthcare costs.
Ventilation Strategies
Protective Ventilation:
Lung-protective ventilation strategies aim to minimize ventilator-induced lung injury (VILI)
This includes using lower tidal volumes (4-6 mL/kg ideal body weight), appropriate positive end-expiratory pressure (PEEP) to maintain lung volume and prevent alveolar collapse, and avoiding high peak airway pressures.
Permissive Hypercapnia:
Permissive hypercapnia, where controlled hypercapnia (PaCO2 up to 80 mmHg) is accepted within certain clinical limits, can be employed to achieve lower tidal volumes and pressures, thereby reducing VILI
Close monitoring of acid-base status and hemodynamic stability is essential.
Non Invasive Ventilation:
Early and judicious use of non-invasive ventilation (NIV), such as nasal continuous positive airway pressure (nCPAP) or nasal intermittent mandatory ventilation (NIMV), can reduce the need for intubation and subsequent mechanical ventilation, thereby lowering BPD risk.
High Frequency Ventilation:
High-frequency oscillatory ventilation (HFOV) may be considered in select cases of severe respiratory failure to achieve lung protection, although its role in primary BPD prevention is still debated
Careful selection of patients and appropriate ventilator settings are key.
Navigator Strategies:
Strategies like synchronized intermittent mandatory ventilation (SIMV) and pressure support ventilation (PSV) aim to improve patient-ventilator synchrony and reduce the work of breathing, potentially minimizing ventilator-induced trauma.
Caffeine Therapy
Pharmacology:
Caffeine citrate is a methylxanthine that acts as a respiratory stimulant
It increases the sensitivity of the respiratory center to CO2, enhances diaphragmatic contractility, and has bronchodilatory effects.
Mechanism Of Action:
Caffeine improves respiratory drive, reduces the frequency of apnea of prematurity, and may stabilize the respiratory system, leading to a reduced need for mechanical ventilation and consequently, a lower incidence of BPD.
Dosing Regimen:
A common regimen involves an initial loading dose of 20 mg/kg intravenously, followed by maintenance doses of 5-10 mg/kg intravenously or orally every 24 hours
Dosing is adjusted based on gestational age and postnatal age.
Evidence Of Efficacy:
Multiple randomized controlled trials and meta-analyses have demonstrated that early initiation of caffeine therapy in preterm infants significantly reduces the risk of BPD and mortality
The CAP trial is a landmark study supporting its use.
Monitoring And Side Effects:
Serum caffeine levels should be monitored, especially in infants with impaired clearance
Potential side effects include irritability, jitteriness, tachycardia, and gastrointestinal upset, though these are usually mild and transient at therapeutic doses.
Prenatal And Perinatal Factors
Antenatal Steroids:
Administration of antenatal corticosteroids to mothers at risk of preterm delivery has been shown to accelerate fetal lung maturation, reduce the severity of respiratory distress syndrome (RDS), and decrease the incidence of BPD.
Avoiding Chorioamnionitis:
Infection, particularly chorioamnionitis, is a significant risk factor for BPD
Strategies to prevent and treat maternal infections are important.
Extubation Readiness:
Careful assessment for readiness to extubate, including adequate spontaneous breathing, adequate tidal volumes, and acceptable arterial blood gas parameters, can help prevent re-intubation and prolonged ventilation.
Fluid Management:
Judicious fluid management and avoidance of fluid overload are crucial, as excessive fluid administration can worsen pulmonary edema and contribute to lung injury.
Nutritional Support:
Early and adequate nutritional support is vital for lung growth and repair
Enteral feeding should be initiated as soon as possible.
Complications Of BPD
Pulmonary Hypertension:
Chronic hypoxia and lung remodeling can lead to pulmonary hypertension, a serious complication that can cause right heart failure.
Growth Failure:
Infants with BPD often experience poor growth due to increased caloric expenditure and malabsorption.
Neurodevelopmental Impairments:
BPD is associated with an increased risk of neurodevelopmental deficits, including cognitive delays, motor impairments, and visual and hearing problems.
Recurrent Respiratory Infections:
Impaired lung defense mechanisms make these infants prone to recurrent viral and bacterial respiratory infections, such as bronchiolitis and pneumonia.
Rehospitalizations:
Infants with moderate to severe BPD have a significantly higher rate of rehospitalization, primarily for respiratory exacerbations.
Key Points
Exam Focus:
Understand the interplay between ventilation strategies and pharmacological interventions like caffeine in preventing BPD
Know the recommended doses and indications for caffeine therapy
Be familiar with lung-protective ventilation principles.
Clinical Pearls:
Early and consistent caffeine administration to preterm infants (<28 weeks gestation) is a cornerstone of BPD prevention
Employing NIV strategies to avoid intubation is preferred whenever feasible
Close monitoring for signs of VILI is paramount.
Common Mistakes:
Delaying caffeine therapy until after BPD is established
Aggressive ventilation settings that lead to VILI
Inadequate assessment for extubation readiness
Failing to optimize nutritional support for lung recovery.