Bronchopulmonary Dysplasia (Chronic Lung Disease of Prematurity)
Definition: It is a chronic potentially reversible lung disease found usually in patients who
have required mechanical ventilation and increased oxygen requirements
at birth, with specific chest radiographic abnormalities and have significant
respiratory symptoms at 28 days of age.
Incidence: generally reported at 20% of ventilated newborns.
Epidemiology:
Prematurity
-risk increases with decreased birthweight and gestational age
-the more premature the infant, the greater the likelihood of chronic lung disease.
-failure of RDS to improve after two weeks will increase risk
-need for mechanical ventilation and oxygen therapy at 1 mo of age increases risk
Term infants
-on vents with high FiO2 for pulmonary hypertension, meconium aspiration, congenital heart
disease, pneumonia all are at increased risk
Pathogenesis: (Multifactorial)
Major factors that determine the lungs response to acute injury.
-lung immaturity
-surfactant deficiency
-lacks antioxidants
-impaired mucociliary function
-hyperoxia (oxygen concentrations over 40% is toxic to neonatal lungs after prolonged exposure
secondary to the generations of superoxides and oxygen-free radicals.)
-barotrauma (mechanical ventilation with high peak pressures)
-inflammation
Selected factors
-infection with RSV (aggravate a preexisting tendency to bronchospasm)
-left-to-right shunt may aggravate the pulmonary dysfunction. ( e.g. PDA)
-increased metabolic need
-increased wob
-tissue repair
Clinical Manifestations: (Criteria)
-chronic respiratory distress
-persistent oxygen dependence
-abnormal chest x-ray at one month.
-hypercapnia
-compensatory metabolic alkalosis
-pulmonary hypertention
-right sided heart failure
-increased airway resistance (reactive airway bronchoconstriction)
-severe chest retractions and cor pulmonale results in fluid retention
Diagnosis:
-premature infant who has RDS and who requires oxygen for more than 28 days.
-tracheal aspirate, culture and sensitivity.
-CXR will go through phases ( classical description)
initially-lung opacifications > cysts > overdistention & atelectasis
Treatment:
-supportive
-optimal nutrition
-thermoneutral environment
-provision of appropriate rest and stimulation.
-ventilator
-mechanical ventilation set to low pa O2 (50mm Hg) and paCO2 (50-75mm Hg)
-tracheotomy to decrease risk of subglottic stenosis (chronic ventilation)
-fluid restriction and the administration of diuretics
Outpatient
-continuous oxygen to keep O2 sat between 92-96% (91-93 % Rudolph)
-follow-up with multiple visits to the physician
Drug therapy:
Bronchodilators (beta-adrenergic, anticholinergic, cromlyn)
Acute improvement in the lung compliance and airways.
Diuretic
long term management of pulmonary edema.
improved lung mechanics
Steroids
may decrease the severity and incidence
vent dependent infants wean more rapidly
Long-Term Outcome (good and bad news)
-improved lung function during early childhood
-progressive increases in lung volumes and changes in the compliance to near normal
-late childhood increased airway reactivity and mild exercise intolerance
Sources:
Nelson Essentials of Pediatrics, Behrman ,1990.
Pathophysiology and Treatment of Bronchopulmonary Dysplasia, Pediatric Clinics of North America, Vol.
41, #2, April 1994.
Rudolph’s Fundamentals of Pediatrics, Appleton and Lange 1994.
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