Chapter 13 Chronic Lung Disease of Infancy
PATHOPHYSIOLOGY
Chronic lung disease (CLD) of infancy, formerly known as bronchopulmonary dysplasia (BPD), is a disorder seen in infants born with severe respiratory distress syndrome. The disease occurs in both full-term and preterm infants who have been treated with prolonged positive pressure ventilation and/or oxygen therapy. Susceptibility to CLD is influenced by the degree of prematurity, the severity of respiratory distress syndrome, the need for mechanical ventilation and supplemental oxygen, and concurrent diseases. It is the most common complication in the care of very low birth weight infants (less than 1000 g) at birth. CLD is a pathologic process related to alveolar damage from lung disease, prolonged exposure to high peak inspiratory pressures and oxygen, and immature alveoli and respiratory tract. The clinical presentation is characterized by ongoing respiratory distress, persistent oxygen requirement (with or without ventilatory support) at 28 days postpartum and/or 36 weeks’ postconceptual age, and a classically abnormal chest radiographic study. The major risk factors that contribute to the development of CLD are prematurity, presence of respiratory distress or failure, severe initial respiratory illness, congenital heart disease, oxygen supplementation, prolonged use of positive pressure ventilation, and lack of antenatal treatment with steroids. Other important risk factors include history of air leaks, fluid overload, poor vitamin A status, sepsis, meconium aspiration, and a patent ductus arteriosus. Pulmonary changes typical of infants with CLD include alterations in lung structure, increased airway and/or vascular resistance, increased airway reactivity, decreased lung compliance, increased mucus production, and increased work of breathing. Although pulmonary function often improves significantly in early childhood, recent research demonstrates that some pulmonary problems may persist for many years. The survival rate is dependent on the infant’s birth weight and gestational age and the severity of the infant’s CLD.
INCIDENCE
1. Incidence varies because of differences in diagnostic criteria, client populations, and client management.
2. There is questionable research indicating that white, male infants are at greater risk for developing CLD.
3. It is estimated that 80% of infants of less than 30 weeks’ gestation develop CLD, and 10,000 infants are treated annually with home oxygen in the United States.
4. The suggestion has been made that the incidence has increased as a result of improved infant survival rates.
5. Mortality has been reported as greater than 40% in hospitalized infants with CLD and is usually due to infection or respiratory failure.
CLINICAL MANIFESTATIONS
COMPLICATIONS
1. Pulmonary: persistent changes in pulmonary function, respiratory infections, and long-term need for supplemental oxygen, tracheostomy, and prolonged mechanical ventilation
2. Cardiovascular: pulmonary hypertension, electrocardiogram (ECG) changes, right ventricular hypertrophy, cor pulmonale, and systemic hypertension
3. Neurologic: cognitive delay
4. Gastrointestinal and fluid, electrolytes, and nutrition: oral feeding aversions, gastroesophageal reflux, and constipation; altered growth and nutrient needs
5. Head, eyes, ears, nose, and throat: hearing loss requiring amplification, bilateral blindness, delayed tooth eruption, altered oral and dental structures from prolonged intubation, and enamel effects
LABORATORY AND DIAGNOSTIC TESTS
Refer to Appendix D for normal values and ranges of laboratory and diagnostic tests.
1. Chest radiographic studies—may include spectrum of findings including bilateral diffuse hazy lung fields, interstitial thickening (mild to very severe), inflammation, normal to increased lung expansion, and chronic findings that change little over time
2. Arterial and venous blood gas values—hypercapnia and compensated respiratory acidosis are common findings
3. Pulmonary function testing—used to assess respiratory status and severity of condition, and to determine therapy
4. Serum electrolyte levels—useful when monitoring effects of long-term diuretic therapy
5. Serial ECGs/echocardiograms—useful to monitor for cor pulmonale and pulmonary hypertension
