Chapter 7: Chronic Respiratory Conditions of the Preterm Infant

I. Intensive care

1. Bronchopulmonary dysplasia (BPD)

   1. Definition: Chronic pulmonary disease characterized by need for supplemental oxygen for at least 28 days after birth and/or oxygen requirement at 36 weeks' postmenstrual age (PMA).

   2. Incidence: Approximately 30% for infants with birthweight <1000 g, 20% for infants born at <1500 g, and estimated gestational age <30 weeks. May be as high as 70% in the tiniest infants.

   3. Pathophysiology

      1. Old: primarily seen prior to the advent of surfactant replacement therapy; characterized by airway injury, inflammation, parenchymal fibrosis

      2. New: found in extremely low birthweight infants; an arrest in lung development with fewer and larger alveoli, decreased pulmonary microvascular development

   4. Risk factors

      1. Prematurity: Incidence increases with decreasing estimated gestational age (EGA) and birthweight.

      2. Chorioamnionitis/sepsis: Increased incidence in infants born with exposure to infection/inflammation.

      3. Prolonged mechanical ventilation: Injury primarily due to tidal volumes that overdistend airways and cause volutrauma/barotrauma.

      4. Patent ductus arteriosus (PDA): Due to pulmonary overcirculation.

      5. Oxygen: Toxicity due to hyperoxia and inadequate levels of antioxidants that leads to cellular damage.

      6. Genetic contribution: Genetic factors largely contribute to the development of BPD in preterm infants.

      7. Poor nutrition: Growth and optimal nutritional status contribute to healing and maturation of lung tissue.

   5. Clinical presentation

      1. Signs and symptoms

         • Respiratory insufficiency: Need for supplemental oxygen or distending pressure via continuous positive airway pressure (CPAP) or high flow nasal cannula (HFNC).

         • Pulmonary edema: Increased microvascular pressure causes fluid filtration into the perivascular interstitium.

         • Tachypnea.

         • Increased work of breathing.

      2. Condition variability

         • Mild BPD: management with medications, on room air

         • Moderate BPD: oxygen requirement up to 30%

         • Severe BPD: oxygen requirement >30%, ventilator/CPAP dependent, or pulmonary hypertension

   6. Diagnosis

      1. Oxygen dependence for at least 28 days after birth.

      2. Oxygen requirement continuing at 36 weeks' PMA for infants born at <32 weeks' EGA or at 56 days of life for infants born >32 weeks.

      3. Chest radiographic findings may include haziness due to pulmonary edema and/or atelectasis and low lung volumes. Findings in severe BPD include hyperinflation, cystic areas, and patchy atelectasis.

      4. Physical examination: Tachypnea is the major finding; may be accompanied by retractions, rales, or wheezing.

   7. Management

      1. Medical

         1. Respiratory Support

            • Mechanical ventilation: Severe BPD.

            • Oxygen: Saturations >94% may be necessary to prevent/treat pulmonary hypertension in the infant with established BPD and to promote growth.

            • Nitric oxide: Acts to reduce pulmonary vascular tone; may prevent BPD in some infants or treat pulmonary hypertension. Used in the acute setting.

         2. Medications

            • Diuretics (for dosing, see the Convalescent Care section later): Treats associated pulmonary edema.

            • Corticosteroids: Due to associated negative impacts on long-term neurodevelopmental outcomes and growth, systemic steroids should be reserved for severe cases of BPD. Dexamethasone course is most common.

            • Inhaled medications (for dosing, see the Convalescent Care section later)

              • Bronchodilators: β-Agonists (albuterol or Xopenex) or anticholinergics (ipratropium bromide) can be used to treat airway hyperactivity/bronchospasm.

              • Steroids (budesonide/Pulmicort) reduce airway inflammation and may be used over a prolonged period (1 to 4 weeks) to achieve reduced inflammation similar to systemic corticosteroids without the adverse effects.

            • Vitamin A: Shown ...