Bronchopulmonary dysplasia (BPD), particularly affects preterm infants causing significant morbidity and mortality.

Terminology

Bronchopulmonary dysplasia and chronic lung disease of prematurity (CLDP) have often been used interchangeably to describe the condition post-treatment of premature infants for respiratory distress syndrome. However, some suggest that there are different underlying pathogeneses and that CLDP encompasses other conditions besides bronchopulmonary dysplasia ^12,13.

Various definitions of BPD are used in the literature. A diagnosis of BPD can be made if supplemental oxygen is required at 36 weeks postmenstrual age (PMA). The National Institute of Child Health and Human Development, 2019, used the mode of respiratory support required at 36 weeks PMA, which correlates with the severity of BPD.

Epidemiology

Risk factors

• prematurity

• intrauterine growth restriction

• maternal smoking during pregnancy.¹⁴

• conventional mechanical ventilation (overdistension)

• oxygen toxicity (free radicals)

• infection

Pathology 

In infants treated with surfactant and steroids, there are fewer, larger alveoli and a smaller surface for gas exchange. The interstitium is thickened and pulmonary vascular development is affected, increasing vascular resistance and causing pulmonary hypertension.

Aetiology

Before the introduction of surfactants and steroids, ventilation and oxygen toxicity led to airway injury, inflammation and fibrosis.

Radiographic features

Plain radiograph

• ill-defined reticular markings with interspersed rounded lucent areas diffusely involving hyperinflated lungs ¹

• the lungs may have relatively normal AP diameter on the lateral film

• presence of cardiomegaly may indicate the development of pulmonary hypertension

• in chronic cases, the lateral film may show a much narrower AP diameter compared with the chest width on the frontal film

• other described features include of established bronchopulmonary dysplasia include ¹⁵

  • interstitial thickening

  • areas of atelectasis

Radiographic phases of bronchopulmonary dysplasia

• Stage 1: first 3 days - identical to respiratory distress syndrome i.e. generalised granular opacities and reduced lung volumes

• Stage 2: 4 to 10 days - bilateral lung whiteout with air bronchograms; heart borders completely obscured by the lung density

• Stage 3: 10 to 20 days - small rounded focal radiolucencies distributed throughout both lungs

• Stage 4: > 1 month - enlargement of radiolucent areas; hyperinflation and cardiomegaly ¹⁷

CT

• mosaic lung parenchymal pattern with areas of low attenuation and focal air trapping on expiratory HRCT (considered the most sensitive finding for predicting severity)

• bronchial wall thickening (considered the most frequent finding)

• small subpleural triangular/linear opacities

Bronchiectatic changes are usually not considered a feature ⁴.

Treatment and prognosis

Infants who survive neonatal bronchopulmonary dysplasia often show a slow but continuous improvement in respiratory status. Young adult survivors who have had moderate and severe bronchopulmonary dysplasia may have residual functional and characteristic structural pulmonary abnormalities; of these, the most notable is pulmonary emphysema ⁷.

History and etymology

It is thought to have been first described in 1967 by W Northway et al. ¹⁶

Differential diagnosis

General imaging differential considerations include:

• pulmonary interstitial emphysema (has an acute course)

• neonatal pneumonia

• Wilson-Mikity syndrome

See also

• neonatal respiratory distress (causes)