Newborn infants are more prone to pulmonary air leaks than at other ages of life. Pulmonary air leaks can be understood as air leakage from the lung into extra-alveolar spaces. These are the areas where the air is usually not present. Air filling in these spaces can cause various conditions such as pneumomediastinum, pneumopericardium, pneumothorax and pulmonary interstitial emphysema. It could also cause a rare condition known as Pneumoperitoneum or subcutaneous emphysema.

In around 1-2% of infants, this is caused by the formation of negative forces when the newborn's breathing starts to disrupt the alveolar epithelium. It is the part that allows air to move from the alveoli into extra-alveolar spaces. The case increases when the infants are on ventilators since birth.

Although it is common at this stage of life, newborns with lung diseases are more prone to pulmonary air leaks due to poor lung functioning or the need for high airway pressure. This could lead to alveolar overdistention. In many cases, the severe condition is asymptomatic, where the diagnosis of pulmonary air leaks is mainly suspected clinically by doctors because of oxygen deterioration or confirmed by an x-ray test.

Pathophysiology

Due to uneven alveolar ventilation, air trapping and high transpulmonary pressure swings, pulmonary air leaks can occur in infants. In the lungs of a newborn, whose lungs are still not mature enough, the pores of Kohn are reduced. Thus a lack of redistribution of pressure compounds uneven ventilation through the connecting channels of the alveolar region. The final common pathway is alveolar over-distension and rupture, which occurs at the alveolar base. The gas then moves along the space present in the pulmonary blood.

Pulmonary interstitial emphysema

Pulmonary interstitial emphysema is a condition of air leakage from the alveolar area into the lymphatics, interstitium, or subpleural area. It generally happens to premature infants with a poor lung condition or RDS, who need support from a ventilator. If the air leak is more significant in the infant, it could become critical because of a sudden decrease in lung capacity. Some infants suffering from this condition could develop bronchopulmonary dysplasia.

The condition is clinically detected using an X-ray test where numerous cystic or linear lucencies are visible in the lungs. Some of these could look elongated and like subpleural cysts, which could be a few millimetres in diameter.

The treatment of the condition for newborns on ventilators is done by switching to a high-frequency oscillatory ventilator or high-frequency jet ventilator, which lowers the tidal volume and airway pressure in the lungs.

Pneumomediastinum

Pneumomediastinum is a condition where air leakage is detected in an infant along the vessels to the hilum and then enters via the visceral pleura into spaces of connective tissue of the mediastinum. It commonly occurs in infants who are on ventilator support or have an underlying condition of pneumonia or meconium aspiration syndrome.

Like other forms, it could be detected clinically by an x-ray test. Pneumomediastinum can form lucencies around the heart, and the air lifts the lobes of the thymus away from the cardiac silhouette (spinnaker sail sign—because it has the appearance of a boat sail).

The condition does not need any particular treatment but could heal automatically.

Pneumothorax

When the pleural space is filled with air causing tension, it is known as tension pneumothorax. The asymptomatic condition could cause worsening of tachypnoea, cyanosis and grunting. It also causes a decrease in the sound of breathing and enlargement of the chest on the affected side and can lead to cardiovascular collapse.

The condition is diagnosed by suspicion if the respiratory condition of the newborn is failing rapidly or by transillumination of the chest with a fibreoptic probe. The clinical confirmation could be given only after an x-ray test. In the case of tension pneumothorax, it is confirmed by the return of air during thoracentesis.

Around 15% of newborns with pneumothorax develop persistent pulmonary hypertension, complicating monitoring in these cases. Most newborns affected with small pneumothoraxes are cured without much complication and quickly. However, the larger and more tense pneumothoraxes require treatment or surgery for air removal from the pleural area.

Pneumoperitoneum

The pneumoperitoneum is leaking air into the peritoneum tissue. It is distinguished from pneumoperitoneum because it could lead to a ruptured abdominal viscus, which requires a surgical emergency.

Abdominal x-ray tests and physical examination diagnose the condition. The clinical symptoms of the condition include abdominal rigidity, signs of sepsis which suggests abdominal viscus injury and absence of bowel sounds.

The complications during newborn delivery can cause pulmonary air leaks, especially in infants with low lung maturity and birth weight. It requires close monitoring of surgery, early diagnosis and immediate treatment, which is essential for the survival of neonatal patients. The treatment in most cases includes intratracheal surfactant therapy, supplementary oxygen and mechanical ventilation.

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