Air leak syndromes in the neonate

Please note: images that have a white symbol at the top right, such as the Pneumothorax image below, indicates an image gallery that has multiple images - click on the image to open the gallery.

Pneumothorax

A pneumothorax may be seen as an isolated finding in an infant with respiratory distress, or may be associated with other forms of lung disease (particularly RDS and MAS). The findings can be subtle with just minimal differences in lucency of lung fields.

Pneumothorax in a ventilated infant may be an emergency if it is under tension. In the circumstance (as shown in the first image on the right), urgent drainage prior to a radiograph is indicated.

Risk factors for pneumothoraces include:

• Assisted ventilation (including CPAP)

• Respiratory Distress Syndrome

• Meconium Aspiration Syndrome

• Other Air Leak Syndromes (e.g. Pulmonary interstitial emphysema)

• Pulmonary hypoplasia

However, up to 2% of infants can develop spontaneous pneumothoraces at birth. These are thought to be secondary to the high pressures that infants can generate themselves when initiating breathing. Many infants have minimal or no symptoms and the air leak resolves spontaneously over time.

The administration of 100% oxygen to term infants ("nitrogen washout") is said to potentially resolve the pneumothorax more rapidly.

The theory is that nitrogen in the air contained in the pleural space passively diffuses across lung into alveoli full of 100% oxygen. This encourages resolution of the intrapleural air leak. It is said that if this treatment is given, the pneumothorax will resolve in 48 hours instead of the 2 days it will take if you just leave it alone (.... think about it).

These images to the right are from a term infant born by caesarean section at term. The baby had respiratory difficulty from birth but no resuscitation (that is, bagging) was needed other than some mask oxygen.

An initial radiograph showed bilateral pneumothoraces (first image). The outline of the right lung is seen clearly. The left pneumonthorax is more subtle. The baby had bilateral chest drains inserted and required ventilation.

The second radiograph shows bilateral intercostal drains. The tip of the left drain is kinked. The lung fields are not well inflated despite high airway pressures at the time. This baby has significant pulmonary hypoplasia.

These images are of a preterm infant born at 24 weeks whose ventilation requirements increased on the second day of life. Transillumination was not diagnostic, perhaps because there was no asymmetry due to the bilateral pneumothoraces. A chest radiograph demonstrated a large tension pneumothorax on the right side, and a smaller air leak on the left.

Chest drains was inserted and the baby clinically improved. Note that the right sided drain was inserted too far (note: in small babies, it is all too easy to insert the drains too far).

In a small infant such as this, a head ultrasound scan should be performed to determine whether any deterioration at the time of the pneumothoraces was associated with intraventricular haemorrhage.

Pulmonary Interstitial Emphysema

Pulmonary interstitial emphysema (PIE) is most commonly seen in small infants with significant RDS. There are microscopic air leaks, with air tracking along the interstitium of the lung. Pneumothorax is a common association, and Chronic Lung Disease is also a common sequelae.

The radiographic appearance may be described as "salt and pepper".

If the PIE is localised to one side, the infant can be nursed with that side "down". Occasionally, selective intubation of the unaffected lung can be performed to "rest" the affected lung.

Pneumatocoele

Occasionally, ongoing air leaks occur which result in localised collections of air within the lung parenchyma.

Strategies have been proposed to treat this, including selective bronchus intubation to aerate the "good" lung, and there are reports of aggressive surgical resection of the affected lobe.