Neonatal Air Leak Syndrome

Neonatal air leak syndrome is escape of air from the airways or alveoli into extra-alveolar spaces. It includes pneumothorax, pneumomediastinum, pneumopericardium, pulmonary interstitial emphysema, pneumoperitoneum and subcutaneous emphysema.

Asymptomatic radiographic pneumothorax occurs in 1 to 2% of term newborns after the first breaths. Symptomatic leaks are much less common in term infants and are most frequent in preterm infants receiving ventilation.

Causes include spontaneous leak at first breaths, respiratory distress syndrome, meconium aspiration, pneumonia, positive pressure ventilation or resuscitation, congenital diaphragmatic hernia, pulmonary hypoplasia and pulmonary hypertension.

Pathophysiology.

The first breaths generate high transpulmonary pressures. Where lung is poorly compliant or airways are partly obstructed, alveoli over distend and rupture.

Air dissects along bronchovascular sheaths into the mediastinum or pleura. Tension develops when a one way valve effect traps air, compressing the lung, shifting the mediastinum and reducing venous return and cardiac output.

• Tachypnoea, grunting, cyanosis, chest asymmetry, reduced breath sounds and displaced heart sounds on the affected side.
• Rising ventilator requirement, falling saturation, hypotension and bradycardia in ventilated infants.
• Transillumination with a cold light source shows a brightly illuminated hemithorax. A false negative is more likely in term infants with a thick chest wall.

Red flags.

• Sudden deterioration with hypotension and bradycardia: tension pneumothorax or pneumopericardium with tamponade.
• Muffled heart sounds and low voltage ECG suggest pneumopericardium.

• Chest ultrasound: absent lung sliding with a lung point is rapid and reliable.
• Chest X-ray, anteroposterior and cross-table lateral: pleural air collection with lung edge, a halo of air around the heart in pneumopericardium, and elevated thymic lobes (sail sign) in pneumomediastinum.
• Arterial blood gas.

Differential diagnosis. Congenital diaphragmatic hernia, congenital pulmonary airway malformation, lobar emphysema, large lung cyst and skin fold artefact.

Asymptomatic or mildly symptomatic infant, not ventilated. Observe with oximetry and repeat imaging. Nitrogen washout with 100% oxygen is not advised in preterm infants because of retinopathy risk.

Tension pneumothorax with collapse.

• Emergency needle aspiration with a 22 gauge cannula connected to a three way tap and syringe, in the second intercostal space at the midclavicular line, or the fourth intercostal space in the anterior axillary line.
• Follow with a chest drain: 8 to 10 Fr in preterm infants and 10 to 12 Fr in term infants, in the fourth or fifth intercostal space anterior to the midaxillary line, directed anteriorly. Connect to an underwater seal with suction of 10 to 20 cmH2O.
• Local anaesthetic lidocaine 1%, maximum 3 mg/kg (0.3 mL/kg), and fentanyl 1 to 2 micrograms/kg IV in a single dose.
• Remove the drain when there has been no bubbling for 24 hours and the lung is expanded on X-ray.

Pneumomediastinum. Usually observed. Drainage is rarely needed.

Pneumopericardium. Needle pericardiocentesis by the subxiphoid route, or a pericardial drain, when tamponade is present. Asymptomatic cases are observed.

Pneumoperitoneum from a thoracic leak. Drain only if abdominal distension compromises ventilation, after excluding bowel perforation.

Ventilation. Reduce pressures and use high frequency ventilation if leaks recur.

Monitoring. Continuous saturations, repeat chest X-ray 4 to 6 hours after drain insertion, and daily while draining.

Referral and escalation. Persistent air leak over 5 to 7 days or bronchopleural fistula requires specialist review.