Chapter 75: Pneumothorax

I. PROBLEM

An infant with respiratory distress may have a pneumothorax. A pneumothorax is the abnormal accumulation of air in the pleural space, between the visceral and parietal pleura. It can develop spontaneously (idiopathic or from underlying lung disease) or be secondary to trauma. Pathophysiology involves an increased intra-alveolar pressure, which causes alveolar rupture and results in interstitial air; this air then dissects along the perivascular spaces and ruptures into the pleural space. A pneumothorax occurs more commonly in the neonatal period than any other time in life. Incidence is approximately 1% to 2% in term newborns and approximately 6% in premature infants. A pneumothorax is generally characterized as spontaneous, traumatic, tension, or persistent.

1. Spontaneous pneumothorax

   1. Primary spontaneous pneumothorax. Occurs when there is no obvious precipitating factor and no clear cause; it is idiopathic, without lung disease. Familial spontaneous pneumothorax (pneumothorax occurring in more than 1 neonate in the same family) is extremely rare but has been described in neonates.

   2. Secondary spontaneous pneumothorax. Occurs from a complication of underlying lung disease (respiratory distress syndrome [RDS], meconium aspiration syndrome [MAS]), pulmonary hypoplasia (can be bilateral), transient tachypnea of the newborn, pneumonia, or congenital pulmonary cystic malformations, among other causes.

2. Traumatic pneumothorax

   1. Iatrogenic occurs from an unintended insult during a procedure, such as central line placement, bronchoscopy, or thoracentesis.

   2. Positive-pressure ventilation (mechanical or noninvasive ventilation) can cause barotrauma and a subsequent pneumothorax. A Cochrane review (2015) found that in preterm infants with RDS, using continuous distending pressure (eg, continuous positive airway pressure or continuous negative pressure) is associated with an increased rate of pneumothorax.

   3. Chest trauma can occur when blunt or penetrating trauma occurs to the chest (rare in neonates).

3. Tension pneumothorax. A life-threatening condition that occurs when air is trapped in the pleural cavity under positive pressure. Air enters the pleural cavity during inspiration, but no air is allowed to escape during expiration. It acts as a 1-way valve. Because air is trapped, intrathoracic positive pressure rises, lung volume decreases, and pressure compresses the mediastinum and causes a shift, with increased pulmonary vascular resistance. This results in an increase in central venous pressure, a decrease in venous return to the heart, and a decrease in cardiac output. In the latest stages, this causes displacement of mediastinal structures and cardiopulmonary compromise.

4. Persistent pneumothorax (persistent air leak). A pneumothorax that persists >5 to 7 days in the absence of mechanical ventilatory problems. In 1 study, the major determinants of persistent pneumothorax and mortality were underlying lung pathology, need for mechanical ventilation, and bilateral pneumothorax.

II. IMMEDIATE QUESTIONS

1. Are you sure it is a pneumothorax? See Section IV.C.2 for classic findings of a pneumothorax on chest x-ray (CXR). Rule out artifacts and mimickers of a pneumothorax such as:

   1. Skin folds are the most common artifact projected over the thoracic cavity. They occur as a broad curvilinear line that travels across or the chest or ...