70: Pneumothorax

I. PROBLEM

An infant may have a pneumothorax (an abnormal accumulation of air or gas in the pleural space, between the visceral and parietal pleura). It can develop spontaneous or be secondary to trauma. A pneumothorax occurs more often in the neonatal period than any other time in life.

1. Spontaneous pneumothorax

   1. Primary spontaneous pneumothorax (PSP). Occurs when there is no obvious precipitating factor, no clear cause, it is idiopathic, without lung disease. Familial spontaneous pneumothorax is a rare cause in neonates.

   2. Secondary spontaneous pneumothorax (SSP). Occurs from underlying lung disease (respiratory distress syndrome [RDS], meconium aspiration syndrome [MAS], and others).

2. Traumatic pneumothorax

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

   2. Positive pressure ventilation (mechanical or noninvasive ventilation) can cause barotrauma.

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

3. Tension pneumothorax. A life-threatening condition that occurs when air is trapped in the pleural cavity under positive pressure. Air goes into 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, decrease in venous return to the heart, and a decrease in cardiac output. This causes displacement of mediastinal structures and cardiopulmonary compromise.

4. Persistent pneumothorax. A pneumothorax that persists >7 days in the absence of mechanical problems.

II. IMMEDIATE QUESTIONS

1. Are symptoms of tension pneumothorax present? A tension pneumothorax occurs when air is trapped in the pleural cavity under positive pressure. A tension pneumothorax presents as a medical emergency, and the patient's status will deteriorate acutely. The following signs may be seen with tension pneumothorax: cyanosis, hypoxia, tachypnea, a sudden decrease in heart rate with bradycardia, a sudden increase in systolic blood pressure followed by narrowing pulse pressure and hypotension, an asymmetric chest (bulging on the affected side), distention of the abdomen (secondary to downward displacement of the diaphragm), decreased breath sounds on the affected side, and shift of the cardiac apical impulse (most consistent finding) away from the affected side. A cyanotic upper half of the body with a pale lower half can be seen.

2. Is the patient asymptomatic? An asymptomatic pneumothorax is present in 1–2% of neonates. It occurs more frequently in males and term and post-term infants. It is usually unilateral. Most of these cases are discovered on chest radiograph at admission. Up to 15% of these infants were meconium stained at birth.

3. Is mechanical ventilation being used? The incidence of pneumothorax in patients receiving positive-pressure ventilation is 15–30%. A life-threatening tension pneumothorax may result from mechanical ventilation.

4. Are there risk factors for a pneumothorax? Neonates delivered between 30 and 36 weeks, moderately preterm, or term by caesarean section have a higher incidence ...