Discussion

Pneumothorax

The intrathoracic pressure gradient changes with pneumothorax. Normally, the pleural space pressure is negative when compared to atmospheric pressure. When the chest wall expands outward, the lung also expands outward due to the surface tension between the parietal pleura and the visceral pleura. The lungs tend to collapse due to elastic recoil. When there is a connection between the alveoli and the pleural space, air fills this space and changes the gradient, and the balance of the lung collapse unit is achieved, or the tear is closed. The pneumothorax enlarges, the lung contracts due to this vital capacity, and the partial oxygen pressure decreases. The clinical presentation of a pneumothorax can range anywhere from asymptomatic pain to chest pain and shortness of breath. A pressure pneumothorax can cause severe hypotension (obstructive shock) and even death. Increased central venous pressure can lead to narrowing of the neck veins and hypotension. Patients may experience tachypnea, dyspnea, tachycardia, and hypoxia.

Spontaneous pneumothorax occurs in most patients due to bullae or rupture of bullae. Primary spontaneous pneumothorax is defined as occurring in patients without underlying lung disease; these patients present with asymptomatic bullae or bullae at thoracotomy. Primary spontaneous pneumothorax occurs in tall, thin young men due to increased shear forces or increased negative pressure at the apex of the lung. Lung inflammation and oxidative stress are necessary to cause primary spontaneous pneumothorax. Current smokers have increased inflammatory cells in the small airways and are more likely to develop a pneumothorax.

Secondary spontaneous pneumothorax occurs in the presence of underlying lung disease, primarily chronic obstructive pulmonary disease; other underlying causes for secondary spontaneous pneumothorax may include tuberculosis, sarcoidosis, cystic fibrosis, malignancies, idiopathic pulmonary fibrosis, and pneumococcal pneumonia.

An iatrogenic pneumothorax results from a complication of a medical or surgical procedure. Thoracentesis is the most common cause.

Traumatic pneumothorax can result from blunt or penetrating trauma. This trauma creates a one-way valve in the pleural space (allowing air to flow in but not out), so there is a compromise in circulation. Compression pneumothorax commonly occurs in intensive care unit settings in patients undergoing positive pressure ventilation.

Treatment

For patients with accompanying symptoms and showing signs of instability, needle decompression is a treatment for pneumothorax. This is usually performed using an angiographic catheter measuring 14 to 16 G and 4.5 cm long, inserted just above the rib in the second intercostal space in the midclavicular line. After needle decompression or with a stable pneumothorax, treatment is by insertion of a thoracostomy tube. This is usually placed above the rib in the anterior fifth intercostal space of the midaxillary line. The size of the thoracostomy tube usually depends on the patient's height and weight and whether there is an associated hemothorax.

References

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Our appreciation is extended to Dr. Abdelaziz Ibrahim Gbril, Al Jalila Children's Specialty Hospital, Dubai, United Arab Emirates, for contributing this case.