Pathogenesis and Classification
The spontaneous pneumothorax was first described in 1933 by Kjaergaard with the pathophysiological mechanism of a rupture of a peripheral lung bleb and air leakage. (1) Free air in the pleural space was first diagnosed as early as 1910 by Laennec in connection with other diseases, often tuberculosis. The incidence is currently reported as 22 cases per 100,000 inhabitants per year, with the ratio of men to women being 3:1. (2)
Clinical Classification
- Primary Spontaneous Pneumothorax
The primary spontaneous pneumothorax affects, by definition, lung-healthy individuals without external influence and spontaneously, with a peak age below 30 years. There is no association with other known lung diseases. Clinically relevant special forms such as tension pneumothorax and spontaneous hemopneumothorax must be distinguished. Both forms occur in up to 5% of cases with spontaneous pneumothorax and require immediate treatment. (3, 4)
- Secondary Spontaneous Pneumothorax
In secondary spontaneous pneumothorax, a lung disease is found in the patient's medical history. This form of pneumothorax therefore occurs more frequently in older age as a manifestation of severe pulmonary emphysema, bronchial carcinoma, and other lung diseases. A tension pneumothorax occurs significantly more frequently here than in spontaneous pneumothorax (15-30%). (3)
- Traumatic Pneumothorax
Traumatic pneumothorax is defined by an external impact, with the most common cause being a medical procedure, for example, iatrogenic after puncture. A penetrating or blunt thoracic trauma can also cause a pneumothorax through direct lung injury or severe contusion with tearing of the lung parenchyma.
- Catamenial Pneumothorax
Catamenial pneumothorax is a rare special form of spontaneous pneumothorax, where endometriosis foci on the lung surface trigger a cycle-dependent pneumothorax.
Clinical Presentation
The clinical symptomatology of a pneumothorax is very variable, but usually consists of a combination of chest pain and shortness of breath. An anamnesis-related connection to physical activity plays no role and is not documented in the literature. In tension pneumothorax, a valve mechanism develops, leading to a continuous increase in intrathoracic pressure with compression of venous return to the heart. The clinical symptoms derived from this include tachycardia, hypotension, tachypnea, dyspnea, and shortness of breath, as well as, in later stages, upper neck vein congestion, hypoxia, and cardiogenic shock. In spontaneous hemopneumothorax, a rapid blood loss of 1-3 liters occurs due to the rupture of a well-vascularized adhesion strand and the combination of negative intrathoracic pressure and good pleural perfusion. In addition to typical imaging, a hemoglobin drop and, over time, a hypovolemic shock can be diagnosed in hemopneumothorax. (4)
Imaging Diagnostics
In variable clinical presentation, imaging plays a crucial role in diagnostics. Thoracic X-ray is compared to thoracic ultrasound. With appropriate experience, ultrasound is superior to simple X-ray and achieves similar sensitivity to computed tomography. Due to its bedside availability, rapid execution, and lack of radiation exposure, ultrasound is the ideal examination for this condition. Ultrasound can also be used later in therapy with drainage to determine the incision height and, for example, to exclude a diaphragmatic elevation. In cases of pronounced pre-existing lung diseases or previous thoracic surgery, the assessment of ultrasound is significantly more difficult, which is why an X-ray and possibly a computed tomography are often useful.
Treatment
The treatment of any form of pneumothorax generally requires the placement of a chest drain and connection to a continuous drainage system to support lung re-expansion. Conservative non-interventional therapy is much debated and practiced differently internationally. In patients with a small pneumothorax (less than 20% of the hemithorax volume) and clinical absence of symptoms, observation is also adequate.
Recurrence and Surgery
The recurrence risk for patients with spontaneous pneumothorax is 20-30%. (6) In cases of large pneumothorax, bullous changes at the lung apex, or anamnesis of recurrence, this risk can increase to 70-100%. (7)
The operation of a pneumothorax is therefore indicated not only in the case of a persistent air fistula or insufficient drainage but also as recurrence prophylaxis in a corresponding risk constellation. Using video-assisted thoracoscopy, lung apex resection, and pleurectomy, the risk can be reduced to 2-8%. (8)