Pneumothorax refers to a condition in which there is air in the pleural cavity. The pleural cavity is a very thin space between the visceral and parietal pleura of the lungs that usually contains minimal fluid. This abnormal air impairs normal ventilation and oxygenation giving a myriad of symptoms seen in pneumothorax.
Very common presentations are sudden chest pain and shortness of breath. The pain is often said to be stabbing, radiates to the ipsilateral shoulder and is worse on inspiration. In primary spontaneous pneumothorax, there is usually resolution in the first 24 hours although it might take up to 12 weeks to resolve. Other symptoms of pneumothorax are cough, anxiety and general feeling of malaise. Hypoxia and hypotension are characteristic of tension pneumothorax.
The mainstay in diagnosis of pneumothorax remains a thorough history and physical examination. In the case of tension pneumothorax, valuable time could be wasted if treatment is not instituted immediately the clinical diagnosis is made. However, investigations still have a role to play in determining the extent of the damage and the extent of the effect of the pneumothorax.
Investigations that may be carried out include blood tests to determine the degree of cardiopulmonary compromise. A chest radiograph would also be done to evaluate the extent of the condition and the effect on the mediastinum . CT scan is the best imaging modality for use in pneumothorax but it is not routinely used. Ultrasound scan is also very useful when employed by a skilled sonologist.
The goal of treatment is to restore lung volume, get air out of the pleural space and to prevent recurrence. Procedures like simple aspiration, insertion of chest tube, insertion of a 1-way valve and thoracostomy with continuous suction will help to restore an air-free pleural space. Other procedures like video assisted thoracoscopic surgery and thoracotomy could be performed for pleurodesis or pleurectomy .
Drugs also have a role to play in pneumothorax caused by an underlying medical condition. Analgesics are used to relieve pain, benzodiazepines provide conscious sedation and antibiotics are used to reduce the risk of infection after a surgical procedure.
In patients who have uncomplicated pneumothorax, complete resolution occurs within 10 days. Primary spontaneous pneumothorax is usually benign and requires no medical intervention. Recurrence however occurs between 6 months to 3 years of the incident. It has a 5-year recurrence rate of 28 to 32% while the secondary type has a 5-year recurrence rate of 43%. Recurrence is commoner in smokers, patients with chronic obstructive pulmonary disease (COPD) and patients with AIDS. Deaths have been recorded in patients with the relatively benign primary spontaneous pneumothorax while the secondary type has a mortality rate of up to 17%. Tension pneumothorax is a rapidly evolving entity that quickly leads to death if intervention is not swift .
During inflation of the lungs, there is negative pressure in the pleural space. When air enters this space, it causes an increase in pressure, leading to a collapse of the lung. One of the major causes of this is trauma which could be either be due to accidents or could be iatrogenic. Other causes are ruptured blebs. Blebs are air blisters which are found on the surface of the lungs, they are harmless if the remain intact. It could also be caused by a chronic lung disease like cystic fibrosis .
The epidemiology is largely dependent on the type of pneumothorax. The primary spontaneous pneumothorax is more common in young adults between the ages of 20 years to 30 years, while the secondary type is more common in people aged between 60 years and 65 years. They are both commoner in men than in women and there is no recorded racial predilection. Smoking is also said to increase the risk of the secondary type spontaneous pneumothorax.
Iatrogenic pneumothorax occurs in 5 to 7 in every 100,000 hospital admissions largely due to the increased use of mechanical ventilation. A rare type, catamenial pneumothorax is seen only in women and occurs within 3 days after menstruation starts .
The pathophysiology varies with the cause of the pneumothorax. In spontaneuos pneumothorax, gas invades the pleural space usually from a ruptured bleb. This causes an increase in the pressure within the pleural space, so the lungs collapses within itself until the rupture is closed or equilibrium is reached. This reduces the size of the lungs equivalent to the amount of gas decreasing the vital capacity of the lung and reducing the partial pressure of oxygen .
Tension pneumothorax results as a consequence of disruption in the visceral or parietal pleura or the tracheobronchial tree. The injured tissue forms a one way valve so that there is inflow of air during inspiration but no outflow. The volume increases with each inspiratory movement and the pressure within the hemithorax builds. The affected lung then collapses and continued increase in pressure pushes the mediastinum to the opposite side. This shift impinges on the contralateral lung and also impairs venous return to the right atrium. The combination of the effects of the collapsed lung and the compressed one leads to hypoxia, which ultimately impairs cardiac function. This condition can rapidly progress to death if intervention is delayed .
Smoking is a recognized risk factor, so avoiding cigarettes reduce the risk of developing a pneumothorax. Other medical preventive measures are geared towards reducing the risk of recurrence.
Individuals with pneumothorax usually have a collapse of the lung on the affected side. The degree of collapse usually determines the clinical consequence. Also, symptoms are dependent on the type of pneumothorax .