The pleural space is a potential space between the visceral pleura (lining covering the lung) and the parietal pleura (lining covering the inside of the chest wall). This space normally makes a small amount of fluid to allow the lungs to slide along the chest wall. Thoracic surgeons treat diseases of the pleural space as well. Some of these conditions include pleural effusions, pneumothorax (air in the pleural space), and hemothorax (blood in the pleural space).
Pleural Effusions are collections of fluid in the pleural space between the lung and chest wall. They can be acute or chronic. Movement of fluid across pleural membranes is governed by Starling’s law and is controlled by oncotic and hydrostatic pressure in the pleural space. Pleural effusions can be classified as either transudates or exudates. Transudates are protein poor fluids that build up as a result of a change in overall fluid balance in the body. Examples of conditions that can lead to transudative pleural effusions include congestive heart failure, cirrhosis, or malnutrition (hypoalbuminemia). Transudative pleural effusions are often treated with medicines or by treating underlying conditions first. They can also be drained by a needle and small catheter during a thoracentesis to provide symptomatic relief while treatment is started.
Exudative pleural effusions are protein rich and build up as a result of disruption of fluid or lymphatic reabsorption. Examples of conditions that can lead to exudative pleural effusions include cancers, infections, and esophageal perforations. Exudative effusions often require surgical procedures to address the effusion, infection, or underlying cause.
Light’s criteria help determine if a pleural effusion is a transudate or exudate after taking a small sample of the pleural fluid during a thoracentesis.
| Transudate | Exudate | |
|---|---|---|
| Pleural fluid protein to serum protein ratio | < 0.5 | > 0.5 |
| Pleural fluid LDH to serum LDH ratio | < 0.6 | > 0.6 |
| Pleural fluid LDH | < 0.6 (upper limit nl) | > 0.6 (upper limit nl) |
A pleural effusion is likely an exudate if at least one of the above criteria are present. These criteria are approximately 98% sensitive and 80% specific in identifying the type of pleural effusion and can help guide treatment recommendations.
A pneumothorax is defined as air in the pleural space. Normally, air is present only in the lung. When air leaks into the pleural space, the pressure collapses the lung and can lead to shortness of breath, elevated heart rate, and decreases in blood pressure. A pneumothorax needs prompt diagnosis and treatment, especially when symptoms are present, as it can become a life threatening emergency. Pneumothorax can be defined as either a primary spontaneous pneumothorax, a secondary spontaneous pneumothorax, or can be related to trauma. Primary Spontaneous Pneumothorax (PSP) affects mostly young patients with normal underlying lungs. These are often caused by localized blebs, our outpouchings of the lungs that burst. The incidence of PSP is approximately 20,000 new cases per year in the US. Men have a much higher risk of developing PSP than women (7.4 to 18 per 100,000 men versus 1.2 to 6 per 100,000 women). The typical patient is described as a tall, thin, 10-30 year old male. Cigarette smoking increases the risk of primary spontaneous pneumothorax twenty-fold. After a first episode of primary spontaneous pneumothorax, the risk of recurrence is about 50%. After a second episode, the risk of recurrence increases to >80%. A history of smoking increases the risk of recurrence.
Secondary spontaneous pneumothorax typically occur in older patients with underlying lung disease. The clinical presentation may vary, but most commonly involves sharp chest pains and shortness of breath. Symptoms may be more severe than in primary spontaneous pneumothorax because of underlying lung disease. These are also more common in men than in women (6.3 out of 100,000 men versus 2 out of 100,000 women).
Pneumothorax is initially treated with either close clinical observation (if small and no symptoms) or chest tube drainage. Surgery for definitive treatment is indicated in recurrent pneumothorax, large or persistent air leaks, incomplete expansion of the lung with a chest tube, bilateral pneumothorax, or high risk professions (scuba divers, pilots, etc).
Hemothorax is defined as blood in the pleural space. This most commonly occurs as a result of trauma and rib fractures or lung injury, but can also be spontaneous and related to common blood thinning medications. Hemothorax may require chest tube placement and/or surgery to clear out the blood and allow the lung to better expand and improve breathing.