The Anatomy of the Pleura

The pleura is a vital part of the respiratory tract whose purpose is to cushion the lungs and reduce any friction which may develop between the lungs, rib cage, and chest cavity. It is made up of two membranes that are separated by a small amount of pleural fluid. A number of medical conditions may affect the pleura ranging from pleural effusions to a pneumothorax to cancer. When fluid accumulates between the membranes comprising the pleura, procedures to drain the fluid or eliminate the space between the membranes may be needed.

The pleura refers to the two membranes that cover the lungs. The space between the two membranes, the pleural cavity, is filled with a thin, lubricating liquid called pleural fluid. The pleura is made up of two distinct layers:

• The visceral pleura is the thin, slippery membrane that covers the surface of the lungs and dips into the areas separating the different lobes of the lungs (called the hilum).
• The parietal pleura is the outer membrane that lines the inner chest wall and diaphragm.

The visceral and parietal pleura join at the hilum of each lung, where the major bronchi, pulmonary arteries, and pulmonary veins enter the lung.

Between the two layers is the intrapleural space, which contains fluid secreted by the membranes. This allows the two layers to slide easily over one another as the lungs inflate and deflate during respiration.

The two membranes that make up the pleura serve primarily to reduce friction when the lungs expand and contract during breathing. The intrapleural space contains a small amount (roughly 4 cc to 5 cc) of pleural fluid between these layers, which helps to act as a cushion.

If the pleura becomes scarred, or if fluid builds up in the space between the membranes, it can restrict movement and interfere with breathing.

There are several conditions that can adversely affect the pleura. If inflammation is involved, the pain tends to be sharp and felt with each breath. Pain that worsens with a deep breath and often feels sharp is specifically referred to as "pleuritic" chest pain. Some conditions that affect the pleura include:

Pleurisy is an inflammation of the pleural membranes in which the surfaces become rough and sticky. It is most commonly caused by viral infections but can be caused by bacterial infections as well as autoimmune diseases such as rheumatoid arthritis and lupus. The discomfort that accompanies pleurisy tends to worsen when going outdoors in cold weather or when taking a deep breath. It may also vary with different positions.

The main symptom of pleurisy is a sharp, stabbing pain when you breathe. The pain will often get worse when you sneeze, cough, or move. Fever, chills, and loss of appetite are also possible symptoms, depending on the underlying condition.

A pleural effusion is the accumulation of excess fluid in the pleural space. When this happens, breathing can be impaired. Congestive heart failure is the most common cause of a pleural effusion, but there is a multitude of potential causes. A pleural effusion can be very small, and only detectable with imaging studies such as a chest x-ray or CT scan, or large, containing several pints of fluid.

Common symptoms of pleural effusion include chest pain, dry cough, shortness of breath, difficulty taking deep breaths, and persistent hiccups.

A malignant pleural effusion refers to an effusion that contains cancer cells. It can be caused by a number of different cancers but is most commonly associated with lung cancer or breast cancer that has spread (metastasized) to the lungs. Even though malignant pleural effusions are associated with cancer, pleural effusions associated with lung cancer are more often benign than malignant.

Pleural mesothelioma is a cancer of the pleura and is most commonly caused by occupational exposure to asbestos. Symptoms include pain in the shoulder, chest or lower back, shortness of breath, trouble swallowing, and swelling of the face and arms.

A pneumothorax is a condition in which air collects in the pleural cavity and is often described as a collapsed lung. It may be caused by any number of things, including chest trauma, chest surgery, and COPD. Some people develop a "spontaneous pneumothorax" and often when young. Along with shortness of breath, people may have a sensation of "crepitus" in which it feels like there is bubble wrap popping under the skin of the neck and chest.

A hemothorax refers to a condition in which the pleural cavity becomes filled with blood. It most often occurs following trauma or chest surgery; rarely, a hemothorax can happen spontaneously. The main symptom is pain or feeling of heaviness in your chest. Other symptoms include a very rapid heartbeat, trouble breathing, cold sweats, pale skin, and a fever.

Disorders of the pleura can sometimes be symptom-free and resolve on their own. Others require medical intervention. Treatment will depend largely on the underlying cause of the disorder.

Treatment options for pleura-related disorders include:

If a condition such as pleural effusion is small, doctors may simply observe the effusion over time to see that it is reabsorbed as long as a cause is identified.

While smaller pleural effusions may go away on their own, larger ones will need to be drained. The first step is usually extracting the fluid with a needle guided through the skin of the chest and into the pleural cavity (thoracentesis). Often times, depending on the cause, a pleural effusion will recur, especially if it is related to cancer.

If an excessive accumulation of fluid, blood (hemothorax), or air (pneumothorax) is involved, a chest tube may be used to help remove it. This involves inserting a chest tube through the skin and into the pleural cavity, then attaching the tube to a suction device so that the fluid can be continually drained. When fluid is no longer accumulating, the tube may be removed.

In people who are relatively healthy, a procedure called pleurodesis is often done. This is a surgery in which an irritating substance, such as talc, is placed between the two layers of the pleura. The talc causes irritation and inflammation, eventually causing the two layers to adhere and become "glued" together, so that the pleural cavity no longer exists for fluid to accumulate.

With cancer, a pleural effusion is often a concern near the end of life. When this is the case, an indwelling catheter may be placed in the pleural cavity so that the effusion can be drained either continuously, or whenever it is causing significant shortness of breath.

In people with mesothelioma, a surgical procedure called a pleurectomy ​may be performed to remove a section of pleura or the whole pleura to prevent the buildup of fluid. It also allows the surgeon to remove any tumors that have developed inside the chest. A pleurectomy may also be considered for people who have recurrent pleural effusion.

Surgical treatment for pneumothorax is required in certain situations. You may need surgery if you’ve had a repeated spontaneous pneumothorax. A large amount of air trapped in your chest cavity or other lung conditions may also warrant surgical repair.

One type of surgery that is used for pneumothorax is thoracotomy. During this surgery, your surgeon will create an incision in the pleural space.

Another option is video-assisted thoracoscopic surgery (VATS). Your surgeon inserts a tiny camera through your chest wall to help them see inside your chest. A thoracoscopy can help your surgeon decide on the treatment for your pneumothorax. The possibilities include sewing blisters closed, closing air leaks, or removing the collapsed portion of your lung, which is called a lobectomy.