The lungs are responsible for the continuous exchange of oxygen and carbon dioxide. Sometimes, small, abnormal air-filled sacs, known as lung blebs, develop on the surface of the lung. These structures are often harmless and cause no symptoms. Though typically benign, they introduce the risk of a serious complication: the sudden collapse of the lung.
Defining Lung Blebs
A lung bleb is an air-filled blister that forms on the surface of the lung tissue, specifically within the layers of the visceral pleura. The pleura is a thin, two-layered membrane that covers the lungs and lines the inside of the chest wall. Blebs are typically small, defined as less than one centimeter in diameter, and have thin walls. They most frequently occur at the apex, or very top, of the lung lobes.
Blebs form when tiny air sacs, called alveoli, rupture just below the lung’s surface, causing air to collect in the pleura layers. It is important to distinguish a bleb from a bulla, which is a larger air-filled cavity, often greater than one centimeter, located deeper within the lung tissue itself. Bullae are more commonly associated with chronic obstructive pulmonary disease (COPD) and emphysema.
Who is at Risk for Developing Blebs?
The development of lung blebs is linked to the demographic profile of individuals who experience Primary Spontaneous Pneumothorax (PSP). This condition often affects young, otherwise healthy men between the ages of 18 and 40. The risk is higher for people who are tall and thin.
Smoking, even light or past smoking, significantly increases the likelihood of bleb formation and subsequent rupture. Cigarette smoke is thought to cause inflammation within the small airways, which can lead to the structural changes that form these air pockets. Certain inherited conditions, such as Marfan syndrome or Birt-Hogg-Dubé syndrome, are also associated with a predisposition to blebs and pneumothorax due to underlying connective tissue abnormalities.
Blebs and the Risk of Collapsed Lung
The primary concern associated with a lung bleb is its potential to rupture, which leads to a collapsed lung, medically termed a pneumothorax. A pneumothorax occurs when air leaks from the lung into the pleural space, the area between the lung and the chest wall. Normally, this space contains a small amount of fluid and maintains a negative pressure, allowing the lung to remain fully expanded.
When a bleb bursts, air rushes into this space, disrupting the pressure balance. The accumulating air places increasing pressure on the outside of the lung, forcing it to partially or completely deflate. Symptoms of this event are typically sudden and include acute chest pain on the affected side and a rapid onset of shortness of breath.
The severity of the symptoms depends on the volume of air that has leaked and the degree of lung collapse. A large pneumothorax can cause a fast heart rate and rapid breathing. In rare, severe cases, the pressure can build up excessively, leading to a life-threatening condition called tension pneumothorax. Even after a first episode, the risk of recurrence is substantial.
Detection and Medical Management
Lung blebs are often asymptomatic and are typically only discovered incidentally on a chest imaging scan. The initial diagnosis of a pneumothorax is generally made using a standard chest X-ray. However, a detailed Computed Tomography (CT) scan is often necessary to confirm the presence and exact location of the underlying blebs or bullae.
Management depends on whether the bleb has ruptured and the size of the resulting lung collapse. Small, asymptomatic pneumothoraces may only require observation and monitoring, as the air can be reabsorbed by the body over time. If the collapse is larger, intervention is necessary, often beginning with the insertion of a fine needle or a chest tube to actively remove the air from the pleural space and allow the lung to re-expand.
For patients who experience recurrent pneumothoraces, surgical treatment may be recommended to prevent future episodes. The standard procedure is Video-Assisted Thoracoscopic Surgery (VATS), a minimally invasive technique used to staple the blebs shut (blebectomy). This procedure is frequently combined with pleurodesis, which involves irritating the pleura to create scarring that causes the lung to adhere to the chest wall, eliminating the potential space for air to collect again.