A pneumatocele, or pneumatocyst, is an air or gas filled cyst that most often develops within lung tissue. Pneumatocele formation can occur in other regions of the body, however, including the brain. Pneumatocysts may occur singly but more often form in clusters. Infections, chemical exposure, or autoimmune diseases may all induce the condition, and trauma can be a contributing factor. Medical intervention generally involves treating the underlying condition and providing symptomatic relief.
Physicians have varying opinions concerning the physiology of pneumatocele formation. Some suggest that inflammation causes bronchiole obstruction, forcing air down into an alveolus. The increased pressure ruptures the alveolar lumen, creating an air pocket. Pneumatocysts in the outer areas of the lung may form when the bronchiolar lumen becomes inflamed, creating a passageway for air to escape. The increased pressure eventually causes tissue to balloon outward into the pleura.
Studies suggest that in the majority of cases, a lung pneumatocele forms secondary to a bacterial infection. Reports indicate that when the condition appears in young children and infants, it is due to bacterial infections over 70% of the time. Fungal or viral infections may also cause pneumatoctyst development. A respiratory infection may evolve from a fever and cough into painful breathing.
Aspiration or inhalation of certain chemical agents, including petroleum based products, often produces inflammation and subsequent lung cyst development. The inflammation accompanying the autoimmune disorders lupus or rheumatoid arthritis may also induce pneumatocele development. Cysts forming in the brain or other organs might be caused by infection, malignancy, or trauma.
Chest trauma may also contribute to pneumatocele formation. Traumatic pneumatocele formation may occur following the initial external blunt force or from the rebound motion of internal tissues. External and internal pressures may crush, shear, and tear tissue, leading to both ruptures and pneumatocysts. Treatment largely depends on the extent of internal injuries and disruption of normal air exchange.
Positive diagnosis of a pneumatocele generally requires an x-ray. Pleural fluid, sputum or urine samples can be used to identify the causative microbe. Once the organism is identified, anti-infective medication can be prescribed. A pneumatocele that arises from exposure to toxins may also be treated with steroids and analgesics to control inflammation and pain. Follow-up monitoring generally ensures resolution of the infection and the associated pneumatocyst.
With the exception of traumatic injury, most pneumatoceles resolve once a patient receives treatment for underlying cause. Medical intervention usually involves measures that are more drastic when lung pneumatocyst formation includes large areas of lung tissue, impedes breathing, or jeopardizes cardiovascular circulation. Physicians may deflate cysts using a syringe or surgically insert catheters. In rare instances, surgeons perform surgical resection, which eliminates the affected tissue.