Bronchiolitis obliterans (BO) is more commonly known as chronic rejection. Between 25% and 50% of lung transplant recipients experience BO.
Its cause is unknown but may be related to previous episodes of acute rejections or infections. There is no specific cure for BO, but there are therapies that may stop or reverse its course. Your physician will discuss an individualized plan of care if you develop chronic rejection.
Chronic rejection is characterized by a narrowing and disintegration of the small bronchioles. These are the smallest of the airways through which air travels into and out of the alveolar sacs. The alveolar sacs are where gas exchange (oxygen taken up and carbon dioxide eliminated) occurs within the lungs.
Symptoms of chronic rejection include a drop in spirometry levels and subsequent shortness of breath. Patients who develop chronic rejection are also at greater risk for lung infections.
A bronchoscopy with biopsy is performed to diagnose chronic rejection. Some of the other conditions which need to be ruled out include airway complications, infection, acute rejection, congestive heart failure and pulmonary hypertension.
Because the cause of BO is unknown, in 1993 the International Society for Heart and Lung Transplantation coined the term "bronchiolitis obliterans syndrome" (BOS) to describe deterioration of lung function for which there is no other identifiable cause. Patients have BOS if there is a 20% reduction in their FEV1 (forced expired volume in 1 second) from their previously established baseline.
Unfortunately, chronic rejection is a difficult condition to treat. There are several medications shown to arrest or stabilize progression of the condition. Radiation therapy has also shown to be effective. New medications currently in clinical trials hold promise for improvements in future treatment and prevention of chronic rejection.