Bronchiolitis Obliterans

In bronchiolitis, inflammation or swelling causes obstruction in the smallest airways in the lungs. The bronchi (airways) are like the branches on a tree. As the air proceeds through the bronchi, these branches get smaller and smaller. The bronchioles are the smallest airways. The bronchioles may become inflamed, and then scarred, by a number of causes. 

Different types of bronchiolitis can be determined when lung tissue is examined under a microscope. These include constrictive, obliterative (also referred to as bronchiolitis obliterans), proliferative, lymphocytic or respiratory bronchiolitis. Identifying the type of bronchiolitis may help determine the best prevention and treatment 

Some forms of bronchiolitis, such as obliterative bronchiolitis following a lung transplant, can be fatal if not treated. However, depending on the type and cause, the prognosis for this condition can range from mild to severe impairment. Some people with bronchiolitis may have mild impairment and slow progression, and others may have irreversible but stable disease.

Communicating with your health care provider will help formulate a comprehensive treatment plan.

Causes

The bronchioles are the smallest airways. The bronchioles may become inflamed and scarred by a number of causes. Inflammation and scarring from bronchiolitis may occur as a result of:

• Respiratory infections
• Autoimmune disorders (e.g., rheumatoid arthritis)
• Inflammatory bowel disease (e.g., ulcerative colitis)
• Medication reactions 
• Bone marrow, lung, or heart transplants
• Smoking or vaping (known as respiratory bronchiolitis)
• Inhalational exposures including:
  1. Irritants such as chlorine, ammonia, sulfur dioxide, nitrogen dioxides
  2. Flavoring chemicals such as diacetyl used in the production of butter-flavored popcorn and coffee roasting 
  3. Vaping flavored e-liquids  
  4. World Trade Center (WTC) dust
  5. Particulate matter from post-9/11 military deployment to Iraq, Afghanistan and Southwest Asia  
  6. Mineral dusts (e.g., coal mine dust, silica, asbestos) 

Sometimes a cause is not identified. Bronchiolitis may be idiopathic (without a known cause). A specific form known as panbronchiolitis has been described in association with sinusitis. This occurs most often in men. It typically responds to treatment with special antibiotics.  

It is important to identify a cause of the bronchiolitis to help determine the best treatment.

Symptoms

The most common symptoms of bronchiolitis are a dry cough and shortness of breath. The earliest symptom may be shortness of breath especially on exertion or strenuous activity. For example, you may notice shortness of breath only when running or hurrying to catch a bus. Later, you may notice shortness of breath when casually walking across the street. The cough may be dry, hacking and persistent. Fatigue and wheezing also may occur. These symptoms may be noticeable within days to weeks after some inhalation exposures or respiratory infections. Symptoms may not occur until months or years after organ transplant or after some particulate/chemical exposures.

Your health care provider will evaluate all your symptoms as part of managing your bronchiolitis.

If left untreated, symptoms of bronchiolitis may progress, causing further damage to the airways in the lungs.

Diagnosis

A complete medical and exposure history is essential for diagnosis. When the diagnosis of bronchiolitis obliterans is suspected, your doctor may have you do a number of tests. Imaging tests (such as high resolution chest CT scan) and pulmonary function tests can help detect bronchiolitis. A surgical lung biopsy is the most definitive way to diagnose the disease.

• Chest X-rays are usually normal, but may be done. 
• High resolution chest CT scan findings in bronchiolitis may be subtle. They often show markers of small airway inflammation (such as air trapping, tiny nodules and a thickening of bronchial walls).
• Lung function in bronchiolitis often shows obstruction. This may be seen with a reduced forced expiratory volume in one second (FEV1) and FEV1/FVC ratio on spirometry.  Lung function may also show restrictive abnormalities. This may be seen with reduced forced vital capacity, FVC. Combined restrictive/obstructive patterns may also be seen. Spirometry also may be normal in bronchiolitis.  Repeat lung function testing and follow up are important to detect an accelerated decline in lung function. 
• Other lung function tests may be helpful in diagnosis. Lung volume testing may show air trapping based on increased residual volume.  Diffusion capacity for carbon monoxide may be reduced. Cardiopulmonary exercise testing may show abnormal ventilation or reduced oxygen levels.

Your doctor may order other tests based on your history and physical exam.

You and your health care provider may choose to have you seen by a specialist, such as a pulmonologist (lung specialist) to confirm a diagnosis and treat you bronchiolitis once it’s diagnosed.

Treatment

Managing bronchiolitis includes partnering with your health care provider to formulate a comprehensive treatment plan.

Several forms of bronchiolitis are not reversible. Treatment of some forms, such as bronchiolitis due to a lung transplant or autoimmune disease, can help to stabilize or slow progression. For that reason, it is important to recognize bronchiolitis early because intervention in the late stages of disease may prove ineffective.

Treatment usually involves medication, primarily the use of corticosteroids. In some cases, immunosuppressive medications, which decrease the body's immune response, and lung transplants are used to treat the disease. Some studies suggest that a class of antibiotics known as macrolides (e.g., azithromycin) may improve symptoms and lung function in people with panbronchiolitis.

Oxygen therapy may be prescribed based on oxygen testing. If oxygen is prescribed, it is used to normalize the oxygen level in blood during sleep, rest and activity.

In the case of inhalational exposures, removal from the causal environment is crucial to controlling progression of the disease. For respiratory bronchiolitis, smoking and vaping cessation is essential.  

Living a healthy lifestyle is important. Ingredients include:

• Regular exercise
• Healthy eating
• Breathing retraining
• Avoiding infections (and getting recommended vaccinations)
• Giving up smoking and vaping (cigarettes, cigars, pipes, marijuana, e-cigarettes)
• Support from others 

Some forms of bronchiolitis, such as obliterative bronchiolitis following a lung transplant, can be fatal if not treated. The prognosis of this condition is variable, ranging from mild to severe impairment. Some people with bronchiolitis may have mild impairment and slow progression, and others may have irreversible but stable disease.