What Is Reactive Airway Disease?

Reactive airway disease (RAD) is an informal term sometimes used by healthcare providers to describe asthma-like breathing problems caused by irritants such as smoke, fumes, or toxic gas. It is also sometimes referred to as reactive airways disease syndrome (RADS).

RAD is not a formal diagnosis but a term that may be used as a placeholder when investigating conditions that cause wheezing and shortness of breath, such as asthma or chronic obstructive pulmonary disease (COPD).

The term crept into use back during the 1980s to describe a broad range of illnesses with asthma-like symptoms. Today, it is may be used when a baby has symptoms of asthma but is too young to undergo certain tests.

This article describes the symptoms that fall under the umbrella of reactive airway disease. It also explains the possible causes of RAD and how those conditions are diagnosed and treated.

What Are the Symptoms of Reactive Airway Disease?

Reactive airway disease was coined by American pulmonologist Stuart Brooks back in 1985 to describe lung conditions similar to COPD that were triggered by the inhalation of smoke, fumes, or corrosive gases.

As the definition evolved over time, a person could be said to have RAD if they were exposed to an inhaled substance and experienced:

• Wheezing
• Shortness of breath
• A persistent, productive cough with mucus

By strict definition, these symptoms occur within 24 hours of a single, massive exposure to an aerosol, gas, vapor, or fume. Because the exposure is huge, it suggests the cause was accidental, such as caused by a fire or a gas leak in a factory. Depending on the severity of exposure, the symptoms can last from minutes to hours and even days.

There are other definitions of RAD. Some regard it as respiratory symptoms triggered by common allergens (allergy-causing substances) such as pollen or dust mites. Others vehemently contend that RAD occurs in the absence of allergens and is not allergy-related.

The lack of a clear definition has led some to call for the abandonment of the term altogether.

What Causes Reactive Airway Disease?

In the broadest terms, RAD is an asthma-like episode that develops in the absence of an allergen within 24 hours of exposure to an aerosol, gas, fumes, or vapor.

Moreover, an episode of RAD is characterized by an acute (sudden and severe) inflammatory response that leads to bronchoconstriction (narrowing of the airways), bronchospasm (spasms of the airways), and the excessive production of mucus.

The shortlist of conditions that meet that definition includes:

• Asthma: A long-term inflammatory disease characterized by acute episodes of breathing restriction (known as exacerbations)
• Bronchiectasis: A chronic lung condition in which the major airways of the lungs (bronchi) have permanently widened, making them hyper-reactive
• Bronchiolitis obliterans: A serious, irreversible lung disease in which the smaller airways of the lungs (bronchioles) are damaged, often due to inhaled toxins
• COPD: A long-term inflammatory lung disease linked to cigarette smoking that also causes acute exacerbations
• Cystic fibrosis: A genetic disease that causes the excess production of mucus accompanied by episodes of coughing, wheezing, and shortness of breath
• Gastroesophageal reflux disease (GERD): A chronic form of acid reflux that can cause asthma-like symptoms when triggered by something you eat or even something you inhale
• Granulomatous lung diseases: A wide range of diseases like sarcoidosis or granulomatosis with polyangiitis that cause hardened granules in the lungs
• Interstitial lung disease (ILD): A category of conditions that cause inflammation and scarring in the lungs, including certain autoimmune diseases like lupus
• Upper respiratory tract infections: A wide range of communicable infections, typically viral, that affect the nose, nasal passages, and upper airways

Diagnostic Tests for Reactive Airway Disease

The approach to diagnosis for RAD is as varied as the possible causes. Based on a physical exam and a review of your medical history, your healthcare provider may order some of the following tests:

• Complete blood count (CBC): A blood test that can detect infection by evaluating the composition and proportion of different types of blood cells in a sample of blood
• C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR): Two blood tests that can detect generalized inflammation in the body
  
• Pulmonary function tests: A body of tests used to measure lung volume, lung capacity, and the rate of airflow from the lungs
• Imaging studies: Includes chest X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) to look at the structure of the lung and lung tissues
• Bronchoscopy; A procedure in which a narrow scope is threaded into the mouth and throat to view the airways of the lungs
• Bronchoprovocation challenge: A test used to see how reactive your lungs are to an inhaled chemical called methacholine
• Skin prick test and RAST blood test: Simple tests used to see if allergies are the cause of your symptoms
• Antinuclear antibody (ANA) test: A blood test used to check for autoimmune lung diseases
• CF gene mutation panel: A panel of blood tests used to diagnose cystic fibrosis
• Lung biopsy: The extraction of lung tissues (typically with a needle and syringe) to evaluate suspicious growths
  

In newborns and infants, RAD may be recorded in their medical records if no apparent cause is found. The aim of the notation is to ensure that the baby's condition is monitored until they are old enough to undergo certain diagnostic procedures.

How Is Reactive Airway Disease Treated?

There are no treatment guidelines for reactive airway disease. Based on the current definition, it is a term most commonly applied to emergency situations.

In such cases, RAD is used as shorthand for when there is severe breathing restriction, whether it is caused by an inhaled toxin or something else entirely. The designation simply indicates that emergency measures are needed, such as:

• Oxygen therapy: Also known as supplemental oxygen
• Bronchodilators: Inhaled or injected drugs used to widen airways
• Epinephrine: An injection of adrenaline used to treat a severe allergic reaction known as anaphylaxis

Outside of an emergency setting, the term RAD is rarely used and, even then, is actively discouraged.

Caveats and Controversy

One reason why the term RAD is not favored in a general setting is that it suggests a disease entity that doesn't actually exist. Even when used in pediatrics, RAD indicates symptoms are strongly suggestive of asthma.

While this may seem reasonable, only around a third of infants who wheeze or have shortness of breath ever develop true asthma. So, if a healthcare provider takes a watch-and-wait approach based on the presumption of asthma, they could very well overlook other causes that require immediate medical attention.

Moreover, from a parent's perspective, the declaration of RAD may lead them to believe that there is an actual "cause" and stop them from asking important questions or seeking a second opinion.

While there is nothing inherently misleading about the term, it is idiosyncratic and one that is almost never used by lung specialists (known as pulmonologists).