What is reactive airway disease?

Reactive Airway Disease: Understanding the Condition

Reactive airway disease (RAD) is not a specific diagnosis but rather a descriptive term used for a condition characterized by symptoms of airway obstruction, including wheezing, cough, chest tightness, and shortness of breath, that may be triggered by various stimuli. This term is often used temporarily until a more specific diagnosis can be established.

Definition and Clinical Features

Reactive airway disease typically presents with the following symptoms:

• Wheezing (diffuse, polyphonic, bilateral and particularly expiratory)
• Shortness of breath
• Chest tightness
• Cough (sometimes as the predominant or only symptom)

The hallmark of this condition is that these symptoms tend to be:

• Variable
• Intermittent
• Worse at night
• Provoked by specific triggers including exercise, allergens, or irritants 1

Relationship to Asthma

RAD is often used as a placeholder term when symptoms suggest asthma but a definitive diagnosis hasn't been established. This is particularly common in:

• Young children (ages 0-4 years) where diagnosis is challenging due to difficulty obtaining objective lung function measurements
• After a single high-level exposure to an irritant (known as Reactive Airways Dysfunction Syndrome or RADS)
• When symptoms are recent and the clinical picture is still evolving

Many clinicians now advocate moving away from this terminology due to its imprecision. As noted in recent literature, "terms such as 'bronchiolitis,' 'reactive airways disease,' 'viral wheeze,' and many more are used to describe the same condition and the same term is frequently used to describe illnesses caused by completely different dominant pathologies" 2.

Pathophysiology

The pathophysiology of RAD can involve:

1. Inflammatory response: Either neutrophil-dominated (in viral bronchitis) or eosinophil-dominated (in asthma)
2. Bronchoconstriction: Smooth muscle contraction in the airways
3. Increased mucus production: Leading to airway obstruction
4. Airway hyperresponsiveness: Exaggerated bronchoconstrictor response to various stimuli

Specific Variants

Reactive Airways Dysfunction Syndrome (RADS)

RADS is a specific subtype of RAD defined as:

• Sudden onset of asthma-like symptoms following a high-level exposure to irritant gas, vapor, or fume
• Symptoms develop within minutes to hours after exposure
• No pre-existing respiratory illness
• Persistence of symptoms and airway hyperreactivity for more than one year in many cases 3, 4

Occupational RAD

Occupational exposures can trigger RAD through:

• Sensitizer-induced mechanisms (immunologic)
• Irritant-induced mechanisms (non-immunologic)
• Common exposures include laboratory animal allergens, bakery ingredients, healthcare exposures, and industrial chemicals 1

Diagnosis

The diagnosis of RAD is clinical and may include:

1. Medical history: Focusing on symptom patterns, triggers, and timing
2. Physical examination: Documenting the presence of wheeze, which should be recorded in clinical notes 1
3. Pulmonary function testing:
   • Spirometry (before and after bronchodilator)
   • Peak flow monitoring
   • Bronchoprovocation testing if spirometry is normal 1
4. Consideration of differential diagnoses:
   • Asthma
   • COPD
   • Vocal cord dysfunction
   • Upper airway obstruction
   • Gastroesophageal reflux
   • Cystic fibrosis
   • Bronchiectasis 1

Management

Management approaches depend on the underlying cause:

• Bronchodilators: Short-acting beta-agonists for symptomatic relief
• Anti-inflammatory agents: Inhaled corticosteroids if inflammation is suspected
• Avoidance of triggers: Identification and elimination of environmental triggers
• Treatment of comorbidities: Such as gastroesophageal reflux or rhinosinusitis
• Specific treatments for RADS: May include high-dose corticosteroids and supportive care 5

Pitfalls in Diagnosis and Management

• Using RAD as a permanent diagnosis rather than working toward a more specific diagnosis
• Failing to distinguish between different underlying pathologies (e.g., bronchoconstriction vs. mucus plugging)
• Treating all cases with the same approach rather than targeting the specific underlying mechanism
• Not considering other diagnoses that can mimic RAD, such as vocal cord dysfunction

Conclusion

Reactive airway disease is a descriptive term rather than a specific diagnosis. Clinicians should work toward identifying the specific underlying condition causing the reactive airway symptoms, whether it's asthma, post-infectious hyperreactivity, or irritant-induced dysfunction. The term should be used as a temporary placeholder while pursuing a more definitive diagnosis.