Bronchial Hyperresponsiveness – Causes and Treatment
Bronchial hyperresponsiveness is an excessive sensitivity of the airways, where even minor stimuli trigger a narrowing of the bronchi. It is a hallmark feature of bronchial asthma.
Things worth knowing about "Bronchial Hyperresponsiveness"
Bronchial hyperresponsiveness is an excessive sensitivity of the airways, where even minor stimuli trigger a narrowing of the bronchi. It is a hallmark feature of bronchial asthma.
What is Bronchial Hyperresponsiveness?
Bronchial hyperresponsiveness (BHR), also referred to as airway hyperresponsiveness (AHR), describes a condition in which the bronchi – the air-conducting passages of the lungs – react excessively to a variety of stimuli. Triggers that cause little or no reaction in healthy individuals lead to a pathological narrowing of the airways (bronchoconstriction) in affected persons. BHR is the defining characteristic of bronchial asthma but can also occur in other conditions such as chronic obstructive pulmonary disease (COPD) or following respiratory tract infections.
Causes and Triggering Factors
Bronchial hyperresponsiveness develops through a combination of chronic airway inflammation and altered reactivity of the smooth bronchial muscles. Key contributing factors include:
- Chronic inflammation: Persistent inflammation of the bronchial mucosa, as seen in asthma, permanently lowers the threshold for airway reactivity.
- Allergens: Pollen, house dust mites, animal dander, and mold spores can heighten airway sensitivity.
- Air pollutants: Cigarette smoke, fine particulate matter, ozone, and other environmental irritants damage and sensitize the airways.
- Respiratory infections: Viral infections – particularly caused by respiratory syncytial virus (RSV) – can induce temporary or long-lasting hyperresponsiveness.
- Physical exertion: Breathing cold, dry air during exercise can provoke bronchoconstriction (exercise-induced bronchoconstriction).
- Genetic predisposition: A family history of asthma or atopic disease increases the risk of developing BHR.
Symptoms
Bronchial hyperresponsiveness manifests in characteristic symptoms that typically occur in episodes:
- A whistling or wheezing sound during exhalation (wheezing)
- Episodes of shortness of breath, particularly at night or in the early morning hours
- Persistent, dry cough, often without mucus production
- A feeling of tightness or pressure in the chest
- Reduced exercise tolerance
The severity of symptoms can vary considerably – from barely noticeable discomfort to severe acute breathlessness.
Diagnosis
The diagnosis of bronchial hyperresponsiveness is based on a combination of medical history, physical examination, and specialized lung function tests:
Spirometry and Bronchodilator Reversibility Test
Spirometry measures lung function parameters. A subsequent bronchodilator reversibility test assesses whether airway obstruction improves after inhalation of a bronchodilator medication – a hallmark finding in asthma.
Bronchial Provocation Test
The bronchial provocation test deliberately challenges the airways using inhaled substances such as methacholine or mannitol. If the bronchi constrict in response to low concentrations of these agents, bronchial hyperresponsiveness is confirmed. This test is considered the gold standard for diagnosis.
Additional Investigations
Complementary tests may include allergy testing (skin prick test, specific IgE in blood), measurement of fractional exhaled nitric oxide (FeNO) as an inflammatory marker, and blood eosinophil counts.
Treatment
Treatment of bronchial hyperresponsiveness aims to control the underlying airway inflammation and relieve acute symptoms.
Pharmacological Treatment
- Inhaled corticosteroids (ICS): These are the cornerstone of long-term asthma management and effectively reduce inflammation-driven airway sensitivity.
- Short-acting beta-2 agonists (SABA): Medications such as salbutamol rapidly relax bronchial smooth muscle and are used for acute symptom relief.
- Long-acting beta-2 agonists (LABA): Combined with ICS, these provide sustained bronchodilation for the maintenance treatment of moderate to severe asthma.
- Leukotriene receptor antagonists: An add-on therapy option, particularly beneficial in allergic asthma.
- Biologics: In severe, uncontrolled asthma, monoclonal antibodies targeting IgE, IL-5, or IL-4/IL-13 pathways may be used.
Non-Pharmacological Measures
- Avoidance of known triggers (allergens, smoke, pollutants)
- Allergen-specific immunotherapy (desensitization) for allergic causes
- Breathing physiotherapy and patient education programs
- Smoking cessation and appropriately adapted physical activity
References
- Global Initiative for Asthma (GINA): Global Strategy for Asthma Management and Prevention. GINA Report 2023. Available at: https://ginasthma.org
- Buhl R. et al.: Guideline for the diagnosis and treatment of asthma patients. Pneumologie 2017; 71: 849–919. German Respiratory Society (DGP).
- Anderson SD, Charlton B, Weiler JM et al.: Comparison of mannitol and methacholine to predict exercise-induced bronchoconstriction and a clinical diagnosis of asthma. Respiratory Research. 2009;10(1):4.
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