What is bronchospasm?

Definition of Bronchospasm

Bronchospasm is defined as a transient narrowing of the lower airway caused by contraction of the bronchial smooth muscle, resulting in difficulty breathing. 1

Pathophysiology and Mechanism

• Bronchospasm occurs when airway smooth muscle contracts, causing narrowing of the bronchial tubes and restricting airflow 1
• It represents an exaggerated response of the airway smooth muscle to various stimuli, mediated through direct or indirect pathways 1
• The contraction of bronchial smooth muscle can be triggered by various mediators acting on airway receptors 1
• Bronchospasm may be part of a protective reflex mechanism that can become pathological in certain conditions 1

Clinical Manifestations

• Patients experiencing bronchospasm typically present with:

  • Wheezing (audible high-pitched sounds during breathing) 1, 2
  • Shortness of breath or dyspnea 1, 2
  • Chest tightness (particularly common in early stages of asthma attacks) 1
  • Coughing 1
  • Increased work of breathing 1

• During bronchospasm, patients may experience a sensation of chest tightness that is distinct from the sensation of increased work of breathing 1

Common Causes and Triggers

• Exercise (exercise-induced bronchoconstriction) 1
• Allergens and irritants 1
• Respiratory infections 1
• Cold air 1
• Medications (paradoxical bronchospasm can rarely occur with bronchodilators) 3, 4
• Underlying conditions like asthma or COPD 1
• Electrolyte abnormalities (rare causes include hypocalcemia) 2
• Pulmonary embolism (can present with bronchospasm in rare cases) 5

Clinical Significance

• Bronchospasm is a key feature of asthma but can occur in many other conditions 1
• It can significantly impair lung function, reducing FEV1 (forced expiratory volume in 1 second) 1, 6
• In patients with COPD, acute bronchospasm can lead to CO2 retention and respiratory failure 6
• Severe bronchospasm can progress to respiratory distress if not properly treated 7
• Bronchospasm can be assessed through pulmonary function testing, with a 15% reduction in FEV1 after exercise being diagnostic of exercise-induced bronchospasm 1

Treatment Approaches

• Short-acting bronchodilators (like albuterol) are first-line treatment for acute bronchospasm 8
• Anticholinergic agents (like ipratropium) can be effective, particularly when used in combination with beta-agonists 3
• In severe cases, systemic corticosteroids, oxygen therapy, and even mechanical ventilation may be required 7
• Caution must be used when administering certain medications (like adenosine) to patients with a history of bronchospasm 7

Important Clinical Considerations

• Bronchospasm must be distinguished from other causes of wheezing and respiratory distress 1
• Paradoxical bronchospasm (worsening of symptoms after bronchodilator use) is a rare but serious adverse effect that requires immediate attention 3, 4
• In patients with asthma, the sensation of chest tightness may be more related to airway receptor stimulation, while work/effort sensations may relate more to increased respiratory motor output 1
• Laryngospasm (closure of the vocal cords) should be distinguished from bronchospasm, as they require different management approaches 1