What causes bronchospasm in gastroesophageal reflux disease (GERD)?

Mechanisms of Bronchospasm in Gastroesophageal Reflux Disease

Bronchospasm in gastroesophageal reflux disease (GERD) is primarily caused by neurally-mediated reflexes between the esophagus and airways, which can trigger bronchial smooth muscle contraction without requiring direct aspiration of gastric contents into the lungs. 1

Primary Pathophysiologic Mechanisms

1. Esophageal-Bronchial Neural Reflex

• Acid in the distal esophagus alone can stimulate an esophageal-bronchial cough reflex 2
• Vagal afferent nerves from the esophagus project to similar brainstem regions as airway afferents, triggering parallel reflex effects in both systems 1
• This neural reflex mechanism allows refluxate in the distal esophagus to cause bronchospasm without proximal reflux or aspiration 2, 1

2. Sensitization of Airway Reflexes

• Acid reflux sensitizes the cough reflex, lowering the threshold for bronchospasm 1
• Studies show acid challenges to the esophagus markedly reduce the concentration of inhaled irritants (like capsaicin) needed to trigger cough 1
• This sensitizing effect can be prevented by atropine inhalation, confirming the CNS-dependent reflex nature 1

3. Direct Autonomic Connections

• Direct neuronal projections exist between esophageal and airway autonomic ganglia 1
• These connections produce physiologic effects in the airways including:
  • Mucous secretion
  • Bronchial smooth muscle contraction
  • Increased airway inflammation 1

Clinical Evidence Supporting These Mechanisms

• Experimental studies demonstrate that acid instillation in the esophagus can trigger bronchoconstriction in asthmatic patients 3
• In controlled studies, patients with asthma showed significant falls in FEV1/FVC after acid infusion into the esophagus, which improved after antacid administration 3
• The relationship is bidirectional - bronchospasm can sometimes increase gastroesophageal reflux, creating a potential vicious cycle 4

Important Clinical Considerations

• GERD-induced bronchospasm can occur without typical GI symptoms in up to 75% of cases (silent reflux) 2
• Bronchospasm can occur without refluxate reaching the proximal esophagus or airways 1
• Aggressive antireflux therapy in patients with asthma and GERD can result in improvements in asthma outcomes in 70-80% of patients 5
• Choice of bronchodilator therapy matters - inhaled bronchodilators (like albuterol) cause less reflux than oral theophylline in patients with both GERD and obstructive lung disease 6

Common Pitfalls in Diagnosis and Management

1. Assuming refluxate must reach the airways to cause bronchospasm
2. Missing GERD as a cause of bronchospasm when GI symptoms are absent
3. Using oral bronchodilators that may worsen reflux and create a vicious cycle
4. Focusing only on acid suppression when non-acid reflux may also trigger symptoms

The evidence clearly demonstrates that GERD can cause bronchospasm through neural reflexes without requiring aspiration, and this mechanism helps explain why many patients with GERD-related respiratory symptoms respond to anti-reflux therapy even without evidence of proximal reflux or aspiration.