GERD is not only a disease of the stomach and esophagus, but its extra-digestive manifestations, especially respiratory complications, are receiving increasing attention, such as chronic pharyngitis, chronic cough, bronchial asthma, and aspiration pneumonia. The pathogenesis of GERD respiratory complications includes direct stimulation of reflux, airway microaspiration, vagal reflex, etc. The diagnosis and treatment of GERD is difficult and has become a hot spot for research in recent years.
1.GERD and chronic pharyngitis
GERD can produce many symptoms and signs of otorhinolaryngology, the most common of which is reflux pharyngitis. Studies in recent years have shown that GERD is one of the major causes of chronic laryngitis that is difficult to cure. Its main symptoms are throat clearing, cough, sore throat, hoarseness, and foreign body sensation in the throat. Laryngoscopy shows edema, erythema, ulceration and granuloma. Another study showed that reflux with mainly pharyngeal symptoms occurs mostly during the day and in the upright position, and many patients do not have typical reflux symptoms such as heartburn and acid reflux; whereas reflux causing typical symptoms of esophagitis and GERD occurs mostly at night and in the lying position.
2. GERD and chronic cough
GERD is considered to be one of the most common causes of chronic cough, 1/3 of which is caused by GERD and is known as gastroesophageal reflux cough, of which about half of the patients do not have typical GERD symptoms. There are also postnasal drip syndrome, cough variant asthma, and eosinophilic bronchitis.
Coughing is mainly caused by direct stimulation of sensory apparatus in the trachea, bronchi and larynx, which is transmitted to the medullary cough center to cause cough reflex. Reflux of gastric contents or inadvertent aspiration of trace amounts of gastric contents into the trachea may be the main mechanism of GERC. When pulmonary imaging is normal, GERD is likely to cause coughing by stimulating the esophago-bronchial reflex. Because most patients do not have typical reflux symptoms such as heartburn and acid reflux, confirming the diagnosis of GERC is difficult. After excluding other common causes of chronic cough, diagnostic treatment with proton pump inhibitors can be tried, which can lead to symptom relief in most GERC patients.
3. GERD and bronchial asthma
Possible mechanisms of GERD causing asthma are postulated to include.
(1) neuroreflex theory: gastroesophageal reflux or esophageal acid perfusion can excite the vagus nerve by stimulating acid-sensitive receptors in the esophageal mucosa and reflexively cause bronchospasm, thus triggering or aggravating asthma.
(2) Airway inflammation theory: Acidic gastric contents entering the respiratory tract stimulate and damage the respiratory mucosa to produce an inflammatory response, which increases the reactivity of the bronchi.
In addition, asthma can also induce and aggravate GERD for the following reasons.
(1) hyperinflation of the lungs in asthmatic patients, which decreases the diaphragm, decreases the lower esophageal sphincter pressure, and weakens the anti-reflux effect.
(2) Significantly elevated levels of endogenous nitric oxide in asthmatics, which inhibits contraction of the lower esophageal sphincter.
(3) The use of bronchodilators such as theophylline and β2 agonists in asthmatic patients can increase gastric acid secretion and decrease LESP.
4.GERD and aspiration pneumonia and hospital-acquired pneumonia
GERD regurgitant is inhaled into the respiratory tract and can produce aspiration pneumonia. On the one hand, the direct stimulation of the airway mucosa by the regurgitant produces an inflammatory response and can be followed by bacterial infection; on the other hand, the regurgitant can stimulate the neuroreceptors in the gastrointestinal tract and respiratory tract, causing vascular endothelial damage and imbalance of endothelin and NO, leading to microcirculatory disorders.
Gram-negative bacilli in the gastrointestinal tract are an important source of pathogenic bacteria for hospital-acquired pneumonia. Their pathway to cause NP may be direct inhalation of gastric juice or retrograde colonization of the oropharynx via gastroesophageal reflux or nasogastric tube. The most important factor affecting gastrointestinal GNB colonization is gastric fluid pH, and inappropriate clinical application of H2 receptor blockers or PPIs to prevent stress ulcers increases gastric fluid pH from 1 to more than 4, leading to increased colonization of GNB. The application of aluminum thioglycollate instead of the above-mentioned drugs can effectively prevent stress ulcers without affecting the gastric fluid pH, which can effectively reduce the colonization of GNB and the occurrence of NP in the gastric lumen.
5.GERD and other pulmonary diseases
GERD and other pulmonary diseases also have a certain connection, such as obstructive sleep apnea hypoventilation syndrome, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, bronchiectasis, etc.. In these diseases, pathophysiological changes in the respiratory system may cause GERD, and GERD may also cause pulmonary lesions through tracheal microaspiration or esophago-bronchial reflex. In addition, there may simply be common risk factors between them.
6.Treatment principles of GERD respiratory complications
Inhibition of gastric acid secretion is the basic treatment for GERD at present. Standard doses of various PPI preparations can bring about rapid relief of GERD symptoms. For GERD patients with combined respiratory complications, PPI is preferred for treatment in addition to medication for pulmonary diseases. because extra-digestive symptoms are more difficult to control than typical symptoms, intensive PPI treatment should be performed: i.e., the initial treatment dose is higher and the duration is longer. Intensive PPI regimens are 50-70% effective in improving extradigestive symptoms of GERD. Anti-reflux surgery is an option for patients for whom drug therapy is ineffective, and endoscopic interventions can be carried out with caution by trained endoscopists. Surgical and endoscopic treatment should be decided carefully after comprehensive consideration.