Acid reflux: How does this condition trigger asthma?
Gastroesophageal reflux disease (GERD), commonly known as acid reflux, is common among asthmatics and can trigger attacks. But scientists and clinicians continue to debate how often the two are related, the precise pathophysiology, and its clinical significance.
Most likely, stomach contents back up, irritating the esophagus. Neuroreflexes cause bronchoconstrictions and, in turn, breathing problems.
The digestive tract is one of the most threatening systems to the lungs, says David Henke, MD, pulmonologist and associate professor of medicine at the University of North Carolina in Chapel Hill. "Just refluxing up into the esophagus is enough to cause problems."
Many of the 15 million Americans who suffer heartburn every day don’t consult their doctors, and therefore, never learn their problem may be the much more serious GERD.
Yet, without proper treatment, acid reflux can cause serious problems, including asthma symptoms, severe chest pain, a narrowing or obstruction of the esophagus, bleeding, and a pre-cancerous condition known as Barrett’s esophagus.
In response, the American College of Gastro enterology has embarked on a national education campaign, hoping to alert people to the potential problem and educate them about the dozens of over-the-counter medications available for heartburn.
How acid reflux occurs
Acid reflux occurs when the muscle valve at the lower end of the esophagus fails to function properly, allowing acid from the stomach to back up into the esophagus. Reflux is more common after meals, especially those high in fat, since fat delays gastric emptying. Typical symptoms of acid reflux include recurrent heartburn that radiates around the chest, that worsens when lying down or bending over, or that’s eased by consuming water or antacids. Other symptoms include a sensation of acid refluxing into the windpipe, causing shortness of breath. Patients also may feel a sense of food being trapped behind the breastbone, black bowel movements, and blood in vomit.
"It really causes some significant problems in people," Henke says. "In pulmonary practices, it’s a pretty important concern in patients that have asthma."
If over-the-counter or prescription medications don’t alleviate persistent heartburn, the problem may be GERD.
The relationship between asthma and GERD
A relationship between asthma and GERD was first found in the 1960s when patients reported their asthma symptoms were eliminated after surgery for acid reflux.
Researchers and clinicians believe there are two mechanisms at play:
• In the leading theory, the acid reflux erodes the epithelial layer of the mucosa, exposing vagal nerve endings. The esophageal receptors become more sensitive to refluxed acid. The receptors then trigger bronchospasms.
"Acid reflux is an important trigger for asthma," says Benjamin Interiano, MD, associate professor of medicine in the pulmonary section at Baylor College of Medicine in Houston. In fact, reflux may be the sole cause of symptoms in some asthmatics.
• In a less-common theory, patients aspirate gastric acid into the lungs. Recent research shows this is not likely to be a primary cause of reflux-triggered asthma.
Coughing also may promote reflux. It weakens the sphincter, allowing for reflux, says Frederick Leickly, MD, associate professor of medicine at the Indiana University School of Medicine and a pediatric pulmonologist at Riley Hospital for Children, which is affiliated with the School of Medicine in Indianapolis.
When asthmatics also have GERD
Just how many asthmatics also suffer from GERD remains unclear. Identifying acid reflux has become much more effective, so clinicians diagnose more people with it.
"Now it’s so common that it’s hard to make for a convincing association," says Peyton Eggleston, MD, professor of pediatrics and pediatric immunologist at Johns Hopkins Children’s at Johns Hopkins University in Baltimore.
Recent studies show that up to 80% of asthmatics will have an abnormal lower sphincter, say physicians and researchers who produce an asthma Web site for The Journal of the American Medical Association (www.ama-assn.org/special/asthma/treatmnt/updates/gerd.htm).
Experts point to these clues that GERD may be aggravating asthma:
• Asthma occurs for the first time during adulthood.
• Asthma gets worse after meals, lying down, or exercise.
• Asthma gets worse at night.
"Questions regarding symptoms of GERD should become standard in the evaluation of patients with asthma," wrote William G. Simpson, MD, in his April 24, 1995, study about the asthma-GERD connection in the journal Internal Medicine.
Patients with nocturnal asthma or who develop nighttime coughing, choking, wheezing, or hoarseness upon wakening also suggest GERD is occurring while they sleep. Asthma also may worsen after events that also affect GERD such as eating meals, drinking alcohol, reclining, and using bronchodilators such as theophylline and systemic beta-adrenergic agonists.
Doctors suggest testing asthma patients for acid reflux if their symptoms are tied to factors known to cause GERD, namely reclining, consuming alcohol, and using the drug theophylline.
And patients whose asthma routinely worsens at night "is one of the first things I look for in their history to suggest reflux may be playing a role," Henke says.
Testing all asthmatics, however, isn’t cost-effective today. Yet, doctors note that the cost of treating severe GERD-related problems, such as Barrett’s esophagus, could easily outweigh the cost of evaluating patients.
"If the asthma is not going as it should go, it’s one of the things you should look for," Leickly says.
Some physicians go ahead and treat patients for presumed GERD, but that can cause problems with patients complying with medication and lifestyle changes, Henke says. It helps to confirm the problem so patients understand the existence and severity of the problem.
There are several testing options, but none can prove definitively that a patient’s asthma is caused by acid reflux. In order to find out if a person has reflux and if it is causing any problems, including asthma, one common test measures the amount of acid that escapes from the stomach into the esophagus. This involves a 24-hour pH monitoring of the esophagus. A pH value of less than 4 for more than 4% of the test time indicates GERD.
Asthmatics also keep a diary of wheezing to see if it relates to changes in pH. Respiratory symptoms that develop either during an episode of acid reflux or within 10 minutes after are considered correlated and suggest GERD is triggering them. However, developing acid reflux after the onset of pulmonary symptoms suggests the opposite, Simpson wrote.
Another reliable method in evaluating an asthma patient for reflux is endoscopy. If endoscopy shows mucosal erosion, GERD can be the problem.
Experts note the most simple treatment is to advise patients to elevate the heads of their beds using a brick, block of wood, or something similar. The idea is to use gravity to help keep stomach contents from backing up.
This often reduces the problem and may even eliminate it. In fact, it’s nearly as useful as therapy with histamine2-receptor blockers, or H2 blockers.
Henke also suggests overweight patients lose weight and that all patients not eat late at night or drink carbonated beverages before bed. Patients also should avoid foods that cause them heartburn.
Considerations for drug therapy
When a patient suffers erosive esophagitis, only drugs that reduce the output of hydrogen by the parietal cell will heal erosions. These include H2 blockers and omeprazole, which is usually effective in patients whose erosive esophagitis is resistant to H2 blockers.
Acid reflux treatments may benefit asthmatics — and vice versa — further evidence supporting a relationship between bronchospasms and GERD.
"In some patients, once you stop the reflux, the asthma goes away," says Allan Rashford, MD, a pulmonologist and internal medicine specialist in private practice in Charleston, SC.
Several studies also have shown that surgery to correct severe reflux may alleviate asthma, perhaps more than long-term treatments. Surgery may be needed if medical therapy isn’t effective, if the patient is noncompliant, or when a patient is young and faced with a lifetime of medical therapy. However, surgery may not benefit patients suffering allergic asthma.
On the other hand, some asthma treatments can worsen acid reflux. Both systemic and oral bronchodilators relax the lower esophageal sphincter and can lead to GERD. The risk to patients is winding up in a therapy cycle of asthma, bronchodilator therapy, and reflux.
For instance, theophylline relaxes the lower esophageal sphincter and stimulates gastric secretion. The reduced sphincter pressure generally lasts about four hours. Eggleston said that use of theophylline is fading due to toxicities, although it’s still used to treat about 15% to 20% of children.