An Ovine Model of GERD-Induced Bronchoconstriction

The association between bronchial asthma and gastroesophageal reflux disease (GERD) has been reported repeatedly over the last 30 years [1–6], although the issue of cause and effect remains controversial. Reports about a certain kind of relationship between asthma and GERD date back to 1912 when Sir William Osier [7] stated that “asthma attacks may be due to direct irritation of the bronchial mucosa or … indirectly, too, by reflex influences from the stomach”. Dr. Osier’s insight about acid-induced bronchoconstriction remains true today. GERD, the retrograde movement of gastric contents into the esophagus, is a prevalent clinical condition affecting millions of adults around the world. An epidemiologic study performed in the USA in the 1970s suggested that 10% of the population has daily heartburn and more than one-third have intermittent symptoms [8]. More recently, another survey reported that 20% of 800 randomly selected adults had heartburn more than three times a month and another 25% noted heartburn at least once a month [9]. Untreated GERD impairs quality of life and can lead to esophageal complications such as esophagitis, ulceration, stricture and Barrett’s esophagus (replacement of squamous epithelium with columnar epithelium) with its tendency to become malignant [10]. However, the spectrum of problems associated with GERD has expanded to extraesophageal sites [11]. Chronic cough and asthma are two clinical problems caused or triggered by GERD [12, 13]. Furthermore, treatment of GERD may result in marked improvement or even disappearance of symptoms in patients with chronic cough or asthma [12,14]. One potentially critical consideration is that many asthmatic patients do not have classic reflux symptoms but only occasional asymptomatic regurgitation. This condition, although being able to elicit cough and asthma, leaves the clinician unaware that GERD may be playing a crucial role in their patients’ symptoms [15,16].