In the present study, air swallowing, belching, acid and non-acid reflux patterns in patients with FD were studied, using combined intraluminal impedance and pH monitoring. This is the first study in which the presence of frequent belching in FD patients has been objectified and confirmed.
Patients with FD showed a higher incidence of air swallows than controls as well as a higher incidence of the total number of swallows. Furthermore, a higher proportion of gas-containing reflux episodes (belches) were found in FD patients, when compared with controls. Strictly speaking, gas-containing reflux episodes are not synonymous with belches, as belches are characterized by air expulsion through the mouth (eructation). As we were not able to measure the number of eructations, we defined belches as gas-containing reflux episodes (pure gas and mixed reflux episodes) in which the gas component reached the most proximal impedance segment and the liquid component (in mixed reflux episodes) did not. As it has been shown that air swallowing promotes belching in healthy volunteers, the higher belch incidence in our dyspeptic patients probably is the result of a high incidence of air swallows.
In the current study, patients with excessive belching were excluded as, according to the Rome II criteria, they are classified as a separate functional disorder category. Although the FD patients included in our study did not report symptomatic belching during recordings, they showed higher incidences of (air) swallowing and gas-containing reflux episodes when compared with healthy volunteers.
We can speculate why FD patients swallow air more frequently and belch more frequently than controls. A possible explanation could be that dyspeptic patients subconsciously swallow (air) more frequently in response to unpleasant gastrointestinal sensations and discomfort. As there is evidence of an association between psychopathology as well as psychosocial factors and FD[13,14], excessive air swallowing and belching could be evoked by several factors such as stress, anxiety and neurosis. This excessive swallowing of air can lead to accumulation of intragastric air, more discomfort and belching. It has to be noted, however, that this behaviour is different from that found in subjects with aerophagia and excessive belching, who suck or inject air in the oesophagus immediately followed by (supragastric) belching. In the current study, supragastric belches were not observed in the patients with FD.
No differences between dyspeptic patients and controls were found regarding LES and oesophageal contraction patterns. The possible contribution of impaired gastric emptying could not be assessed as no gastric emptying tests were performed in healthy volunteers.
We also found that there was no difference in the number of swallows between patients and controls at night. As the higher incidence of swallows and belches only occurs during the day, this finding supports the notion that the high swallow and belch rate in FD patients is caused by an acquired abnormal behavioural pattern.
Various pathophysiologic mechanisms such as delayed-gastric emptying, impaired gastric accommodation and hypersensitivity to gastric distention have been proposed to play a role in the dyspepsia symptom complex and several studies have been performed to assess the association between symptoms and the different mechanisms. However, only very few studies have addressed the association with belching symptoms. In a study in patients with FD, no association was found between impaired gastric accommodation and belching. Theoretically, frequent air swallowing in FD patients with proximal stomach dysrelaxation could lead to a greater increase in gastric pressure and thus to more belching than in healthy subjects. As, according to a large study, hypersensitivity to gastric distention is associated with belching, one may postulate that the high incidence of air swallowing in FD patients found in the current study led successively to gastric distention and (excessive) belching.
Lin et al. described that belching is as common and as severe in patients with dyspepsia as it is in patients with GERD. In Lin's study only questionnaires and pH-metry were used to count belches. Using impedance monitoring, we were able to study more accurately the relation between air swallows, belching, acid and non-acid reflux in patients with FD.
Although a higher proportion of belches was found in FD patients when compared with controls, no differences were found regarding reflux time and acid reflux episodes, suggesting that belching is an entity independent to acid reflux. These results are in concordance with a recent study in FD patients by Tack et al. in which no association between acid reflux and belching was found. In agreement with the results of the current study, they showed that the majority of patients with FD seen at a tertiary centre have normal 24-h oesophageal pH monitoring. We have recently shown that GERD patients have a higher incidence of air swallows and belches when compared with healthy subjects, but also that air swallowing was not the likely cause of their increased reflux. Lin et al. described a similar prevalence and severity of belching in FD patients and in GERD patients, but belching events correlated more frequently with acid reflux episodes in GERD patients than in FD patients and belching scores in FD patients remained unchanged after proton pump inhibitor therapy.
In the current study, most of the reflux episodes in dyspepsia patients were non-acid (70.1%) and these patients showed a higher incidence of non-acid reflux episodes when compared with controls. Also the majority of the belches in dyspeptic patients were non-acid (75.6 %), whereas the belches in controls showed a similar proportion of acid and non-acid content (51.9 and 48.1 %, respectively). These outcomes lead further support for the concept that belching and acid reflux are different entities. A possible explanation for the high proportion of non-acid reflux episodes in FD patients could be the neutralizing effect of saliva on the gastric content as these patients showed a high incidence of swallows. It might also be that delayed-gastric emptying prolongs the neutralization of the gastric content by food.
The higher incidence of non-acid reflux episodes in the dyspepsia patients in our study may help to understand the high frequency at which heartburn symptoms are reported by patients with FD. This finding can also explain the outcomes in the study of Lin et al., in which episodes of heartburn in FD patients were not associated with acid reflux events, although heartburn was reported as frequently by FD patients as by patients with GERD.
In conclusion, patients with FD swallow air more frequently than controls, and this is associated with an increased incidence of non-acid gaseous gastro-oesophageal reflux. Further studies are needed to assess the pathophysiological mechanisms underlying these abnormalities.
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J. M. Conchillo, Department of Gastroenterology and Hepatology, University Medical Center Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands. E-mail: firstname.lastname@example.org .
Aliment Pharmacol Ther. 2007;25(8):965-971. © 2007 Blackwell Publishing
Cite this: Air Swallowing, Belching, Acid and Non-acid Reflux in Patients With Functional Dyspepsia - Medscape - Apr 01, 2007.