Normal 24-hr ambulatory esophageal pH values. Influence of study center, pH electrode, age, and gender

Ambulatory esophageal pH testing. Referral patterns, indication, and treatment in a Canadian teaching hospital

Over a 30-month period, 867 esophageal pH studies were conducted in a Canadian teaching hospital; of these, 315 tests were recorded in patients who were first-time referrals having no chest or upper gastrointestinal surgery and taking no medication that would affect the results. Patients were referred by gastroenterologists, general surgeons, ENT surgeons, thoracic surgeons, and a miscellaneous group. Patients were classified based on: pH results [abnormal = % total time pH < 4.0 (ie, > 6.0%)], manometry (abnormal = LES resting pressure < 5 mm Hg and/or abnormal peristalsis), and gender. Fifty-one percent (162/315) of the patient records demonstrated abnormal reflux. Intergroup comparisons of severity of reflux using two-way analysis of variance demonstrated no significant differences (P = 0.13). In the 162 patients who refluxed, 70% (N = 108) had normal motility studies; however, when the severity of reflux was compared, patients with abnormal motility (N = 54) demonstrated significantly more severe reflux (19.8 +/- 12.8 vs 16.2 +/- 11.3) P = 0.02. In those patients with abnormal manometry, no significant differences (P = 0.44) in the severity of reflux were found among those with abnormal peristalsis (N = 27), low resting pressure (N = 17), or a combination of aperistalsis and low LES pressure (N = 10). Symptomatic patients with reflux (N = 107) demonstrated a significantly greater percent time pH < 4.0 than those with asymptomatic reflux (N = 55); 18.1 +/- 11.5% vs 16.2 +/- 12.7%, P = 0.04. When the severity of reflux by gender was compared, no significant differences were found [18.3 +/- 11.9 (male) N = 91 vs 16.2 +/- 11.9 (female) N = 71, P = 0.11]. The results from this study show that: (1) esophageal pH testing is important in subspecialties other than gastroenterology and that the clinical yield is high in all referring groups, (2) esophageal pH testing and manometry are complimentary tests, but that reflux occurs commonly in association with normal manometry, (3) asymptomatic reflux was found in 34% of the patients with abnormal reflux scores, and (4) the severity of reflux in male and female patients is similar.

Prevalence of esophageal disorders in patients with chest pain newly referred to the cardiologist

STUDY OBJECTIVE

The prevalence of esophageal disorders (dysmotility and/or gastroesophageal reflux) in patients with chest pain newly referred to a cardiologic clinic is unknown. The aims of our study were to investigate the prevalence of esophageal abnormalities in these patients and to assess the value of medical history in predicting the origin of the patient's chest pain.

DESIGN

We evaluated 28 consecutive patients who were newly referred to the cardiologist because of angina-like chest pain. Patients with evidence of severe myocardial ischemia were excluded. Cardiologic evaluation included medical history, physical examination, ECG, and exercise testing; further cardiologic workup was carried out only when considered necessary. Gastroenterologic evaluation consisted of medical history, esophageal manometry, endoscopy, and 24-h ambulatory monitoring of esophageal pH and pressure.

MEASUREMENTS AND RESULTS

In five patients a diagnosis of ischemic coronary artery disease was made. In only two of these five patients, the cardiologic history strongly suggested a cardiac origin of the pain. Twelve patients had a pathologic 24-h pH profile, four of whom also had reflux esophagitis. Ten patients had symptomatic reflux. In only three of these ten patients, the history was judged to be indicative of an esophageal origin of the chest pain. No motility disorders were found.

CONCLUSIONS

Thirty-six percent of the patients with chest pain newly referred to a cardiologic out-patient clinic have symptomatic gastroesophageal reflux. Neither cardiologic nor gastroenterologic history data have a high predictive value with respect to the origin of the chest pain.

Asthma and gastroesophageal reflux: acid suppressive therapy improves asthma outcome

PURPOSE

To determine (1) the appropriate omeprazole (Prilosec) dose required for adequate acid suppression in asthmatics with gastroesophageal reflux, (2) whether aggressive acid suppressive therapy of gastroesophageal reflux improves asthma outcome in asthmatics with gastroesophageal reflux, (3) the time course of asthma improvement, and (4) demographic, esophageal, or pulmonary predictors of a positive asthma response to antireflux therapy.

PATIENTS AND METHODS

Thirty nonsmoking adult asthmatics with gastroesophageal reflux (asthma defined by American Thoracic Society criteria and reflux defined by symptoms and abnormal 24-hour esophageal pH testing) were recruited from the outpatient clinics of a 900-bed university hospital. Patients underwent baseline studies including a demographic questionnaire, esophageal manometry, dual-probe 24-hour esophageal pH test, barium esophogram, and pulmonary spirometry. During the 4-week pretherapy phase, patients recorded reflux and asthma symptom scores and peak expiratory flow rates (PEFs) upon awakening, 1 hour after dinner, and at bedtime. Patients began 20 mg/d omeprazole, and the dose was titrated until acid suppression was documented by 24-hour pH test. Patients remained on this acid suppressive dose for 3 months. Responders were identified by a priori definitions: asthma symptom reduction by >20% and/or PEF increase by >20%. Asthma symptom scores, PEF's baseline and posttherapy pulmonary spirometry were analyzed.

RESULTS

Twenty-two (73%) patients were asthma symptom and /or PEF responders: 20 (67%) were asthma symptom responders, and 6 (20%) were PEF responders. Responders reduced their asthma symptoms by 57% (P<0.001), improved their morning and night PEFs by 8% and 9% (both P <0.005), and had improvement in forced expiratory volume at 1 second (P <0.02), mean forced expiratory flow during the middle half (25% to 75%) of the forced vital capacity (P <0.04), and peak expiratory flow (P <0.01) with acid suppressive therapy. Mean acid suppressive dose of omeprazole was 27 mg/d (+/-2.2) with 27% (8) patients requiring more than 20 mg/d. The presence of regurgitation or excessive proximal esophageal reflux predicted asthma response with 100% sensitivity, 100% negative predictive value, specificity of 44% and a positive predictive value of 79%.

CONCLUSIONS

Acid suppressive therapy with omeprazole improves asthma symptoms and/or PEFs by >20% and improves pulmonary function in 73% of asthmatics with gastroesophageal reflux after 3 months of acid suppressive therapy. Many asthmatics (27%) required >20 mg/d of omeprazole to suppress acid. The presence of regurgitation and/or excessive proximal esophageal reflux predicts a positive asthma outcome.

Placebo-controlled trial of cisapride in postgastrectomy patients with duodenogastroesophageal reflux

Medical treatment of duodenogastroesophageal reflux in postgastrectomy patients has been disappointing. Using ambulatory esophageal bilirubin monitoring, we evaluated the efficacy of cisapride in this disorder. Ten chronically symptomatic partial gastrectomy patients (5 Billroth I, 5 Billroth II; 8 men; average age 57) with duodenogastroesophageal reflux were randomized to four weeks of either placebo or cisapride (20 mg four times a day) in a double-blind crossover study. Significantly improved patients continued to take cisapride for an additional four months. Duodenogastroesophageal reflux was assessed at baseline and after four weeks on each therapy. Daily diary recorded symptoms and mean monthly scores were determined. Global symptom improvements were assessed at the end of each treatment period. Compared to placebo, cisapride significantly (P < 0.05) decreased duodenogastroesophageal reflux. Overall symptom improvements were assessed at the end of each treatment period. Compared to placebo, cisapride significantly (P < 0.05) decreased duodenogastroesophageal reflux. Overall symptoms improved in 70% of patients on cisapride compared to 10% on placebo (P < 0.01). Mean monthly scores significantly (P < 0.05) improved for abdominal pain, regurgitation, and belching. These symptoms remained improved after four months of chronic therapy. We conclude that cisapride significantly reduces duodenogastroesophageal reflux and results in short- and long-term symptom improvements in postgastrectomy patients and that cisapride offers the first successful medical therapy for duodenogastroesophageal reflux in postgastrectomy patients.

Esophageal motility and reflux testing. State-of-the-art and clinical role in the twenty-first century

Esophageal function testing has an important place in the investigation of a significant proportion of patients with esophageal disorders. Appropriate application of these tests requires a proper understanding of their capabilities and limitations and careful primary assessment by other modalities. Esophageal manometry is most useful for assessing significant troublesome dysphagia in the absence of organic obstruction. Esophageal pH monitoring is an important adjunct to clinical assessment and endoscopy in the diagnosis of reflux disease. Although it is the gold standard for the measurement of esophageal acid exposure and assessment of the relationship of symptoms to reflux, there are weakness in both of these functions that should be understood when applying the test to the diagnosis of reflux disease.

Coronary flow reserve and oesophageal dysfunction in syndrome X

The relative prevalence of abnormalities of coronary flow reserve and oesophageal function was ascertained in 32 syndrome X patients with typical angina chest pain, a positive exercise test, and normal coronary arteries. Coronary flow reserve in response to a hyperaemic dose of papaverine was measured using an intracoronary Doppler catheter positioned in the left anterior descending coronary artery. An abnormal coronary flow reserve was defined as being < 3.0. Patients were investigated for oesophageal dysfunction by manometry and 24-hour pH monitoring. Thirteen patients had an impaired coronary flow reserve (group 1) and 19 patients had a normal flow reserve (group 2). Eight of the 13 group 1 patients (62%) and 13 of the 19 group 2 patients (68%, p = NS) had evidence of oesophageal dysfunction on either manometry or pH studies. Therefore, a total of 26 (81%) syndrome X patients had either an abnormality of coronary flow reserve or oesophageal dysfunction suggesting that chest pain in these patients may be due to myocardial ischaemia or oesophageal dysfunction, thus confirming the heterogeneous nature of this syndrome. The prevalence of oesophageal abnormalities was independent of any abnormalities of coronary flow reserve.

Reproducibility of ambulatory esophageal pH monitoring in the aperistaltic esophagus

The reproducibility of ambulatory 24-h esophageal pH monitoring was evaluated in 16 consecutive patients by comparing the difference in two consecutive 24-h periods. The study group included 8 patients with scleroderma esophagus and 8 treated achalasia patients. The amount of reflux was expressed as the percentage of time the pH was < 4.0. Both groups demonstrated excellent intrapatient reproducibility overall: 96% in scleroderma patients and 95% in those patients with achalasia. The least concordance was found in the lengths of the longest reflux events-70% when supine in scleroderma patients and 59% when upright in patients with achalasia. There was no significant difference (p > 0.05) between day 1 and day 2 for either group of patients for any of the elements studied. These results indicate that intrapatient variability of gastroesophageal reflux in patients with scleroderma esophagus and treated patients with achalasia is very low and following therapeutic intervention, a high level of confidence can be placed in subsequent pH monitoring as an indicator of treatment effect.

Gastroesophageal reflux-induced bronchoconstriction. Is microaspiration a factor?

STUDY OBJECTIVE

To evaluate the role of microaspiration in gastroesophageal reflux-induced bronchoconstriction.

DESIGN

Prospective study blinded to the subject.

SETTING

Outpatient laboratory of a 908-bed university hospital.

PARTICIPANTS

Thirty nonsmoking adults divided into two groups: asthmatics with reflux (AR), 20; and subjects with gastroesophageal reflux (R), 10.

INTERVENTIONS

Dual esophageal pH probe placed. Esophageal infusions of normal saline solution, 0.1N hydrochloric acid, then normal saline solution, each lasting 18 min, were followed by two 20-min recovery periods. Subjects remained in the supine position throughout. Spirometry and specific airway resistance (SRaw) performed at baseline, after each esophageal infusion and recovery period. Proximal esophageal acid exposure, a requirement for microaspiration, was assessed by the proximal esophageal pH probe.

RESULTS

Peak expiratory flow rate (PEF) decreased with esophageal acid in the AR group and did not recover immediately despite esophageal acid clearance with a significant main effect of subject groups (p < 0.021) by repeated measures analysis of covariance. This decrease in PEF was not associated with the presence of proximal esophageal acid exposure (p = 0.618). Specific airway resistance increased in the AR group with esophageal acid and worsened despite acid clearance, especially during the second recovery phase, with a significant phase (p < 0.009) and group by treatment effect (p < 0.009). The presence of proximal esophageal acid exposure was not associated with this deterioration in SRaw (p = 1.0).

CONCLUSIONS

Esophageal acid infusions given in the supine position caused a decrease in PEF and an increase in SRaw in the asthma with reflux group, which did not improve despite acid clearance. These responses were not dependent on proximal esophageal acid exposure. Also, SRaw continued to worsen during the recovery phase in the AR group, which may represent a delayed bronchoconstrictor effect. These data suggest that microaspiration does not play a significant role in esophageal acid-induced bronchoconstriction.

24 hour ambulatory oesophageal pH monitoring in uncomplicated Barrett's oesophagus

The aim of this study was to compare acid reflux in 16 patients with uncomplicated Barrett's oesophagus with 37 patients with reflux oesophagitis and 10 control subjects of comparable age. All patients had 24 hour ambulatory pH monitoring within one week of endoscopy. The controls differed significantly from the other groups in all indices of reflux but there was no difference between the Barrett's oesophagus patients and the reflux oesophagitis patients in any index of reflux over the total 24 hour period. Barrett's oesophagus patients differed significantly, however, with respect to the percentage time pH < 4 and the number of reflux episodes of > five minutes during the supine period when compared with patients with grade I reflux oesophagitis, but not when compared with patients with grade II and III reflux oesophagitis. Barrett's oesophagus patients with associated grade II reflux oesophagitis had more reflux than those with no oesophagitis or grade I reflux oesophagitis. Within each disease group patients > or = 50 years had more acid reflux than patients < 50 years. The severity of acid reflux in patients with uncomplicated Barrett's oesophagus was no greater than in patients with reflux oesophagitis of comparable age. It seems probable that other factors must be important in the development of Barrett's oesophagus.

Gastroesophageal reflux-induced bronchoconstriction. An intraesophageal acid infusion study using state-of-the-art technology

STUDY OBJECTIVE

To study mechanisms of gastroesophageal reflux-induced bronchoconstriction during intraesophageal infusions.

DESIGN

Prospective study blinded to the subject.

SETTING

Outpatient pulmonary function laboratory at a 908-bed university hospital.

PARTICIPANTS

Forty-seven adult subjects divided into four groups: asthmatics with reflux, 20; asthmatics, 7; gastroesophageal refluxers, 10; and normal controls, 10. Asthmatics were defined by American Thoracic Society criteria, and refluxers were defined by symptoms and 24-hour pH monitoring.

INTERVENTIONS

Dual antimony esophageal pH probe placed just below the upper esophageal sphincter and 5 cm above the lower esophageal sphincter. Intraesophageal infusions of normal saline solution followed by 0.1N hydrochloric acid then normal saline solution were given for 15 to 18 min. Spirometry and specific airway resistance (SRaw) were performed after placement of pH probes, insertion of esophageal infusion tube, and after each infusion. Bernstein tests were assessed during esophageal infusions.

MEASUREMENTS AND RESULTS

Peak expiratory flow rate (PEF) decreased with intraesophageal acid in all four groups (p < 0.014). Esophageal acid clearance improved PEF in all groups except the asthmatics with reflux group that had a further decrease in PEF. These effects were not dependent on a positive Bernstein test or evidence of proximal reflux. The asthmatics with reflux group also had an increase in SRaw with intraesophageal acid, which continued to increase despite acid clearance.

CONCLUSIONS

Intraesophageal acid infusions caused a decrease in PEF in all groups without evidence of microaspiration, implying a vagally mediated reflex may be involved. Esophageal mucosal inflammation, assessed by a positive Bernstein test, was not required. Asthmatics with reflux also had further decline in PEF despite acid clearance.

Duodenogastroesophageal reflux: relationship to pH and importance in Barrett's esophagus

BACKGROUND/AIMS

Several reports suggest that duodenogastroesophageal reflux may produce esophagitis, Barrett's esophagus, and esophageal adenocarcinoma. The purpose of this study was to understand better the relationship of pH (< 4 and > 7), duodenogastroesophageal reflux, and fasting bile acid concentrations in producing esophageal damage.

METHODS

Using a spectrophotometric technique to measure bile reflux, four groups were studied: healthy subjects, reflux patients, patients with Barrett's esophagus, and patients with esophageal symptoms after partial gastrectomy.

RESULTS

Simultaneous 24-hour pH and bile monitoring of distal esophagus found close association between total percent of time pH < 4 and duodenogastroesophageal reflux (r = 0.78; P < 0.001) but a poor relationship (r = -0.06) with total percent of time pH > 7, suggesting that the term alkaline reflux is a misnomer. Duodenogastroesophageal reflux increased significantly with the severity of reflux disease, being greatest in patients with Barrett's esophagus and comparable with that in patients with partial gastrectomy. Fasting bile acid concentrations did not distinguish patients with Barrett's esophagus from those with reflux. Rather, increased quantity of acid reflux was the single factor most characterizing patients with Barrett's esophagus. Omeprazole (20 mg twice daily) normalized acid reflux parameters (13.8% +/- 1.6% to 0.8% +/- 0.6%) and significantly (P < 0.001) decreased duodenogastroesophageal reflux (32.8% +/- 6.9% to 4.7% +/- 1.7%).

CONCLUSIONS

Acid reflux is the primary factor in the development of Barrett's esophagus. Bile reflux parallels acid reflux and, at best, may have a synergistic role. Aggressive acid suppression with omeprazole markedly decreases both.

Gastroesophageal reflux in patients with angiographically normal coronary arteries: an uncommon cause of exertional chest pain

OBJECTIVES

To investigate the association between exertional chest pain and gastroesophageal reflux in patients with normal coronary angiograms and in controls by measuring oesophageal pH during treadmill exercise tests and to compare the results with routine ambulatory monitoring.

DESIGN

Case control study.

SETTING

Tertiary referral cardiac unit.

PATIENTS

50 consecutive patients with chest pain and completely normal coronary angiograms and 16 controls with coronary artery stenoses.

MAIN OUTCOME MEASURES

Episodes of acid reflux and chest pain during treadmill exercise; a symptom index expressing the percentage of episodes of pain related to acid reflux during ambulatory monitoring.

RESULTS

Four (8%) patients and two (12%) controls had reflux during treadmill exercise (NS). 32 (64%) and 16 (100%) reported chest pain, but only three (6%) and two (12%) had coincident reflux (NS). Reflux was as frequent before, during, and after treadmill exercise (five (8%) v six (9%) v two (3%)) in the 66 subjects; (NS). 19 (38%) patients and three (19%) controls had abnormal reflux on ambulatory monitoring (NS). Eight (16%) and three (19%) had a symptom index > 50%, but six and two of these reported pain without coincident reflux during treadmill exercise.

CONCLUSION

There are many potential causes of chest pain in patients with angiographically normal coronary arteries. Although gastroesophageal reflux is commonly implicated and many patients have a high incidence of spontaneous reflux during ambulatory monitoring, it rarely occurs during exertion and the association with chest pain is poor.

Relaxation training reduces symptom reports and acid exposure in patients with gastroesophageal reflux disease

BACKGROUND/AIMS

Previous studies have shown that psychological factors play a role in symptom perception among patients with gastroesophageal reflux disease. This report describes the first controlled study showing the effects of relaxation training on symptom reports and esophageal acid exposure in patients with reflux disease.

METHODS

Twenty subjects with documented reflux disease were studied during psychologically neutral and stressful tasks, followed immediately by either a relaxation or attention-placebo control intervention.

RESULTS

Stressful tasks, relative to neutral tasks, produced significant increases in blood pressure, subjective ratings of anxiety, and reports of reflux symptoms. Despite increased symptom reports, stressful tasks did not significantly increase objective measures of esophageal acid exposure. Subjects who received a relaxation intervention after the stressful task had significantly lower heart rate values and subjective ratings of anxiety compared with subjects who received the attention-placebo control intervention. Subjects who received relaxation training also had significantly lower reflux symptom ratings and total esophageal acid exposure than subjects who received the attention-placebo control intervention.

CONCLUSIONS

Relaxation may be a useful adjunct to traditional antireflux therapy in patients who experience increased symptoms during stress.

Review article: gastro-oesophageal reflux and laryngeal symptoms

There is some evidence from clinical, experimental and multiprobe ambulatory pH studies that gastro-oesophageal reflux is more common in patients with laryngeal symptoms and could potentially play a role in the causation of these symptoms. The proportion of unselected patients with laryngeal symptoms who have gastro-oesophageal reflux as the primary aetiology may be overestimated in some series. The symptom that has been most evaluated is hoarseness, but even for this symptom the proportion of patients who have significant reflux varies widely. There is even less agreement for other symptoms, and the data on globus sensation remains confused. It is likely that these patients present to ear, nose and throat (ENT) clinics because of the relative insensitivity of the oesophageal mucosa to acid exposure. Given the lack of specificity for routine diagnostic tests for gastro-oesophageal reflux, it is necessary to perform ambulatory pH monitoring for a secure diagnosis in these patients. Treatment studies have been surprisingly few and inadequate in design. It is suspected that there is a strong placebo response for these symptoms. No clear information on efficacy can be provided until placebo-controlled randomised studies are available.

Effects of oral erythromycin on esophageal pH and pressure profiles in patients with gastroesophageal reflux disease

Erythromycin, a possible motilin agonist, is a potent gastrokinetic agent that may increase the lower esophageal sphincter pressure. Therefore, we assessed the effects of erythromycin in two dosages (250 and 500 mg per os four times a day) on esophageal pH and pressure profiles in reflux patients using prolonged ambulatory monitoring systems. Studies were blinded, placebo-controlled with randomized crossover design. Patients took each drug for three days prior to studies, with erythromycin serum levels obtained the day of esophageal studies. Erythromycin 250 mg four times a day had no effect on esophageal contraction pressures or peristalsis during the day or meal periods. In the supine position, however, erythromycin significantly (P = 0.012) decreased esophageal contraction velocity and showed a strong trend (P = 0.059) towards increasing the percentage of peristaltic waves. Despite these potentially beneficial effects on esophageal clearance, no significant difference in acid exposure times during 24-hr pH studies were observed between placebo and low-dose erythromycin. High-dose erythromycin (500 mg four times a day) was associated with drug levels in the typical antibiotic efficacy range (normal 1-3 micrograms/ml; patients 1.7-7.0 micrograms/ml), but, here again, there was no significant difference in all acid reflux parameters between placebo and erythromycin phases. Therefore, "standard" doses of erythromycin have no important clinical effects on esophageal pressures or acid reflux parameters.

The symptom index. Differential usefulness in suspected acid-related complaints of heartburn and chest pain

The symptom index is a quantitative measure developed for assessing the relationship between gastroesophageal reflux and symptoms. Controversy exists, however, over its accuracy and the appropriate threshold for defining acid-related symptoms of heartburn and chest pain. Therefore, a retrospective review was done of 153 consecutive patients referred to our esophageal laboratory. Three groups were identified: patients with normal 24-hr pH tests and no esophagitis, patients with abnormal 24-hr pH tests and no esophagitis, and patients with abnormal 24 hr pH values and endoscopic esophagitis. If symptoms occurred during the pH study, a symptom index (number of acid related symptoms/total number of symptoms x 100%) was calculated separately for heartburn and chest pain. Heartburn and chest pain episodes were similar among the three groups. However, the mean symptom index for heartburn was significantly (P < 0.001) higher in the patient groups with abnormal pH values [abnormal pH/no esophagitis: 70 +/- 7.1% (+/- SE); abnormal pH/esophagitis: 85 +/- 4.6%] as compared to those with normal studies, ie, functional heartburn (26 +/- 10.7%). The mean symptom index for chest pain was similar for all three groups. Using receiver operating characteristic curves, a heartburn symptom index > or = 50% had excellent sensitivity (93%) and good specificity (71%) for acid reflux disease, especially if patients complain of multiple episodes of heartburn. In contrast, an optimal symptom index threshold for defining acid-related chest pain episodes could not be defined.

Determinants of oesophageal 'alkaline' pH environment in controls and patients with gastro-oesophageal reflux disease

The determinants of the oesophageal alkaline pH environment are poorly understood. Saliva (pH 6.4-7.8) may be a major contributor, although some argue the importance of refluxed alkaline duodenal contents. Acid and alkaline reflux parameters were studied over 2 days in 30 subjects (control, oesophagitis and Barrett's patients; 10 each) using glass pH electrodes. In phase 1, one pH electrode was placed 1 cm below the upper oesophageal sphincter to assess the influence of saliva and the other 5 cm above the lower oesophageal sphincter. Phase 2 was identical except that one pH probe was 5 cm below the lower oesophageal sphincter to record duodenogastric reflux. Patient groups spent, on average, 50 fold more time during the upright and supine periods at acidic pH than controls. Saliva was responsible for the percentage of time the pH > 7 and contributed significantly to the percentage of time the pH > 6 in both the proximal and distal oesophagus of control subjects, as shown by an absence of pH > 7 and a significant (p < 0.001) fourfold decrease in pH > 6 during sleep. A similar pattern was seen in the proximal oesophagus of both reflux groups. The reflux and Barrett's patients, however did not show a significant decrease in the percentage of time the pH > 6 at night in the distal oesophagus suggesting a relative increase in 'alkaline' exposure from another source. This was not because of duodenogastric reflux as the corresponding pH rises in the fundus of the stomach were non-existent. Although this was not studied specifically, it is believed to be a protective meachanism, the result of alkaline secretion produced by submucosal oesophageal glands.