Ambulatory monitoring of oesophageal pH in reflux oesophagitis using a portable radiotelemetry system

Review article: Current status and future directions of ingestible electronic devices in gastroenterology

BACKGROUND

Advances in microelectronics have greatly expanded the capabilities and clinical potential of ingestible electronic devices.

AIM

To provide an overview of the structure and potential impact of ingestible devices in development that are relevant to the gastrointestinal tract.

METHODS

We performed a detailed literature search to inform this narrative review.

RESULTS

Technical success of ingestible electronic devices relies on the ability to miniaturise the microelectronic circuits, sensors and components for interventional functions while being sufficiently powered to fulfil the intended function. These devices offer the advantages of being convenient and minimally invasive, with real-time assessment often possible and with minimal interference to normal physiology. Safety has not been a limitation, but defining and controlling device location in the gastrointestinal tract remains challenging. The success of capsule endoscopy has buoyed enthusiasm for the concepts, but few ingestible devices have reached clinical practice to date, partly due to the novelty of the information they provide and also due to the challenges of adding this novel technology to established clinical paradigms. Nonetheless, with ongoing technological advancement and as understanding of their potential impact emerges, acceptance of such technology will grow. These devices have the capacity to provide unique insight into gastrointestinal physiology and pathophysiology. Interventional functions, such as sampling of tissue or luminal contents and delivery of therapies, may further enhance their ability to sharpen gastroenterological diagnoses, monitoring and treatment.

CONCLUSIONS

The development of miniaturised ingestible microelectronic-based devices offers exciting prospects for enhancing gastroenterological research and the delivery of personalised, point-of-care medicine.

Developments in Gastroesophageal Reflux Disease over the Last 40 Years

BACKGROUND

The last 40 years have seen a remarkable change in our understanding of reflux disease.

SUMMARY

These changes encompass disease definition and impact, pathophysiology, diagnostic testing, regulatory oversight of clinical trials, pharmacotherapy, endoscopic, and surgical treatment. We have also seen a number of promising therapies fail.

KEY MESSAGES

The future holds the promise of further advances. Adaptive artificial intelligence will take over diagnostics in manometry and pH impedance testing and patient-driven outcomes may be changed by interactions with artificial intelligence rather than humans. Changes in chip technology will allow higher resolution chips to be carried on smaller devices making extra-esophageal areas where reflux may play a role more accessible to prolonged observation and testing.

Gastrointestinal Transit Times in Health as Determined Using Ingestible Capsule Systems: A Systematic Review

BACKGROUND

Ingestible capsule (IC) systems can assess gastrointestinal (GI) transit times as a surrogate for gut motility for extended periods of time within a minimally invasive, radiation-free and ambulatory setting.

METHODS

A literature review of IC systems and a systematic review of studies utilizing IC systems to measure GI transit times in healthy volunteers was performed. Screening for eligible studies, data extraction and bias assessments was performed by two reviewers. A narrative synthesis of the results was performed.

RESULTS

The literature review identified 23 different IC systems. The systematic review found 6892 records, of which 22 studies were eligible. GI transit time data were available from a total of 1885 healthy volunteers. Overall, seventeen included studies reported gastric emptying time (GET) and small intestinal transit time (SITT). Colonic transit time (CTT) was reported in nine studies and whole gut transit time (WGTT) was reported in eleven studies. GI transit times in the included studies ranged between 0.4 and 15.3 h for GET, 3.3-7 h for SITT, 15.9-28.9 h for CTT and 23.0-37.4 h for WGTT. GI transit times, notably GET, were influenced by the study protocol.

CONCLUSIONS

This review provides an up-to-date overview of IC systems and reference ranges for GI transit times. It also highlights the need to standardise protocols to differentiate between normal and pathological function.

Research on Gastroesophageal Reflux Disease Based on Dynamic Features of Ambulatory 24-Hour Esophageal pH Monitoring

Ambulatory 24-hour esophageal pH monitoring has been considered as the gold standard for diagnosing gastroesophageal reflux disease (GERD), and in clinical application, static parameters are widely used, such as DeMeester score. However, a shortcoming of these static variables is their relatively high false negative rate and long recording time required. They may be falsely labeled as nonrefluxers and not appropriately treated. Therefore, it is necessary to seek more accurate and objective parameters to detect and quantify GERD. This paper first describes a new effort that investigated the feasibility of dynamic features of 24-hour pH recording. Wavelet energy, information entropy, and wavelet entropy were estimated for three groups (severe, mild-to-moderate, and normal). The results suggest that wavelet energy and entropy are physiologically meaningful since they differentiated patients with varying degrees of GERD. K-means clustering algorithm was employed to obtain the sensitivity and specificity of new parameters. It is obvious that information entropy goes with the highest sensitivity of 87.3% and wavelet energy has the highest specificity of 97.1%. This would allow a more accurate definition of the best indicators to detect and quantify GERD as well as provide an alternative insight into the early diagnosis of GERD.

Pediatric gastroesophageal reflux clinical practice guidelines: joint recommendations of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN)

OBJECTIVE

To develop a North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) and European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) international consensus on the diagnosis and management of gastroesophageal reflux and gastroesophageal reflux disease in the pediatric population.

METHODS

An international panel of 9 pediatric gastroenterologists and 2 epidemiologists were selected by both societies, which developed these guidelines based on the Delphi principle. Statements were based on systematic literature searches using the best-available evidence from PubMed, Cumulative Index to Nursing and Allied Health Literature, and bibliographies. The committee convened in face-to-face meetings 3 times. Consensus was achieved for all recommendations through nominal group technique, a structured, quantitative method. Articles were evaluated using the Oxford Centre for Evidence-based Medicine Levels of Evidence. Using the Oxford Grades of Recommendation, the quality of evidence of each of the recommendations made by the committee was determined and is summarized in appendices.

RESULTS

More than 600 articles were reviewed for this work. The document provides evidence-based guidelines for the diagnosis and management of gastroesophageal reflux and gastroesophageal reflux disease in the pediatric population.

CONCLUSIONS

This document is intended to be used in daily practice for the development of future clinical practice guidelines and as a basis for clinical trials.

Manometry and 24-hour pH monitoring in diagnosis and management of GORD

Gastro-oesophageal reflux disease (GORD) is mainly diagnosed on symptoms and endoscopy findings. At least 50% of patients with GORD will have a normal oesophagus at endosopy. Twenty four-hour ambulatory pH monitoring together with manometry offers an accurate objective diagnosis of GORD and is helpful in directing appropriate treatments including surgery.

Wireless esophageal pH monitoring: new technique means new questions

INTRODUCTION

The introduction of wireless pH monitoring has been touted as a significant advance in the diagnosis of gastroesophageal reflux and associated disorders. We prospectively enrolled patients in a research registry to assess the feasibility and safety in clinical use.

METHODS

All patients undergoing endoscopy with wireless pH studies (Medtronic Bravo pH system) for a 12-month period starting in April 2004 were prospectively enrolled. Probes were placed 6 cm above the endoscopically localized squamocolumnar junction. Successful completion was defined as at least 24 hours of pH recording. Safety data were obtained by review of patient diaries. All results are given as median with 25% to 75% confidence interval (CI).

RESULTS

A total of 217 studies with endoscopy and capsule placement were performed (65% women; median age, 51 years; range, 42-58 years) and included in the study; 1 patient refused participation in the registry and 5 studies were performed without preceding endoscopy and were excluded from this analysis. The pH study was successfully completed in 95.1%; early capsule detachment (1 hours; CI, 0-5 hours) or receiver malfunction occurred in 7 and 2 cases, respectively. There were no immediate adverse effects; 18 patients (9%) complained about significant chest discomfort, associated with odyno- or dysphagia, requiring removal of the capsule in 3 patients (1.5%). Of the completed studies, 56% were abnormal with 32.2% being abnormal on both days, whereas 16.1% and 6.9% only showed increased acid exposure on day 1 or 2, respectively. The higher likelihood of abnormal results for day 1 was associated with a significantly increased esophageal acid exposure during the first 6 hours after capsule insertion on day 1 (total time with pH < 4: 6.9%; CI, 3.2%-16.5%) compared with the corresponding time on day 2 (5.0%; CI, 0.9%-10.8%; P < 0.01), without differences esophageal acidification during the remaining time or differences in recorded activity.

CONCLUSIONS

Using a large registry of patients with suspected gastroesophageal reflux symptoms, our data show that wireless pH studies can be safely completed in more than 90% of patients. Whereas variability during prolonged recordings should be expected, the significantly higher likelihood of abnormal findings during the initial period of pH monitoring suggests a systematic influence of endoscopy and associated premedication, typically performed prior to capsule insertion, which needs to be considered when pH data are analyzed.

Ambulatory 24-hour esophageal pH monitoring: why, when, and what to do

The incidence of gastroesophageal reflux disease (GERD) is increasing and if left untreated can lead to significant patient morbidity and even death. The disease results from the abnormal reflux of gastric contents into the distal esophagus causing symptoms in most and subsequent mucosal damage in some. Several investigations can be used to confirm the diagnosis, but most are dependent on the presence of sequelae and complications of the disease. The physiologic test of ambulatory 24-hour esophageal pH monitoring has proved to be the most sensitive and specific diagnostic investigation. It measures increased esophageal exposure to gastric juice by detecting the concentration of hydrogen ions (pH <4) in the distal esophagus. The technique measures gastric juice exposure at a point 5 cm above the manometrically determined upper border of the lower esophageal sphincter. The exposure is measured in components of frequency of reflux episodes, duration of reflux episodes, and accumulated exposure time. The components are integrated into a composite score, which is reproducible, gender and race independent, and correlates with the degree of esophageal epithelial damage determined histologically. The composite score has been shown to be the most reliable measurement of a therapeutic acid suppression regimen or an effective antireflux operation.

Postprandial Acid Reflux is Reduced by Delayed Gastric Emptying

The aim of this study was to investigate influence of delayed gastric emptying on postprandial reflux in esophageal pH. Sixty-nine consecutive patients underwent 24 hour (h) esophageal pH monitoring and gastric emptying. In 24 h esophageal pH monitoring, % postprandial reflux pH<4 for 2 h after each meal (% PRT) was extracted from the 24 h pH profile. After solid test meal (1 mCi, Tc99m) was given, gastric emptying was measured with a gamma detector placed transnasally 5 cm below lower esophageal sphincter. % PRT was similar among the 34 normal, 26 delayed and 9 rapid gastric emptying rate patients. Thirty-five with a positive pH study and 34 with a negative had a similar prevalence of gastric emptying disorder. In the positive pH study group, patients with normal gastric emptying had significantly higher % PRT than those with delayed gastric emptying (22.0 vs 12.1%, P<0.05). In the same population, patients with a normal %PRT had a significantly higher prevalence of delayed gastric emptying compared with those with a positive % PRT (6/8 vs 9/27, P<0.05). In patient with abnormal acid exposure but normal % PRT on 24 h esophageal pH monitoring, gastric emptying may be delayed.

Esophageal pH monitoring, indications, and methods

Symptomatic gastroesophageal reflux disease (GERD) is a common problem that affects a substantial proportion of the American population. It is estimated that the symptoms of GERD may afflict 40% to 45% of Americans each month. The diagnosis of GERD can be difficult, as its symptoms vary from typical symptoms like heartburn to atypical symptoms such as hoarseness, coughing, and chest pain. Most patients present with typical symptoms and are diagnosed with GERD if they respond to empiric trials of acid suppression. Many tests are available to help with diagnosing GERD in patients who either present with atypical symptoms or who do not respond to acid suppression; however, each test has its own shortcomings. The only test that directly measures whether acid is refluxing into the esophagus is the pH probe, but this test is uncomfortable for the patient, can be difficult to interpret, and may not be necessary in all cases. This article reviews the indications for pH monitoring, its technique, its advantages and limitations, and its role the diagnosis of GERD.

Ambulatory esophageal pH monitoring: technique, interpretations, and clinical indications

Gastroesophageal reflux disease (GERD) is the most common esophageal disorder and perhaps among the most prevalent conditions seen in the primary care setting. The clinical manifestations of GERD, typical or atypical, such as noncardiac chest pain, respiratory or ear, nose, and throat symptoms, result from the reflux of gastric contents into the esophagus. Thus the clinical spectrum is wide and requires accurate diagnosis. Ambulatory 24-hr esophageal pH monitoring is not useful in all patients suspected to have GERD. This review describes the technique of ambulatory 24-hr esophageal pH monitoring, the interpretation of findings, and clinical applications of this test.

Twenty-four hour pH monitoring in the assessment of esophageal function

Ambulatory 24-hour esophageal pH monitoring is an important test in the management of patients with gastroesophageal reflux disease. It quantifies esophageal acid exposure while patients pursue their everyday activities without restrictions. The test is performed with a compact portable data logger, miniature pH electrode, and computerized data analysis. The pH electrode should be positioned 5 cm above the manometrically defined lower esophageal sphincter. The patient is asked to press a button on the data logger indicating the onset of the symptom in question, which allows symptoms and acid reflux correlation. Twenty-four hour pH monitoring is generally performed after a therapeutic trial of antireflux medications, preferably proton pump inhibitors.

Reproducibility of 24-hour intraesophageal pH monitoring in pediatric patients

OBJECTIVE

Despite the widespread use of 24-hour intraesophageal pH monitoring for evaluation of gastroesophageal reflux in infants and children, there is little published information regarding the reproducibility of ambulatory pH studies in this patient population. The purpose of our study was to evaluate the reproducibility of 24-hour intraesophageal pH monitoring in pediatric patients.

METHODS

We prospectively investigated 26 patients with symptoms suggestive of gastroesophageal reflux (14 females and 12 males) ranging in age from 1 month to 18 years (mean, 9.2 years). The patients underwent extended intraesophageal pH monitoring over two consecutive 24-hour periods.

RESULTS

Data analysis revealed that the overall reproducibility of ambulatory 24-hour pH monitoring is only 69% (r = 0.32). Eight of 26 patients had conflicting results on day 1 compared with results on day 2. Of the 8 patients with conflicting results on day 1 versus day 2, 5 had normal studies on day 1, but demonstrated pathologic reflux on day 2. Thus, the false-negative rate for day 1 was 19.2%. The kappa statistic calculated for the total time the pH was abnormal was 0.32, with values < 0.4 representing poor correlation. Spearman correlation coefficients indicated that the percentage of time with pH < 4 (r = 0.64) and the number of reflux episodes (r = 0.71) per 24-hour period are the most reproducible pH parameters.

CONCLUSION

The reproducibility of 24-hour intraesophageal pH monitoring in the pediatric population is suboptimal. The investigation should be extended or repeated if the result does not correlate with the patient's clinical history.

Patterns of food and acid reflux in patients with low-grade oesophagitis--the role of an anti-reflux agent

BACKGROUND

Food and acid have been shown to be refluxed independently of each other in healthy volunteers, and anti-reflux agents decrease the reflux of both parameters. Until now this phenomenon had not been studied in patients with low-grade oesophagitis, who are the group most likely to use anti-reflux medication.

AIM

To assess patterns of gastro-oesophageal reflux of acid and food in 12 ambulant patients with endoscopically proven oesophagitis of between grades I and II, but who were otherwise healthy. Also to assess the effectiveness of a single dose of an alginate-containing anti-reflux agent in controlling food and acid reflux in this patient group.

METHODS

Oesophageal pH monitoring and external ambulatory gamma detection were used to study food and acid reflux. A pH electrode was positioned 5 cm above the cardia and the gamma detector was positioned externally over the pH electrode. The patients then received a technetium-99m labelled meal designed to provoke reflux. Thirty minutes later the patients were given a 20 ml dose of alginate (Liquid Gaviscon), or 20 ml of tap water. Incidence of reflux was monitored for approximately 4 h from the end of the meal. Allocation to treatment group was randomized, with patients receiving the alternative treatment on the second study day after approximately a 7-day washout period.

RESULTS

The mean percentage time oesophageal pH remained below 4 was 16.3 min for the control group and 5.4 min for the treatment group (P = 0.03). Food reflux was detected 23.7% of the time in the control group compared to 12% of the time in the treatment group (P = 0.02). The anti-reflux agent was also successful in decreasing the number of events, but the duration of the reflux events was not significantly different.

CONCLUSIONS

Patients with grades I and II oesophagitis reflux food and acid independently, and are predominantly either food refluxers or acid refluxers, but not both. Liquid alginate decreases the number of both food and acid reflux events, but does not change their duration.

Gastroesophageal reflux, motility disorders, and psychological profiles in the etiology of globus pharyngis

The aim of this study was to investigate the origin of globus pharyngis with particular reference to esophageal disorders such as gastroesophageal reflux disease (GERD), motility disorders, structural abnormalities, other gastrointestinal tract diseases, and psychological profile. Previous studies on this subject using 24-hour pH monitoring give conflicting results and are hampered by the high background prevalence of asymptomatic GERD in the normal Western population. The local Chinese population is known to have a very low background level of GERD and therefore is an ideal study population. Twenty-six patients with globus pharyngis underwent 24-hour ambulatory pH monitoring, esophageal manometry, and esophagogastroduodenoscopy with lower esophageal biopsy. A control group of 20 patients presenting with non-ulcer dyspepsia was similarly investigated. Personality profiles of the globus pharyngis subjects and an appropriate control group were assessed. Eight of the globus pharyngis group (30.7%) had evidence of GERD, whereas only one of the controls (5%) demonstrated GERD on 24-hour esophageal pH monitoring (P < 0.05). The manometric and personality profile studies did not show significant differences between study and control groups. We concluded that the finding of GERD in patients with globus pharyngis is not a coincidental finding but that there is a true association between GERD and globus pharyngis.

Motor events underlying gastro-oesophageal reflux in ambulant patients with reflux oesophagitis

Information on the mechanism of gastro-oesophageal reflux in patients with reflux disease is limited largely to studies in resting recumbent subjects. Evidence exists that both posture and physical activity may influence reflux. The aim of this study was to investigate reflux mechanisms in ambulant patients with reflux oesophagitis. Concurrent ambulatory oesophageal manometry and pH monitoring were performed in 11 ambulant patients with erosive oesophagitis. Lower oesophageal sphincter (LOS) pressure was monitored with a perfused sleeve sensor. Recordings were made for 90 min before and 180 min after a meal. At set times patients sat in a chair or walked. LOS pressure was < or = 2 mmHg at the time of reflux for 98% of reflux episodes. Transient LOS relaxation was the most common pattern overall and the predominant pattern in seven patients, whilst persistently absent basal LOS pressure was the most common pattern in four patients. The pattern of LOS pressure was not altered by the presence of hiatus hernia or by walking. Straining occurred at the onset of 31% of acid reflux episodes but often followed the development of an oesophageal common cavity. The occurrence of straining was not influenced by walking. In ambulant patients with reflux oesophagitis: (1) LOS pressure is almost always absent at the time of reflux, usually because of transient LOS relaxation, (2) persistently absent basal LOS pressure is an important mechanism of reflux in a few patients, (3) straining may help to induce acid reflux in a variable proportion of occasions and may in some instances be a response to gas reflux, and (4) walking does not influence the occurrence of reflux or its mechanisms.

Gastroesophageal reflux in childhood

Gastroesophageal reflux (GER) is one of the most frequent symptomatic clinical disorders affecting the gastrointestinal tract of infants and children. During the past 2 decades, GER has been recognized more frequently because of an increased awareness of the condition and also because of the more sophisticated diagnostic techniques that have been developed for both identifying and quantifying the disorder. Gastroesophageal fundoplication is currently one of the three most common major operations performed on infants and children by pediatric surgeons in the United States. Normal gastroesophageal function is a complex mechanism that depends on effective esophageal motility, timely relaxation and contractility of the lower esophageal sphincter, the mean intraluminal pressure in the stomach, the effectiveness of contractility in emptying of the stomach, and the ease of gastric outflow. More than one of these factors are often abnormal in the same child with symptomatic GER. In addition, in patients with GER disease, and particularly in those patients with neurologic disorders, there appears to be a high prevalence of autonomic neuropathy in which esophagogastric transit and gastric emptying are frequently delayed, producing a somewhat complex foregut motility disorder. GER has a different course and prognosis depending on the age of onset. The incompetent lower esophageal sphincter mechanism present in most newborn infants combined with the increased intraabdominal pressure from crying or straining commonly becomes much less frequent as a cause of vomiting after the age of 4 months. Chalasia and rumination of infancy are self-limited and should be carefully separated from symptomatic GER, which requires treatment. The most frequent complications of recurrent GER in childhood are failure to thrive as a result of caloric deprivation and recurrent bronchitis or pneumonia caused by repeated pulmonary aspiration of gastric fluid. Children with GER disease commonly have more refluxing episodes when in the supine position, particularly during sleep. The reflux of acid into the mid or upper esophagus may stimulate vagal reflexes and produce reflex laryngospasm, bronchospasm, or both, which may accentuate the symptoms of asthma. Reflux may also be a cause of obstructive apnea in infants and possibly a cause of recurrent stridor, acute hypoxia, and even the sudden infant death syndrome. Premature infants with respiratory distress syndrome have a high incidence of GER. Esophagitis and severe dental carries are common manifestations of GER in childhood. Barrett's columnar mucosal changes in the lower esophagus are not infrequent in adolescent children with chronic GER, particularly when Heliobacter pylori is present in the gastric mucosa. Associated disorders include esophageal dysmotility, which has been recognized in approximately one third of children with severe GER. Symptomatic GER is estimated to occur in 30% to 80% of infants who have undergone repair of esophageal atresia malformations. Neurologically impaired children are at high risk for having symptomatic GER, particularly if nasogastric or gastrostomy feedings are necessary. Delayed gastric emptying (DGE) has been documented with increasing frequency in infants and children who have symptoms of GER, particularly those with neurologic disorders. DGE may also be a cause of gas bloat, gagging, and breakdown or slippage of a well-constructed gastroesophageal fundoplication. The most helpful test for diagnosing and quantifying GER in childhood is the 24-hour esophageal pH monitoring study. Miniaturized probes that are small enough to use easily in the newborn infant are available. This study is 100% accurate in diagnosing reflux when the esophageal pH is less than 4.0 for more than 5% of the total monitored time.

Small bowel biopsy by remote control: experimental study on dogs

Telemetry has been used for 30 years in medicine because it requires no link between patients and apparatus. To take advantage of this, we have developed a multipurpose intestinal capsule for the small bowel, with interchangeable tips triggered by remote control. A new tip, performing small bowel mucosal biopsy by remote control is presented. The location of the capsule is radiotransmitted by means of a cogwheel, which is rotated by contact with the intestinal wall. At the chosen site (ie, a number of centimeters from the pylorus), the remote control is activated and the mucosal biopsy is performed through a suction port and kept inside the tip. The capsule then passes throughout the bowel and is recovered in the stool to allow examination of the biopsies. The results of 24 studies on a dog (crossing of the pylorus, length, transit time, velocity) are analyzed to validate the method. Biopsies were accomplished in the stomach, the small bowel (ileum), and the colon. The device failed two times, but no complications occurred. Biopsies, with average surfaces were 6mm2, never penetrated the longitudinal muscular layer. The system is precise to within 3 cm, efficient, reliable, noninvasive, and causes minimal discomfort during investigation.

How well can quantitative 24-hour intraesophageal pH monitoring distinguish various degrees of reflux disease?

Twenty-four normal subjects and 64 symptomatic patients with various degrees of reflux disease (24 with reflux symptoms without esophagitis and 21 with mild and 19 with severe esophagitis) underwent quantitative 24-hr intraesophageal pH monitoring. Various reflux parameters during supine, interprandial, and postprandial periods were examined by binary logistic regression and by CART analysis to determine the sensitivity and specificity to separate the various groups of subjects and patients. The distinction was excellent between asymptomatic controls and patients with severe erosive esophagitis (sensitivity and specificity both 100% by logistic regression and 95% and 88%, respectively, by CART), but discrimination was poor when asymptomatic controls were compared to symptomatic patients without esophagitis (71% and 79% by logistic regression and 75% and 92% by CART), which is the most important indication for pH recording in clinical practice. A 3-hr postprandial pH recording was inadequate to distinguish the various groups. The acidity of the reflux episodes during the night appeared to be a crucial factor in the development of severe erosive esophagitis. The duration of esophageal acid exposure was another important factor in the development of reflux lesions.

Mechanisms of gastroesophageal reflux in ambulant healthy human subjects

BACKGROUND/AIMS

Investigation of the motor events underlying gastroesophageal reflux has largely been confined to resting, recumbent subjects. The motor events associated with reflux during physical activity remain unknown. The aim of this study was to investigate the patterns of lower esophageal sphincter (LES) function underlying reflux in healthy subjects and the effect of exercise and physical activity on reflux mechanisms.

METHODS

LES pressure was recorded with a perfused sleeve sensor in 10 healthy subjects; intraluminal transducers recorded pressure in the stomach, esophagus, and pharynx, and pH was recorded 5 cm above the LES. Signals were stored in a portable data-logger. Recordings were made for 24 hours, including moderate physical activity, periods of rest and sleep, standardized meals, and standardized exercise.

RESULTS

Most reflux episodes (81 of 123; 66%) occurred in the 3 hours after food intake; only 2 episodes occurred during exercise. LES pressure was < or = 3 cm H2O in 79% of reflux episodes. Transient LES relaxation was the mechanism of reflux in 82% of episodes, irrespective of activity or body position, whereas swallow-related LES relaxations accounted for 13% and persistently absent LES pressure accounted for 1%. Straining occurred in only 20% of episodes.

CONCLUSIONS

In ambulant healthy subjects, accurate continuous recording of LES function is possible, reflux usually occurs during transient LES relaxations, and straining is not a major factor in the induction of reflux.

Implications of upright gastro-oesophageal reflux

The presentation, oesophageal profile and management of 27 symptomatic patients with daytime (upright) gastro-oesophageal reflux only is reported. Oesophagitis was a presenting feature in 11 patients and its development was most closely correlated with postprandial reflux, which was characterized by cumulative acid exposure rather than by clearance abnormalities. Upright reflux was not associated with a hypotensive lower oesophageal sphincter or with oesophageal dysmotility. Antireflux surgery is indicated when conservative measures fail and was not associated with gas-bloat syndrome after operation.

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.

Non-invasive detection of gastro-oesophageal reflux using an ambulatory system

The aim of this study was the separate measurement of reflux of food and acid into the oesophagus in 37 healthy, ambulant subjects. This was performed by radiolabelling the food and monitoring its reflux with a small directional gamma detector, which was placed externally over the oesophagus, and connected to an ambulatory data recorder. The pH was measured with a conventional oesophageal pH electrode. This method permitted the separate characterisation of acid and neutral (food) components of gastro-oesophageal reflux. The gastric emptying characteristics of the test meal were also monitored by gamma scintigraphy in a separate experiment. The oesophageal pH fell below 4 for 3.2 + 8.6/-2.3% (mean (SD)) of the recording time. Food reflux alone occurred for 17.8 + 53.2/-13.8% of the recording time. Simultaneous food and acid reflux occurred for only 0.95 + 5.2/-1.2% of the time. Not every reflux event detected by a fall in pH was seen as an increase in counts as a result of reflux of food, and vice versa. This poor correlation of food and acid reflux implies incomplete mixing of food and acid in the stomach, and further shows the inadequacy of reflux diagnosis methods that depend on pH detection alone.

Prolonged intraesophageal pH monitoring with 16-hr overnight recording. Comparison with "24-hr" analysis

From studies in 43 patients (17 male, 26 female, mean age 51 years), we compared the analysis of the routine complete "24-hr" ambulatory esophageal pH monitoring study to that of the 16-hr overnight interval (4:00 PM to 8:00 AM). The latter included a major meal with an upright postprandial period and a recumbent period. All patients were monitored for at least 20 hr (median = 22.6 hr). The percent distal esophageal pH less than 4.0 and number of reflux episodes were measured for the total, upright, and recumbent periods of both the 16-hr and "24-hr" monitoring times. Significant (P less than 0.001) positive correlations were found for all comparisons between the two monitoring periods including percent time of pH less than 4.0 (total: r = 0.98; upright: r = 0.96) and number of episodes (totals r = 0.97; upright: r = 0.93). Patients were separated into normal and abnormal refluxers based on results of "24-hr" monitoring (pH below 4.0 greater than 4.2% total time; greater than 6.0% upright; greater than 1.2% recumbent). Based on this, sensitivity and specificity for 16-hr monitoring were as follows: total study: 86% and 95%; upright: 80% and 91%; recumbent: 100% for both.

CONCLUSIONS

(1) a 16-hr overnight pH monitoring period can provide a reliable representation of "24-hr" distal esophageal acid exposure, (2) this shorter monitoring may improve patient acceptability and compliance, and (3) the symptom index was changed in 26.3% of patients using the 16-hr evaluation.

Oesophageal pH-metry: should meals be standardized?

To assess the effect of a late-evening, high-fat meal on nocturnal supine gastro-oesophageal reflux, eight healthy volunteers (aged 20 to 38 years) underwent two ambulatory oesophageal pH-metry recordings, the first after a standardized light meal at 1930 h and the second after a high-fat meal including peppermint and chocolate, at 2130 h. Between 2300 and 0700 h, when subjects were supine, the median acid exposure time (percentage recording with pH less than 4) increased from 0.0% (range, 0.0-6.8%) after the standardized meal to 7.9% (0.0-17.8%) after the high-fat meal (p = 0.031). Similarly, the median number of reflux episodes increased from 0 (0 to 11) after the standardized meal to 7 (0 to 26) after the high-fat meal (p = 0.031). Reflux occurred after both meals, but, in general, persistent nocturnal reflux was observed only after the high-fat meal. Thus, the analysis of oesophageal pH recordings should consider the effects of meal composition and timing on oesophageal acid exposure.

Alternative method of positioning the pH probe for oesophageal pH monitoring

The most reliable method of positioning a pH probe for oesophageal pH monitoring is to use manometry to determine the upper margin of the lower oesophageal sphincter and to place the probe 5 cm above this point. Manometry is expensive, however, requires special equipment and training, and is not widely available. An alternative cheaper way of determining the site of the lower oesophageal sphincter has been evaluated. A fine bore nasogastric tube with a latex balloon at its tip was inserted transnasally into the stomach. The balloon was inflated with 10 ml of water and the tube withdrawn until resistance was met. The distance from the nose (in cm) was noted and compared with the upper margin of the lower oesophageal sphincter as determined by oesophageal manometry. The manometric distance agreed closely with the balloon distance minus 1 cm (bias 0.29 cm; 95% CI of bias, 0.03 to 0.55 cm; 2 SD, limits of agreement, 1.58 cm). We conclude that where oesophageal manometry is not available, balloon localisation is a suitably accurate way of identifying the lower oesophageal sphincter.

Twelve hour overnight oesophageal pH monitoring in patients with reflux symptoms

Results of continuous 12 hour overnight pH monitoring (duration of pH less than 4) were reviewed in 112 patients with heartburn or regurgitation, or both, and in 56 normal subjects. Patients had more reflux than normal subjects. Medically controlled patients (n = 51) had less acid reflux than patients who subsequently underwent reflux surgery (n = 61), but there was a considerable overlap between those two groups. Surgery was followed by a reduction in acid reflux to a value similar to that in normal subjects. Patients in whom surgery was deemed to have failed had more reflux after the operation than those in whom it was successful, but no difference could be found in the preoperative reflux values of these two subgroups. Monitoring pH is not of value in selecting candidates for surgery since the results are not a good predictor of outcome, but it is useful in the objective evaluation of surgical results.

Do nasogastric feeding tubes cause gastro-oesophageal reflux in healthy subjects?

The potential relationship between nasogastric intubation and acid gastro-oesophageal reflux was investigated. Ten healthy volunteers underwent 24h oesophageal pH monitoring following intubation with (i) a pH monitor alone, (ii) a pH monitor plus a Ryles nasogastric tube and (iii) a pH monitor plus a fine-bore nasogastric feeding tube. Neither of the nasogastric intubations were associated with significant reflux.

Reproducibility of 24 hour oesophageal pH studies in infants

Thirteen infants who had undergone 24 hour oesophageal pH monitoring to diagnose gastro-oesophageal reflux had a second study carried out to see if the results were reproducible. The studies were done without restricting the babies' activities. Appreciable differences were found, the percentage of the total time during which the pH was less than 4 varying by up to 3.7-fold between the two tests. The differences were largely the result of biological rather than technical variability. From these results estimates were made of the reliability of a single diagnostic study and the size of changes that would be necessary to show the effect of treatment. These findings have a considerable impact on the diagnosis of abnormal gastro-oesophageal reflux and its response to treatment whether using 24 hour pH monitoring or any other method of measurement.

Most asthmatics have gastroesophageal reflux with or without bronchodilator therapy

The relationship between gastroesophageal reflux and asthma has not been clearly defined. We measured the lower esophageal sphincter pressures and studied gastroesophageal reflux patterns over 24 hours using an ambulatory Gastroreflux Recorder (Del Mar Avionics, Irvine, CA) in 44 controls and 104 consecutive adult asthmatics. The presence or absence of reflux symptoms was not used as a selection criterion for asthmatics. All asthmatics had discrete episodes of diffuse wheezing and documented reversible airway obstruction of at least 20%. Patients underwent reflux testing while receiving, if any, their usual asthmatic medications: 71.2% required chronic bronchodilators and 28.8% required no bronchodilators. Compared with controls, asthmatics had significantly decreased lower esophageal sphincter pressures, greater esophageal acid exposure times, more frequent reflux episodes, and longer clearance times in both the upright and supine positions (P less than 0.0001 for all parameters tested). There were no differences in any of the measured reflux parameters between asthmatics who required bronchodilators and those who did not. Thus, the decreased lower esophageal sphincter pressures and increased levels of acid reflux in asthmatics were not entirely caused by the effects of bronchodilator therapy. Receiver-operating characteristic analysis generated reflux values that discriminated asthmatics from controls. More than 80% of adult asthmatics have abnormal gastroesophageal reflux. We conclude that most adult asthmatics, regardless of the use of bronchodilator therapy, have abnormal gastroesophageal reflux manifested by increased reflux frequency, delayed acid clearance during the day and night, and diminished lower esophageal sphincter pressures.

The interpretation of oesophageal pH monitoring data

Continuous monitoring of oesophageal pH is regarded as the gold standard for all reflux investigations. However, since gastro-oesophageal reflux is considered a normal phenomenon which occurs to a certain extent in each individual, the distinction between "normal" and "abnormal" is not always obvious and is not possible to achieve with a single test. Moreover, data depend on technical hardware such as recording devices and electrodes together with such patient characteristics as age, position, activity, and medication. Although much literature on pH monitoring has appeared recently, many investigations have failed to take into account the basic principles that are of major importance for any biomedical test such as reproducibility, sample reliability, and indications. There is a need to standardize the technique in order to compare studies performed in different centres, provided the technique is reproducible.

Value of the 24 hour intraoesophageal pH monitoring in children

Twenty four hour oesophageal intraluminal pH probe studies were performed in 114 children (range age: one month-12 years) referred for symptoms or signs compatible with gastroesophageal reflux. Forty five patients had reflux disease alone, 69 had evidence of oesophagitis which was assessed endoscopically and histologically. Recordings were also performed in 63 control patients. The occurrence of reflux was analysed for the total study period and particularly while awake, asleep, fasting, and during postcibal periods. Oesophageal acid exposure time and the number of reflux episodes lasting greater than five minutes during the total study period provided the best discrimination between patients and controls; however, 20% and 30% of all reflux patients had both normal (with 2 SD of control) acid exposure time and number of long lasting reflux episodes, respectively. Patients with oesophagitis had significantly more acid reflux than those with simple uncomplicated disease during postcibal, fasting, awake periods, but not during sleep; however, increasing severity of oesophagitis was not associated with increasing acid exposure. The ability of the intraluminal oesophageal pH test to discriminate patients with various degrees of reflux disease decreased if only postprandial pH variables were taken into account. We conclude that: (1) the 24 hour intraoesophageal pH monitoring may present false negative results that limit overall sensitivity of the test; (2) the presence of oesophagitis does not seem to be associated with increased oesophageal acid exposure during sleep; (3) limiting the pH recording to postprandial periods reduces the discriminatory power of the test.

Reliability of 24-hour home esophageal pH monitoring in diagnosis of gastroesophageal reflux

Twenty-four-hour home esophageal pH monitoring is proposed in order to study gastroesophageal reflux (GER) so that prolonged use of costly hospital equipment and staff can be curtailed and the diagnostic accuracy of the examination improved. Eighty-six patients affected by GER symptoms and 20 healthy volunteers underwent 24-hr home esophageal pH monitoring, x-rays, and endoscopy of the upper gastrointestinal tract to investigate reliability of outpatient recording. Fifteen more patients consecutively underwent out- and inpatient recording to detect possible differences between these methods in the two daily periods. Outpatient monitoring was well tolerated in 94.7% of the patients; 14.3% of them markedly reduced their routine activities. The range of normality of outpatient recording does not differ from that of inpatients. In the 15 patients who consecutively underwent out- and inpatient monitoring, no significant differences were reported. The sensitivity of 24-hr home esophageal pH recording is 0.85, the specificity 1, the accuracy for negative prediction 0.68, and the accuracy for positive prediction 1. The reliability of 24-hr home esophageal pH monitoring is comparable to inpatient recording. It allows hospital cost reduction and is also better tolerated by patients but has not greatly improved the diagnostic accuracy of the gastroesophageal reflux pH monitoring.

Intragastric and intraoesophageal pH monitoring in duodenal ulcerpatients: effect of the new histamine H2-receptor antagonist ramixotidine

The effect of the new histamine H2-receptor antagonist ramixotidine 750 mg p.o., administered at 22.00 h, on intragastric and intraoesophageal pH monitored from 22.00 h to 08.00 h, was studied in a double-blind cross-over trial in 11 duodenal ulcer patients. Placebo and ramixotidine were given to each patient on 2 consecutive days in a randomized sequence. Three patients were excluded from the intragastric pH analysis as the records on the second study day were technically inadequate. No significant carry-over or sequence effect was noted. Intragastric hydrogen ion activity was significantly lower (p = 0.01) after ramixotidine than after placebo: median (range) 24 (9-100) vs 97 (27-188) mmol/l. The percentage of time with intraoesophageal pH less than 4 was less than 5% in all but three recordings, with a maximum value of 12%, and it was not significantly different after the two treatments.

The effect of omeprazole or ranitidine treatment on 24-hour esophageal acidity in patients with reflux esophagitis

Twenty-two consecutive patients with gastroesophageal reflux and erosive or ulcerative esophagitis entered a double-blind, randomized study comparing the effect of 20 mg omeprazole once daily with that of 150 mg ranitidine twice daily on esophageal acidity. Ambulatory 24-h esophageal pH measurements were performed within 1 month before inclusion and after 3 weeks of medication. Omeprazole significantly (p less than 0.05) reduced the number of reflux (pH less than 4) episodes, the number of refluxes lasting greater than 5 min, and the total reflux time. In contrast, ranitidine significantly reduced only the total reflux time. When the two treatment groups were compared, a significant difference in favor of omeprazole was found for daytime and total reflux values, except for the longest reflux and the number of reflux episodes lasting greater than 5 min. Substantial differences, also in favor of omeprazole, were found with regard to the effect on endoscopic healing of the esophagitis.

Measurement of gastrointestinal pH profiles in normal ambulant human subjects

Gastrointestinal (GI) pH has been measured in 66 normal subjects using a pH sensitive radiotelemetry capsule passing freely through the gastrointestinal tract. Signals were recorded with a portable solid state receiver and recording system, enabling unconstrained measurements with normal ambulatory activities for up to 48 h during normal GI transit. Capsule position in the gut was monitored by surface location using a directional detector. Gastric pH was highly acidic (range 1.0-2.5) in all subjects. The mean pH in the proximal small intestine was 6.6 (0.5) for the first hour of intestinal recording. By comparison the mean pH in the terminal ileum was 7.5 (0.4) (p less than 0.001). In all subjects there was a sharp fall in pH to a mean of 6.4 (0.4) (p less than 0.001) as the capsule passed into the caecum. Values are means (SD). pH then rose progressively from the right to the left colon with a final mean value of 7.0 (0.7) (p less than 0.001).

Comparison of three methods of intraesophageal pH recordings in the diagnosis of gastroesophageal reflux

Three different periods of intraesophageal pH-recording (24 h, 12 h, and 10 h postprandially) have been compared in 20 healthy subjects and in 20 outpatients with symptoms and endoscopic signs of peptic esophagitis, to assess their relative values of sensitivity and specificity in the diagnosis of gastroesophageal reflux. No false-positive results were obtained during any of the periods, thus yielding a 100% specificity. However, the sensitivity shown by the 24-h period of esophageal pH-recording was 81%, whereas that for the 12-h period was 50% and that for 10 h postprandially 70%. Also, no significant differences were observed in terms of the patients' tolerability for the test during any of the three periods. We therefore conclude that 24-h esophageal pH-recording is the method of choice in ambulatory diagnosis of gastroesophageal reflux.

Reproducibility of ambulatory oesophageal pH monitoring

To evaluate the reproducibility of ambulatory 24 hour intraoesophageal pH monitoring, 20 patients were randomly selected to undergo two consecutive investigations. Fifteen patients were classified as either abnormal, or normal on both test days. The amount of acid reflux, expressed as percentage of time with oesophageal pH below 4.0 during the two 24 hour periods, showed 77% concordance. The upright and recumbent periods of measurement showed different degrees of concordance: 83% and 62%, respectively. The reproducibility during time periods of different length was found to increase with increasing length of day time pH recording. A 16 hour period during evening and night had a reproducibility of only 58%, however. It is concluded that there is fairly good reproducibility when measuring gastro-oesophageal reflux over 24 hours, but that the reproducibility is poorer at night, during the postprandial period and when daytime monitoring is shorter than 10 hours.

The diagnostic value of computerized short-term oesophageal pH-monitoring in suspected gastro-oesophageal reflux

In 109 consecutive patients suspected of having gastro-oesophageal reflux (GOR) a 3.5-h pH-monitoring in the oesophagus was performed during the daytime. The data were stored in a portable recording system, and three different variables (mean pH, mean acid clearance rate, and number of spikes) were calculated. Compared with a combined endoscopic-histologic score for the diagnosis of oesophagitis, assumed to be due to GOR, the 3.5-h pH-monitoring had a sensitivity of 85% and a specificity of 81%. The data suggest that the short-term pH-monitoring is almost as accurate as the traditional 24-h pH-monitoring and more convenient both for the patient and the gastroenterologic unit.

Computerized ambulatory esophageal pH monitoring in 50 asymptomatic volunteer subjects. Results and clinical implications

Fifty asymptomatic volunteer subjects underwent prolonged computerized ambulatory distal esophageal pH monitoring to characterize acid reflux patterns. A bimodal distribution of data, which corresponded to the erect and supine positions, occurred in 45 subjects, and separate mean baseline pH values were noted for the erect and supine positions (pH 6.46 and pH 5.46, respectively, p less than 0.001). At esophageal pH 4, reflux episodes occurred more commonly in the erect position (44 percent) than in the supine position (20 percent). There were also significantly greater numbers of reflux events and longer durations when the pH was below 3 (p less than 0.02) and 4 (p less than 0.001) in the erect compared with the supine position, but prolonged events (more than 10 minutes) occurred in both positions. Postprandial reflux occurred in 78.7 percent of the subjects, with an average of 5.1 episodes. A slight but significant correlation between age and erect reflux was seen (p less than 0.04). In the pH 3 to 5 range, 18 percent of the subjects had acid exposure in excess of the group mean plus 2 standard deviations and 10 percent in excess of the mean plus 3 standard deviations. Overall, a nonnormal distribution of pH data was found with 28 subjects having less than 1.6 percent of their values below pH 4. This finding may represent either the true spectrum of normal acid reflux or a subclinical pathologic state that will become symptomatic over time.

Acid gastro-oesophageal reflux and oesophageal pressure activity during postprandial and nocturnal periods. A study in subjects with and without pathologic acid gastro-oesophageal reflux

The aim of the investigation was to evaluate the relative quantity of acid gastrooesophageal reflux during different time periods in subjects with and without pathologic reflux. Twenty duodenal ulcer patients, 10 with and 10 without pathologic acid gastro-oesophageal reflux, and 26 asymptomatic volunteers were subjected to 12 h of simultaneous monitoring of pH and pressure activity in the oesophagus. The monitoring period was divided into a 3-h postprandial period, a night period of 6 h, and a 3-h period in the morning. The highest reflux frequency and the longest duration of oesophageal acid exposure were found in the postprandial hours (p less than 0.001). Thereafter, all groups had an even reduction in reflux rate. A greater absolute reduction in the duration of oesophageal acid exposure could be measured in patients with pathologic reflux as compared with the other groups (p less than 0.001). In spite of this, both reflux frequency and time with acid in the oesophagus were increased during the night in patients with pathologic reflux (p less than 0.001). Pathologic refluxers had in total 11 times as much reflux as normal subjects, and in addition 37.9% of the reflux took place during the 6 night hours. In contrast, only 5.4% of the reflux recorded in normal subjects occurred during this period. The pressure activity during periods with a normal intraoesophageal pH was reduced in all three groups during the night (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory 24 hour intraesophageal pH-monitoring in the diagnosis of gastroesophageal reflux disease

The results of ambulatory 24 hour oesophageal pH monitoring in 20 patients with established gastro-oesophageal reflux disease were compared with those of 20 healthy individuals with normal endoscopy. Cut off limits of pH 3, 4, and 5 were superior to pH 2 with respect to the discrimination of patients from normal subjects, and for the detection of pathological reflux. Using pH 4 as a cut off limit, the ambulant and recumbent periods of pH monitoring were more discriminatory than the postprandial period. Furthermore, it was possible to get complete separation between patients and normal subjects using several combinations of two reflux variables. Another group of 30 patients and 30 controls were investigated. Using percentage time at pH less than 4 as a single determinant of gastro-oesophageal reflux, the sensitivity and specificity were 87% and 97%, respectively, with 3.4% as upper limit for normality. Twenty four hour oesophageal pH monitoring in an ambulatory outpatient environment afforded clinically useful diagnostic accuracy in separating patients with gastro-oesophageal reflux disease from asymptomatic controls.

Globus sensation is not due to gastro-oesophageal reflux

Oesophageal manometry and prolonged ambulatory pH monitoring were performed in 47 patients with the globus sensation, 48 control subjects and 28 patients with documented oesophagitis. Globus patients also underwent video-recorded barium examination and rigid endoscopy. Manometry was normal in 38 of the globus group (94%). The mean percentage time below pH 4 was 4.16 in controls, 5.11 in globus patients (NS) and 18.54 in oesophagitis patients (P less than 0.0005). Oesophageal acid exposure did not correlate with sex, smoking or heartburn and correlated with age only in oesophagitis patients (P less than 0.001). Biopsy showed mild laryngitis in 2 globus patients and distal oesophagitis in 6 (13%). Abnormal oesophageal acid exposure and distal oesophageal dysmotility are not aetiological factors in the majority of patients with globus pharyngis.

Optimal thresholds, sensitivity, and specificity of long-term pH-metry for the detection of gastroesophageal reflux disease

Long-term esophageal pH-metry has become the preferred test to quantify acid gastroesophageal reflux, but its accuracy in separating physiologic from pathological reflux is not well defined. To establish optimal thresholds of 24-h pH-metry, we studied 45 patients with clinically proven gastroesophageal reflux disease and 42 healthy volunteers. Twenty-four-hour esophageal pH was measured while the subject was ambulatory, using a combined glass electrode connected to a portable recorder. Percentage of time with esophageal pH less than 4, the number and mean duration of reflux episodes, the number of episodes lasting longer than 5 min, and the duration of the longest episode were calculated for periods of upright and supine body position, respectively. Discriminant analysis and receiver-operating-characteristic analysis were used to define optimal thresholds. A maximum of sensitivity (93.3%) and specificity (92.9%) was obtained using receiver-operating-characteristic analysis with the following criteria. Only percentage of time with esophageal pH less than 4 is considered. A subject is classified as "normal" if both values for the upright and supine body position are below the thresholds, otherwise the subject is classified as "pathological." The thresholds are 10.5% of time with esophageal pH less than 4 for the upright position and 6.0% for the supine position. Within the limits of this retrospective study, it is concluded that rather simple criteria yield a high diagnostic accuracy in the evaluation of long-term esophageal pH-metry. Nevertheless, a prospective and independent confirmation of these criteria is needed.

Influence of smoking and esophageal intubation on esophageal pH-metry

The effect of cigarette smoking on gastroesophageal reflux and the effect of the pH electrode on salivary secretion and swallowing frequency were studied in 30 healthy volunteers (15 habitual smokers, 15 non-smokers) and in 10 smoking patients with proven gastroesophageal reflux disease. Twenty-four-hour pH profiles were measured while the subjects were ambulatory using a combined glass electrode connected to a portable recorder. In 8 of the smoking volunteers, swallowing frequency and salivary secretion were measured, both when smoking and when not. Smokers had more reflux episodes than nonsmokers [median per hour 2.8 (range 0.4-7.1) for the upright body position and 0.5 (range 0.0-1.7) for the supine body position vs. 1.4 (range 0.0-2.1) upright and 0.0 (range 0.0-0.7) supine, p less than 0.01], but the total time of exposure of the esophageal mucosa to acid was affected neither by the status of being a smoker nor by actual smoking. Nasopharyngeal intubation with the pH electrode did not affect the swallowing frequency, but it increased salivary secretion two-to threefold for a period of 4 h. Six hours after introduction of the pH electrode and later, salivary flow was similar to baseline. It is concluded that smoking and nasopharyngeal intubation does not adversely affect the results of 24-h pH-metry.