Gastroesophageal reflux and respiratory phenomena in infants: status of the intraluminal impedance technique

Evaluation of gastroesophageal reflux in pediatric patients with asthma using impedance-pH monitoring

OBJECTIVES

To determine the proportion of acid and nonacid reflux events in children with asthma suspected to have gastroesophageal reflux (GER) using combined impedance-pH monitoring, and to determine the symptom index (SI) for nonacid and acid reflux events.

STUDY DESIGN

This was a prospective study of children with asthma (age 5 months to 6 years) referred for evaluation of GER. Exclusion criteria were congenital anomalies, cerebral palsy, mental retardation, and cardiac disease. The children underwent a 20-hour multichannel intraluminal impedance (MII)-pH study.

RESULTS

A total of 24 children (17 male; mean age, 33 months) were enrolled from March 2004 to February 2005. MII-pH detected 1184 reflux events, versus 419 reflux events by pH alone; 51% (605 events) were nonacid. The proportion of nonacid reflux events decreased with time elapsed from last meal (P < .0001 by Pearson's chi2 test). A total of 555 symptoms were recorded, including 331 cases of cough, 243 of which (73.4%) were not associated with a reflux event. The SI for MII-pH was significantly different than that for the pH probe (37% vs 0%; P = .008).

CONCLUSIONS

Acid and nonacid reflux occurs with equal frequency in children with asthma. Most symptoms occur in the absence of a reflux event.

Twenty-four-hour esophageal impedance-pH monitoring in healthy preterm neonates: rate and characteristics of acid, weakly acidic, and weakly alkaline gastroesophageal reflux

OBJECTIVE

Gastroesophageal reflux is a physiologic process and is considered pathologic (gastroesophageal reflux disease) when it causes symptoms or results in complications. It is common in preterm infants and occurs in healthy neonates. Twenty-four-hour pH monitoring commonly is used in children for diagnosis of gastroesophageal reflux disease, and abnormal reflux is considered with detection of increased esophageal acid exposure. However, in neonates, relatively few gastroesophageal reflux episodes cause esophageal acidification to pH < 4. Premature infants receive frequent feeds, which can induce a weaker acid secretory response than that observed in older infants and adults. As a consequence, gastric pH may be > 4 for prolonged periods, and reflux of gastric contents might be less acidic or even alkaline. Esophageal impedance monitoring can detect weakly acidic and even alkaline gastroesophageal reflux. The role of weakly acidic reflux in the pathophysiology of gastroesophageal reflux disease in preterm infants is not clear. To date, studies that have used impedance-pH in neonates assessed the association between nonacid reflux and cardiorespiratory symptoms, but no impedance data from healthy preterm neonates have been available to determine whether those symptomatic neonates had an increased number of weakly acidic reflux episodes or increased reactivity to a physiologic number of reflux events. Our aim with this study was to provide impedance-pH values for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates.

METHODS

Esophageal impedance was recorded for 24 hours in 21 asymptomatic preterm neonates by replacing the conventional feeding tube with a specially designed feeding tube that included 9 impedance electrodes (8 French). All neonates were asymptomatic, with spontaneous breathing. Reflux monitoring was performed after comprehensive explanation and on receipt of written parental consent. Esophageal and gastric pH were monitored using a separate parallel pediatric catheter (6 French). According to the corresponding pH change, impedance-detected reflux was classified as acid, weakly acidic, and weakly alkaline. For each infant, the total number of reflux events, the acid exposure and bolus exposure times at 2 cm above the respiratory inversion point, and average proximal extent of reflux were calculated.

RESULTS

Twenty-six preterm neonates were recruited into this study. A preliminary analysis was performed, and tracings were classified according to their quality and the presence of technical artifacts (spontaneous pH and impedance drifts, esophageal probe migration, and dysfunction of 1 or more impedance channels). Five studies were excluded because of 1 or more technical artifacts; a total of 21 neonates represent the final cohort included. At birth, the infants had a median postmenstrual age of 32 weeks, and the measurements were performed at a median age of 12 days. The total recording time was 23.7 +/- 2 hours. Gastric pH was higher than 4 during 69.3 +/- 20.4% of the recording time. The median number of reflux events in 24 hours was 71, 25.4% (range: 0%-53.1%) of which were acid, 72.9% (range: 45.3%-98.0%) were weakly acidic, and 0% (range: 0%-8.1%) were weakly alkaline. Compared with fasting periods, feeding periods tended to be associated with a higher number of total reflux events per hour. The acidity of reflux, however, was significantly different: during fasting, the number of acid reflux episodes per hour was higher, whereas during feeding, the number of weakly acidic reflux episodes was increased. Most reflux events were only liquid, whereas gas was present either mixed with liquid or pure only in 7.7% of all reflux episodes detected. The proximal esophageal segments were reached in 90% of reflux episodes. Reflux-related acid exposure (pH drops associated with impedance-detected reflux) was 1.66% (range: 0%-6.43%), whereas total acid exposure (associated and not associated with reflux detected by impedance) was 5.59% (range: 0.04%-20.69%). There was no relationship between the number or acidity of reflux events and anthropometric parameters such as weight and gestational age.

CONCLUSIONS

We present the first study using 24-hour impedance-pH recordings in asymptomatic premature neonates. Previous studies that used pH-metry suggested that neonatal cardiorespiratory symptoms could be related to acid gastroesophageal reflux. However, pH-metry could not detect accurately weakly acidic or nonacid reflux. Our healthy premature neonates had approximately 70 reflux events in 24 hours, 25% of which were acid, 73% were weakly acidic, and 2% were weakly alkaline. The number of reflux events per hour (2-3 per hour) was slightly lower than that described in premature neonates with cardiorespiratory events (4 per hour). We confirmed that weakly acidic reflux is more prevalent than acid reflux, particularly so during the feeding periods. In contrast, similar to healthy adults, weakly alkaline reflux was very rare. We confirmed findings from previous studies in which most reflux events were pure liquid during both fasting and during postprandial periods and gas reflux was very rare. As in neonates with cardiorespiratory symptoms, the majority of reflux events in asymptomatic preterms reached the proximal esophagus or pharynx, and there were no differences between acid and weakly acidic reflux. The lack of differences between asymptomatic and diseased infants contravenes the hypothesis for macro- or microaspiration but does not exclude hypersensitivity to reflux as a cause for respiratory symptoms. The acid exposure that was related to reflux events and detected by impedance was significantly lower than the total acid exposure during 24 hours. Increased acid exposure could be attributable to pH-only reflux events or, less frequently, to slow drifts of pH from baselines at approximately 5 to values < 4. These changes were not accompanied by a typical impedance pattern of reflux but by slow drifts in impedance in 1 or 2 channels. Our findings confirm the need for the use of impedance together with pH-metry for diagnosis of all gastroesophageal reflux events. The relationship between gastroesophageal reflux and cardiorespiratory events in neonates and older infants has been studied extensively. The current evidence for such a relationship is controversial. This study provides values of impedance-pH monitoring for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates that can be used for comparison when evaluating gastroesophageal reflux in preterm infants with a cardiorespiratory disease.

Technology Insight: the role of impedance testing for esophageal disorders

Classic techniques like videofluoroscopy, stationary manometry, and ambulatory 24 h pH-metry are routinely used in the clinic to study patients with dysphagia, chest pain and reflux-related symptoms. Although these techniques have been very useful over the years, both for diagnosis and for therapeutic guidance, there are still many patients with dysphagia or chest pain who remain undiagnosed even after testing, and patients with typical and atypical symptoms of gastroesophageal reflux disease, with normal pH-metry findings, who do not respond adequately to antisecretory therapy. Esophageal impedance monitoring is a new technique that can be used alone and in combination with pH-metry and manometry to evaluate bolus transport and all types of gastroesophageal reflux (acid and nonacid). This review describes the esophageal impedance monitoring technique and summarizes the published validation studies that compare impedance monitoring with other methods, as well as normal values and reproducibility of impedance patterns and their association with symptoms.

New techniques to evaluate esophageal function

Classical techniques like videofluoroscopy, stationary manometry and ambulatory 24-hour pH-metry are routinely used in the clinic to study patients with dysphagia, chest pain and reflux-related symptoms. Although many patients can be accurately diagnosed and their therapy successfully guided with these techniques, in many other patients, non-obstructive dysphagia or chest pain cannot be attributed to clear fluoroscopic or manometric abnormalities. Furthermore, ambulatory 24-hour pH-metry often shows a poor association between spontaneous acid reflux events and esophageal or extraesophageal symptoms, particularly in patients 'on' treatment. Non-obstructive dysphagia can be assessed with high-resolution manometry to detect segmental disturbances of peristalsis, increase in pressure gradient across the lower esophageal sphincter (LES) or abnormal axial movement of the LES during esophageal spasm. Impedance evaluation of bolus transit is a non-radiological method that can evaluate the functional relevance of manometric abnormalities. Patients with non-cardiac chest pain that do not respond to proton pump inhibitor therapy can be further assessed with intraluminal high-frequency ultrasound to detect sustained esophageal contractions of the longitudinal muscle layer. Impedance planimetry, with multimodal esophageal stimulation, may contribute to evaluate the sensitivity to mechanical, thermal and chemical stimuli. Finally, patients with persistent symptoms of gastroesophageal reflux in spite of adequate treatment with proton pump inhibitors may still have weakly acidic reflux and/or bile reflux associated with their symptoms. These types of refluxates can now be detected with combinations of pH-impedance or pH-Bilitec monitoring. This review will describe the available new techniques to evaluate patients with non-obstructive dysphagia, non-cardiac chest pain and persistent gastroesophageal reflux symptoms.

Evaluation of infantile acid and nonacid gastroesophageal reflux using combined pH monitoring and impedance measurement

OBJECTIVE

Characterize the proportion of acid and nonacid esophageal reflux events in young infants with suspected gastroesophageal reflux (GER) using combined pH-multichannel intraluminal impedance (MII) monitoring. Determine the symptom index correlation with nonacid reflux and acid reflux events.

STUDY DESIGN

Prospective study of children, aged 2 weeks to 1 year, referred to The Children's Hospital of Denver Gastroenterology Clinic for evaluation of GER. Exclusion criteria were congenital anomalies or syndromes, cerebral palsy, mental retardation, and pulmonary or cardiac disease. The children were admitted to The Children's Hospital General Clinical Research Center for a 20 hour pH-MII study. Acid suppression was either never used or discontinued 2 weeks before testing.

RESULTS

Thirty-four infants were enrolled from February 2004 to February 2005. Ages ranged from 2 months to 11 months, median = 7 (20 females/14 males). One thousand eight hundred ninety reflux events were detected by MII, and 588 reflux events were detected by pH probe alone. The percent of reflux that was acid was 47% (888 events) versus 53% of (1,002 events) nonacid reflux events. The proportion of nonacid reflux decreased with age (P < 0.0001 by Pearson chi test) and with increasing time elapsed from last meal. There were 958 total symptoms evaluated. The most frequently reported symptom was fussiness/pain, which correlated with nonacid reflux events 24.6% and acid reflux 25.2%. The proximal height of a reflux was predictive for symptoms of fussiness/pain, arching, and burping.

CONCLUSION

MII detects more reflux events than pH monitoring alone. The proportion of nonacid reflux to acid reflux events in infants is more similar to adults than previously reported. Combined pH-MII esophageal monitoring identifies more reflux events and improves clinical correlation with symptoms.

Ultrasonographic study of postcibal gastro-esophageal reflux and gastric emptying in infants with recurrent respiratory disease

AIM

To check the utility of postcibal ultrasonography for the evaluation of reflux in relation to gastric emptying in infants with recurrent respiratory symptoms and to link imaging with clinical data.

METHODS

Esophageal reflux (hyperechoic retrograde filling) and gastric emptying (antral areas) were quantified before and after ingestion of a standard formula in 35 untreated infants (13 with chronic cough, 22 with recurrent bronchitis) and in 31 controls.

RESULTS

The prevalence of abnormal (> or =8 episodes) postcibal refluxes was 74% in patients and 3% in controls. Number, duration of the longest episode and extent of refluxes were significantly higher in patients compared to controls. Number of refluxes was higher in patients with symptomatic refluxes than in those without. Infants with recurrent bronchitis had more refluxes than those with chronic cough and controls. Extent and timing of gastric emptying were similar in patients and controls.

CONCLUSION

Esophageal ultrasonography is a useful and physiological test in infants with recurrent respiratory diseases, which have a high prevalence of abnormal postcibal esophageal reflux and a gastric emptying similar to that of normal controls. Esophageal reflux is more severe in subjects with recurrent bronchitis than in those with chronic cough.

Apnea is not prolonged by acid gastroesophageal reflux in preterm infants

OBJECTIVE

To examine the temporal relationship between apnea and gastroesophageal reflux (GER) and to assess the effect of GER on apnea duration.

METHODS

A total of 119 preterm infants underwent 12-hour cardiorespiratory monitoring studies using respiratory inductance plethysmography, heart rate, oxygen saturation (SaO2), and esophageal pH. The studies were scored for GER (pH <4 for > or =5 seconds) and apnea > or =15 seconds or > or =10 seconds that occurred within 30 seconds of GER. Apnea > or =10 seconds was used to assess whether GER would prolong apnea duration.

RESULTS

There were 6255 episodes of GER. Only 1% of GER episodes were associated with apnea > or =15 seconds, and there was no difference in apnea rate before, during, or after GER. There was also no difference in rate of apnea > or =10 seconds before versus during GER; however, there was a decrease in apnea rate immediately after GER. The presence of GER during apnea did not prolong apnea duration, and GER had no effect on the lowest SaO2 or heart rate during apnea.

CONCLUSION

There is no evidence of a temporal relationship between acid-based GER and apnea in preterm infants. In addition, GER does not prolong apnea duration and does not exacerbate the resultant decrease in heart rate and SaO2.

Testing the association between gastroesophageal reflux and apnea in infants

BACKGROUND

There is controversy regarding the association between gastroesophageal reflux and apnea. The controversy is further confused by the variety of ways reflux is detected, the varying methods of data analysis and the heterogeneity of subjects studied.

OBJECTIVES

To determine if apnea is associated with reflux and to determine whether the association differs with acid or non acid reflux.

METHODS

We prospectively evaluated infants with apparent life-threatening events or apnea by simultaneous pneumography, esophageal pH and multichannel intraluminal impedance monitoring. Apneic events and reflux frequency, duration, acidity and height were recorded. Apneic events were considered to be temporally linked to gastroesophageal reflux when they occurred during a gastroesophageal reflux episode or within 5 minutes after clearance of the refluxate. Data described with frequency tables, scatterplots and time series graphs were analyzed by regression analysis and chi testing.

RESULTS

Twenty-five infants (10 males) aged 1 to 19 months were studied for up to 24 hours. Of 527 total apneic episodes, only 80 (15.2%) were temporally linked with gastroesophageal reflux: 37 (7.0%) with acid reflux and 43 (8.2%) with non-acid reflux. Scatterplots revealed no significant correlation between apnea and frequency or duration of reflux episodes. Individual chi analyses within subjects found limited associations between reflux and apnea. Regression analyses showed a significant association between apnea and reflux in 4 of 25 subjects.

CONCLUSIONS

We found little evidence for an association between apnea and total reflux, acid reflux or non-acid reflux. There was no difference between acid gastroesophageal reflux and non-acid gastroesophageal reflux in the frequency association with apnea. Either a chi statistic for each subject or R value computed from a lagged regression model for each subject can be used as an index of association in patient evaluation.

Effect of Gaviscon Infant on gastro-oesophageal reflux in infants assessed by combined intraluminal impedance/pH

BACKGROUND

Gaviscon Infant (GI) has been recommended for gastro-oesophageal reflux (GOR) in infants. Its efficacy has not been examined with a physiologically appropriate denominator to define the degree of GOR.

AIM

To investigate the influence of Gaviscon Infant on GOR in infants using combined pH and intraluminal impedance measurement.

METHODS

Twenty infants (mean age 163.5 days, range 34-319 days) exclusively bottle fed, with symptoms clinically suggestive of GOR, underwent 24 hour studies of intra-oesophageal 6 channel impedance and dual channel pH monitoring, during which six random administrations (3+3) of Gaviscon Infant (625 mg in 225 ml milk) or placebo (mannitol and Solvito N, 625 mg in 225 ml milk) were given in a double blind fashion. Impedance/pH reflux data were recorded and analysed blind by one observer.

RESULTS

The median number of reflux events/hour (1.58 v 1.68), acid reflux events/hour (0.26 v 0.43), minimum distal or proximal pH, total acid clearance time per hour (time with pH below pH 4), and total reflux duration per hour were not significantly different after GI than after placebo. Reflux height was marginally lower after GI (median 66.6% v 77.3% oesophageal length) compared with placebo.

CONCLUSIONS

Results showed a marginal but significant difference between Gaviscon Infant and placebo in average reflux height, and raises questions regarding any perceived clinical benefit of its use.

The importance of multichannel intraluminal impedance in the evaluation of children with persistent respiratory symptoms

OBJECTIVES

Previous evidence suggests an association between gastroesophageal reflux disease and chronic respiratory disease in children. Despite antisecretory antacid therapy, respiratory symptoms often persist supporting a role for nonacid reflux. The aim of this study was to determine whether nonacid reflux occurs in children with chronic respiratory disease.

METHODS

Twenty-eight children (mean age: 6.5 +/- 5.6 yr) with persistent respiratory symptoms on antacid medications underwent 24 h pH/multichannel intraluminal impedance (pH/MII) recording. The symptom index (SI) and the symptom sensitivity index (SSI) were calculated for each patient. Logistic regression was performed to determine which reflux characteristics were associated with a high degree of symptom correlation present during the occurrence of symptoms.

RESULTS

A total of 1,822 reflux episodes were detected by pH/MII, 45% of which were nonacidic. The mean SI increased using pH/MII (35.7 +/- 28.5) compared to pH probe alone (14.6 +/- 18.9; p= 0.002); no differences in the mean SSI using pH/MII compared to pH probe alone were identified. Significantly more patients had a positive SI using pH/MII than pH probe alone (p= 0.035); there was no difference in the number of patients with a positive SSI using pH/MII compared to pH probe alone. Multivariate analysis revealed that symptoms occurred more frequently when the reflux was nonacidic, mixed, and full column. Also, younger children were more likely to have the simultaneous occurrence of symptoms and reflux.

CONCLUSIONS

Nonacid reflux may be an important predictor of respiratory symptoms. pH/MII provided important information in the evaluation of children with intractable respiratory symptoms.

Acid, weakly acidic and non-acid gastro-oesophageal reflux: differences, prevalence and clinical relevance

In patients with gastro-oesophageal reflux disease (GORD), oesophageal symptoms and mucosal damage traditionally are related to acid-reflux episodes with pH lower than 4. Oesophageal or extra-oesophageal symptoms of GORD may also be associated with less acidic reflux (pH 4-7). New methodologies have evolved to complement pH monitoring for characterisation of less acidic gastro-oesophageal reflux. This review will focus on definition, detection, pathophysiology and symptom association of weakly acidic and non-acid reflux, in both adult and paediatric populations.

The yield of esophageal pH monitoring during polysomnography in infants with sleep-disordered breathing

This study evaluates the yield of adding simultaneous esophageal pH monitoring to polysomnography (PSG) in 41 infants with unexplained sleep disordered breathing. The relationships of respiratory events to episodes of gastroesophageal reflux (GER) were analyzed. The major causes for referring the infants were cyanotic episodes (22%), apneas (20%), and choking events (15%). PSG was abnormal in 8/41 (20%). Abnormal pH studies were observed in 12/41 (29%) infants. In 4/12 (33%), respiratory events correlated with GER episodes. Adding simultaneous pH monitoring to PSG may identify associated conditions and thus focus treatment.

Relevance of the pH probe in sleep study analysis in infants

BACKGROUND

To establish the relationship between sleep apnoea and gastro-oesophageal reflux in infants and describe the clinical, demographic and pHmetric profile and the characteristic of the sleep polysomnography with a pH probe.

METHODS

A total of 102 consecutive patients were evaluated. Parents were requested to fill out a questionnaire about symptoms and previous therapy. Gastro-oesophageal reflux was considered abnormal when the percentage of time with pH less than 4 was higher than 4% of total sleep time.

RESULTS

A total of 102 infants were enrolled, 53% males. Seventy-four per cent of the infants were full-term babies. At the moment of the polysomnography, the mean age of the sample was 2.6 months. Suspicion of apnoea was the most common clinical diagnosis prior to the study. Only two infants have abnormal electroencephalogram. Mild gastro-oesophageal reflux was seen in 37 (36%) infants, while 22 (21.5%) did not have any reflux episode, and the remaining 43 (42%) infants had reflux index in the pathologic range. Only one patient had an unequivocal temporal relationship between acid oesophageal reflux and respiratory pause with oxygen desaturation.

DISCUSSION

Infants with history of apnoea or acute life threatening event frequently had gastro-oesophageal reflux episodes which did not correlated with respiratory events, suggesting that gastro-oesophageal reflux and apnoea often occur in the same infant as two separate events.

24-Hour Electrocardiogram before and during Cisapride Treatment in Neonates and Infants

We studied prospectively the effects of cisapride on heart rate and rhythm using standard ECG and 24-hour ECG recordings in term and preterm neonates and infants. We studied subjects with gastroesophageal reflux disease (apparent life-threatening events, apneas, bradycardias) before and 3 days after starting cisapride (0.8 mg/kg/day in 4 doses). We performed standard ECGs for determination of corrected Q-T interval (QTc) and Q-T dispersion (QTd) and 24-hour ECG recordings for analysis of heart rate, heart rate variability, and heart rhythm. Fourteen term and 17 preterm subjects (gestational age range 28-36 weeks) were studied at a median chronological age of 29 (range 3-132) days. Cisapride significantly increased the QTc in preterm infants (before vs. after: 408 +/- 7 vs. 433 +/- 7 ms, p = 0.001). Two preterm and 1 term infant had a QTc >450 ms before cisapride. Four preterm (4/15 = 27%) and 2 term (2/13 = 15%) subjects had a QTc >450 ms on cisapride. After cisapride the QTd remained normal, and no relevant arrhythmias were documented on Holter recordings. Cisapride significantly decreased peak and mean heart rates of all study subjects without affecting the heart rate variability, while it increased the minimal heart rate of preterm infants only (before vs. after: 66 +/- 5 vs. 78 +/- 5 bpm, p = 0.02). The maximally measured R-R intervals (pauses) decreased after cisapride in preterm infants (before vs. after: 1.33 +/- 0.2 s vs. 1.05 +/- 0.2 s, p = 0.04). Although cisapride did cause a significant prolongation of the ventricular action potential duration in preterm infants, the QTd remained unaffected, and no clinically relevant arrhythmias were documented in this small sample. On the other hand, cisapride had a direct lowering effect on the maximal and mean heart rates of both term and preterm infants, while the drug increased the minimal heart rate and reduced the severity of bradycardia episodes in preterm infants.

Investigation of regurgitation and other symptoms of gastroesophageal reflux in Indonesian infants

AIM: To evaluate the incidence of regurgitation and other symptoms of gastroesophageal reflux in Indonesian infants.

METHODS: In a cross-sectional study at the University Outpatient Clinic for vaccination in Jakarta, 138 mothers of healthy infants less than 12-mo old were prospectively asked to report the frequency of regurgitation.

RESULTS: Whatever the age was, some infants did not regurgitate (from 10% during the first month of life to 67% in 1-year-old infants). Regurgitation of at least once a day was reported in 77% of infants younger than 3 mo. Daily regurgitation decreased to 12% in the 9-12 mo old group. Reported peak prevalence was 81% (26/32) during the first month of life. Regurgitation decreased sharply between the 4-6 and 7-9 mo old groups (from 44% to 9%). The longer the regurgitation persisted, the more frequently the mother perceived regurgitation as a problem. Volume and frequency of regurgitation, back arching, irritability, crying and refusal of feeding were the symptoms causing maternal anxiety. The longer the regurgitation persisted, the more frequently the mothers viewed it as a health problem.

CONCLUSION: Regurgitation occurs frequently in Indonesian infants, and is a frequent cause of concern to mothers.

Inter- and intraobserver agreement for gastroesophageal reflux detection in infants using multiple intraluminal impedance

The multiple intraluminal impedance (MII) technique is a new method that allows pH-independent gastroesophageal reflux detection via changes in impedance caused by a liquid bolus inside the esophagus. We wanted to know whether this technique yields objective and reproducible results. Twenty 3- to 6-hour recordings of MII from 19 preterm infants (median gestational age at birth 30 weeks, range 24-34 weeks; age at study 26 days, range 13-93 days) were divided into 23-second segments and analyzed for reflux episodes by three investigators; one investigator analyzed the data set twice. Observer agreement was assessed using kappa statistics. Each investigator analyzed 16,627 23-second segments, with a median of 854 (range 486-979) segments per recording. Median kappa values for the 20 recordings were 0.79, 0.83, and 0.83 for the three pairs of investigators and 0.84 for the repeated scoring procedure. MII recordings could be analyzed with a high level of inter- and intraobserver agreement.

Evaluation of gastroesophageal reflux events in children using multichannel intraluminal electrical impedance

The majority of gastroesophageal reflux (GER) episodes in infants and children are nonacidic (pH >4). However, extraesophageal symptoms (e.g., breathing irregularities, apnea, aspiration) apparently can be caused by both acidic (pH <4) and nonacidic reflux. The standard diagnostic tool for suspected GER is pH monitoring. However, physicians should be aware of the limitations of pH monitoring in the pediatric population, because most reflux episodes in this age group are undetectable by this method. In contrast, the pH-independent multiple intraluminal electrical impedance technique (IMP) allows all bolus movements in the esophagus to be detected. Data can be analyzed for bolus composition and reflux height, duration, and clearance. Combining IMP with pH monitoring on a single catheter has proved to be a valuable tool for diagnosing GER and associated symptoms in infants and children.

Use of multichannel intraluminal impedance to document proximal esophageal and pharyngeal nonacidic reflux episodes

Recent studies in adults and children suggest that combined multichannel intraluminal impedance and pH measurement (MII-pH) has the potential to become the new "gold standard" for gastroesophageal reflux testing. In combined MII-pH, reflux is detected by changes in resistance to alternating current induced by the presence of intraluminal materials with different conductivities, and is characterized as acid or nonacid reflux based on concomitant pH measurements. Proximal distribution and duration of nonacid reflux events, predominantly in postprandial periods and during acid-suppressive therapy, can now be quantified. The ability to associate symptoms with nonacid reflux events will help guide therapy in select groups of patients, such as patients with ongoing symptoms on acid-suppressive therapy as well as in the pediatric population.

Detection of small bolus volumes using multiple intraluminal impedance in preterm infants

BACKGROUND

Multiple intraluminal impedance (MII) is a new technique that allows detection of reflux and swallows via changes in impedance caused by a liquid bolus inside the esophagus. The method is independent of pH. The authors studied the ability of this technique to detect the small bolus volumes potentially occurring in young infants.

METHODS

Ten preterm infants (median gestational age at birth, 33 weeks; range, 25-36 weeks; age at study, 9 days; range, 2-39 days) underwent 10 instillations each of 0.1 mL to 0.5 mL saline while MII was recorded via a 2.4-mm nasogastric catheter. MII signals were analyzed for swallows, defined as a decrease in impedance starting within 1 minute. From the liquid instillation in the most proximal channel and extending downward, impedance changes during these induced swallows were compared with those occurring during spontaneous swallows.

RESULTS

All 100 liquid instillations resulted in a typical impedance pattern, occurring after a median interval of 4.4 seconds (range, 1.8-8.9 seconds). The decrease in impedance was more pronounced than after spontaneous swallows (30% vs. 24%, P < 0.03) and extended downward more rapidly (12.3 cm/s vs. 5.8 cm/s, P < 0.01).

CONCLUSION

Bolus transport of small liquid volumes can be detected via MII.

Baclofen decreases acid and non-acid post-prandial gastro-oesophageal reflux measured by combined multichannel intraluminal impedance and pH

BACKGROUND

Omeprazole controls acid but not non-acid reflux. The GABA B agonist baclofen decreases acid reflux through the inhibition of transient lower oesophageal sphincter relaxations (TLESRs) and should similarly decrease non-acid reflux. Using combined multichannel intraluminal impedance and pH (MII/pH), we compared acid and non-acid reflux after placebo and baclofen.

METHODS

Nine healthy volunteers and nine heartburn patients underwent two 2-h studies of combined MII/pH in right lateral decubitus after a refluxogenic meal in random order: on placebo and after baclofen 40 mg p.o. Tracings were analysed for acid and non-acid reflux episodes, re-reflux and symptoms in the heartburn patients.

RESULTS

In normal subjects baclofen significantly reduced the median number of episodes of acid (7 vs. 1, P = 0.02), non-acid (2 vs. 0, P = 0.005), and all reflux combined (10 vs. 2, P = 0.006); re-reflux was not reduced (0 vs. 0, P = N.S.). In heartburn patients, baclofen significantly decreased the median number of episodes of acid (15 vs. 6, P = 0.004), non-acid (4 vs. 2, P = 0.003), re-reflux (2 vs. 0, P = 0.02), and all reflux combined (23 vs. 8, P = 0.004); it also reduced the median number of acid-related (9 vs. 1, P = 0.008) and non-acid-related (1 vs. 0, P = 0.04) symptoms.

CONCLUSIONS

Baclofen reduces post-prandial acid and non-acid reflux and their associated symptoms. GABA B agonists may have a role in treating GERD.

Influence of nasogastric tubes on gastroesophageal reflux in preterm infants: a multiple intraluminal impedance study

To investigate whether a nasogastric tube predisposes to gastroesophageal reflux, 16 preterm infants underwent 48-hour recordings of multiple intraluminal impedance with the catheter tip in the lower esophagus or stomach for 24 hours each. There were 72 (range, 40-145) reflux episodes with the esophageal placement and 122 (range, 60-147) during the gastric position (P <.01).

Esophageal pH monitoring and impedance measurement: a comparison of two diagnostic tests for gastroesophageal reflux

BACKGROUND

pH monitoring is the standard diagnostic tool for gastroesophageal reflux in infants. However, this method does not document the reflux of all kinds of fluid from the stomach into the esophagus, but only documents acid material. The parameters that define reflux episodes by pH monitoring have been derived empirically from observations of many infants considered healthy and ill. Acid reflux is a continuum, some reflux is normal and doubt exists as to how much reflux is abnormal. In this study, one of the standardized protocols for analyzing pH recordings was evaluated and compared with simultaneously obtained intraesophageal impedance measurement (IMP), a pH-independent method of detecting bolus movement within the esophagus.

METHODS

The esophagi of 50 infants with reflux symptoms were measured, using both standard pH probe and multiple-site impedance measurement. A standard protocol for analyzing esophageal pH records was used. The sampling rate for pH values was 15/min. Acid reflux was defined as pH less than 4.0 (threshold pH) for at least 15 seconds (minimal duration) with at least 30 seconds (latency time) between separate episodes. The software used could adjust independently or in combinations the sampling rate and these reflux criteria. Thereby it was determined whether changes in the criteria for acid reflux improved the sensitivity and predictive value of pH monitoring when compared with reflux episodes defined by IMP.

RESULTS

During 318 hours of recording in 50 infants, 1,887 episodes of reflux occurred according to IMP. Only 282 (14.9%) of the IMP-determined episodes were acid reflux episodes. No alkaline reflux episodes occurred. Among the 270 pH probe-determined episodes using the standard criteria of acid reflux, only 153 (sensitivity, 54.3%; positive predictive value, 56.7%) were accompanied by unmistakable retrograde bolus movement using IMP measurements. Retrograde bolus movement did not accompany the other 117 episodes. Using a sampling rate of 15/min, a pH threshold of 4.0, a minimal duration of reflux episodes of 8 seconds, and a latency time of 60 seconds, the positive predictive value of pH probe results increased to 60.7%. Variations in the sampling rate or criteria for defining acid reflux did not significantly improve the accuracy of the pH probe results versus IMP-defined episodes.

CONCLUSIONS

Most reflux episodes that occur in infants are undetectable by standard pH probe monitoring. pH monitoring does not detect all reflux in the esophagus but is useful for detecting acidity in the esophagus and determining the duration of its presence. Combining pH monitoring with impedance measurement is a valuable diagnostic tool for gastroesophageal reflux in infants.

Motility disorders. Diagnosis and treatment for the pediatric patient

Motility disorders are common in children and may affect any area of the GI tract. The past decade has brought significant advances in the understanding of motility disorders in pediatrics. More sophisticated testing techniques have helped to differentiate normal from abnormal motility in children of different ages. Manometry now may be used to clarify the pathophysiologic defect underlying chest pain, dysphagia, rumination, gastroparesis, chronic intestinal pseudo-obstruction, and colonic neuromuscular disorders. Motility testing also may be used to identify the motor defect responsible for persistence of symptoms after surgery for GER or HD. New investigational techniques and prokinetic agents likely to be available in the future also were discussed.

Gastroesophageal reflux and apnea of prematurity: no temporal relationship

OBJECTIVE

A relationship between gastroesophageal reflux (GER) and apnea of prematurity (AOP) has long been suspected but is difficult to prove because most GER in this age group is nonacidic and thus undetectable by pH monitoring, the current standard for GER detection. The new multiple intraluminal impedance (MII) technique allows pH-independent reflux detection via changes in impedance caused by a liquid bolus inside the esophagus. We used this technique to investigate whether there is a temporal relationship between GER and AOP and whether GER occurs predominantly before a cardiorespiratory (CR) event.

METHODS

Nineteen infants with AOP (median gestational age at birth: 30 weeks; range: 24-34; age at study: 26 days [13-93]) underwent 20 6-hour recordings of MII, breathing movements, nasal airflow, electrocardiogram, pulse oximeter saturation, and pulse waveforms. MII signals were analyzed, independent of CR signals, for reflux episodes (RE), defined as a fall in impedance in at least the 2 most distal channels. CR signals were analyzed for CR events, ie, apneas of >/=4-second duration, desaturations to </=80%, and falls in heart rate to </=100/min. A temporal relationship between an RE and a CR event was considered present if both commenced within 20 seconds of each other.

RESULTS

There were 2039 apneas (median: 67; range: 10-346), 188 desaturations (6; 0-25), 44 bradycardias (0; 0-24), and 524 RE (25; 8-62). The frequency of apnea occurring within +/- 20 seconds of an RE was not significantly different from that during reflux-free epochs (0.19/min [0.00-0.85] vs 0.25/min [0.00-1.15]); the same was true for desaturations and bradycardias. Also, RE occurred similarly often within 20 seconds before as after an apnea (2; 0-14 vs 1; 0-17). A minority of apneas (3.5%) was associated with an RE reaching the pharyngeal level; of these, significantly more (45 vs 26; median: 1; 0-10 vs 1; 0-7) occurred after rather than before an RE.

CONCLUSION

Both CR events and GER were common in these infants but, with few exceptions, did not seem to be temporally related.

Acid, nonacid, and gas reflux in patients with gastroesophageal reflux disease during ambulatory 24-hour pH-impedance recordings

BACKGROUND & AIMS

Gastroesophageal reflux can be acid, nonacid, pure liquid, or a mixture of gas and liquid. We investigated the prevalence of acid and nonacid reflux and the air-liquid composition of the refluxate in ambulant healthy subjects and patients with reflux disease (GERD).

METHODS

Twenty-four-hour ambulatory recordings were performed in 30 patients with symptomatic GERD and erosive esophagitis and in 28 controls. Esophageal pH and impedance were used to identify acid reflux (pH drop below 4.0), minor acid reflux (pH drop above 4.0), nonacid reflux (pH drop less than 1 unit + liquid reflux in impedance), and gas reflux.

RESULTS

The total rate of gastroesophageal reflux episodes was similar in patients and controls. Patients with GERD had a higher proportion (45% vs. 33%) and rate of acid reflux than controls (21.5 [9-35]/24 h vs. 13 [6.5-21]/24 h; P < 0.05). One third of reflux events was nonacid in both groups. Mixed reflux of gas and liquid was the most frequent pattern with gas preceding liquid in 50%-80% of cases. Pure liquid reflux was more often acid in patients with GERD than controls (45% vs. 32%; P < 0.05).

CONCLUSIONS

Reflux of gastric contents was similarly frequent in patients with GERD and controls. Although there was no difference in the overall number of reflux episodes, more acidic reflux occurred in symptomatic patients with GERD, suggesting differences in gastric acid secretion or distribution.

Simultaneous intraesophageal impedance and pH measurement of acid and nonacid gastroesophageal reflux: effect of omeprazole

BACKGROUND & AIMS

Nonacid reflux may explain symptoms in acid-suppressed patients. Simultaneous intraesophageal impedance and pH measurement was used to evaluate the frequencies of postprandial acid and nonacid reflux before and after omeprazole administration.

METHODS

Twelve heartburn patients underwent two 2-hour studies of intraesophageal impedance and pH in the right lateral decubitus position after a refluxogenic meal; session 1 without medication, session 2 after 7 days of omeprazole twice daily. Acid and nonacid reflux were quantified.

RESULTS

Two hundred seventeen reflux episodes were detected before and 261 after omeprazole treatment (P > 0.05). Percentage of acid reflux decreased (from 45% to 3%, P = 0.02) and nonacid reflux increased (from 55% to 97%, P = 0.03) after omeprazole. Heartburn and acid taste were more commonly linked to acid reflux but were also produced by nonacid reflux. Regurgitation was reported equally in acid and nonacid reflux. Delta(pH) > 1 did not help predict the presence of symptoms during nonacid reflux.

CONCLUSIONS

During treatment with omeprazole, postprandial reflux becomes predominantly nonacid. Symptoms are more common with acid reflux but are also produced by nonacid reflux. Simultaneous intraesophageal impedance and pH may be useful in evaluating the role of nonacid reflux in symptoms that persist despite adequate acid suppression.

Simultaneous monitoring of gastric and oesophageal pH reveals limitations of conventional oesophageal pH monitoring in milk fed infants

BACKGROUND

Monitoring oesophageal pH conventionally detects "acid reflux" (pH less than 4). The pH of the gastric contents determines whether or not reflux can be detected.

AIM

To monitor gastric and oesophageal pH simultaneously in order to determine the effect of milk feeds on gastric pH and how this would influence interpretation of the oesophageal pH record.

METHODS

Milk fed infants for whom oesophageal pH monitoring was requested underwent simultaneous gastric and oesophageal pH monitoring using a dual channel pH probe.

RESULTS

Twenty of 24 records were technically satisfactory. Mean reflux index was 1.0%, range 0.0-4.0%. Gastric pH was less than 4 for 24.5% (range 0.6-69.1%) of the total time. The average time the gastric pH was greater than 4 after feeds was 130 minutes (range 29-212 minutes). The corrected reflux index (limited to the time the gastric pH was less than 4) was 2.6% (range 0.0-11.0%).

CONCLUSION

The pH of the gastric contents may be greater than 4 for prolonged intervals, during which oesophageal pH monitoring using current criteria cannot detect reflux nor correlate it with clinical events. A low reflux index may reflect prolonged buffering of gastric acidity rather than the absence of reflux.

Review article: the role of non-acid reflux in gastro-oesophageal reflux disease

The role of acid in the pathogenesis of gastro-oesophageal reflux disease (GERD) has been extensively studied and is well accepted. The role, if any, of non-acid reflux, in particular duodenogastro-oesophageal reflux, is much debated. The availability of new technology to detect non-acid reflux has heightened interest in this question. This article reviews the following: How do we define non-acid reflux? Does duodenogastro-oesophageal reflux (alone or in combination) cause oesophageal injury, symptoms or both? What is its role in complicated GERD? What methods are available to assess non-acid reflux? Does non-acid reflux need treatment and if so what modalities are available?

Reflux in children

Gastro-oesophageal reflux (GOR) is an extremely common paediatric problem that often runs a harmless and self-limited course. Physiological GOR however can lead to marked parental anxiety, many unnecessary investigations and often unwarranted and potentially harmful therapeutic interventions. Our ability to better define GOR and gastro-oesophageal reflux disease (GORD) has improved in the past 15 years with a better understanding of the pathophysiology in infants and children due to the development and wider use of flexible endoscopy, 24-hour oesophageal pH monitoring and, more recently, the use of micromanometric methods for studying oesophageal motility. This will be further enhanced in the future with the development of non-invasive breath testing to study gastrointestinal motility and the use of electrical impedance to study fluid movement. Our therapeutic interventions have also improved particularly in the areas of acid suppression, improved surgical techniques and most recently laparoscopic fundoplication. This chapter reviews these advances in the paediatric area especially with regard to pathophysiology, diagnostic testing and therapeutic intervention.

Intraluminal impedance: an ideal technique for evaluation of pediatric gastroesophageal reflux disease

Gastroesophageal reflux (GER) in infants becomes gastroesophageal reflux disease (GERD) through association with distinct clinical symptoms. Monitoring of pH is considered the standard diagnostic tool through which episodes of acidity can be detected. Apparently, however, the major amount of GER occurs in the physiologic esophageal pH range, which is concealed to pHmetry. Intraluminal impedance is a new method for pH-independent detection of esophageal bolus movement. Long-term measurements and combination with other diagnostic methods, e.g., pHmetry or polygraphic recordings, are possible. Intraluminal impedance has proved especially useful in diagnosing GER and GERD in infants. It may develop into the ideal technique for this group of patients.