OBJECTIVE: To quantify normal proximal and distal oesophageal acid parameters in healthy Chinese. DESIGN: Observational study. SETTING: University teaching hospital, Hong Kong. SUBJECTS AND METHODS: Twenty healthy adults who were not on medication and were free from gastrointestinal symptoms were recruited by advertisement. Ambulatory oesophageal acid (pH5 minutes, 4/0; and the longest single acid exposure episode, 11.2/3.0 minutes. CONCLUSION: Physiological gastroesophageal reflux occurs in healthy Chinese. These initial data provide a preliminary reference range that could be utilised by laboratories studying Chinese subjects.published_or_final_versio

Chan, AO

Chan, CK

Hu, WH

Hui, WM

Lai, KC

Lam, KF

Lam, SK

Tsang, KW

Wong, BC

Wong, NY

Wong, WM

Xia, HH

Hong Kong Medical Journal

HKU Scholars Hub

Title Normal 24-hour ambulatory proximal and distalgastroesophageal reflux parameters in Chinese.Author(s) Hu, WH; Wong, NY; Lai, KC; Hui, WM; Lam, KF; Wong, BC; Xia,HH; Chan, CK; Chan, AO; Wong, WM; Tsang, KW; Lam, SKCitation Hong Kong Medical Journal = Xianggang Yi Xue Za Zhi / HongKong Academy Of Medicine, 2002, v. 8 n. 3, p. 168-171Issued Date 2002URL http://hdl.handle.net/10722/45119Rights Creative Commons: Attribution 3.0 Hong Kong License168      HKMJ Vol 8 No 3 June 2002ORIGINAL ARTICLEKey words:Gastroesophageal reflux;Hong Kong ! !"#Normal 24-hour ambulatory proximaland distal gastroesophageal refluxparameters in ChineseObjective. To quantify normal proximal and distal oesophageal acid parametersin healthy Chinese.Design. Observational study.Setting. University teaching hospital, Hong Kong.Subjects and methods. Twenty healthy adults who were not on medication andwere free from gastrointestinal symptoms were recruited by advertisement. Ambu-latory oesophageal acid (pH <4) exposure parameters were recorded at distal andproximal sites, 5 and 20 cm, respectively above the lower oesophageal sphincter.Results. The 95th percentile for reflux parameters assessed in the distal/proximal oesophagus were: percent total time pH <4, 4.6/0.7%; percent uprighttime pH <4, 7.0/1.1%; percent supine time pH <4, 4.5/0.5%; number of refluxepisodes, 73/12; number of reflux episodes with pH <4 for >5 minutes, 4/0;and the longest single acid exposure episode, 11.2/3.0 minutes.Conclusion. Physiological gastroesophageal reflux occurs in healthy Chinese.These initial data provide a preliminary reference range that could be utilised bylaboratories studying Chinese subjects.  !"#$%&'()*+,*- !./0  !"#  !"#$%& !"#20 !"#$%&'()*+,-./0123456 24 pH !"#$%&'()*+,-./012345 20 cm() 5 cm() 24 !"#$%&'()*+,  !"#! 95% !"#$% pH<4 !" 4.6/0.7%  pH<4 !" 7.0/1.1%  pH<4 !" 4.5/0.5% !" ! 73/12 pH<4 !"#$ 5 4/0 !"#$%&'11.2/3.0   !"#$%&'()*+,-./0123456789:;<= !"#$%&'()*+,○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○WHC Hu  NYH Wong  KC Lai  WM Hui  KF Lam  BCY Wong  HHX Xia  CK Chan  AOO Chan WM Wong  KWT Tsang  SK Lam  HKMJ 2002;8:168-71 !OQ !"#$%&'()*+,-The University of Hong Kong, Queen MaryHospital, 102 Pokfulam Road, Hong Kong:Department of MedicineWHC Hu, MRCP, FHKCPNYH Wong, MDKC Lai, MRCP, FHKCPWM Hui, MD, FRCPBCY Wong, MD, FHKCPHHX Xia, MD, PhDCK Chan, FRCP, FHKCPAOO Chan, MB, BS, MRCPWM Wong, MRCP, FHKCPKWT Tsang, MD, FRCPSK Lam, MD, FRCPDepartment of Statistics and ActuarialScienceKF Lam, PhDCorrespondence to: Dr WHC HuIntroductionAmbulatory oesophageal pH recording, using a catheter with built-in pHelectrode connected to a digitised solid-state recorder, is a commonly employedtest. It provides quantitative data on both oesophageal acid exposure as wellas the temporal correlation between symptoms and actual reflux events. Sincereflux is a physiological event even in normal subjects,1 delineation betweenphysiological and pathological reflux is often difficult. Good temporal cor-relation between a well-defined pathological event such as chest pain, and adecrease in pH shown on the recording provides evidence of pathogenicity.2,3However, in the absence of symptomatic correlation, oesophageal acid exposuremay be the only quantifiable parameter to determine abnormality. Johnson andDemeester4 have derived a composite score for oesophageal acid exposure basedon six variables:(1) percent total time pH <4;(2) percent upright time pH <4;(3) percent recumbent time pH <4;CMEHKMJ Vol 8 No 3 June 2002      169Ambulatory gastroesophageal reflux parameters(4) number of reflux episodes;(5) number of reflux episodes with pH <4 for more than5 minutes; and(6) the longest single acid exposure episode.Richter et al5 defined a similar set of normal values inanother population studied.It is possible that population differences in gastro-esophageal reflux may exist and it is important that stand-ard reference ranges are established for different populations.There is no previously published study on normal refluxparameters in Chinese. This study aims to establish normalvalues for gastroesophageal acid exposure in healthy HongKong residents.MethodsPatientsThe study design was approved by the research and ethicscommittee of the Faculty of Medicine, University of HongKong. Healthy subjects were recruited by advertisement.Each volunteer was carefully interviewed and underwentphysical examination. Additional laboratory investigationswere performed where appropriate to exclude systemic dis-orders affecting oesophageal motility and reflux. Volunteerswere excluded if there was a history of heartburn morethan once a month, dysphagia, regurgitation, odynophagia,chest pain, or dyspepsia. They were free of any significantmedical diseases or gastric surgery, and had not taken anymedication in the week prior to the study. Upper endoscopywas performed on all volunteers to exclude hiatus hernia.ProcedureThe ambulatory oesophageal pH studies were completed asan out-patient procedure. Patients arrived at the motilitylaboratory, Queen Mary Hospital after an overnight fast.The location of the lower oesophageal sphincter was firstdetermined using a low-compliance pneumohydrauliccapillary infusion system (Dentsleeve Pty Ltd, Belair,Australia) and the station-pull-through technique. A sleevecatheter with 5 cm spacing (Dentsleeve Pty Ltd, Belair,Australia) was used. The upper border of the lower oesopha-geal sphincter was defined by the pressure inversion point.Patients were excluded if they had abnormal motilitypatterns in the oesophageal body (simultaneous contractions≥20%, non-propagated contractions ≥30%, retrogradecontractions ≥10%).Two channel antimony pH probes with internal refer-ences were spaced 15 cm apart. Before and after each study,the pH electrodes were calibrated using buffer solutions atpH=7 and pH=4. The probes were connected to a solid-statedata logger (Synectics microdigitrapper Mk 3, Synectics,Stockholm, Sweden) with an event marker to documentmeals, symptoms, and body recumbency. The pH probe wasinserted transnasally and advanced until an acidic gastricpH <2.5 was reached. The pH probe was subsequentlywithdrawn slowly until the distal sensor was positioned 5 cmabove the previously determined upper border of thelower oesophageal sphincter. The proximal sensor was thus20 cm above the lower oesophageal sphincter. Subjects wereencouraged to undergo normal activities, sleep schedules, andmeal times. A normal diet was encouraged, but subjects wereasked to refrain from acidic food or drinks, as well as alcoholand smoking. They were also asked to remain as upright aspossible when awake, and to lie down flat when asleep.After an interval of 24 hours, subjects were asked toreturn and the pH assembly was removed. Data weredownloaded into a personal computer. Each individual tracewas inspected by one of the authors to ensure good qualityand the absence of artefacts. Data were analysed by pro-prietary software (Multigram version 6.31, GastrosoftInc., Stockholm, Sweden). Acid reflux was defined as anoesophageal pH <4 for at least 7.5 seconds. The reflux epi-sode was considered to have terminated if pH ≥4. Thesix pH parameters proposed by Johnson and Demeester4were evaluated for both the proximal and distal channels.Other parameters were also included for comparison.Statistical analysisNormal values for each of the above parameters were as-sessed by calculating the 95th percentile for the subjectgroup. Relation between age, sex, and weight to the variousreflux parameters was tested by multivariate regressionanalysis. Correlation between proximal and distal refluxparameters was obtained by Kendall’s tau. Statistical analy-ses were performed using the Statistical Package for SocialScience (Windows version 7.5, SPSS Inc., Chicago, US).ResultsTwenty healthy subjects (70% male; mean age, 36 years;age range, 20-50 years) were recruited. Values for distal pHparameters are shown in Table 1 and for proximal pH par-ameters in Table 2. Corresponding values from westernstudies are included for comparison.Age was found to be associated with an increasedpercent total time pH <4 (P=0.01), and with the number ofacid reflux episodes (P=0.02). These data are illustrated inthe Fig. Men had a significantly greater percent total timepH <4 (P=0.02), but there was no sex difference seen in thenumber of reflux episodes. Weight was not associated withdifferences in the reflux parameters. Proximal and distal acidexposure measurements were well correlated (Table 3).DiscussionSince the introduction of intraesophageal pH monitoring byMiller6 in 1964, this method has become the gold standardfor documenting gastroesophageal reflux. Reflux is a nor-mal physiological event and occurs with a greater frequencypostprandially. In healthy individuals, reflux occurs mainlydue to transient relaxation of the lower oesophageal170      HKMJ Vol 8 No 3 June 2002Hu et alsphincter.7 Studies have generally demonstrated some over-lap of reflux parameters between patients with symptomaticgastroesophageal reflux disease and normal controls.This study identified a normal reference range for reflux inhealthy Chinese subjects. A study comparing reflux par-ameters across three different centres did not show anydifference in parameters obtained,5 and thus the use ofnormal values from this study by different centres acrossthe territory appears appropriate.Although 12 different reflux parameters can be gener-ated from total, supine, and upright periods, early studieshave established that the six parameters measured in thisstudy are the most useful. There is intrasubject variabilityseen on retesting, however. Later studies have generallyfound time pH <4 (total, upright, supine) to be the mostreproducible of these parameters.8,9Dual channel pH monitoring is most useful in the studyof atypical reflux presentations, such as asthma, chroniccough, and non-cardiac chest pain,10 especially if micro-aspiration of the refluxate into airways is considered. Anadditional pH sensor situated more proximally in theoesophagus allows for documentation of the extent of travelTable 1. Distal reflux parameters measured 5 cm above the lower oesophageal sphincterReflux parameter Data from this study* Richter et al study5 Johnson and Demeester study4Percent time <4, total period 4.6 (0-6.2) 5.78 4.2Number of episodes >5 min, total period 4.0 (0-6.9) 4.00 3.0Duration of longest episode (min), total period 11.2 (0-34.0) 18.45 9.2Number of reflux episodes, total period 73.0 (0-90.0) 46.00 50.0Percent time <4, upright period 7.0 (0-7.9) 8.15 6.3Number of long episodes >5 min, upright period 3.0 (0-4.0) - -Duration of longest episode (min), upright period 11.0 (0-11.2) - -Number of reflux episodes, upright period 62.0 (0-86.0) - -Percent time <4, supine period 4.5 (0-6.0) 1.20 1.2Number of long episodes >5 min, supine period 0 (0-1.0) - -Duration of longest episode (min), supine period 4.0 (0-34.0) - -Number of reflux episodes, supine period 4.0 (0-30.0) - -* Data are shown as 95th percentile (range)Table 2. Proximal reflux parameters measured 20 cm above the lower oesophageal sphincterReflux parameter Data from this study* Dobhan and Castell study11Percent time <4, total period 0.7 (0-0.80) 0.9Number of episodes >5 min, total period 0 (0-0) 0 (0-2.0)Duration of longest episode (min), total period 3.0 (0-5.0) N/A†Number of reflux episodes, total period 12.0 (0-18.0) 18.0Percent time <4, upright period 1.1 (0-1.7) 1.3Number of long episodes >5 min, upright period 0 (0-0) 0 (0-2.0)Duration of longest episode (min), upright period 1.4 (0-5.0) 3.0 (0-32.0)Number of reflux episodes, upright period 12.0 (0-17.0) 18.0Percent time <4, supine period 0.5 (0-1.10) 0Number of long episodes >5 min, supine period 0 (0-0) 0 (0-0)Duration of longest episode (min), supine period 0.4 (0-3.0) 0 (0-3.0)Number of reflux episodes, supine period 8.0 (0-9.0) 1.0* Data are shown as 95th percentile (range)† N/A not applicable01234567Age (years)Total time pH below 4 (%)10 20 30 40 50 60Table 3. Correlation between reflux parameters at proximaland distal channelsReflux parameter P valuePercent time <4, total period 0.02Number of episodes >5 min, total period N/A*Duration of longest episode (min), total period <0.01Number of reflux episodes, total period <0.01Percent time <4, upright period 0.04Number of long episodes >5 min, upright period N/ADuration of longest episode (min), upright period 0.02Number of reflux episodes, upright period <0.01Percent time <4, supine period <0.01Number of long episodes >5 min, supine period N/ADuration of longest episode (min), supine period <0.01Number of reflux episodes, supine period <0.01* N/A not applicableFig. Correlation between age and total percent acid exposuremeasured at the distal oesophageal site (5 cm above thelower oesophageal sphincter)HKMJ Vol 8 No 3 June 2002      171Ambulatory gastroesophageal reflux parametersof refluxate. A good correlation between proximal anddistal oesophageal acid exposure parameters was seen inthis study, indicating the source and mechanism of acidreflux to be the same for both sites.Age and male sex were associated with increased acidexposure according to this study. A western study reportedan association between age and total acid exposure, refluxepisodes, and duration of the longest reflux episode whichwas close to being statistically significant.5 Whether age-related changes seen are due to increased transient loweroesophageal sphincter relaxation or other mechanismsdeserves further investigation.References1. Rokkas T, Sladen GE. Ambulatory esophageal pH recording ingastroesophageal reflux: relevance to the development of esophagitis.Am J Gastroenterol 1988;83:629-32.2. Lam HG, Breumelhof R, van Berge Henegouwen GP, Smout AJ. Tem-poral relationships between episodes of non-cardiac chest pain andabnormal oesophageal function. Gut 1994;35:733-6.3. Lam HG, Breumelhof R, Roelofs JM, Van Berge Henegouwen GP,Smout AJ. What is the optimal time window in symptom analysisof 24-hour esophageal pressure and pH data? Dig Dis Sci 1994;39:402-9.4. Johnson LF, Demeester TR. Twenty-four-hour pH monitoring of thedistal esophagus. A quantitative measure of gastroesophageal reflux.Am J Gastroenterol 1974;62:325-32.5. Richter JE, Bradley LA, DeMeester TR, Wu WC. Normal 24-hr am-bulatory esophageal pH values. Influence of study center, pH electrode,age, and gender. Dig Dis Sci 1992;37:849-56.6. Miller FA. Utilization of inlaying pH probe for evaluation of acid-peptic diathesis. Arch Surg 1964;89:199-203.7. Dent J. Patterns of lower esophageal sphincter function associated withgastroesophageal reflux. Am J Med 1997;103:29S-32S.8. Wiener GJ, Morgan TM, Copper JB, et al. Ambulatory 24-houresophageal pH monitoring. Reproducibility and variability of pHparameters. Dig Dis Sci 1988;33:1127-33.9. Johnsson F, Joelsson B. Reproducibility of ambulatory oesophagealpH monitoring. Gut 1988;29:886-9.10. Gastal OL, Castell JA, Castell DO. Frequency and site of gastro-esophageal reflux in patients with chest symptoms. Studies using proxi-mal and distal pH monitoring. Chest 1994;106:1793-6.11. Dobhan R, Castell DO. Normal and abnormal proximal esophagealacid exposure: results of ambulatory dual-probe pH monitoring. Am JGastroenterol 1993;88:25-9.

Normal 24-hour ambulatory proximal and distal gastroesophageal reflux parameters in Chinese.

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Normal 24-hour ambulatory proximal and distal gastroesophageal reflux parameters in Chinese.

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