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pH monitoring of the esophagus
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Brief description of the three modalities of monitoring esophageal pH for the diagnosis of GERD.

Brief description of the three modalities of monitoring esophageal pH for the diagnosis of GERD.

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  • Intragastric pH Monitoring:The evidence supporting the clinical significance and applicability of gastric pH monitoring is insufficient to recommend its routine use inclinical practice.Proximal pH Recording:available evidence does not support the routine use of proximal pH monitoring in clinical practice.
  • Subgroups of Endoscopy-Negative reflux disease (ENRD)2 distinctive subgroups exist- Nonerosive reflux disease (NERD) Functional heartburnThese groups are separated by the presence or absence of abnormal levels of acid reflux.
  • Therefore, pH recordings using the wireless pH system improve patients’ ability to perform their daily activities and thus provide a more accurate picture of their acid exposure profile as well as improve their compliance with the study.
  • Using the wireless pH system, the 95th percentile for distal esophageal acid exposure for control subjects was 5.3%, a value higher than values reported in several although not all catheter-based system studies. The higher acid exposure threshold reported in healthy controls using the wireless pH system may be the consequence of less restriction in daily activities or the result of a thermal calibration error that existed in the pH catheter systems.The 48-h data could be interpreted using an average of the 2 days or only the 24-h period with the greatest acid exposure (worst day analysis). A significant increase in the sensitivity of pH testing and small decrease in specificity were evident when utilizingthe worst day data compared with either the initial 24-h or overall 48-h data in comparing controls with GERD patients.
  • Strong correlation in esophageal acid exposure between 2 systemsCFS under recorded acid exposure
  • Relatively new technique developed in early 1990s at Helmholtz Institute in Aachen (Germany)Silny* provided first description of this technique that assesses intraluminal bolus movement by measuring changes in conductivity of intraluminal content
  • A recent, multicenter study examined the impedance characteristics of 60 healthy subjects during 24-h ambulatory monitoring. Based on impedance values 5 cm above the LES, the median number of total reflux episodes per 24 h was 30, the majority of which occurred in the upright position.Approximately two-thirds of the episodes were acid and another third weakly acidic reflux. Weakly alkaline reflux was distinctly uncommon in this healthy cohort. Similar frequencies were recently reported from a multicenter European study. References:Shay S, Tutuian R, Sifrim D, et al. Twenty-four hour ambulatory simultaneous impedance and pH monitoring: A multicenter report of normal values from 60 healthy volunteers. Am J Gastroenterol 2004;99:1037–43.Zerbib F, Bruley des Barannes S, Roman S, et al. 24 hour ambulatory esophageal multichannel intraluminal impedance-pH in healthy European subjects. Gastroenterology 2005;128:A396.

pH monitoring of the esophagus pH monitoring of the esophagus Presentation Transcript

  • 24 hour pH monitoring of the esophagusSamir Haffar M.D.Assistant Professor of Gastroenterology
  • pH monitoring of the esophagus Standard 24 hours pH monitoring Bravo capsule (tubeless capsule) Combined Multiple Intraluminal Impedance-pH(MII-pH)
  •  Standard 24 hours pH monitoring ofesophagus
  • Sites of 24 hour pH Monitoring• Single monitoring site: 5 cm above LES• Multiple monitoring sites: 5 & 20 cm above LES• One in the esophagus & one in proximal stomach• One or more in esophagus & another in hyopharynx
  • 5 cm above LES
  • Why 5 cm above LES?• Has been standard for many years• Chosen to avoid catheter migration into stomach• Moving by a 1 cm or two would not change results• Moving it 10 cm above LES miss a number of patientswho are identified by the more distal location
  • Typical monitoring sites of 5 & 20 cmabove manometrically determined LES
  • Location of LES• Manometric localization Reference method• pH step-up method Sudden rise to pH > 4• LES locator Prior to pH• Fluoroscopic techniques Not accurate• Endoscoic technique Not accurate
  • Ideal pH electrode“No single probe meets all of these criteria”• Small• Firm enough• Rapid response time between pH 7 to pH 1• Minimally affected by temperature• No hysteresis effect• No drift during 24 hours• Inexpensive• Simple to calibrate or disposable
  • Which pH Electrode ?Either can be used satisfactorilyGlass electrodes Antimony electrodes40 – 50 studies 10 studiesMost linear responseMost rapid response Less response fidelityLeast recording driftLarge diameter SmallerSiff bulky catheters More flexibleExpensive Less expensive
  • Indications of Esophageal pH Recording• Normal endoscopic findings & reflux symptoms refractory to PPI• Endoscopy-negative patient before surgical anti-reflux repair• Patients suspected to have abnormal reflux after surgery• Refractory reflux in pts with chest pain after cardiac evaluation• Suspected ENT manifestations after failure of 4 weeks of PPI• GERD in an adult onset non-allergic asthmaAGA Medical Position Statement. Gastroenterology 1996 ; 110 : 1981 - 96
  • No indications of esophageal pH recording• Esophageal pH recording not indicated to detect orverify reflux esophagitis (this is an endoscopic dg)• Esophageal pH recording not indicated to evaluate„„alkaline reflux‟‟AGA Medical Position Statement. Gastroenterology 1996 ; 110 : 1981 - 1996
  • Why pH < 4?• Defined early in development of the technology• Its choice was based on:- Marked difference from normal esophageal pH of 7- Pepsinogen converted to pepsin at pH 4- pH < 4 was one that tends to produce symptoms• Some believe that drops in pH that do not reach levelof 4.0 still may represent reflux that these eventsshould also be used in calculations of indices
  • Composite scoring systemsJohnson & DeMeester is the most commonly usedPercentage of total time pH < 4Percentage of upright time pH < 4Percentage of supine time pH < 4Number of reflux episodesNumber of reflux episodes >5 minLongest reflux episodeDeMeester scoreNormal < 14,72
  • Normal values of DeMeester’s score50 healthy volunteersDeMeester TR et al. Ann Surg 1976 ; 184 :459 – 470.
  • Normal 24 hours esophageal pH monitoringComposite DeMeester score: 8.4DeMeester normal < 14.72 (95th percentile)Bremner CG et al. Esophageal disease & testing. Taylor & Francis Group, 2005.
  • Typical distal & proximal 24 hour esophageal pH
  • Nocturnal acid breakthrough• Defined arbitrarily as intragastric pH < 4 for > 1 hovernight during administration of PPI• Occurs even on twice-daily therapy• Common enough: rule rather than exception• Not without controversy: little to do with reflux• Addition of H2RAs at bedtime to PPI bid controlsNAB better than PPI therapy alone?
  • Nocturnal acid breakthroughGastric pH < 4 for at least 1 h during the night in patientswith persistent heartburn on standard dose PPIs twice dailyCombined gastric & esophageal 24 hr pH monitoring
  • Qualitative analysisSymptom–reflux correlation• Symptom index: Positive if ≥ 50%• Symptom sensitivity index: Positive if > 10 %• Symptom association probability Positive if > 95%Determine relationship between heartburn episodes & acidreflux events, regardless if pH test is normal or abnormal
  • Symptom indexPositive if 50 % or moreNot take into account overall number of reflux episodes
  • Symptom Sensitivity IndexPositive if 10 %Not take into account overall number of symptoms
  • Symptom Association Probability CalculationPositive if 95%• Divides tracing into 2-min segments & looks atwhether a symptom & acid are present during each 2minute segment• The analysis uses contingency table analysis of 4possible outcomes for each segment:acid + symptom +acid + symptom –acid – symptom +acid – symptom –
  • Overall amount of acid exposure & number ofreflux episodes are the focus of many studiesusing ambulatory pH testingRelationship between symptoms & esophagealacid is equally (or perhaps more) important
  • 24 hour pH esophageal monitoringOn & off therapy• Off therapyUncertainty about diagnosis of refluxMildest grades of esophagitis: redness - friabilityVery short segments of BE• On therapyPatient who has failed a therapeutic trialPatient has known reflux or highly likely to have refluxpH probe in esophagus & another in stomach (NAB)
  • 24 hours pH monitoring & medications• PPI should be stopped for 5 – 7 days• Other medications should be stopped for 1 – 3 days• Patient must not use antacids or other OTCmedications for duration of the study
  • Percentage of total time pH < 4Normal values• Off therapy5 cm above LES20 cm above LES 1 %Periods of meals or acidic beverages excluded• On therapy5 cm above LES20 cm above LES ?* Based on 95% CI obtained in healthy subjects treated with omeprazole 40 mg qdKuo B et al. Am J Gastroenterol 1996 ; 91 : 1532 – 8.4 – 5.5 %1.6 – 4 %*
  • Abnormal acid exposure time in heartburnDisease Percentage of total time pH < 4Barrett‟s esophagus 93 %* ENRD: Endoscpic Negative Reflux Disease* *NERD: Non Erosive Reflux DiseaseErosive esophagitis 75 % (in one study)ENRD*NERD**Functional heartburn- SI > 50%- SI < 50%50 %100 %0 %Hypersensitive esophagusNon acid reflux or motor event24 hr pH monitoring is not gold standard for diagnosis of GERD
  •  Bravo capsule
  • Bravo system (Medtronics)Esophageal Probe25 x 6 x 5.5 mmBatterypHelectrodeSuctionchamberRadiotransmitterDelivery systemReceiver100 x 70 x 30 mm - 165 g
  • Advantages of Bravo capsule• Better tolerance by patients• Fixed position of the capsule (6 cm above SCJ*)• Prolonged monitoring under more physiologicconditions (48 hours)* SCJ: squamocolumnar junction
  • Bravo normal values50 asymptomatic volunteers1st 24 h 2nd 24 hMean(+ SD)95thpercentileMean(+ SD)95thpercentile% total time at pH < 4 1.79 (2.16 5.89 1.78 (1.78) 5.64% upright time at pH < 4 2.45 (3.14) 7.81 2.54 (2.57) 7.46% supine time at pH < 4 0.37 (1.18) 1.58 0.34 (1.28) 1.29Number of reflux episodes 21.2 (18.5) 55.30 22.3 (19.8) 56.15No of reflux episodes >5 min 0.62 (1.21) 3.55 0.75 (1.15) 3.00Longest reflux episode 3.79 (4.31) 11.23 5.95 (4.52) 17.03DeMeester score 6.02 (4.82) 15.93 5.95 (4.52) 15.48
  • Conventional pH vs Bravo capsuleHead to head comparison – 40 patientsBruley des Varannes S. Gut 2005 ; 54 ; 1682 – 1686.
  • Bravo capsuleCauses of under-recording• Data drop-up• Short reflux event not recorded• Reflux events appear shorter
  • Bravo capsuleData drop-outMalfunctions in the electronics or the receiverInterpreted as artifact & not represented in final pH reportImproved by 7 cm antenna & use of fiberglassGastrointest Endoscopy Clin N Am 2005 ; 15 : 307 – 318.
  • Bravo capsuleShort reflux events not recordedBruley des Varannes S. Gut 2005 ; 54 ; 1682 – 1686.
  • Bravo capsuleReflux events appear shorterBruley des Varannes S. Gut 2005 ; 54 ; 1682 – 1686.
  • Trouble shooting in Bravo capsule• Severe odynophagia & chest pain (5%)Chest radiography to exclude perforationViscous lidocaineEndoscopic removal if symptoms continue• Capsule detachment• Failure to dislogeEndoscopic removal similar to polypectomy
  • Bravo capsuleClassic early detachment (10% of patients)Easily recognized during inspection of pH tracingGastrointest Endoscopy Clin N Am 2005 ; 15 : 307 – 318.Sudden prolonged drop in pH represents capsule in stomachSharp rise as capsule enters small intestine through pylorus
  • Endoscopic removal of Bravo capsuleGastrointest Endoscopy Clin N Am 2005 ; 15 : 307 – 318.
  •  Combined MII-pH(MII-pH)
  • Principle of “MII”• 2 steel rings separated by isolator• Alternating-current generator to apply electrical PD• Circuit closed through electrical charges (ions)contained in structures surrounding the catheterGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 – 264.
  • Impedance scaleRefluxate: High conductivity & low impedanceAir: Low conductivity & high impedanceBremner CG et al. Esophageal disease & testing.Taylor & Francis Group, New York, 1st edition, 2005.
  • Advantages of MII• Content of refluxate Liquid – Gas – Mixed• Direction of bolus Anterograde – retrograde• Height of refluxate• pH characteristics Acid(combined MII-pH) Weekly acidWeekly alkalineAcid re-reflux
  • Liquid bolusGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 – 264.1) Initial drop Liquid enters impedance-measuring segment2) Rise Bolus cleared from this segment3) Overshoot Decreased luminal cross-section during contraction4) Return to baseline
  • Air bolus(Belch, Air swallow)1) Rapid rise Presence of air bolus inside esophagus2) Rapid decrease Air bolus clears from this segmentGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 - 264.
  • Mixed air – liquid Bolus1) Rapid Rise Air in front of the bolus2) Rapid drop Liquid component of mixed bolus3) Rise Liquid being cleared from this segment4) Return to baselineGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 – 264.
  • Antegrade bolus movement (MII)Observed during swallowingProgression of impedance from proximal to distalGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 – 264.
  • Retrograde bolus movement (MII)Observed in refluxProgression of impedance from distal to proximalGastrointest Endoscopy Clin N Am 2005 ; 15 : 257 – 264.
  • Combined MII• MII used clinically only in combination– With esophageal manometry (MII-EM)– With pH (MII-pH)• MII not considered as replacement for manometry &pH techniques but as complementary procedure thatexpands diagnostic potential of esophageal functiontesting & reflux monitoring
  • Combined MII-pH probe• Impedance orifices3, 5, 7, 9, 15, & 17 cm from the tip• pH orifice5 cm from the tip• MII-pH probe = pH probeDo not change patient comfortBremner CG et al. Esophageal disease & testing.Taylor & Francis Group, NY, 1st edition, 2005.
  • “Sleuth” monitor – Sandhill“Sleuth” monitor attached to the catheter& worn around a belt during the recording period
  • GERD classification by combined MII-pH Acid refluxReflux with drop of pH from above 4.0 to below 4.0 Superimposed acid reflux (Acid re-reflux)Acid reflux occurs while pH < 4.0 Weakly acidic refluxReflux results in esophageal pH between 4.0 & 7.0 Weakly alkaline refluxReflux with nadir esophageal pH does not drop < 7.0Sifrim D et al. Gut 2004 ; 53 ; 1024 – 1031.
  • Acid reflux (MII-pH)Gastrointest Endoscopy Clin N Am 2005 ; 15 : 361 – 371.
  • GERD classification by combined MII-pH Acid refluxReflux with drop of pH from above 4.0 to below 4.0 Superimposed acid reflux (Acid re-reflux)Acid reflux occurs while pH < 4.0 Weakly acidic refluxReflux results in esophageal pH between 4.0 & 7.0 Weakly alkaline refluxReflux with nadir esophageal pH does not drop < 7.0Sifrim D et al. Gut 2004 ; 53 ; 1024 – 1031.
  • Superimposed acid reflux (MII-pH)Gastrointest Endoscopy Clin N Am 2005 ; 15 : 361 – 371.
  • GERD classification by combined MII-pH Acid refluxReflux with drop of pH from above 4.0 to below 4.0 Superimposed acid reflux (Acid re-reflux)Acid reflux occurs while pH < 4.0 Weakly acidic refluxReflux results in esophageal pH between 4.0 & 7.0 Weakly alkaline refluxReflux with nadir esophageal pH does not drop < 7.0Sifrim D et al. Gut 2004 ; 53 ; 1024 – 1031.
  • Weakly acidic reflux (MII-pH)Gastrointest Endoscopy Clin N Am 2005 ; 15 : 361 – 371.
  • GERD classification by combined MII-pH Acid refluxReflux with drop of pH from above 4.0 to below 4.0 Superimposed acid reflux (Acid re-reflux)Acid reflux occurs while pH < 4.0 Weakly acidic refluxReflux results in esophageal pH between 4.0 & 7.0 Weakly alkaline refluxReflux with nadir esophageal pH does not drop < 7.0Sifrim D et al. Gut 2004 ; 53 ; 1024 – 1031.
  • Weakly alkaline reflux (MII-pH)Gastrointest Endoscopy Clin N Am 2005 ; 15 : 361 – 371.
  • Recommendations for MII-pH monitoring• Endoscopy-negative patients with heartburn orregurgitation despite PPI & performed on PPI therapy• Utility of impedance in refractory reflux patients withchest pain or extraesophageal symptoms unproven• Current interpretation relies on SI, SSI or SAP• Therapeutic implications of abnormal test unprovenACG Practice Guidelines: Esophageal reflux testing.Am J Gastroenterol 2007 ; 102 : 668 – 685.
  • Advantages of 3 major types of pH testingpH Tubeless CombinedMII-pHComfort _ + _Monitoring > 24 h _ + _Nonacid reflux _ _ +Normal values + _ _Proximal reflux + ? +Gastric monitoring + ? +
  • Thank You