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New Ways to Investigate Esophageal Function: pH, Impedance, Manometry, Capsules, and More... (Slides With Transcript)

  • Authors: Michael F. Vaezi, MD, PhD
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Target Audience and Goal Statement

This activity has been designed to meet the educational needs of gastroenterologists, nurse practitioners, nurses and pharmacists, and other healthcare providers involved in the care of patients with esophageal disorders.

Upon completion of this activity, participants should be able to:

  1. Evaluate the role of new diagnostic techniques in investigating esophageal function: pH and/or impedance monitoring, high-resolution manometry, wireless Bravo technology, etc.
  2. Describe the increasing prevalence of eosinophilic esophagitis in the adult population, its presentation, natural history, and treatment.
  3. Discuss the changing epidemiology of GERD, Barrett's esophagus, and esophageal adenocarcinoma, and appreciate what interventions might affect natural history and disease progression.
  4. Evaluate the underlying causes, the diagnosis and subsequent management of the extraesophageal manifestations of GERD, including persistent cough, asthma, hoarseness, and sleep disturbance.
  5. Identify the benefits and the challenges of managing the spectrum of acid-related disorders and be familiar with the potential advantages of some of the evolving therapies and their possible role in future management.


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  • Michael F. Vaezi, MD, PhD

    Professor of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee


    Disclosure: Grant/Research Support: AstraZeneca, Restech, TAP; Consultant: AstraZeneca, Restech; Speaker Honoraria: AstraZeneca, TAP

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New Ways to Investigate Esophageal Function: pH, Impedance, Manometry, Capsules, and More... (Slides With Transcript)

Authors: Michael F. Vaezi, MD, PhDFaculty and Disclosures



  • We are going to be talking about things that you may or may not be using in your motility lab. If you have a motility lab, these are things that perhaps you should have. We are going to talk about the advantages and disadvantages of each of the devices.

  • Slide 1.

    Slide 1.

    (Enlarge Slide)

Ambulatory Monitoring

  • Ambulatory monitoring -- we are going to talk about manometry second, first the monitoring devices. These are what you have currently available. Acid, to monitor acid reflux you have the catheter-based system, the Bravo or the wireless system, the Restech, which you may or may not have heard about. These are the new devices that are supposedly more sensitive, but we're doing the studies. These are placed in the oral pharynx. I'll show you a picture of that. All of these devices measure acid. Then the new devices, the one that's new, Impedance, measures non- or weakly acid. This is in patients that you may have on proton pump inhibitor (PPI) therapies that are not responding. Could it be weakly or nonacidic material that is causing the patient's symptom?

  • Slide 2.

    Slide 2.

    (Enlarge Slide)
  • We are going to ask the first audience response question. Respond to this with "yes" or "no": "pH monitoring is the gold standard for detecting gastroesophageal reflux disease."

  • Slide 3.

    Slide 3.

    (Enlarge Slide)
  • Seventy-two percent said true. That used to be the case, so this is somewhat of a trick question; it no longer is. That's why what we currently do is empiric therapy. That is the gold standard. Then the best next test is going to be impedance-pH monitoring for physiologic reasons, but we'll discuss the pluses and minuses of that. pH monitoring is no longer the gold standard. But, we will not be using these devices on a patient who has symptoms up front. The current recommendations suggest empiric therapy. So by default, the tests that we do in the esophagus for these patients are because they have not or partially responded to therapy. Lack of response to therapy is an indication. We are assessing compliance or reflux-related cause for the patient's continued symptom, whether it be typical reflux or extraesophageal reflux as Dr Wong will be discussing. Physiologic assessment prefundoplication. If you are sending a patient to have reflux surgery, you want to make sure that they havethe disease for which they are having surgery.

  • Slide 4.

    Slide 4.

    (Enlarge Slide)
  • If you do that in patients that are off therapy, there is a spectrum of disease, physiologically. That is the degree of acid reflux increases as you go from left to right. Nonerosive disease, reflux disease with erosions (that's GERD), or Barrett's esophagus patients that may have uncomplicated Barrett's or complicated intraepithelial (IE) esophagitis or ulcers. There is clearly an increased amount of acid reflux in these patients.

  • Slide 5.

    Slide 5.

    (Enlarge Slide)

pH Monitoring Systems

  • When we do the studies on therapy, so if you have a patient that has symptoms on therapy and you do pH monitoring on therapy, the likelihood that you have abnormality goes down. It makes sense. If you have typical reflux, the likelihood that it going to be normal is 93%, as shown here. More important, especially in the extraesophageal, the studies show that 99% of the time your pH monitoring is going to be normal. Pretest likelihood, before you do the test, you know it's going to be normal. We do it to document it, but that's the pretest probability.

  • Slide 6.

    Slide 6.

    (Enlarge Slide)
  • We could monitor patients in the distal esophagus, in the proximal esophagus, or the hypopharynx, depending on what we're looking for. Most of us are doing distal esophageal pH monitoring. Proximal and hypopharyngeal pH monitoring are reserved for research purposes and/or if you have extraesophageal patients.

  • Slide 7.

    Slide 7.

    (Enlarge Slide)
  • Next question: "For your pH monitoring, do you routinely use wireless capsule, the Bravo pH, catheter-based pH monitoring, or you don't use anything?"

  • Slide 8.

    Slide 8.

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  • Twenty-three percent use the wireless, 42% catheter. There's no right or wrong answer, obviously, here. It depends on what you have in your lab. A third of you do not use it; therefore, you are referring to centers that do have them. The key here is the indication for which you should refer to those centers. Both are correct -- wireless if you have it. We'll talk about the pluses and minuses of this device. For patient comfort, it's probably the better of the two. The catheter-based system has been around and they work very well. This is the wireless device, those of you that do it, small capsule that's placed in the distal esophagus. The placement is usually either through direct visualization when you do the endoscopy, which is how I do it, or you take the endoscope out and then advance the introducer.

  • Slide 9.

    Slide 9.

    (Enlarge Slide)
  • The advantage here is that, obviously, not only are you monitoring for 24 hours, you can monitor for longer, 48 or even 96 hours. The recent studies are suggesting that we can even do off-and-on therapy. You have the patient off therapy for the first 48, then do on-therapy, and there is perhaps increased sensitivity the longer you monitor patients.

  • Slide 10.

    Slide 10.

    (Enlarge Slide)
  • Bravo vs catheter, patient comfort is the main reason for the wireless devices, because patients don't have anything in their nose and in the hypopharynx or traversing the upper esophageal sphincter. Increased sensitivity, some studies suggest that there is increased clinical yield with these devices because we are monitoring them longer. Improved patient compliance, reduced impairment of daily activity, and decreased likelihood of catheter movement. We talked about monitoring the effect of PPI on patients.

  • Slide 11.

    Slide 11.

    (Enlarge Slide)
  • This is the new Restech device. This is placed in the oral pharynx. In this picture, the 2 catheters are the ones that we traditionally use. We place that through the nose, into the esophagus or upper esophagus. Patients feel this a lot more. This is the tip of the catheter, the Restech catheter. It sits in the oral pharynx. Supposedly, it's more sensitive. Supposedly, you can pick up vapors of acidic material. This becomes important in patients that may have throat symptoms, your laryngopharyngeal (LPR) patients and such. But, studies need to be done here -- there were a couple of posters at this American College of Gastroenterology (ACG) -- but there will be more studies in this to come.

  • Slide 12.

    Slide 12.

    (Enlarge Slide)
  • Another question: "Impedance monitoring along with measurement of pH provides the most useful data on esophageal refluxate. Is that true or is that false?"

    Eighty-six percent of you said true. That is true. Consensus statement on this suggests from a physiologic standpoint it's probably the best test we have because we can monitor various refluxate, whether it be gas or liquid at various pHs. I'll show you a picture of that.

  • Slide 13.

    Slide 13.

    (Enlarge Slide)

Measuring Impedance

  • This is the catheter. The disadvantage is it's still a catheter. It's not wireless. But, the catheter has these rings. A voltage is applied to this catheter. Then a current is generated between the rings. Current and impedance are opposites. If there is good current, your impedance is going to be higher. If you have bad current, your impedance is lower. What happens when there is liquid around the rings, current is flowing better; therefore, impedance is going to be the opposite. I'll show you a picture of that.

  • Slide 14.

    Slide 14.

    (Enlarge Slide)
  • Here's when you have the catheter in the esophagus and a bolus that's traversing that correlates with each of these impedance traces. As you see, as the bolus goes through along those 2 catheters, the impedance drops, then here, then here. What's happening is you're having a swallow. A drop in impedance is liquid, so this is telling us that this is a swallow. You can imagine if this occurred in a reverse fashion, shown in this light, this would be a reflux event.

  • Slide 15.

    Slide 15.

    (Enlarge Slide)
  • What happens here is a refluxate comes up. Liquid, therefore, impedance drops first in the distal esophagus, then followed by more proximal migration of the liquid. This is how we can tell if you are refluxing liquid or gas. What happens with gas is impedance would actually go up.

  • Slide 16.

    Slide 16.

    (Enlarge Slide)
  • This is an example of liquid. But, because it also has a pH on it, you can actually tell whether this liquid that is refluxing proximally is acidic or not. In this case it was. The way we use this device is if someone is on PPI, what we're looking for is predominantly nonacidic reflux. The pH would not change, but impedance would. Then we would count the numbers or look at the symptom index. On this side you actually see a gas reflux, the best example of gas reflux being burping. This patient was burping here, and what you see is impedance goes up distally to proximally. pH doesn't change, so this is a nonacidic gas reflux. We can tell physiologically what the patient has.

  • Slide 17.

    Slide 17.

    (Enlarge Slide)
  • When you look at studies, this is a Dr Vela study published in Gastroenterology, looking at no treatment and the number of reflux events that are acidic or nonacidic and what happens. Not surprisingly, when you put patients on PPIs, you are converting them from acidic refluxate to nonacidic reflux. The biggest question here is, is that nonacidic reflux the cause of the patient's problem, not whether it's occurring. Is it causing the symptom?

  • Slide 18.

    Slide 18.

    (Enlarge Slide)
  • The limitation of this device, automation is a problem. You have to really look at this tracing. It takes me about 15 to 20 minutes to go through 1 tracing. You can't just look at the number that it spits out. It's still not highly accurate, but it's getting better. Inability to quantify volume, and if you have a patient that has Barrett's or esophagitis, the impedance numbers are low; therefore, it will be harder to interpret.

  • Slide 19.

    Slide 19.

    (Enlarge Slide)

Nonacid Reflux in GERD

  • Another question: "The most likely diagnosis for patients with refractory GERD symptoms is nonacid reflux. True or false?"

    This was a trick question. The answer is "yes." You do have nonacid reflux that occurs, but remember the presence of nonacid doesn't equal causality. The most likely diagnosis for patients may be nonacid reflux, but not as the cause of their refractory symptom. Those studies are still ongoing. This is somewhat controversial. For you to know that it is a great device physiologically, but whether or not it tells us a refractory patient is truly nonacid has yet to be determined.

  • Slide 20.

    Slide 20.

    (Enlarge Slide)
  • To address this question, Dr Castelle's group published this. This is a multi-center study looking at 144 patients that were on twice a day PPI, but they were still having symptoms. In their study they found that 37% of patients had nonacid reflux using symptom index, and 11% had acid defined by pH of greater than on 1.6%. But again, causal association is not well established right now.

  • Slide 21.

    Slide 21.

    (Enlarge Slide)

Manometry and Diagnosis

  • Switching gears going to manometry, I'm going to show you some abnormal tracings. This is a normal tracing. If you have a manometry catheter in the esophagus, with a swallow, what happens is, there is peristalsis and with that swallow there is initiation of lower esophageal sphincter (LES) relaxation. It stays open to accommodate the bolus. Then it recovers. This is a normal motility.

  • Slide 22.

    Slide 22.

    (Enlarge Slide)
  • This is diffuse esophageal spasm. What makes this spasm not achalasia is this swallow here. There is a mixed peristaltic with simultaneous contraction. As long as you have peristalsis it's not achalasia; therefore, it's diffuse esophageal spasm.

  • Slide 23.

    Slide 23.

    (Enlarge Slide)
  • This is nutcracker esophagus. The name suggests what it is -- high pressure. It's normal except it's high pressure. Peristaltic, but very high amplitude.

  • Slide 24.

    Slide 24.

    (Enlarge Slide)
  • The problem with manometry is there is a high degree of variability on who is reading it. If you read it and you are not adequately trained or you are unsure, you are going to read it, perhaps, incorrectly. We did a study looking at 6 gastroenterologists, esophagologists, and there is a high degree of variability if patients do not have achalasia or they are not normal. The end extremes are easier to diagnose. If you have achalasia or if you are normal, it's easier to diagnose than if you have anything else in between.

  • Slide 25.

    Slide 25.

    (Enlarge Slide)
  • High-resolution manometry is developed in order to help with this variability, and I think it probably does a good job. With high resolution manometry, this is your normal tracing, so you look at 1 time period and what you do is, you plot that time period the way you see here. This is a pressure time plot. You notice that there is higher pressure here and there is higher pressure here. Lower pressures, therefore, low pressures.

  • Slide 26.

    Slide 26.

    (Enlarge Slide)
  • Then you convert this into color. Red color is going to indicate higher pressure, such as seen here. Blue color is lower pressure. When you look at a swallow, what is happening here is you have higher pressure here and lower pressure here. This is a swallow. I'll show you a better example in a second.

  • Slide 27.

    Slide 27.

    (Enlarge Slide)
  • This is the catheter. What happens is you have 12 pressure sensors that are along the catheter, so it gives you more information and actually looks almost like a video when you look at it.

  • Slide 28.

    Slide 28.

    (Enlarge Slide)
  • A normal peristalsis, this is 1 swallow. Upper esophageal sphincter, lower esophageal sphincter, with a swallow the upper esophageal sphincter is contracted; therefore, the color turns blue, lower pressure. It's opening up. Then there is peristalsis. These are contracting states. The lower esophageal sphincter has opened, and then it recovers after the swallow goes through. All the color is doing is showing you the same thing I showed you on manometry, but it's a bit easier to read.

  • Slide 29.

    Slide 29.

    (Enlarge Slide)
  • This is achalasia. What you see is upper esophageal sphincter (UES), LES with a swallow it opens. UES should, but not the LES. And, there is no peristalsis. Everything is occurring simultaneously. Visually, it's a pattern recognition. You look at this, that's achalasia or scleroderma if the pressure was low.

  • Slide 30.

    Slide 30.

    (Enlarge Slide)
  • The clinical significance of this is shorter acquisition time. It does take less time instead of having to pull the catheter back. Shorter acquisition time, no need to pull through, less discomfort, and decreased technical variability.

  • Slide 31.

    Slide 31.

    (Enlarge Slide)


  • Conclusions: In patients unresponsive to PPI therapy, new technologies allow monitoring of acid and weakly or nonacidic material in the esophagus, oral pharynx, and hypopharynx. Wireless pH monitoring has clearly increased our patients' comfort and acceptance and possibly the sensitivity of the test.

  • Slide 32.

    Slide 32.

    (Enlarge Slide)
  • High-resolution manometry simplifies manometric diagnosis, decreases the variability technically, and increases physiologic data and reduces procedure time. Thank you very much.

    DR DAVID PEURA: Thank you very much, Michael. Our next speaker is Joel Richter. Joel is Chair of Medicine at Temple University here in Philadelphia. He is going to be talking about Eosinophilic Esophagitis: New Insights.

  • Slide 33.

    Slide 33.

    (Enlarge Slide)