pH metry

What is acid reflux?

When you eat, digestive juices are added to the food, which contain acid. As the stomach churns the food to a paste, all the contents are contained in its closed space. A valve between the food pipe and the stomach prevents escape of the acid rich contents upwards. If this is not competent, you will feel acid like burning after meals, which is called “Reflux”.

What are all the tests available for continuous pH measurement?

Fine catheters have been made that are passed through the nose and the lower most tip is placed 5 cm above the GE junction (the junction between the food pipe and the stomach). This has a sensor that detects a change in the pH to acid. Some catheters have 2 sensors; the lowermost in placed as usual above the GE junction, and a higher sensor is placed close to the throat to detect how high the acid rose. A “Bravo” capsule is a ‘wireless’ method of achieving the same purpose. This capsule is clipped inside  the esophagus 5 cm above the GE junction; and it remotely sends information to a detector outside the body. A recent innovation is MII-pH metry (Multichannel intraluminal impedence) which can detect acid as well as non-acid reflux into the esophagus.

How do I prepare for the test?

24 hour pH metry is done for 2 purposes. 

  • Off treatment it is done to find out if you have reflux of acid at all.
  • On treatment it is done to find out whether the treatment has really suppressed the acid, and what the reasons are, that you still complain of acid reflux. 

In case your test is being done to diagnose acid reflux, I may choose to stop mediation, and allow your natural acid to form normally. 

  • PPIs such as Ompeprazole / Pantoprazole will be discontinued 2 weeks before the test. 
  • H2 blockers (Ranitidine / Famotidine) as well as pro motility drugs (like Metoclopramide –Reglan, Perinorm; Itopride – Ganaton, Domperidone – Domstal, Motilium M will be stopped the day before the test. You may use 2 tablespoons of Liq Gelucil as frequently as every 4 hourly. Another option is Sy Gaviscon 2 tablespoons just after every meal.

Even these antacids should not be taken on the morning of the test (thus, no medication since the midnight prior to the test).

Why have I been advised 24 hour pH metry test?

It seems you have been suffering from “Acid Peptic” symptoms since some time. Typically, these are described as“heartburn” – a burning pain behind the breastbone that comes after meals (or some trigger food in the meals), or if you lie down after a meal. This happens because acid in the stomach actually does come into the food pipe (esophagus). Over the last 2 to 3 decades, Medicine has progressed to a point where most persons can get permanent relief with a short course of tablets.

However, this may unfortunately not happen all the time.

  1. You may be having typical “acid peptic” symptoms, and; in spite of optimum medication as well as lifestyle modifications, your symptoms may continue to hamper your living to an extent that you cannot go off medication, or you may be considered better off with surgery. Before this life changing decision, your doctor may consider proving that acid is actually getting into your esophagus and staying there long enough to cause damage; in spite of all the treatment.
  2. On the other hand, acid in the esophagus may be felt as an atypical symptom like sour fluid coming into the throat, diffuse chest pain not always after meals, choking / wheezing and hoarseness, etc. These atypical symptoms often respond to standard treatment as reflux too. You possibly have been using medication, either “on demand” or after doctor’s orders; and you have not been completely relieved of you symptoms. Now, your doctor is not sure if all the symptoms are due to acid reflux.
  3. You may be reporting acid-peptic symptoms, respond to standard therapy; but your endoscopy may not reveal acid related injury to the esophagus. Doctors often label this as NERD (non erosive reflux disease). If you fail to go off therapy, the presence of acid in the esophagus will need to be proved.

Thus, you have been advised a test called “24 hour pH metry”; a test that is meant to detect, and quantify a reflux event and correlates it to a “symptom event” during a study period.

What will the doctor ask me on the morning of the test?

Before coming for the test, try giving your symptoms a name that will best describe them. When you come for the test, the doctor will ask you which the symptom that bothers you the most is, and key this in as “Number 1”. Usually, patients have up to 3 symptoms that commonly describe their reflux; these will be ranked 2 and 3. More symptoms can also be accommodated. The following is a list of symptoms patients use to describe reflux, but they have minor differences in cause or management:

  • Heart burn burning sensation in the midline behind the breast bone.
  • Regurgitation a feeling of a sour tasting fluid flowing up to the throat
  • Chest pain a diffuse pain over the chest
  • Laryngospasm a sense of choking of breath
  • Wheeze a spasm restricting breathing, audible breathing
  • Globus a sense of something stuck in the throat
  • In case there is any other way to describe the symptom, feel free to do so.

What is the equipment used for the test?

A fine catheter called the “sensor” is passed through the nose; this detects the pH in your food pipe. It will be taped to your cheek on one side, so it does not interfere with eating. It is connected to a “Recorder” that contains a “Memory Card” where all data is being stored. The Recorder is given to you in a “Carrying Case”, which helps you safely carry with you over your shoulder or on your belt all the time. After the procedure is done, the ‘Memory card’ is removed from the recorder, and inserted into a Computer where software generates the information as well as the report.

How should you care for the equipment?

The pH sensing catheter is a single-use catheter; any damage to it will mean we will need to buy another catheter for you. The junction of the catheter into its socket is secure. Any displacement will not set off an alarm, but the device will have stopped receiving signals from the probe. So, do be careful with it. 

Obviously, you are not allowed to open the Recorder, or the battery. The Recorder is not water proof (no showers / tub baths), and will get damaged if it falls. You may wear it under your clothes if it will keep it safe; but it should be accessible to key-in events. We advise the Recorder to be in a Back-pack when used in children; so they do not use it like an X-Box game; but will be accessible to a parent / guardian for keying in events.

 While in bed, do not keep the carrying case around your neck. It is not to be kept in temperatures outside the 0 – 40oC (32 – 104 oF) range. 

If you are wandering about in the hospital, do not go near the X-ray or MRI departments, or through a metal detector. Persons with implanted devices (pacemakers, etc) should inform us in advance as we would need to assess the safety.

Patients with ‘special needs’, like children, visually handicapped, or those with cognitive impairment (find it difficult to follow instructions) should be assisted through their stay by an adult or a guardian.

I have returned to the room after the device has been inserted.

As you are leaving the Procedure room, make sure you have understood the use of the buttons on the Recorder device. You will see that the screen is empty, thus is conserving battery in the standby mode.

Display: To light up the screen, push on the ‘display light’. Pushing any buttons firmly gives an audible ‘beep’ as a feedback, and its function will be displayed on the screen. You need not keep pressing the button repeatedly.

Position: Your position (erect / supine) affects your tendency to reflux. Thus push the ‘Upright key’ when erect, and the ‘recumbent key’ when lying down. The software will be able to tell us how much & how long you reflux lying down. If you are awake through the day, remain erect. Unless you would wish to sleep – don’t stay on a recliner that is neither flat nor sitting. You are expected to spend the day as you normally do; do not assume you are a sick patient and lie down all the time.

Meals: Meals may contain acidic food; we don’t want that to confound the readings. You should key in ‘Begin meal’ when you start a meal; and ‘End meal’ when you finish. eat at least 2 meals at your normal times; prefer the food you know will cause symptoms (provoke symptoms, but don’t overdo it; needing to treat you during the test is a lost cause!). Avoid snacking, sucking on sweets, and chewing gum during the test; it will mess with the results.

Acid related symptoms: There are 3 other keys numbered 1, 2, 3. These keys are to be used to tell the recorder when you are having symptoms. The keys will be programmed by the doctor; he will tell you which number key is to be used for which symptom. It may happen that only 2 keys have been programmed for use. Pressing key number 3 will still produce a beep, but no event will be recorded. On the other hand, you may wish to track more than 3 symptoms. The doctor will then program the most important 3 to designated keys; for other symptoms you will push the ‘Diary key’, note the time as shown on the Recorder device at that time; and note the symptom you wished to report.

Alarms: The battery in the device usually will last through the procedure. But if it gives an alarm for “Low Battery”, inform the nurse. A designated person / nurse with put the device on standby (press ‘light’ + ‘Event1 / Enter’; and press ‘v’ to stop recording). After a fresh battery has been inserted, the device will automatically initiate startup, but will need to be turned on.