Catheterless oesophageal pH monitoring (interventional procedures consultation document)


Interventional Procedure Consultation Document

Catheterless oesophageal pH monitoring

The National Institute for Health and Clinical Excellence is examining catheterless oesophageal pH monitoring and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute’s Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about catheterless oesophageal pH monitoring.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

  • comments on the preliminary recommendations
  • the identification of factual inaccuracies
  • additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.

The Advisory Committee will then prepare draft guidance which will be the basis for the Institute’s guidance on the use of the procedure in the NHS in England, Wales and Scotland.

Closing date for comments: 27 April 2006

Target date for publication of guidance: July 2006

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

1 Provisional recommendations

Current evidence on the safety and efficacy of catheterless pH monitoring appears adequate to support the use of this technique provided that normal arrangements are in place for consent, audit and clinical governance.

2 The procedure
2.1 Indications
2.1.1 Gastro-oesophageal reflux disease (GORD) is a common disorder in which a backwash of gastric juices into the oesophagus leads to inflammation and pain. Symptoms may include heart burn, belching and regurgitation of gastric contents. Complications of GORD may include oesophageal stricture and Barrett’s oesophagus – the latter is associated with carcinoma of the oesophagus. The frequency of exposure to gastric acid over a given period provides a measure of the severity of the disease, and this can be measured by oesophageal pH monitoring. Common indications for pH monitoring include symptoms refractory to proton pump inhibitor therapy, evaluation before surgery and recurrence of symptoms following anti-reflux surgery.

Ambulatory oesophageal pH monitoring is commonly undertaken by transnasal placement of a pH probe on a catheter. This may cause nasal and pharyngeal discomfort, which may alter the patient’s normal diet and activity, giving potentially misleading results.

2.2 Outline of the procedure

A catheterless pH monitoring system comprises a plastic capsule that houses a pH sensor and a transmitter. The capsule continuously senses oesophageal pH and transmits the data every few seconds to a small receiver worn by the patient. After endoscopy the capsule is inserted into the oesophagus and attached at a chosen site on the oesophageal wall by a vacuum that sucks the oesophageal mucosa into a well on the side of the capsule. A spring-loaded pin is then released across the well, tangential to the axis of the oesophagus, to provide fixation. Correct placement and attachment of the capsule is confirmed endoscopically. The capsule detaches from the oesophageal wall after a few days and is excreted through the digestive tract.

2.3 Efficacy

A randomised controlled study (n = 50) found that during a 24-hour period, acid exposure time (defined as oesophageal pH < 4) in patients receiving proton pump inhibitors was recorded as 1.9% by catheterless monitoring and 4.8% by catheter-based monitoring. This difference was not statistically significant. During this study the frequency of GORD symptoms was similar during monitoring with each technique. Overall quality-of-life scores based on the SF-36 scale were also similar between the groups. Significantly more patients undergoing the catheterless monitoring (88%) than the catheter-based monitoring (48%) were willing to have a repeat test if necessary (p = 0.005).

2.3.2 In a within-patient study of 33 patients who had both catheterless and catheter-based monitoring, 1388 reflux episodes were recorded in total over a 24-hour period. Of these reflux episodes, 41% (563/1388) were recorded by both devices, 52% (724/1388) were recorded only by the catheter-based system and 7% (101/1388) only by the catheterless monitor. Overall the reflux episode concordance was 88% (Kappa statistic 0.76).

A non-randomised controlled study in healthy volunteers found that after calibration, the catheterless monitor identified significantly fewer reflux episodes (mean 37.9) during 24-hour monitoring than a catheter-based system (mean 69.8) (p < 0.05). Whether these findings relate to asymptomatic reflux among healthy volunteers or previously undetected disease is unclear. For more details, refer to the sources of evidence (see appendix).


The Specialist Advisors noted that oesophageal pH monitoring may provide accurate recording under conditions of normal daily activity.


2.4 Safety

Follow-up across all the studies included in the overview is based solely on the period of monitoring used; no longer-term data are available.

2.4.2 Among patients in a case series and the catheterless monitoring arms of controlled studies, the incidences of chest pain were 5% (4/85), 33% (26/80) and 36% (9/25). In one of these studies, after the 48-hour monitoring period immediate removal of the capsule because of chest pain was requested by 2% (2/85) of patients.
2.4.3 In a randomised controlled trial the incidence of chest pain was higher with a catheterless monitor (60%) compared with a catheter-based system (24%) (p = 0.01). However, fewer patients reported difficulty swallowing (36%) with the catheterless system than with the catheter-based approach (68%) (p = 0.024). In the same study significantly fewer patients with the catheterless monitoring had nose pain, runny nose, throat pain, throat discomfort and headache. Also, among patients in employment, 58% of the patients with a catheterless capsule were able to return to work during monitoring compared with 11% of those with the catheter-based system (p = 0.049).
2.4.4 In a study of 44 children aged 6–19 years having catheterless oesophageal pH monitoring, 94% (36/38) of parents were willing to allow their child to undergo further wireless pH monitoring, and all 12 patients who had previously had nasal-catheter monitoring were reported to prefer the catheterless method.
2.4.5 There were no reports in the reviewed literature of adverse events relating to the endoscopic component of the procedure. For more details, refer to the sources of evidence (see appendix).
2.4.6 The Specialist Advisors reported adverse events including chest discomfort, mucosal tear, failure of the capsule to detach and failure of data retrieval. They also noted additional theoretical complications including haemorrhage, oesophageal perforation, oesophageal ulceration, capsule misplacement and failure to pass the capsule once detached.
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2.5 Other comments
2.5.1 It was noted that this procedure would be particularly appropriate in children and other patients who may tolerate catheter-based monitoring poorly.

3 Further information

The Institute has issued the following related guidance: ‘Dyspepsia: management of dyspepsia in adults in primary care’ (NICE clinical guideline no. 17). Available from

Bruce Campbell
Chairman, Interventional Procedures Advisory Committee
April 2006

Appendix: Sources of evidence

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

This page was last updated: 04 February 2011