PTU-176 Implementation of Objective Activity Monitoring to Supplement the Interpretation of Ambulatory Oesophageal pH Investigations

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Conventional catheter-based systems used for ambulatory oesophageal pH monitoring have been reported to affect patient behaviour. As physical activity has been associated with gastro-oesophageal reflux disease (GORD), there is a risk that abnormal behaviour will degrade the value of this diagnostic investigation and consequent management strategies. Our aim was to provide the reporting physician with objective peri-investigational changes in activity, and the means to assess the association between activity and pH during the test, using a wearable activity monitor.


Trial registered at (NCT01507298) and ethics approved (11/LO/1981). Twenty patients listed for 24h pH monitoring underwent activity monitoring using a lightweight ear-worn accelerometer (e-AR sensor, Imperial College London) 2 days prior to, and during their investigation. PH was measured and recorded using a conventional naso-gastric catheter and waist worn receiver. Objectively measured activity levels, including subject-specific activity intensity quartiles, were calculated and compared over the 3 days. Physical activity was added to standard test outputs to supplement interpretation and diagnosis.


Average patient activity levels decreased by 26.5% during pH monitoring (Range -4.5–51.0%, p = 0.036). The amount of high intensity activities decreased by 24.4% (Range –4.0–75.6%, p = 0.036), and restful activity increased on average by 34% although this failed to reach statistical significance (-24.0–289.2%, p = 0.161). Some patients exhibited consistent associations between bouts of activity and acidic episodes (Figure 1).


The results of this study support the previously reported reduction in activity during ambulatory oesophageal pH monitoring,1,2 with the added reliability of objective activity data. In the absence of more pervasive pH monitoring systems (e.g. wireless), quantifying activity changes in the setting of activity-induced reflux might facilitate recalibration of patient DeMeester scores and therefore more appropriate management of GORD.

Disclosure of Interest

None Declared.

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