This is an observational study, which aims to compare the outcomes of ambulatory gastrointestinal investigations with physical activity using accelerometry. An ambulatory study refers to one in which the patient is monitored freely, often outside of the hospital environment. For this the investigators will use a lightweight (7.4g) tri-axial accelerometer worn behind the ear.

Hypothesis 1 There is no change in the amount or nature of physical activity taken by patients during ambulatory oesophageal pH monitoring or capsule endoscopy.

Hypothesis 2 There is no correlation between physical activity levels and speed of gastrointestinal transit.

For capsule endoscopy, the investigators are interested in how physical activity affects the speed of capsule transit through the GI tract. Capsule endoscopy involves a patient swallowing a pill which contains a camera, in order to image the parts of the bowel that a conventional endoscope cannot reach. A rapid transit may result in insufficient mucosal visualisation, which would reduce the sensitivity of the investigation.

For oesophageal pH monitoring, it is essential that the patient behaves as they would normally to produce measurements that represent a standard day. Using accelerometry, the investigators can compare the amount, and nature, of physical activity taken throughout the investigation to that of the preceding day, or week. In addition, further analysis of motion data captured will allow us to correlate specific activities and body orientation with pH readings to get a better insight into the pathophysiology of a patient's condition.

The studies will be conducted over 6-9 months in Imperial College Trust's medical outpatient service. All patients undergoing capsule endoscopy or ambulatory oesophageal monitoring will be asked to consider participating. Patients will receive the eAR sensor up to 2 days before their investigation, and will be asked to wear it until the end of their investigation (not whilst sleeping). Capsule endoscopy normally takes less than 12 hours, and pH monitoring takes between 24 and 48 hours. Participation makes no difference to the standard or type of care that they will receive, the sensor data is additional.

Inclusion Criteria:

• Planned 24 hour oesophageal pH monitoring study, or capsule endoscopy

Exclusion Criteria:

1. Undergone previous capsule endoscopy or ambulatory oesophageal pH test
2. Currently a hospital in-patient
3. Severe mobility disorder (unable to walk or mobilise independently)
4. Age less than 18 or above 65
5. Physically unable to wear eAR sensor (eg. bilateral hearing aids or particularly small ears)

Those who have been advised to undergo 24 hour oesophageal pH monitoring, or capsule endoscopy (from GI outpatients clinic)

2 days

No adverse events were anticipated from participation in this study.