Table 1. Summary of available literature on gastrointestinal pH measurement with freely moving devices in healthy volunteers and / or inflammatory bowel diseases.
| Study | Device | Subjects | Battery life | pH Sampling interval | Position detection | Food intake during study | Data loss | pH drift device during study | Total transit time | Remarks |
|---|---|---|---|---|---|---|---|---|---|---|
| Watson et al, 1972 [8] | Radiotelemetry Capsule | 2 healthy subjects 7 patients with miscellaneous gastrointestinal disorders | 10 days | 60 min | Abdominal x-ray | Device intake after breakfast. No restrictions in food and beverages | - a | 0.1 unit | - | |
| Evans et al, 1988 [9] | Radiotelemetry capsule (Remote control systems Ltd, UK) | 72 healthy subjects | - | 12 seconds | “locator” to detect highest signal intensity | Device intake after overnight fasting. breakfast after leaving the stomach. No restrictions in food and beverages | In 14 subjects > 75% loss in the small intestine | pH 4: < 0.6 unit pH 9.2 < 1.0 unit | Mean: 23.3 h | Measurement up to 48 h. Median signal loss 20.4%. 2 subjects > 1.0 unit pH drift |
| Fallingborg et al, 1989 [10] | Radiotelemetry Capsule (Remote control systems Ltd, UK) | 39 healthy subjects | - | 15–120 min (not between 11 pm and 8 am) | Fluoroscopy | Device intake after overnight fasting; breakfast after leaving the stomach. Food and beverages according to the protocol | - | < 0.9 unit | 9–129 h | |
| Raimundo A et al 1992 [11] | Radiotelemetry Capsule | 7 patients with acute colitis 6 patients with ulcerative colitis in remission | - | - | Based on pH | - | - | - | - | |
| Fallingborg et al, 1993 [12] | Radiotelemetry Capsule | 7 patients with ulcerative colitis | - | 30 min (not between 11 pm and 8 am) | Fluoroscopy | Device intake after overnight fasting; breakfast after leaving the stomach. No restrictions in food and beverages | - | < 0.4 unit | 8 - > 123 h | Measurement max 39h. |
| Sasaki et al, 1997 [13] | Radiotelemetry Capsule (Remote control systems Ltd, UK) | 4 healthy subjects 4 patients with Crohn’s disease | 1 | 1 second | Based on pH, x-ray, contrast colonogram and a radio-directional probe | Device intake after overnight fasting; breakfast after leaving the stomach. Food according to the protocol | - | < 0.5unit | - | |
| Press et al, 1998 [14] | Radiotelemetry Capsule (7036, Oakfield instruments, UK) | 12 healthy subjects 11 patients with ulcerative colitis 15 patients with Crohn’s disease | - | - | “locator” to detect highest signal intensity | Device intake after overnight fasting; breakfast after leaving the stomach. No restrictions in food and beverages | In 4 subjects > 75% loss in 24h | < 0.5 unit | - | Measurement in the colon was marked as unpredictable. 4 subjects had to repeat the study |
| Fallingborg et al, 1998 [15] | Radiotelemetry Capsule (remote control systems Ltd, UK) | 13 healthy subjects 9 patients with Crohn’s disease | - | 10–15 min | Fluoroscopy | Device intake after > 8h fasting; breakfast after leaving the stomach | - | <0.4 unit | - | Difference in small intestine transit time between resected patients and healthy volunteers |
| Ewe et al, 1999 [16] | Radiotelemetry Capsule (7036, Oakfield instruments, UK) | 15 healthy subjects 15 patients with Crohn’s Disease 5 patients with ulcerative colitis | 24 h | 6 seconds | Metal detector | Device intake after > 8h fasting; breakfast after leaving the stomach | 6 subjects excluded, several reasons | - | Median 24–31 h | In 1 subject > 2 weeks retention of RTC |
| Maqbool et al, 2009 [17] | SmartPill, (Buffalo, NY, USA) | 10 healthy subjects | 5 days | 5 seconds, after 24 h 20 seconds | Based on pH | 2000 kcal diet, 30% fat. Device intake after breakfast | - | - | - | |
| Rubin et al, 2009 [18] | Smartpill, (Buffalo, NY, USA) | 10 patients with active ulcerative colitis | - | - | Based on pH, motility and temperature | - | - | - | Median 24.6 h | No complications with the device |
| Lalezari et al, 2012 [19] | SmartPill, (Buffalo, NY, USA) | 10 healthy subjects 9 patients with IBS | 5 days | 5 seconds | Based on pH | Device intake after > 8h fasting; breakfast after leaving the stomach | - | - | - | |
| Schaar et al, 2013 [20] / Koziolek et al, 2014 [21] | (IntelliCap MedimetricsEindhoven, NL) | 2x 10 healthy volunteers | > 48 h | 10 seconds | Study 1: based on pH and temperature. Study 2: also based on 99MTc | Device intake with water after overnight fasting. Food 4 h after device intake | Mean 3.5% (one subject 13%) | - | Average 30:34 h | Two publications, same studies |
a- = no information in publication.