An implantable batteryless wireless impedance sensor for gastroesophageal reflux diagnosis
ABSTRACT A new method for long term monitoring of gastroesophageal reflux is presented. The impedance of the reflux in the esophagus can be determined remotely without the need of a battery in the sensor implant. The implant includes an energy harvesting circuit, sensing electrodes, an antenna and an impedance to frequency converter. An external reader provides power to the implant and measures the impedance values simultaneously. A prototype with an overall size of 0.5 × 1 × 3.1 cm3 was made with a printed circuit board and discrete components, and packaged in polydimethylsiloxane. In vivo experiments were conducted in pig cadavers. The results show good correlation between impedance and pH values of the acid solutions flushed into the esophagus, and good signal-to-noise ratios with the transducer inside the body. The impedance sensor can detect nonacid materials due to the frequency shift differences between air and solutions. The batteryless wireless impedance sensor is able to detect every reflux episode, either acid or non-acid, which provides more accurate diagnosis for the gastroesophageal reflux disease.
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ABSTRACT: Prolonged, 4-day (96 h) measurement by the wireless Bravo system provides an opportunity to assess the variance, diagnostic reproducibility, and yield of 24- and 48-h pH and symptom association studies. Retrospective analysis of 83 patients with suspected reflux symptoms undergoing wireless pH monitoring with the intention of 96-h measurement. Study periods were classified based on esophageal acid exposure, the DeMeester score (DMS), and the association of reflux events and symptoms (symptom index). The technical success of prolonged pH recording and diagnostic accuracy of 24-, 48-, and 72-h pH studies compared to the 96-h "gold standard" were assessed. Prolonged Bravo pH studies were possible and well tolerated in routine clinical practice. Complete 96-h recordings were available for 34/83 (41%) patients. Variation in pH measurements reduced with increasing study duration (24-h 45%vs 48-h 27%, P<0.01), but no change in reflux severity over time was observed (ANOVA, P=ns). Abnormal acid exposure was found in 7 (19%) on every test day and 21 (58%) on at least one of four test days. A diagnosis consistent with the 96-h "gold standard" was present in 22 (63%), 29 (83%), and 32 (91%) patients for 24-, 48-, and 72-h test periods, respectively, with a significant improvement of diagnostic sensitivity with study duration (P<0.01). Similar findings were present for symptom association. Increasing the duration of pH studies progressively improves measurement variance and the diagnostic reproducibility of reflux studies. Future studies must address the impact of prolonged pH studies on clinical management.The American Journal of Gastroenterology 12/2007; 102(12):2642-7. · 7.55 Impact Factor
Article: Surgical therapy for reflux disease.JAMA The Journal of the American Medical Association 06/2001; 285(18):2376-8. · 29.98 Impact Factor
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ABSTRACT: Impedance monitoring is a new diagnostic method for gastroesophageal reflux disease (GERD) where multiple impedance electrode pairs are placed on a standard pH catheter. It detects reflux of a liquid and/or gas bolus into the esophagus, as well as its distribution, composition, and clearing. The aim of this collaborative study is to define normal values for 24-h ambulatory simultaneous impedance and pH monitoring (24-h Imp-pH), and compare bolus parameters by impedance monitoring to changes in [H(+)] measured by pH monitoring. Sixty normal volunteers without GER symptoms underwent 24-h Imp-pH with impedance measured at six sites (centered at 3, 5, 7, 9, 15, and 17 cm above lower esophageal sphincter) and pH 5 cm above the LES. Reflux detected by impedance was characterized by the pH probe as either acid, weakly acidic, nonacid, or superimposed acid reflux. Proximal reflux was defined as reflux that reached the impedance site 15 cm above the LES. Reflux frequency was common upright (median-27, 25th and 75th quartile-16, 42), but rare recumbent (median-1; 0, 4). A median of 34% (14%, 49%) of upright reflux reached the proximal esophagus. There was a similar number of mixed composition (liquid + gas; 49%) and liquid-only reflux (51%). Acid reflux was two-fold more common than weakly acidic reflux (p < 0.001). Superimposed acid reflux and nonacid reflux were rare. Acid neutralization to pH 4 took twice as long as volume clearance measured by impedance. Combining impedance and pH monitoring improves the detection and characterization of GER. This study characterizes the frequency, duration, and extent of reflux in health and provides normal values for 24-h Imp-pH for future comparison with GERD patients.The American Journal of Gastroenterology 06/2004; 99(6):1037-43. · 7.55 Impact Factor