The ESO-Pill™: a non-invasive MEMS capsule for bolus transit monitoring in the esophagus

Monitoring bolus transit in the esophagus has been pivotal for the diagnosis of achalasia, diffuse spasm, motor abnormalities associated with systemic disorders, and gastro-esophageal reflux disease. Despite recent advances in X-ray imaging and the introduction of multichannel intraluminal impedancometry, these studies remain moderately invasive. Barium radiography subjects the patient to X-ray radiation, while the new technique of impedance monitoring employs catheters introduced either transnasally or transorally. Rapid developments in microelectronics, micro-electromechanical systems (MEMS) and wireless radio-frequency (RF) transmission created the possibility of suggesting a conceptually different and completely noninvasive technique for esophageal bolus transit testing. In the present study, the concept of the ESO-Pill™ is introduced, a noninvasive swallowable "smart" microelectronic capsule, which can monitor in real time its acceleration, velocity of propagation, position, and the contractile force that pushes it as it passes through the esophagus. The capabilities and the limitations of the ESO-Pill™ are discussed in the context of the radically different type of measurements that such device could offer, while every attempt is made to associate these measurements with the presently available bolus transit monitoring standards in esophageal testing.