In vivo and in situ measurement of electrical impedance for determination of distention in proximal stomach of rats

We present a non-invasive, in vivo and in situ study of proximal stomach (PS) distention based on electrical impedance measurements that could be used together with distal stomach (DS) motility measurements as a response to different boluses. Stomach motility has been reported in the literature, as a response to different boluses, under in vivo conditions. However, previous studies on stomach motility have been mainly considered clinical parameters of the digestive process. The physiological complexity of the stomach requires the use of biological models when a detailed analysis of stomach function due to bolus ingestion is required. In this work, the determination of the PS distention in rats is presented. It is based on electrical resistive impedance measurements of the external stomach wall, related to different liquid bolus volumes. Trials were performed under in vivo and in situ conditions. A four-point technique with a vacuum-affixed linear electrode array was used for impedance measurements. A pouch was created in the stomach to retain the saline solution bolus in the PS for a longer time. Resulting impedance changes were directly related to the bolus volumes introduced into the PS and dependent on initial conditions and compensation mechanisms of the in vivo system. With the stomach pouch, a direct relationship between resistive impedance and bolus volume was obtained in all measurements. With no stomach pouch, 93% of the cases showed this relationship. Therefore, the obtained relationship will permit new non-invasive studies in the stomach about the effects of different types of bolus on the distention in the PS of rats.