Bibliography: p. 110-120Includes copy of ethics approval and copyright permissions. Original copies with original Partial Copyright Licence.Technical innovations for esophageal testing are continuously evolving to help people better understand and treat various esophageal disorders. In this work, efforts have been focused on the developments of two innovative systems for improving the diagnosis of gastroesophageal reflux disease (GERD) and esophageal motility disorders (EMDs). Determining the volume of gastroesophageal reflux (GER) is important for the diagnosis and treatment of GERD. However, a reliable diagnostic method for accomplishing this task is still missing. This research provided an integrated tool for automated monitoring of GER volume. A simple, low-cost ultrasonic probe was developed as a volumetric sensing component and it was combined with a commercially available multichannel intraluminal impedance catheter. The integrated tool was successfully tested in in-vitro laboratory and in-vivo human studies. In-vitro testing results demonstrated the accuracy of the volumetric measurement. In-vivo human testing was undertaken on two healthy human subjects. Results confirmed the feasibility of the proposed system for measuring volume of liquid GER in the vicinity of the ultrasonic probe. The proposed method paved the way towards an improved diagnosis and treatment of GERD. Ambulatory esophageal manometry has been considered the optimal technique for precise classification of various types of EMDs. However, current ambulatory manometry systems are not widely accepted due to their high costs, incomplete circumferential pressure sensing capabilities, and other practical issues. In this study, a novel manometry catheter containing a cost-effective pressure sensor capable of circumferential sensing was presented to overcome these limitations. A portable-size capacitance measurement device was used as an interface between the sensor and a graphical user interface on a personal computer. Experimental results confirmed the feasibility of the new manometry system for measuring circumferential pressure. This study provided a significant contribution towards a disposable esophageal manometry catheter to facilitate a low-cost and reliable ambulatory monitoring of esophageal motility