A method and system that provides for minute-to-minute EBC pH monitoring of a subject that greatly assists in determining the time-course of airway pH changes in evolving disease processes, and may assist in determining the predictive ability of these tests, as well as determining response to therapy. The back surface of this metal plate and the back surface of a first supporting member are substantially within a same plane, so that it is readily affixed to a second supporting member. An arcuate light dispersion piece is connected to the bite block so that, in use, the light dispersion piece is orientated in a rear, central part of the oral cavity of the patient’s mouth so that dispersed light can be transmitted outward from the rear, central part of the oral cavity.