Abstract: An improved remote sensing tonometric catheter apparatus (20) and method for sampling of a fluid or gas property of interest in a hollow internal organ. The tonometric catheter (20) assists in early detection of the problems of stress ulceration and/or intestinal ischemia. The tonometric catheter (20) can be one or more sampling chambers (40) for introduction into an internal organ or area adjacent thereto. Preferably, the wall (36) of the sampling chamber (40) is freely permeable to the gas or fluid to be measured by the sensor (42), but is poorly permeable to other gases or fluids which may interfere with the sensor (42).

Abstract: The method is accomplished by introducing the catheter (20) into the organ such that the sampling chamber (40) is disposed at a portion of the wall of the organ. The sampling chamber (40) is left in position at the wall of the organ for a time sufficient to allow the fluid or gas of interest to diffuse into the sampling chamber (40). The concentration of the liquid fluid or gaseous fluid of interest is analyzed. The pH of the wall of the organ may be calculated based on the concentration of the fluid or gas property of interest.