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: A radiation source assembly for optical transducers used for the analysis of material components of media, whereby the radiation source assembly comprises: two thermal radiation sources (1, 2), of which the first radiation source (1) is located, in relation to the second radiation source, in such a position that it emits through the second radiation source (2); a band-stop filter (10) located between the first and the second radiation sources, so that the radiation (6) emitted by the first radiation source passes through it. Both thermal radiation sources (1, 2) comprise a substrate (3, 11) made of silicon, of a silicon mixture or of a silicon compound, and a recess (53) made in the substrate, and micro-filaments (4, 5), which are fastened at their ends to the outer surface (51, 52) of the substrate, their radiation (6, 8) emitting regions being at a distance (H) from the bottom surface (54) of the recess.