pCO/sub 2/, pO/sub 2/, and pH monitoring using micro-flow colorimetry

pCO/sub 2/, pO/sub 2/ and pH levels are optically monitored using continuous micro-flow of colorimetric indicators through hollow fiber membranes in contact with blood. Optical monitoring is achieved using LEDs and photodetectors coupled to outlet micro-bore capillary tubes. Three separate hollow fiber membranes are selected based on membrane permeability to the measurand. The sensors are exposed to blood in an extracorporeal loop using continuous flow or blood withdrawal-reinfusion.