| Tissue oxygenation has been recognized as an important index of tissue metabolic state and perfusion. A method of continuous recording of tissue oxygenation would be of use in the therapy of shock, various respiratory diseases, surgical recovery, and other conditions. Currently there is no practical method for continuous, long-term tissue oxygen monitoring. An implantable electrochemical oxygen sensor developed previously for use in conjunction with a long-term intravenous blood glucose sensor may be adaptable for implantation in the tissues for continuous tissue oxygen measurements. There are, however, many phenomena that may effect the oxygen signal when the sensor is employed in tissue, such as metabolic oxygen consumption, variations in local microvascular perfusion, the wound healing response, and tissue heterogeneity. The role of these phenomena are explored in this thesis.; To study these effects, a hamster skinfold window chamber preparation was employed for visualization of specific superficial tissues in the hamster, into which electrochemical oxygen sensors were implanted. This preparation allowed study of the tissue without the inhibitory effects of anesthetics on microvascular function. The preparation was used in conjunction with a novel tissue scanning technique based on the oxygen quenching of phosphorescence decay to measure oxygen concentrations in the vicinity of the sensor and to evaluate tissue oxygen heterogeneity during the wound healing process. The system also allowed examination of the tissue response over several days.; The results of these studies indicate that the tissue oxygen distribution is spatially and temporally heterogeneous, and this feature must be taken into account in interpretation of the sensor response. An observed decay in sensitivity of the sensor to oxygen concentration during the initial period of implantation may be related to modifications of the tissue structure in the vicinity of the sensor with time. |
