An in vitro characterization of a silicone tonometer system for synchronous measurement of tissue oxygen- and carbon dioxide tension.
A new tonometry system for continuous and synchronous measurement of tissue oxygen- and carbon dioxide tension is described and characterized in vitro. The tonometer system consists of an O2 and CO2 permeable silicone tube continuously flushed with isotonic saline by an injection pump. When the saline passes through the tonometer tube it equilibrates with O2 and CO2 outside the tube. The oxygen- and carbon dioxide tension of the flushing solution after passage of the tonometer tube are measured by a transcutaneous combined oxygen/carbon dioxide electrode (E5280 Radiometer A/S, Copenhagen, Denmark), connected to the tonometer tube via an airtight polycarbonate chamber. In order to characterize the tonometer system in vitro the tonometer tube was submerged in a test chamber containing isotonic saline, 33 degrees C to 41 degrees C, with varying partial pressures of O2 and CO2. For various lengths of the tonometer and flushing rates through the tonometer the partial pressures of oxygen and carbon dioxide in the flushing solution (pO2eq and pCO2eq), after passage through the tonometer were recorded and compared to the known partial pressures of oxygen and carbon dioxide in the test chamber solution (pO2 test and pCO2test). PO2eq and pCO2eq approached pO2test and pCO2test, when the length of the tonometer was increased, and the flushing rate through the tonometer was decreased. The relative differences (D) between pO2eq and pCO2eq at the one hand and pO2test and pCO2test at the other hand were calculated, and equilibration curves were constructed.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Surgical Gastroenterology C, Rigshospitalet, University Hospital, Copenhagen, Denmark.
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Larsen
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Pedersen
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Moesgaard
D002245:Carbon Dioxide / Q000032:analysis*; D004566:Electrodes; D006801:Humans; D010100:Oxygen / Q000032:analysis*; D012828:Silicones
D012828:Silicones; D002245:Carbon Dioxide; D010100:Oxygen