[Continuous measurement of oxygen uptake using the Engström Metabolic Computer]

A new system for continuous measurement of oxygen uptake was tested (EMC). Delivered tidal volumes of the system, the accuracy of the oxygen sensor cell, measurement of the oxygen uptake related to different inspiratory oxygen concentrations as well as comparative tests of oxygen uptake according to Fick's principle were studied. Furthermore, we looked for possible leakages in the system. Following to our results even thorough maintenance could not entirely prevent leakages. There was a remarkable increase in measured oxygen uptake if inspiratory oxygen concentration was increased. While carbon-dioxide output was measured at constant levels this led to low respiratory quotients, some of these were less than 0.5. This was caused by a construction error of the system which could be corrected in the meantime. In 70 comparative tests of oxygen uptake between EMC and Fick's principle (measurement of cardiac output and arteriovenous oxygen content difference) we found a mean difference of about 10% (p less than or equal to 0.001) with nearly identical standard deviations. The EMC measured the higher oxygen uptake. Based on our experience the EMC is suitable for continuous measurement of oxygen uptake but it needs good knowledge of the system and the underlying measuring procedures. Additional technical improvements seem to be possible.