, Volume 20, Issue 4, pp 331-334

Effects of the electrode temperature of a new monitor, TCM4, on the measurement of transcutaneous oxygen and carbon dioxide tension

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The transcutaneous measurement of oxygen (tcPO 2) and carbon dioxide (tcPCO 2) tensions may serve as a surrogate of arterial oxygen (PaO2) and carbon dioxide (PaCO 2) tensions, respectively. We investigated the effects of the electrode temperature of a new device, TCM4, on the measurement of tcPO 2 and tcPCO 2. Twenty-five patients scheduled for major lower abdominal surgery were enrolled. The electrode of the TCM4 was attached to the chest, with its temperature set to 37°C, 40°C, 42°C, 43°C, or 44°C. tcPO 2, tcPCO 2, end-tidal carbon dioxide tension (EtCO 2), PaO 2, and PaCO 2 were simultaneously measured at various EtCO 2 levels and inhaled oxygen concentrations. The times required for stabilization of the tcPO 2 and tcPCO 2 values were measured. A Bland-Altman plot was used to compare the two measurements. The time required for stabilization was shorter with a higher electrode temperature, but the shortest time was still more than 150 s. TcPO 2 correlated well with PaO 2 at 43°C and 44°C. TcPCO 2 correlated well with PaCO 2 and EtCO 2 at 43°C. The bias and limits of agreement were larger with lower electrode temperature for TcPO 2—PaO 2, tcPCO 2—PaCO 2, and tcPCO 2—EtCO 2. We concluded that the electrode of the TCM4 should be heated to at least 43°C to measure tcPO 2 and tcPCO 2. However, the absolute values of tcPO 2 and tcPCO 2 could not be used as surrogate measurements of PaO 2 and PaCO 2, respectively.