Agreement of Mixed Venous Carbon Dioxide Tension (PvCO(2)) and Transcutaneous Carbon Dioxide (PtCO(2)) Measurements in Ventilated Infants

BACKGROUND: Noninvasive transcutaneous carbon dioxide monitoring has been shown to be accurate in infants and children, limited data are available to show the usefulness and limitations of partial transcutaneous carbon dioxide tension (PtCO(2)) value. OBJECTIVES: The current study prospectively determines the effectiveness and accuracy of PtCO(2) measurements in newborns. MATERIALS AND METHODS: Venous blood gas sampling and monitoring of the PtCO(2) level (TCM TOSCA, Radiometer) were done simultaneously. All measurements are performed on mechanically ventilated infants. Partial venous carbon dioxide tension (PvCO(2)) values divided into three groups according to hypocapnia (Group 1: < 4.68 kPa), normocapnia (Group 2: 4.68–7.33 kPa), hypercapnia (Group 3: > 7.33 kPa) and then PvCO(2) and PtCO(2) data within each group were compared separately. RESULTS: A total of 168 measurements of each PvCO(2) and PtCO(2) data were compared in three separated groups simultaneously (13 in Group 1, 118 in Group 2, and 37 in Group 3). A bias of more than ± 0.7 kPa was considered unacceptable. PtCO(2) was related to PvCO(2) with acceptable results between the two measurements in hypocapnia (mean difference 0.20 ± 0.19 kPa) and normocapnia (0.002 ± 0.30 kPa) groups. On the other hand in hypercapnia group PtCO(2) values were statistically significant (P < 0.001) and lower than PvCO(2) data (mean difference 0.81 ± 1.19 kPa) CONCLUSIONS: PtCO(2) measurements have generally good agreement with PvCO(2) in hypocapnic and normocapnic intubated infants but there are some limitations especially with high level of CO(2) tension. Monitoring of PtCO(2) is generally a useful non-invasive indicator of PvCO(2) in hypocapnic and normocapnic infants.