We prospectively compared the accuracy of end-tidal CO(2) (ETCO(2)) and transcutaneous CO(2) (TCCO(2)) monitoring in older pediatric patients (4 yr or older) receiving mechanical ventilation for respiratory failure. ETCO(2) and TCCO(2) were simultaneously monitored and compared with arterial CO(2) (PaCO(2)) values when arterial blood gas analysis was performed. Eighty-two sample sets were compared. The ETCO(2) to PaCO(2) difference was 6.4 +/- 6.3 mm Hg, whereas the TCCO(2) to PaCO(2) difference was 2.6 +/- 2.0 mm Hg (P < 0.0001). The absolute difference of ETCO(2) and PaCO(2) was 5 or less in 47 of 82 measurements, whereas the absolute TCCO(2) to PaCO(2) difference was 5 or less in 76 of 82 measurements (P < 0.00001). Regression analysis of ETCO(2) and PaCO(2) values revealed a correlation coefficient of 0.5418 and an r value of 0.8745. Regression analysis of TCCO(2) and PaCO(2) values revealed a correlation coefficient of 1.0160 and an r value of 0.9693. Bland-Altman analysis revealed a bias of -5.68 with a precision of +/-6.93 when comparing ETCO(2) with PaCO(2) and a bias of 0.02 with a precision of +/-3.27 when comparing TCCO(2) and PaCO(2) (P < 0.00001). TCCO(2) monitoring provided an accurate estimation of PaCO(2) over a wide range of CO(2) values and was superior to ETCO(2) monitoring in older pediatric patients with respiratory failure. TCCO(2) monitoring may be considered as a useful adjunct to monitoring of ventilation in this patient population.
Implications: The authors report on the accuracy of noninvasive, transcutaneous CO(2) monitoring during mechanical ventilation in children 4 yr or older. Application of this technique should be useful by decreasing the need for repeated, costly, and sometimes painful arterial blood gas analysis, and the continuity of assessment should facilitate proactive, rather than reactive, ventilator manipulations.