Accuracy of Transcutaneous CO 2 Values Compared With Arterial and Capillary Blood Gases

Transcutaneous monitors are utilized to monitor a patient's respiratory status. Some patients have similar values when comparing transcutaneous carbon dioxide (P ) values with blood gas analysis, whereas others show extreme variability. A retrospective review of data was performed to determine how accurately P correlated with CO values obtained by arterial blood gas (ABG) or capillary blood gas. To determine whether P values correlated with ABG or capillary blood gas values, subjects' records were retrospectively reviewed. Data collected included the P value at the time of blood gas procurement and the ABG or capillary blood gas P value. Agreement of pairs of methods (ABG vs P and capillary blood gas vs P ) was assessed with the Bland-Altman approach with limits of agreement estimated with a mixed model to account for serial measurements per subject. A total of 912 pairs of ABG/P values on 54 subjects and 307 pairs of capillary blood gas/P values on 34 subjects were analyzed. The P range for ABG was 24-106 mm Hg, and P values were 27-133 mm Hg. The P range for capillary blood gas was 29-108 mm Hg, and P values were 30-103 mm Hg. For ABG/P comparisons, the Pearson correlation coefficient was 0.82, 95% CI was 0.80-0.84, and was