The utility of transcutaneous carbon dioxide measurements in the emergency department: A prospective cohort study

Background Rapid identification of patients with occult injury and illness in the emergency department can be difficult. Transcutaneous carbon dioxide (TCO 2 ) and oxygen (TO 2 ) measurements may be non‐invasive surrogate markers for the identification of such patients. Objectives To determine if TCO 2 or TO 2 are useful adjuncts for identifying severe illness and the correlation between TCO 2 , lactate, and end tidal carbon dioxide (ETCO 2 ). Methods Prospective TCO 2 and TO 2 measurements at a tertiary level 1 trauma center were obtained using a transcutaneous sensor on 300 adult patients. Severe illness was defined as death, intensive care unit (ICU) admission, bilevel positive airway pressure, vasopressor use, or length of stay >2 days. TCO 2 and TO 2 were compared to illness severity using t tests and correlation coefficients. Results Mean TO 2 did not differ between severe illness (58.9, 95% CI 54.9–62.9) and non‐severe illness (58.0, 95% CI 54.7–61.1). Mean TCO 2 was similar between severe (34.6, 95% CI 33–36.2) vs non‐severe illness (35.9, 95% CI 34.7–37.1). TCO 2 was 28.7 (95% CI 24.0–33.4) for ICU vs. 35.9 (95% CI 34.9–36.9) for non‐ICU patients. The mean TCO 2 in those with lactate > 2.0 was 29.8 (95% CI 25.8–33.8) compared with 35.7 (95% CI 34.9–36.9) for lactate < 2.0. TCO 2 was not correlated with ETCO 2 (r = 0.32, 95% CI 0.22–0.42). Conclusion TCO 2 could be a useful adjunct for identifying significant injury and illness and patient outcomes in an emergency department (ED) population. TO 2 did not predict severe illness. TCO 2 and ETCO 2 are only moderately correlated, indicating that they are not equivalent and may be useful under different circumstances.