Erratum: Concordance and limits between transcutaneous and arterial carbon dioxide pressure in emergency department patients with acute respiratory failure: a single-center, prospective, and observational study

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 (TCO2) and oxygen (TO2) measurements may be non-invasive surrogate markers for the identification of such patients.

OBJECTIVES

To determine if TCO2 or TO2 are useful adjuncts for identifying severe illness and the correlation between TCO2, lactate, and end tidal carbon dioxide (ETCO2).

METHODS

Prospective TCO2 and TO2 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. TCO2 and TO2 were compared to illness severity using t tests and correlation coefficients.

RESULTS

Mean TO2 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 TCO2 was similar between severe (34.6, 95% CI 33-36.2) vs non-severe illness (35.9, 95% CI 34.7-37.1). TCO2 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 TCO2 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. TCO2 was not correlated with ETCO2 (r = 0.32, 95% CI 0.22-0.42).

CONCLUSION

TCO2 could be a useful adjunct for identifying significant injury and illness and patient outcomes in an emergency department (ED) population. TO2 did not predict severe illness. TCO2 and ETCO2 are only moderately correlated, indicating that they are not equivalent and may be useful under different circumstances.

Transcutaneous PCO2 monitoring in critically ill patients: update and perspectives

The physiology of venous and tissue CO₂ monitoring has a long and well-established physiological background, leading to the technological development of different tissue capnometric devices, such as transcutaneous capnometry monitoring (TCM). To outline briefly, measuring transcutaneous PCO₂ (tcPCO₂) depends on at least three main phenomena: (I) the production of CO₂ by tissues (VCO₂), (II) the removal of CO₂ from the tissues by perfusion (wash-out phenomenon), and (III) the reference value of CO₂ at tissue inlet represented by arterial CO₂ content (approximated by arterial PCO₂, or artPCO₂). For this reason, there are, at present, roughly two clinical uses for tcPCO₂ measurement: a respiratory approach where tcPCO₂ is likely to estimate and non-invasively track artPCO₂; and a hemodynamic under-estimate use where tcPCO₂ can reflect tissue perfusion, summarized by a so-called "tc-art PCO₂ gap". Recent research shows that these two uses are not incompatible and could be combined. The spectrum of indications and validation studies in ICUs is summarized in this review to give a survey of the potential applications of TCM in critically ill patients, focusing mainly on its potential (micro)circulatory monitoring contribution. We strongly believe that the greatest benefit of measuring tcPCO₂ is not to only to estimate artPCO₂, but also to quantify the gap between these two values, which can then help clinicians continuously and noninvasively assess both respiratory and hemodynamic failures in critically ill patients.