Can transcutaneous carbon dioxide pressure be a surrogate of blood gas samples for spontaneously breathing emergency patients? The ERNESTO experience

End-tidal CO2 and transcutaneous CO2 : Are we ready to replace arterial CO2 in awake children?

INTRODUCTION

Arterial blood gas analysis (ABG) is the gold standard test for carbon dioxide measurement. End-tidal PCO₂ (PetCO₂ ) and transcutaneous PCO₂ (PtcCO₂ ) are noninvasive alternative methods.

OBJECTIVE

To examine the use of PetCO₂ and PtcCO₂ as PaCO₂ surrogates in awake children.

METHODS

A prospective observational study. Consecutive awake children in a stable condition referred to the Sleep Unit of Hospital de Pediatría Dr. J. P. Garrahan with suspected or confirmed sleep-related respiratory disorders requiring ABG were included. PetCO₂ and PtcCO₂ were recorded simultaneously during arterial puncture. PetCO₂ and PtCO₂ values were compared with PaCO₂ . Correlation coefficient and Bland-Altman analysis were applied. The sample size was calculated considering a mean difference ≤3 mmHg as clinically acceptable.

RESULTS

Sixty-eight sample sets were obtained from 67 patients. The median age was 9.11 years (0.23-18.76). During 94.1% of the procedures patients breathed spontaneously, 30% needed multiple punctures and 92% resulted in pain. Median (IQR) PaCO₂ (mmHg) was 36.3 (31.45; 40.90), PetCO₂ 33.0 (29; 39) and PtcCO₂ 38.8 (32.95; 43.32). Correlation and agreement for PaCO₂ /PetCO₂ and PaCO₂ /PtcCO₂ was r = .6 and .9, and media of bias = 2.83 (-9.97; 15.64) and -1.88 (-9.01; 5.24), respectively. Hypercapnia (PaCO₂  > 45.0 mmHg) was present in 8/68 (11.8%) samples. Sensitivity, specificity, positive predictive value and negative predictive value to detect hypercapnia with PetCO₂ was 38%, 98%, 75%, and 92%, respectively, and with PtcCO₂ , 100%, 90%, 57%, and 100%, respectively.

CONCLUSION

PtcCO₂ showed better agreement with PaCO₂ than PetCO₂ but because of the wide dispersion of values, neither method can replace the gold standard. Transcutaneous CO₂ might be a good screening tool to detect hypercapnia in awake children.

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.

Quality of Documentation as a Surrogate Marker for Awareness and Training Effectiveness of PHTLS-Courses. Part of the Prospective Longitudinal Mixed-Methods EPPTC-Trial

OBJECTIVE

Care for severely injured patients requires multidisciplinary teamwork. A decrease in the number of accident victims ultimately affects the routine and skills. PHTLS ("Pre-Hospital Trauma Life Support") courses are established two-day courses for medical and non-medical rescue service personnel, aimed at improving the pre-hospital care of trauma patients worldwide. The study aims the examination of the quality of documentation before and after PHTLS courses as a surrogate endpoint of training effectiveness and awareness.

METHODS

This was a prospective pre-post intervention trial and was part of the mixed-method longitudinal EPPTC (Effect of Paramedic Training on Pre-Hospital Trauma Care) study, evaluating subjective and objective changes among participants and real patient care, as a result of PHTLS courses. The courses provide an overview of the SAMPLE approach for interrogation of anamnestic information, which is believed to be responsible for patient safety as relevant, among others, "Allergies," "Medication," and "Patient History" (AMP). The focus of the course is not the documentation.

RESULTS

In total, 320 protocols were analyzed before and after the training. The PHTLS course led to a significant increase (p < 0.001) in the "AMP" information in the documentation. The subgroups analysis of "allergies" (+47.2%), "drugs" (+38.1%), and "medical history" (+27.8%) before and after the PHTLS course showed a significant increase in the information content.

CONCLUSION

In summary, we showed that PHTLS training improves documentation quality, which we used as a surrogate endpoint for learning effectiveness and awareness. In this regard, we demonstrated that participants use certain parts of training in real life, thereby suggesting that the learning methods of PHTLS training are effective. These results, however, do not indicate whether patient care has changed.