Recent Insights into the Measurement of Carbon Dioxide Concentrations for Clinical Practice in Respiratory Medicine

Abstract

In the field of respiratory clinical practice, the importance of measuring carbon dioxide (CO2) concentrations cannot be overemphasized. Within the body, assessment of the arterial partial pressure of CO2 (PaCO2) has been the gold standard for many decades. Non-invasive assessments are usually predicated on the measurement of CO2 concentrations in the air, usually using an infrared analyzer, and these data are clearly important regarding climate changes as well as regulations of air quality in buildings to ascertain adequate ventilation. Measurements of CO2 production with oxygen consumption yield important indices such as the respiratory quotient and estimates of energy expenditure, which may be used for further investigation in the various fields of metabolism, obesity, sleep disorders, and lifestyle-related issues. Measures of PaCO2 are nowadays performed using the Severinghaus electrode in arterial blood or in arterialized capillary blood, while the same electrode system has been modified to enable relatively accurate non-invasive monitoring of the transcutaneous partial pressure of CO2 (PtcCO2). PtcCO2 monitoring during sleep can be helpful for evaluating sleep apnea syndrome, particularly in children. End-tidal PCO2 is inferior to PtcCO2 as far as accuracy, but it provides breath-by-breath estimates of respiratory gas exchange, while PtcCO2 reflects temporal trends in alveolar ventilation. The frequency of monitoring end-tidal PCO2 has markedly increased in light of its multiple applications (e.g., verify endotracheal intubation, anesthesia or mechanical ventilation, exercise testing, respiratory patterning during sleep, etc.).

End‐tidal and transcutaneous CO2 monitoring during sleep in children aged under three with suspected sleep apnea

“…The percentage of time without an interpretable PetCO 2 signal was higher than that previously reported in older children by Paruthi et al 6 and similar to that found by Kirk et al 4 Our study is the first to focus on children under 3 years of age. We found that the loss of the than for PetCO 2 is as expected with these techniques 7 and is in agreement with what was described during PSG in children. 3 We think that the difference in interpretable time between the two sensors has determined this lack of concordance detected in our patients during the sleep study.…”

Anaesthetic and peri-operative management for thrombectomy procedures in stroke patients

“…In this population, the correlation (R = 0.62), mean bias (13.9 mmHg) and limits of agreement (-5.6-33.6 mmHg) between the measurements provided by the 2 techniques did not suffice to render them interchangeable. Conversely, the values provided by measurement of PtcCO 2 were better correlated with PaCO 2 (R = 0.97), mean bias (1.7 AE 3.9 mmHg) and limits of agreement (-5.8-9 mmHg), which were more compact and closer to those recommended by the American Association for Respiratory Care (1.96 AE 7.5 mmHg) [46]. Present-day limitations to widespread utilization of PtcCO 2 technology stem from its high cost, its uneven availability, a need for regular calibration and an incompressible time lapse (a few minutes) between its installation on a patient's skin, and complete calculation of a value [46].…”

“…Argumentation: As regards the recommendation of systematic monitoring of etCO 2 during thrombectomy under sedation, it is essentially based on the contribution of this technique to the reduction of per-procedure episodes of desaturation and hypoxemia; this was illustrated in 2 meta-analyses [42,43]. Over recent years, etCO 2 monitoring has been substantially improved [44][45][46], and it now ensures reliable surveillance of respiratory frequency and early detection of hypoventilation episodes in spontaneously breathing patients. In these situations, however, non-invasive evaluation of PaCO 2 by etCO 2 is neither reliable nor precise; moreover, it is influenced by supplemental oxygen flow rates, contamination by atmospheric air, and preferential ventilation of dead space in patients suffering from chronic respiratory disease [44,45,47].…”

Health effects of filtering facepiece respirators: Systematic review of pulmonary and cardiovascular effects

“…Transcutaneous carbon dioxide (PtcCO 2 ) measures CO 2 that has diffused through a heated area of skin. 21 Since PtcCO 2 may overestimate PaCO 2 , 32 , 50 its main utility may be to track trends rather than determine actual PaCO 2 .…”