Transcutaneous Carbon Dioxide Monitoring More Accurately Detects Hypercapnia than End-Tidal Carbon Dioxide Monitoring during Non-Intubated Video-Assisted Thoracic Surgery: A Retrospective Cohort Study

Transcutaneous carbon dioxide (PtcCO(2)) monitoring is known to be effective at estimating the arterial partial pressure of carbon dioxide (PaCO(2)) in patients with sedation-induced respiratory depression. We aimed to investigate the accuracy of PtcCO(2) monitoring to measure PaCO(2) and its sensitivity to detect hypercapnia (PaCO(2) > 60 mmHg) compared to nasal end-tidal carbon dioxide (PetCO(2)) monitoring during non-intubated video-assisted thoracoscopic surgery (VATS). This retrospective study included patients undergoing non-intubated VATS from December 2019 to May 2021. Datasets of PetCO(2), PtcCO(2), and PaCO(2) measured simultaneously were extracted from patient records. Overall, 111 datasets of CO(2) monitoring during one-lung ventilation (OLV) were collected from 43 patients. PtcCO(2) had higher sensitivity and predictive power for hypercapnia during OLV than PetCO(2) (84.6% vs. 15.4%, p < 0.001; area under the receiver operating characteristic curve; 0.912 vs. 0.776, p = 0.002). Moreover, PtcCO(2) was more in agreement with PaCO(2) than PetCO(2), indicated by a lower bias (bias ± standard deviation; −1.6 ± 6.5 mmHg vs. 14.3 ± 8.4 mmHg, p < 0.001) and narrower limit of agreement (−14.3–11.2 mmHg vs. −2.2–30.7 mmHg). These results suggest that concurrent PtcCO(2) monitoring allows anesthesiologists to provide safer respiratory management for patients undergoing non-intubated VATS.