Is End-tidal Carbon Dioxide Tension Useful to Predict Arterial Carbon Dioxide Tension during One Lung Ventilation? - A Comparison with during Two Lung Ventilation

Abstract

End-tidal carbon dioxide tension (PETCO2) is widely used to estimate arterial carbon dioxide tension (PaCO2) under various clinical conditions. This study was conducted to determine if PETCO2 during one lung ventilation (OLV) is as useful as PETCO2 during two lung ventilation (TLV) for predicting PaCO2. Methods: Forty patients undergoing thoracic surgery were enrolled in this study. During OLV (n = 20) and TLV (n = 20), PaCO2 and PETCO2 were measured. The arterial-end tidal carbon dioxide difference (Pa-ETCO2) was then calculated and a correlation between PaCO2 and PETCO2 was evaluated during OLV and TLV. Results: Pa-ETCO2 was significantly higher during OLV (8.9 ± 5.1 mmHg) than during TLV (6.1 ± 3.9 mmHg). In addition, the correlation between PETCO2 and PaCO2 was less significant during OLV (R2 = 0.43) than during TLV (R2 = 0.59). Conclusions: PETCO2 during OLV was not as accurate as PETCO2 during TLV for predicting PaCO2, which indicates that greater attention should be given to the maintenance of normocarbia during OLV than during TLV.