The association between the initial end-tidal carbon dioxide difference and the lowest arterial oxygen tension value obtained during one-lung anesthesia with propofol or sevoflurane.

OBJECTIVE: The purpose of this study was to examine the correlation between the lowest PaO(2) value recorded during the first 45 minutes of one-lung ventilation (OLV) and the end-tidal CO(2) (ETCO(2)) difference between two-lung ventilation (TLV) and the early phase of OLV. DESIGN: A prospective, randomized study. SETTING: A university hospital. PARTICIPANTS: Thirty-six patients scheduled for elective thoracic surgery. INTERVENTIONS: Thoracic surgery patients were randomly assigned to 1 of 2 groups (group P [n = 18], maintained with propofol; group S [n = 18], maintained with sevoflurane). After setting up, the authors measured arterial blood gases at F(I)O(2) = 1.0 as follows: during TLV and at 5 minutes, 15 minutes, 30 minutes, and 45 minutes after the start of OLV. ETCO(2) was recorded just before and at 3 minutes after the start of OLV. The authors examined the relationship between the initial ETCO(2) difference and the lowest PaO(2) value recorded during the first 45 minutes of OLV. MEASUREMENTS AND MAIN RESULTS: There was a significant negative correlation between the lowest PaO(2) (x) value and the initial ETCO(2) difference (y) during OLV in each group (group P: y = -0.0203x + 7.2571, r(2) = 0.5351; group S: y = -0.0257x + 7.3158, r(2) = 0.6129). This correlation was not significantly different between the groups. CONCLUSION: The present study indicates that the ETCO(2) difference between TLV and early OLV has an association with impaired oxygenation later during OLV. This would be a simple and clinically convenient predictor of the lowest PaO(2) value likely to be reached during one-lung anesthesia with either propofol or sevoflurane.