Arterial pCO2 changes during thoracoscopic surgery with CO2 insufflation and one lung ventilation

INTRODUCTION: The respiratory effects (changes in pH and PaCO(2)) of carbon dioxide insufflation in thoracoscopic surgery in adult patients with pulmonary disease were not documented previously. METHODS: In this observational study 21 patients scheduled for elective thoracoscopic surgery with one lung ventilation using a double lumen tube and intraoperative carbon dioxide insufflation were studied. Arterial blood gas findings were correlated with demographic and intraoperative variables. RESULTS: When compared to baseline (10-15 minutes of one lung ventilation before carbon dioxide insufflation), carbon dioxide insufflation lowered the pH, 7.31±0.08 vs 7.40±0.05 (p<0.001) caused increased PaCO(2), 53±12 vs 42±6.0 (p<0.001) at 40-60 minutes after carbon dioxide insufflation. These derangements in arterial blood gases persisted in the post-anesthetic care unit with pH 7.33±0.04 vs 7.40±0.05 (p<0.001) and PaCO(2) 51±6.7 vs 42±6.0 (p<0.001). Moderate hypercarbia defined as PaCO(2) >50 mmHg, developed in 12 of 21 patients (57%) and was associated to lower FEV1/FVC ratios 60±21 vs 81±3%, older age 69±9 vs 56±17 years, and history of smoking, 43 ± 30 vs 16±21 pack years, p<0.05. CONCLUSIONS: Intrathoracic carbon dioxide insufflation causes significant derangements in pH and PaCO(2) which is worse in patients with lower FEV1/FVC, increased age and smoking history.