Two hundred seventy-eight patients undergoing thoracic surgery were retrospectively analyzed to determine whether which variable can predict the identification of patients at risk of arterial hypoxemia developing during one-lung ventilation (OLV). Methods: According to the value of SpO2, the patients were divided two groups. Group L (n = 62) had SpO2 values of less than 95%, whereas group H (n = 216) those of more than 95%. Preoperative and intraoperative data, including past medical history,

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... rrent therapy, and usual preoperative and intraoperative tests, were collected and used as predictable variables for arterial hypoxemia during OLV by binary logistic regression (forward conditional method) subsequent to independent t-test and Chi-square test, as appropriate. Results: Preoperative (past medical history with pulmonary resection of a lobectomy in dependent lung, hypertension, arrhythmias, and predicted diffusion capacity for carbon monoxide ≤ 70%) and intraoperative (arterial oxygen tension/inspiratory oxygen fraction during two-lung ventilation < 528 mmHg, right thoracotomy) variables were considered as predictable factors that identified patients at risk of arterial hypoxemia during OLV. Conclusions: Caution to the increased risk of arterial hypoxemia during OLV is needed in patients that have aforementioned preoperative and intraoperative variables.