The main objective of this study is to investigate the possible benefits of using the oxygen reserve index (ORi) parameter during one-lung ventilation (OLV) and elective thoracic operations. For this purpose, ORi values are compared to primary hemodynamical parameters of blood pressure (BP) and heart rate (HR) and Meanwhile, a device from Masimo Inc, USA, provides oximeter-related parameters, including peripheral oxygen saturation, perfusion index (PI), and pleth variability index (PVI). The secondary objective is to investigate possible statistically significant correlations between these hemodynamical and oximeter parameters using appropriate statistical methods.

The study participants are patients undergoing video-assisted thoracotomy surgical procedures (VATS) or open thoracotomy for suspicion and possible lung tumor removal. The surgical operation of either lobectomy, pneumonectomy, lung biopsy, or wedge resection is considered during this procedure. The inclusion and exclusion criteria are summarized in another section of the clinicaltrials.gov registration document. All patients in the study receive a similar anesthetic management protocol. Premedication is not required in the study. After admitting a patient to the operating theatre, pulse oximetry SpO2, electrocardiogram, and noninvasive blood pressure monitoring are established. Heart rate (HR), mean arterial pressure (MAP), systolic blood pressure (SBP), and diastolic blood pressure (DBP) are measured at certain time points. Anesthesia requires induction of anesthesia with intravenous doses of propofol (Pofol, Fresenius Pharmaceutical, Turkey), 2 to 3 mg/kg, rocuronium (Esmeron, Organon Pharmaceuticals, U.S.A.) at a dose of 0.6 mg/kg, and fentanyl (Janssen fentanyl, Janssen Pharmaceutical, Belgium) at a dose of 2 to 3 mcg/kg. Tracheal intubation requires the use of a left Robertshaw double-lumen tube. During anesthesia, one-lung ventilation (OLV) is provided to all patients in addition to mechanical ventilation. The anesthesia maintenance includes inhalational anesthetic of sevoflurane (Sevorane, Abbott Pharmaceutical, USA) at an end-tidal concentration of 1 to 2% to provide a sufficient minimum alveolar concentration to establish anesthesia and intravenous fentanyl boluses at a dose of 0.2 mcg/kg every hourly to provide analgesia and to keep mean arterial blood pressure between 60 and 80 mmHg. In addition to standard follow-up parameters, oxygen reserve index (ORi), perfusion index (PI), pleth variability index (PVI) is monitored for each patient at certain time points. Hypoxemia during OLV was defined as peripheral oxygen saturation (SpO2) value of less than 95% when the inspired oxygen fraction (FiO2)value is equal to or greater than 60% on a pulse oximetry device. Hemodynamic and oximeter data were continuously monitored. The parameters that are in need of investigation include; MAP, SBP, DBP, HR, SpO2, PaO2, ORi, PI, and PVI values. These data are monitored at thirteen different time points during the period of anesthesia induction and maintenance of the surgery. The device used in this study is called the Radical-7 Pulse CO-Oximeter device for the measurement of ORi, PI, and PVI. A correlation between these values was investigated on the continuous graphs. The duration of surgery, anesthesia, OLV, and total 100% oxygen application time are recorded. Blood gas analysis was provided at DL5 at a 5-minute time point and blood gas analysis was performed for prolonged surgeries and for surgeries with high bleeding performance that required other analysis. Routinely, patients are ventilated with 50% FiO2 (50% oxygen + 50% air mixture, 1 liter/minute fresh gas flow) after induction. The value of FiO2 rises depending on pulse oximeter values between the values of 60% and 100% in order to keep SpO2 values greater than 94. The incidence of thromboembolic complications, arrhythmia, pneumonia, the duration of hospital and intensive care unit stay is recorded.