Evaluation of the Effects of Volume-Controlled and Pressure-Controlled Ventilation on Cerebral Oxygen Saturation, Perfusion Index, and Pleth Variability Index in Septoplasty Surgical Cases: An Observational Prospective Study

Background: This study aimed to assess the reliability of pleth variability index (PVI), perfusion index (PI), and regional cerebral oxygen saturation (rSO₂) across two ventilation strategies in patients un-dergoing septorhinoplasty under general anaesthesia. Materials and Methods: After induction, patients were ventilated with a volume-controlled mode for 20 minutes, during which heart rate (HR), PI, PVI, peripheral oxygen saturation (SpO₂), non-invasive blood pressure (NIBP), and rSO₂ were recorded at 5-minute intervals. Subsequently, ventilation was switched to a pressure-controlled mode for another 20 minutes with repeated measurements at the same intervals. Results: Fifty patients with American Society of Anesthesiologists (ASA) I–III classification and a body mass index (BMI) under 30 were included. Preoperative PI values were significantly lower compared with intraoperative recordings under both ventilation strategies (p<0.05). Preoperative PVI was higher than subsequent measurements, with significantly elevated values during volume-controlled ventilation (VCV) at the 10-minute mark (p<0.05). Left-sided rSO₂ values showed a gradual decrease relative to baseline, whereas right-sided rSO₂ demonstrated progressive increases; however, fluctua-tions remained within 10%. Conclusions: Parameters including HR, PI, PVI, SpO₂, NIBP, and rSO₂ were not interchangeable between the two ventilatory modes. Overall, the transition from VCV to pressure-controlled ventila-tion (PCV) did not yield significant alterations in these variables.