Abstract:Objective To evaluate the effect of setting the optimal positive end-expiratory pressure (PEEP) based on static compliance (Cstat) on pulmonary function in patients undergoing thoracic surgery. Methods Sixty patients scheduled for elective video-assisted thoracoscopic lobectomy at Linyi People’s Hospital from September 2022 to May 2023 were randomly divided into an experimental group and a control group, with 30 cases in each group. In the experimental group, after one-lung ventilation, lung recruitment was first performed, followed by finding the optimal PEEP using a decremental PEEP trial guided by Cstat. PEEP was set at 5 cmH₂O after one-lung ventilation in the control group. Hemodynamic parameters [heart rate (HR), mean arterial pressure (MAP)], and respiratory mechanics parameters [airway plateau pressure (Pplat), Cstat, driving pressure (DP)] were recorded at four time points: after induction of anesthesia and intubation (T₁), immediately after the start of one-lung ventilation (T₂), and 30 min (T₃) and 60 min (T₄) after PEEP setting. Arterial and mixed venous blood gas analyses were performed at these time points to measure pressure of arterial oxygen (PaO₂) and calculate the oxygenation index (OI), intrapulmonary shunt fraction (QS/QT), and dead space fraction (VD/VT). Inflammatory cytokines [interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-ɑ)] levels were also measured in arterial blood samples taken at the beginning and end of one-lung ventilation. Results When the Cstat of the experimental group reached its maximum, the PEEP value was (7.67±0.80) cmH₂O. After transitioning from two-lung to one-lung ventilation, both groups experienced a decrease in OI, an increase in QS/QT, and reduced Cstat. During one-lung ventilation, compared to the control group, the experimental group had higher Cstat (P＜0.05), lower DP (P＜0.01), higher OI (P＜0.05), and lower QS/QT (P＜0.05) at T₃ and T₄. The experimental group also had significantly lower IL-6 levels than the control group after one-lung ventilation ended (P＜0.05). Conclusion During one-lung ventilation in thoracic surgery, patients experience a decrease in OI, an increase in QS/QT, and reduced lung compliance; compared to a fixed PEEP (5 cmH₂O), individualized PEEP values set based on Cstat can significantly reduce intrapulmonary shunt, improve intraoperative oxygenation, decrease DP, increase lung compliance, and suppress inflammatory responses.