Effects of individualized positive end-expiratory pressure on pulmonary function in patients undergoing thoracic surgery

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.