Optimal PEEP Obtained by Titrating Inspiratory Oxygen Fraction Versus Electrical Impedance Tomography in Patients with High Risk of Intraoperative Atelectasis: A Randomized Controlled Trial

Background: The optimal intraoperative positive end-expiratory pressure (PEEP) obtained by titrating to the lowest tolerable fraction of inspired oxygen (FiO2) has been proposed recently; however, whether its performance in obtaining optimal PEEP is comparable to that from electrical impedance tomography (EIT) titration remains unknown. Methods: Ninety-three adult patients undergoing robotic-assisted laparoscopic prostatectomy under general anesthesia were enrolled in this study. They underwent the determination of optimal PEEP obtained either by titrating to the lowest tolerable FiO2 (PEEPO2) or using EIT (PEEPEIT). The primary endpoint was intraoperative optimal PEEP values. Secondary endpoints included pre-extubation arterial oxygen partial pressure (PaO2)/FiO2, intraoperative mean arterial blood pressure (MAP), the incidence of hypoxemia in the postanesthesia care unit (PACU), and postoperative pulmonary complications (PPCs) up to discharge from hospital. Results: Group PEEPO2 (n = 47) exhibited a higher optimal PEEP compared to Group PEEPEIT (n = 46) Median (IQR): 18 (16–18 cmH2O) vs. 16 (14–16 cmH2O), p < 0.001. Pre-extubation PaO2/FiO2 was higher in Group PEEPO2 (510.5 ± 80.0 vs. 471.8 ± 69.0 mmHg, p = 0.015), while lung dynamic compliance (41.1 ± 7.7 vs. 37.3 ± 6.4 mL cmH2O−1, p = 0.011) and static compliance (36.4 ± 5.8 vs. 33.6 ± 5.5 mL cmH2O−1, p = 0.017) were also higher in Group PEEPO2. Additionally, driving pressure (11.0 ± 2.0 vs. 12.1 ± 1.9 cmH2O, p = 0.006) was lower in Group PEEPO2. There were no significant differences in intraoperative MAP and the incidences of PACU hypoxemia and PPCs between the two groups. Conclusions: The optimal PEEP obtained by titrating to the lowest tolerable FiO2 is a clinically acceptable alternative of that obtained using EIT. Therefore, this technique could be a viable alternative to EIT for obtaining optimal PEEP.