Longitudinal changes of electrical impedance tomography-based best PEEP in obese patients undergoing laparoscopic surgery: A prospective physiological study
Gaetano Scaramuzzo, P Priani, Pierluigi Ferrara, Marco Verri, Federica Montanaro, Riccardo La Rosa, Gianmaria Cammarota, Carlo Alberto Volta, Savino Spadaro
Abstract
Background During laparoscopic surgery, there is an increased tendency for lung collapse. Individualized PEEP has shown possible advantages in obese patients undergoing laparoscopic procedures, but the optimal timing for titration and the evolution of lung regional mechanics have not been extensively explored. Methods Patients with Class I/II Obesity undergoing laparoscopic surgery for abdominal procedures were monitored using 16 electrodes Electrical Impedance Tomography (EIT) and underwent a decremental PEEP titration trial at 3 timepoints: after anesthesia induction (T1), after positioning and pneumoperitoneum (T2) and after laparoscopy (T3). EIT-derived lung regional collapse (EIT CO ) and overdistension (EIT OD ) were recorded, as well as respiratory mechanics, hemodynamic and surgical data. The best PEEP according to EIT (PEEP EIT ) was calculated at each timepoint as the intersection between regional collapse and overdistention. Results We enrolled 31 patients with a median age of 63 [49-74] years and a BMI of 36 [32-37] kg m -1 . During surgery, PEEP EIT at T1 and T2 were respectively 10[9-11.5] and 13.9[12.6-15] cmH 2 O ( p < 0.001), with a median increase of 3 [2–4] cmH 2 O, a range of increase of 0-7 cmH 2 O and a coefficient of increase variation of 60.8%. The difference in PEEP EIT between T2 and T1 did not correlate with intrabdominal pressure (r=-0.03, p = 0.88), while a significant association was found with trunk inclination ( p = 0.018, r=0.42). Conclusions EIT-based best PEEP changes dynamically and non-homogeneously during laparoscopic surgery in class I/II obese patients. PEEP reassessment is required to guarantee the application of protective mechanical ventilation throughout the entire course of anesthesia. Registration ClinicalTrials.gov, registration number NCT05554536.