Individualized Positive End-expiratory Pressure Titration Strategies in Superobese Patients Undergoing Laparoscopic Surgery: Prospective and Nonrandomized Crossover Study

Abstract

Background Superobesity and laparoscopic surgery promote negative end-expiratory transpulmonary pressure, which causes atelectasis formation and impaired respiratory mechanics. We hypothesized that end-expiratory transpulmonary pressure differs between fixed and individualized PEEP strategies, and mediates their effects on respiratory mechanics, end-expiratory lung volume, gas-exchange, and hemodynamic parameters in superobese patients. Methods In this prospective, non-randomized crossover study including 40 superobese patients (body mass index 57.3 ± 6.4 kg·m-2) undergoing laparoscopic bariatric surgery, PEEP was set according to A) a fixed level of 8 cmH2O (PEEPEmpirical), (B) the highest respiratory system compliance (PEEPCompliance) or (C) an end-expiratory transpulmonary pressure targeting 0 cmH2O (PEEPTranspul) at different surgical positioning. The primary endpoint was end-expiratory transpulmonary pressure at different surgical positioning, secondary endpoints were respiratory mechanics, end-expiratory lung volume, gas-exchange, and hemodynamic parameters. Results Individualized PEEPCompliance compared to fixed PEEPEmpirical resulted in higher PEEP (supine, 17.2 ± 2.4 vs. 8.0 ± 0.0 cmH2O; supine with pneumoperitoneum, 21.5 ± 2.5 vs. 8.0 ± 0.0 cmH2O; and beach chair with pneumoperitoneum; 15.8 ± 2.5 vs. 8.0 ± 0.0 cmH2O; P < 0.001 each) and less negative end-expiratory transpulmonary pressure (supine, −2.9 ± 2.0 vs. −10.6 ± 2.6 cmH2O; supine with pneumoperitoneum, −2.9 ± 2.0 vs. −14.1 ± 3.7 cmH2O; and beach chair with pneumoperitoneum, −2.8 ± 2.2 vs. −9.2 ± 3.7 cmH2O; P < 0.001 each). Titrated PEEP, end-expiratory transpulmonary pressure and lung volume were lower with PEEPCompliance compared to PEEPTranspul (P < 0.001 each). Respiratory system and transpulmonary driving pressure, and mechanical power normalized to respiratory system compliance were reduced using PEEPCompliance compared to PEEPTranspul. Conclusions In superobese patients undergoing laparoscopic surgery, individualized PEEPCompliance may provide a feasible compromise regarding end-expiratory transpulmonary pressures compared to PEEPEmpirical and PEEPTranspul, since PEEPCompliance with slightly negative end-expiratory transpulmonary pressures improved respiratory mechanics, lung volumes, and oxygenation while preserving cardiac output.

Pressure for High Positive End-expiratory Pressure in Obese Surgical Patients Is Growing

“…Individualized mean PEEP levels were never lower than 15.8 cm H 2 O and were as high as 25.4 cm H 2 O depending on position and pneumoperitoneum insufflation. 2 Such values of PEEP are still unusual in routine practice, 9 but they are well within the range of individualized PEEP values found by other groups utilizing other PEEP optimization methods, such as electrical impedance tomography. 4,12 Also, in line with previous studies in obese patients, 4 end-expiratory lung volume was more than doubled with most individual PEEP settings compared to PEEP 8 cm H 2 O (table 3 in Boesing et al 2 ), resulting in improved oxygenation and lung mechanics.…”

“…2 Such values of PEEP are still unusual in routine practice, 9 but they are well within the range of individualized PEEP values found by other groups utilizing other PEEP optimization methods, such as electrical impedance tomography. 4,12 Also, in line with previous studies in obese patients, 4 end-expiratory lung volume was more than doubled with most individual PEEP settings compared to PEEP 8 cm H 2 O (table 3 in Boesing et al 2 ), resulting in improved oxygenation and lung mechanics. However, recommendations using absolute esophageal pressure should be interpreted with caution because of errors related to balloon placement or filling volumes, and artifacts from cardiac or esophageal muscle activity.…”

“…, cardiac output 6.44 vs . 6.25 l ⋅ min -1 , P = 0.018; table 3 in Boesing et al 2 ). Of course, caution with high PEEP levels is required in patients with known cardiac failure or untreated hypovolemia.…”

“…1,2 Using different approaches for identifying the optimal PEEP level, both studies found individualized PEEP levels to be greater than 15 cm H 2 O in obese (body mass index 30 kg/m 2 or greater) 1 and superobese (body mass index 50 kg/m 2 or greater) patients. 2…”

“…Another PEEP titration approach was used by Boesing et al ., 2 who present a physiologic crossover design comparing three different strategies for PEEP optimization in each of 40 superobese patients undergoing laparoscopic surgery. PEEP titrations were performed in the supine position, with and without pneumoperitoneum, and in the beach-chair position.…”