Evaluation of response to PEEP in patients with severe acute respiratory syndrome due to COVID-19 in a multicenter retrospective cohort

Abstract

Introdution: Positive end-expiratory pressure (PEEP) adjustment serves as a potential tool for mitigating airway driving pressure (dPaw) in individuals afflicted with acute respiratory distress syndrome (ARDS), a condition for which enhanced survival has been correlated. Methods: This study represents a prospective physiological investigation involving patients admitted to the intensive care units of six hospitals afflicted with COVID-19-related ARDS (C-ARDS) ion different regions from Brazil. A standardized PEEP titration protocol was executed on deeply sedated and paralyzed patients. All subjects were subjected to Volume-Controlled Ventilation (VCV) with a tidal volume (VT) of 6 ml per kilogram of ideal body weight (IBW). PEEP titration was conducted within the range of 20 cmH2O to 6 cmH2O. The optimal PEEP value derived from the titration (PEEPTIT) was defined as the PEEP level associated with the minimum dPaw. Each dPaw versus PEEP curve was categorized into one of three patterns based on the differences between the minimum dPaw and the dPaw values at the lowest (dPlow) and highest (dPhigh) PEEP settings: J-shaped, inverted-J-shaped, and U-shaped. In one of the hospitals, patients underwent Electrical Impedance Tomography (EIT) examinations during the PEEP titration procedure. The EIT-derived optimal PEEP (PEEPEIT) was defined as the PEEP level that represented the best compromise between hyperdistension and collapse estimation. Results: This study delineates the alterations in airway dPaw induced by PEEP adjustments during a decremental PEEP titration process involving 184 patients with C-ARDS. Among them, 41 patients underwent PEEP titration while being monitored with Electrical Impedance Tomography (EIT). Among the cohort, 126 (68%) patients exhibited enhanced compliance and reduced dPaw during the decremental PEEP trial, thus being classified as non-responders to PEEP. These patients displayed a J-shaped dPaw versus PEEP curve, with an average PEEPTIT value of 7.5 cmH2O. In contrast, 40 (22%) patients manifested a U-shaped curve, indicating superior compliance and minimal dPaw, with an average PEEPTIT value of 12.2 cmH2O. Only 18 (10%) patients exhibited an inverted-J-shaped profile, characterized by increasing dPaw and decreasing PEEP levels, with an average PEEPTIT value of 14.6 cmH2O. These patients were characterized by higher body mass indices and lower PaO2/FiO2 ratios. Conclusion: The PEEP titration strategy employing EIT, which considers the estimation of collapse and overdistension, yielded comparable results when compared to the shape of the driving pressure versus PEEP curve obtained solely at the bedside using mechanical ventilation. The responsiveness to PEEP was found to be linked to disease severity, along with alterations in respiratory system mechanics associated with obesity