Gravitational distribution of regional opening and closing pressures, hysteresis and atelectrauma in ARDS evaluated by electrical impedance tomography

Critical Care

Alessandro Santini¹  Elena Spinelli²  Giacomo Grasselli³  Tommaso Mauri³  Antonio Pesenti³  Savino Spadaro⁴  Francesca Dalla Corte⁴  Gaetano Scaramuzzo⁴  Donatella Tortolani⁴  Carlo Alberto Volta⁴ 

[1] Department of Anaesthesia and Intensive Care Medicine, Humanitas Clinical and Research Centre-IRCCS, Rozzano, Milan, Italy;Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy;Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via F. Sforza 35, 20122, Milan, Italy;Department of Pathophysiology and Transplant, University of Milan, Milan, Italy;Department of Morphology, Surgery and Experimental Medicine, Intensive Care Unit, Azienda Ospedaliera Universitaria Sant’Anna Hospital, Ferrara, Italy;

关键词: Electrical impedance tomography;    Hysteresis;    VILI;    ARDS;   

DOI  :  10.1186/s13054-020-03335-1

来源: Springer

【 摘 要 】

BackgroundThe physiological behavior of lungs affected by the acute respiratory distress syndrome (ARDS) differs between inspiration and expiration and presents heterogeneous gravity-dependent distribution. This phenomenon, highlighted by the different distribution of opening/closing pressure and by the hysteresis of the pressure–volume curve, can be studied by CT scan, but the technique expose the patient to radiations, cannot track changes during time and is not feasible at the bedside. Electrical impedance tomography (EIT) could help in assessing at the bedside regional inspiratory and expiratory mechanical properties. We evaluated regional opening/closing pressures, hysteresis and atelectrauma during inspiratory and expiratory low-flow pressure–volume curves in ARDS using electrical impedance tomography.MethodsPixel-level inspiratory and expiratory PV curves (PVpixel) between 5 and 40 cmH2O were constructed integrating EIT images and airway opening pressure signal from 8 ARDS patients. The lower inflection point in the inspiratory and expiratory PVpixel were used to find opening (OPpixel) and closing (CPpixel) pressures. A novel atelectrauma index (AtI) was calculated as the percentage of pixels opening during the inspiratory and closing during the expiratory PV curves. The maximal hysteresis (HysMax) was calculated as the maximal difference between normalized expiratory and inspiratory PV curves. Analyses were conducted in the global, dependent and non-dependent lung regions.ResultsGaussian distribution was confirmed for both global OPpixel (r2 = 0.90) and global CPpixel (r2 = 0.94). The two distributions were significantly different with higher values for OPpixel (p < 0.0001). Regional OPpixel and CPpixel distributions were Gaussian, and in the dependent lung regions, both were significantly higher than in the non-dependent ones (p < 0.001). Both AtI and the HysMax were significantly higher in the dependent regions compared to the non-dependent ones (p < 0.05 for both).ConclusionsGravity impacts the regional distribution of opening and closing pressure, hysteresis and atelectrauma, with higher values in the dorsal lung. Regional differences between inspiratory and expiratory lung physiology are detectable at the bedside using EIT and could allow in-depth characterization of ARDS phenotypes and guide personalized ventilation settings.Graphic abstract

【 授权许可】

CC BY