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Calculation of Transpulmonary Pressure from Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

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Calculation of Transpulmonary Pressure from Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome ORIGINAL RESEARCH published: 19 July 2021 doi: 10.3389/fphys.2021.693736 Calculation of Transpulmonary Pressure From Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome Gaetano Scaramuzzo 1*, Savino Spadaro 1, Elena Spinelli 2, Andreas D. Waldmann 3, Stephan H. Bohm 3, Irene Ottaviani 1, Federica Montanaro 1, Lorenzo Gamberini 4, Elisabetta Marangoni 1, Tommaso Mauri 2,5 and Carlo Alberto Volta 1 1 Department of Translational Medicine and for Romagna, University of Ferrara, Ferrara, Italy, 2 Department of Anesthesia, Critical Care and Emergency, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy, 3 Department of Anesthesiology and Intensive Care Medicine, Rostock University Medical Center, Rostock, Germany, 4 Department of Anaesthesia, Intensive Care and Prehospital Emergency, Ospedale Maggiore Carlo Alberto Pizzardi, Bologna, Italy, 5 Department of Pathophysiology and Transplant, University of Milan, Milan, Italy Transpulmonary driving pressure (DPL) corresponds to the cyclical stress imposed on the Edited by: lung parenchyma during tidal breathing and, therefore, can be used to assess the risk Paolo Pelosi, University of Genoa, Italy of ventilator-induced lung injury (VILI). Its measurement at the bedside requires the use Reviewed by: of esophageal pressure (Peso), which is sometimes technically challenging. Recently, it Carmen Silvia Valente Barbas, has been demonstrated how in an animal model of ARDS, the transpulmonary pressure University of São Paulo, Brazil = Hsin-Kuo Bruce Ko, (PL) measured with Peso calculated with the absolute values method (PL Paw—Peso) Taipei Veterans General is equivalent to the transpulmonary pressure directly measured using pleural sensors Hospital, Taiwan in the central-dependent part of the lung. We hypothesized that, since the PL derived *Correspondence: from Peso reflects the regional behavior of the lung, it could exist a relationship between Gaetano Scaramuzzo [email protected] regional parameters measured by electrical impedance tomography (EIT) and driving PL (DPL). Moreover, we explored if, by integrating airways pressure data and EIT data, Specialty section: it could be possible to estimate non-invasively DPL and consequently lung elastance This article was submitted to Respiratory Physiology, (EL) and elastance-derived inspiratory PL (PI). We analyzed 59 measurements from a section of the journal 20 patients with ARDS. There was a significant intra-patient correlation between EIT Frontiers in Physiology derived regional compliance in regions of interest (ROI1) (r = 0.5, p = 0.001), ROI2 Received: 11 April 2021 (r = −0.68, p < 0.001), and ROI3 (r = −0.4, p = 0.002), and DP . A multiple linear Accepted: 14 June 2021 L Published: 19 July 2021 regression successfully predicted DPL based on respiratory system elastance (Ers), ideal 2 Citation: body weight (IBW), roi1%, roi2%, and roi3% (R = 0.84, p < 0.001). The corresponding Scaramuzzo G, Spadaro S, Spinelli E, Bland-Altmann analysis showed a bias of −1.4e-007 cmH2O and limits of agreement Waldmann AD, Bohm SH, Ottaviani I, − 2 Montanaro F, Gamberini L, (LoA) of 2.4–2.4 cmH2O. EL and PI calculated using EIT showed good agreement (R Marangoni E, Mauri T and Volta CA = 0.89, p < 0.001 and R2 = 0.75, p < 0.001) with the esophageal derived correspondent (2021) Calculation of Transpulmonary variables. In conclusion, DP has a good correlation with EIT-derived parameters in Pressure From Regional Ventilation L Displayed by Electrical Impedance the central lung. DPL, PI, and EL can be estimated with good accuracy non-invasively Tomography in Acute Respiratory combining information coming from EIT and airway pressure. Distress Syndrome. Front. Physiol. 12:693736. Keywords: driving pressure, transpulmonary pressure, acute respiratory distress syndrome, precision medicine, doi: 10.3389/fphys.2021.693736 electric impedance tomography Frontiers in Physiology | www.frontiersin.org 1 July 2021 | Volume 12 | Article 693736 Scaramuzzo et al. EIT and Transpulmonary Pressure in ARDS INTRODUCTION selection criteria for the current data analysis were: ARDS according to the Berlin criteria (ARDS Definition Task Force Monitoring transpulmonary pressure can be important in et al., 2012), EIT images for at least 2 min containing an end- patients affected by acute respiratory distress syndrome (ARDS) inspiratory and end-expiratory pauses, simultaneous recording (ARDS Definition Task Force et al., 2012; Chiumello et al., 2014). of airway opening pressure, and airway flow and Peso. Enrolled Pressure measured at airway opening, indeed, does not yield patients were all mechanically ventilated in volume-controlled information about the different components of the respiratory ventilation (VCV) with a tidal volume (TV) = 6 ml/kg/IBW. system, i.e., the chest wall and the lung. Chest wall and An occlusion test was performed for each patient (Baydur lung elastance (EL) can differ unpredictably such that, patients et al., 1982) to assess the correct positioning of the esophageal having the same airway pressures can have significantly different balloon. All patients were sedated and paralyzed, as per clinical transpulmonary pressures (Gattinoni et al., 2004; Chiumello decision and no recruitment maneuver was performed before the et al., 2008). The current approach to evaluate transpulmonary measurements. We collected three measures from each patient pressure (PL) is based on the use of esophageal pressure (Peso) at three different levels of PEEP, based on clinical practice, and assumes that it could be a good surrogate for pleural pressure transpulmonary pressure, and EIT. The method for PEEP setting (Grieco et al., 2017). The transpulmonary driving pressure guided by EIT and PL was described previously by Scaramuzzo (DPL), i.e., the variation of transpulmonary pressure between et al. (2020b). end-expiration and end-inspiration, corresponds to the cyclical stress imposed on the lung parenchyma. Unlike driving pressure Respiratory Mechanics calculated from airway opening pressure (DP), DPL is the The following mechanical measurements were collected from pressure imposed on the lung during the tidal breathing, since it the airway opening pressure end-inspiratory and end-expiratory does not consider the amount of pressure needed to overcome the pauses: TV, total positive end-expiratory pressure (PEEP), peak chest-wall compartment (Loring and Malhotra, 2015). Evaluating pressure (peak), and plateau pressure (Pplat). The DP of the DPL can be important to limit the stress on the lung parenchyma respiratory system was calculated as Pplat-PEEP. The elastance and, therefore, may be useful to monitor the risk for ventilator- of the respiratory system (Ers) was calculated as Ers = DP/TV induced lung injury (VILI). Recently, it has been demonstrated and was expressed in cmH2O/L. Transpulmonary pressure (PL) in an animal model of ARDS how transpulmonary pressure was calculated as the difference between airway pressure and calculated with the classical absolute subtractive method (i.e., Peso (PL = Pao–Peso) and DPL as the difference between end- PL = Paw—Peso) corresponds to the transpulmonary pressure inspiratory and end-expiratory PL. EL was calculated as EL = in the central to dependent lung (Yoshida et al., 2018). When DPL/TV while chest-wall elastance (Ecw) as Ecw = Ers–EL. we consider transpulmonary pressure, we should consider that The elastance-derived inspiratory PL (PI) was calculated as PI its value is not unique along with the whole lung but changes = Pplat–[Pplat∗(Ecw/Ers)]. regionally according to regional differences in pleural pressures which reflects the forces acting in favor of lung collapse or EIT Analysis opening (regional heterogeneity of core disease, gravitational An average of 10 respiratory acts was used to analyze EIT and the distribution of edema, and mediastinum weight) (Silva and Gama regional analysis was conducted by dividing the EIT image into de Abreu, 2018). Electrical impedance tomography (EIT) is a four craniocaudal regions of interest (ROIN; ROI1: most ventral; non-invasive monitoring technique that can help to monitor ROI4: most dorsal). The percentage of tidal ventilation (ROI%N) regional lung ventilation distribution at the bedside (Frerichs in four ROIs was calculated as the fraction of tidal delivered to et al., 2017; Yoshida et al., 2019; Scaramuzzo et al., 2020c). the ROI in the analyzed acts and was expressed in percentage (Frerichs et al., 2017). The weighted regional compliance in the Since the PL derived from Peso reflects the behavior of the central to dependent part of the lung, we aimed to evaluate the four ROIs was calculated as follows: relationship between regional mechanics variables, derived by TV×ROI% DP EIT, and transpulmonary pressure in patients affected by ARDS. RCROI = Moreover, we tested if, by integrating the information from EIT IBW and airway opening pressure, we could predict non-invasively and expressed as ml/cmH2O/kg of ideal body weight (IBW). DPL. Finally, we wanted to verify if EL and the elastance-based inspiratory PL derived by EIT, agree with the one classically Statistical Analysis calculated using esophageal manometry. Data are expressed as median [IQR]. Repeated measures correlation (rmcorr) [Bakdash and Marusich (2020)]. R package METHODS version 0.4.1. https://CRAN.R-project.org/package=rmcorr) was used to test correlation among variables with repeated measures. This is a secondary analysis of data collected from a database To predict measured DPL,
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