Dataset Information

Effect of PEEP and I:E ratio on cerebral oxygenation in ARDS: an experimental study in anesthetized rabbit.

ABSTRACT:

Background

Although PEEP and inversed I:E ratio have been shown to improve gas exchange in ARDS, both can adversely affect systemic hemodynamics and cerebral perfusion. The goal of this study was to assess how changes in PEEP and I:E ratio affect systemic and cerebral oxygenation and perfusion in normal and injured lung.

Methods

Eight anesthetized Chinchilla-Bastard rabbits were ventilated at baseline with pressure-regulated volume control mode, V_T?=?6?ml/kg, PEEP?=?6 cmH₂O, FIO₂?=?0.4; respiratory rate set for ETCO₂?=?5.5%, and I:E?=?1:2, 1:1 or 2:1 in random order. Ultrasonic carotid artery flow (CF), arterial (PaO₂), jugular venous blood gases and near infrared spectroscopic cerebral oxygenation (?HBO₂) were recorded for each experimental condition. After induced lung injury, the animals were ventilated with PEEP?=?9 followed by 6 cmH₂O.

Results

At baseline, inverse-ratio ventilation (IRV) significantly reduced cerebral oxygenation (?O₂HB; -?27 at 1:2; -?15 at 1:1 vs. 0.27 ?mol/L at 2:1; p?2 (67.5?±?19.3 vs. 42.2?±?8.4, p 2 (-?13.8?±?14.7 vs. -43.5?±?21.3, p?ConclusionsOur data suggest that unlike moderate PEEP, IRV is not effective in improving brain oxygenation in ARDS. In normal lung, IRV had a deleterious effect on brain oxygenation, which is relevant in anesthetized patients.

SUBMITTER: Lovisari F

PROVIDER: S-EPMC6582519 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Publications

Effect of PEEP and I:E ratio on cerebral oxygenation in ARDS: an experimental study in anesthetized rabbit.

Lovisari Federica F Fodor Gergely H GH Peták Ferenc F Habre Walid W Bayat Sam S

BMC anesthesiology 20190619 1

<h4>Background</h4>Although PEEP and inversed I:E ratio have been shown to improve gas exchange in ARDS, both can adversely affect systemic hemodynamics and cerebral perfusion. The goal of this study was to assess how changes in PEEP and I:E ratio affect systemic and cerebral oxygenation and perfusion in normal and injured lung.<h4>Methods</h4>Eight anesthetized Chinchilla-Bastard rabbits were ventilated at baseline with pressure-regulated volume control mode, V<sub>T</sub> = 6 ml/kg, PEEP = 6 c ...[more]

PMID: 31216981

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Project description:BackgroundMortality in patients with acute respiratory distress syndrome (ARDS) remains high. These patients require mechanical ventilation strategies that include high positive end-expiratory pressure (PEEP). It remains controversial whether high PEEP can improve outcomes for ARDS patients, especially patients who show improvement in oxygenation in response to PEEP. In this meta-analysis, we aimed to evaluate the effects of high PEEP on ARDS patients.MethodsWe electronically searched randomized controlled trials (RCTs) reported in the MEDLINE, CENTRAL, EMBASE, CINAHL and Web of Science databases from January 1990 to December 2017. Meta-analyses of the effects of PEEP on survival in adults with ARDS were conducted using the methods recommended by the Cochrane Collaboration.ResultsA total of 3612 patients from nine randomized controlled trials (RCTs) were included. There were 1794 and 1818 patients in the high and low PEEP groups, respectively. Hospital mortality showed no significant difference between the high and low PEEP groups (RR?=?0.92; 95% CI, 0.79 to 1.07; P?=?0.26). Similar results were found for 28-d mortality (RR?=?0.88; 95% CI, 0.72 to 1.07; P?=?0.19) and ICU mortality (RR?=?0.83; 95% CI, 0.65 to 1.07; P?=?0.15). The risk of clinically objectified barotrauma was not significantly different between the high and low PEEP groups (RR?=?1.24; 95% CI, 0.74 to 2.09, P?=?0.41). In the subgroup of ARDS patients who responded to increased PEEP by improved oxygenation (from 6 RCTs), high PEEP significantly reduced hospital mortality (RR?=?0.83; 95% CI 0.69 to 0.98; P?=?0.03), ICU mortality (RR?=?0.74; 95% CI, 0.56 to 0.98; P?=?0.04),but the 28-d mortality was not decreased(RR?=?0.83; 95% CI, 0.67 to 1.01; P?=?0.07). For ARDS patients in the low PEEP group who received a PEEP level lower than 10 cmH2O (from 6 RCTs), ICU mortality was lower in the high PEEP group than the low PEEP group (RR?=?0.65; 95% CI, 0.45 to 0.94; P?=?0.02).ConclusionsFor ARDS patients who responded to increased PEEP by improved oxygenation, high PEEP could reduce hospital mortality, ICU mortality and 28-d mortality. High PEEP does not increase the risk of clinically objectified barotrauma.

Project description:BackgroundPEEP selection in severe COVID-19 patients under extracorporeal membrane oxygenation (ECMO) is challenging as no study has assessed the alveolar recruitability in this setting. The aim of the study was to compare lung recruitability and the impact of PEEP on lung aeration in moderate and severe ARDS patients with or without ECMO, using computed tomography (CT).MethodsWe conducted a two-center prospective observational case-control study in adult COVID-19-related patients who had an indication for CT within 72 h of ARDS onset in non-ECMO patients or within 72 h after ECMO onset. Ninety-nine patients were included, of whom 24 had severe ARDS under ECMO, 59 severe ARDS without ECMO and 16 moderate ARDS.ResultsNon-inflated lung at PEEP 5 cmH2O was significantly greater in ECMO than in non-ECMO patients. Recruitment induced by increasing PEEP from 5 to 15 cmH2O was not significantly different between ECMO and non-ECMO patients, while PEEP-induced hyperinflation was significantly lower in the ECMO group and virtually nonexistent. The median [IQR] fraction of recruitable lung mass between PEEP 5 and 15 cmH2O was 6 [4-10]%. Total superimposed pressure at PEEP 5 cmH2O was significantly higher in ECMO patients and amounted to 12 [11-13] cmH2O. The hyperinflation-to-recruitment ratio (i.e., a trade-off index of the adverse effects and benefits of PEEP) was significantly lower in ECMO patients and was lower than one in 23 (96%) ECMO patients, 41 (69%) severe non-ECMO patients and 8 (50%) moderate ARDS patients. Compliance of the aerated lung at PEEP 5 cmH2O corrected for PEEP-induced recruitment (CBABY LUNG) was significantly lower in ECMO patients than in non-ECMO patients and was linearly related to the logarithm of the hyperinflation-to-recruitment ratio.ConclusionsLung recruitability of COVID-19 pneumonia is not significantly different between ECMO and non-ECMO patients, with substantial interindividual variations. The balance between hyperinflation and recruitment induced by PEEP increase from 5 to 15 cmH2O appears favorable in virtually all ECMO patients, while this PEEP level is required to counteract compressive forces leading to lung collapse. CBABY LUNG is significantly lower in ECMO patients, independently of lung recruitability.

Project description:BackgroundProne positioning is recommended for patients with moderate-to-severe acute respiratory distress syndrome (ARDS) receiving mechanical ventilation. While the debate continues as to whether COVID-19 ARDS is clinically different from non-COVID ARDS, there is little data on whether the physiological effects of prone positioning differ between the two conditions. We aimed to compare the physiological effect of prone positioning between patients with COVID-19 ARDS and those with non-COVID ARDS.MethodsWe retrospectively compared 23 patients with COVID-19 ARDS and 145 patients with non-COVID ARDS treated using prone positioning while on mechanical ventilation. Changes in PaO2/FiO2 ratio and static respiratory system compliance (Crs) after the first session of prone positioning were compared between the two groups: first, using all patients with non-COVID ARDS, and second, using subgroups of patients with non-COVID ARDS matched 1:1 with patients with COVID-19 ARDS for baseline PaO2/FiO2 ratio and static Crs. We also evaluated whether the response to the first prone positioning session was associated with the clinical outcome.ResultsWhen compared with the entire group of patients with non-COVID ARDS, patients with COVID-19 ARDS showed more pronounced improvement in PaO2/FiO2 ratio [adjusted difference 39.3 (95% CI 5.2-73.5) mmHg] and static Crs [adjusted difference 3.4 (95% CI 1.1-5.6) mL/cmH2O]. However, these between-group differences were not significant when the matched samples (either PaO2/FiO2-matched or compliance-matched) were analyzed. Patients who successfully discontinued mechanical ventilation showed more remarkable improvement in PaO2/FiO2 ratio [median 112 (IQR 85-144) vs. 35 (IQR 6-52) mmHg, P = 0.003] and static compliance [median 5.7 (IQR 3.3-7.7) vs. - 1.0 (IQR - 3.7-3.0) mL/cmH2O, P = 0.006] after prone positioning compared with patients who did not. The association between oxygenation and Crs responses to prone positioning and clinical outcome was also evident in the adjusted competing risk regression.ConclusionsIn patients with COVID-19 ARDS, prone positioning was as effective in improving respiratory physiology as in patients with non-COVID ARDS. Thus, it should be actively considered as a therapeutic option. The physiological response to the first session of prone positioning was predictive of the clinical outcome of patients with COVID-19 ARDS.

Project description:BackgroundIn mechanically ventilated patients with acute respiratory distress syndrome (ARDS), electrical impedance tomography (EIT) provides information on alveolar cycling and overdistension as well as assessment of recruitability at the bedside. We developed a protocol for individualization of positive end-expiratory pressure (PEEP) and tidal volume (VT) utilizing EIT-derived information on recruitability, overdistension and alveolar cycling. The aim of this study was to assess whether the EIT-based protocol allows individualization of ventilator settings without causing lung overdistension, and to evaluate its effects on respiratory system compliance, oxygenation and alveolar cycling.Methods20 patients with ARDS were included. Initially, patients were ventilated according to the recommendations of the ARDS Network with a VT of 6 ml per kg predicted body weight and PEEP adjusted according to the lower PEEP/FiO2 table. Subsequently, ventilator settings were adjusted according to the EIT-based protocol once every 30 min for a duration of 4 h. To assess global overdistension, we determined whether lung stress and strain remained below 27 mbar and 2.0, respectively.ResultsProspective optimization of mechanical ventilation with EIT led to higher PEEP levels (16.5 [14-18] mbar vs. 10 [8-10] mbar before optimization; p = 0.0001) and similar VT (5.7 ± 0.92 ml/kg vs. 5.8 ± 0.47 ml/kg before optimization; p = 0.96). Global lung stress remained below 27 mbar in all patients and global strain below 2.0 in 19 out of 20 patients. Compliance remained similar, while oxygenation was significantly improved and alveolar cycling was reduced after EIT-based optimization.ConclusionsAdjustment of PEEP and VT using the EIT-based protocol led to individualization of ventilator settings with improved oxygenation and reduced alveolar cycling without promoting global overdistension. Trial registrationThis study was registered at clinicaltrials.gov (NCT02703012) on March 9, 2016 before including the first patient.

Project description:ObjectivesA recent individual patient data (IPD) meta-analysis suggested that patients with moderate or severe acute respiratory distress syndrome (ARDS) benefit from higher positive end-expiratory pressure (PEEP) ventilation strategies. However, thresholds for continuous variables (eg, hypoxaemia) are often arbitrary and linearity assumptions in regression approaches may not hold; the multivariable fractional polynomial interaction (MFPI) approach can address both problems. The objective of this study was to apply the MFPI approach to investigate interactions between four continuous patient baseline variables and higher versus lower PEEP on clinical outcomes.SettingPooled data from three randomised trials in intensive care identified by a systematic review.Participants2299 patients with acute lung injury requiring mechanical ventilation.InterventionsHigher (N=1136) versus lower PEEP (N=1163) ventilation strategy.Outcome measuresPrespecified outcomes included mortality, time to death and time-to-unassisted breathing. We examined the following continuous baseline characteristics as potential effect modifiers using MFPI: PaO2/FiO2 (arterial partial oxygen pressure/ fraction of inspired oxygen), oxygenation index, respiratory system compliance (tidal volume/(inspiratory plateau pressure-PEEP)) and body mass index (BMI).ResultsWe found that for patients with PaO2/FiO2 below 150 mm Hg, but above 100 mm Hg or an oxygenation index above 12 (moderate ARDS), higher PEEP reduces hospital mortality, but the beneficial effect appears to level off for patients with very severe ARDS. Patients with mild ARDS (PaO2/FiO2 above 200 mm Hg or an oxygenation index below 10) do not seem to benefit from higher PEEP and might even be harmed. For patients with a respiratory system compliance above 40 mL/cm H2O or patients with a BMI above 35 kg/m(2), we found a trend towards reduced mortality with higher PEEP, but there is very weak statistical confidence in these findings.ConclusionsMFPI analyses suggest a nonlinear effect modification of higher PEEP ventilation by PaO2/FiO2 and oxygenation index with reduced mortality for some patients suffering from moderate ARDS.Study registration numberCRD42012003129.

Dataset Information

Effect of PEEP and I:E ratio on cerebral oxygenation in ARDS: an experimental study in anesthetized rabbit.

Background

Methods

Results

Publications

Effect of PEEP and I:E ratio on cerebral oxygenation in ARDS: an experimental study in anesthetized rabbit.

Similar Datasets

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