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Purpose To investigate whether COVID-19-ARDS differs from all-cause ARDS. Methods Thirty-two consecutive, mechanically ventilated COVID-19-ARDS patients were compared to two historical ARDS sub-populations 1:1 matched for PaO.sub.2/FiO.sub.2 or for compliance of the respiratory system. Gas exchange, hemodynamics and respiratory mechanics were recorded at 5 and 15 cmH.sub.2O PEEP. CT scan variables were measured at 5 cmH.sub.2O PEEP. Results Anthropometric characteristics were similar in COVID-19-ARDS, PaO.sub.2/FiO.sub.2-matched-ARDS and Compliance-matched-ARDS. The PaO.sub.2/FiO.sub.2-matched-ARDS and COVID-19-ARDS populations (both with PaO.sub.2/FiO.sub.2 106 ± 59 mmHg) had different respiratory system compliances (Crs) (39 ± 11 vs 49.9 ± 15.4 ml/cmH.sub.2O, p = 0.03). The Compliance-matched-ARDS and COVID-19-ARDS had similar Crs (50.1 ± 15.7 and 49.9 ± 15.4 ml/cmH.sub.2O, respectively) but significantly lower PaO.sub.2/FiO.sub.2 for the same Crs (160 ± 62 vs 106.5 ± 59.6 mmHg, p < 0.001). The three populations had similar lung weights but COVID-19-ARDS had significantly higher lung gas volume (PaO.sub.2/FiO.sub.2-matched-ARDS 930 ± 644 ml, COVID-19-ARDS 1670 ± 791 ml and Compliance-matched-ARDS 1301 ± 627 ml, p < 0.05). The venous admixture was significantly related to the non-aerated tissue in PaO.sub.2/FiO.sub.2-matched-ARDS and Compliance-matched-ARDS (p < 0.001) but unrelated in COVID-19-ARDS (p = 0.75), suggesting that hypoxemia was not only due to the extent of non-aerated tissue. Increasing PEEP from 5 to 15 cmH.sub.2O improved oxygenation in all groups. However, while lung mechanics and dead space improved in PaO.sub.2/FiO.sub.2-matched-ARDS, suggesting recruitment as primary mechanism, they remained unmodified or worsened in COVID-19-ARDS and Compliance-matched-ARDS, suggesting lower recruitment potential and/or blood flow redistribution. Conclusions COVID-19-ARDS is a subset of ARDS characterized overall by higher compliance and lung gas volume for a given PaO.sub.2/FiO.sub.2, at least when considered within the timeframe of our study., Author(s): Davide Chiumello [sup.1], Mattia Busana [sup.2], Silvia Coppola [sup.1], Federica Romitti [sup.2], Paolo Formenti [sup.1], Matteo Bonifazi [sup.2], Tommaso Pozzi [sup.1], Maria Michela Palumbo [sup.2], Massimo Cressoni [sup.3], Peter [...]

Rationale: Weaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) is based on oxygenation and not on carbon dioxide elimination. Objectives: To predict readiness to wean from VV-ECMO. Methods: In this multicenter study of mechanically ventilated adults with severe acute respiratory distress syndrome receiving VV-ECMO, we investigated a variable based on CO2 elimination. The study included a prospective interventional study of a physiological cohort (n = 26) and a retrospective clinical cohort (n = 638). Measurements and Main Results: Weaning failure in the clinical and physiological cohorts were 37% and 42%, respectively. The main cause of failure in the physiological cohort was high inspiratory effort or respiratory rate. All patients exhaled similar amounts of CO2, but in patients who failed the weaning trial, [Formula: see text]e was higher to maintain the PaCO2 unchanged. The effort to eliminate one unit-volume of CO2, was double in patients who failed (68.9 [42.4-123] vs. 39 [20.1-57] cm H2O/[L/min]; P = 0.007), owing to the higher physiological Vd (68 [58.73] % vs. 54 [41.64] %; P = 0.012). End-tidal partial carbon dioxide pressure (PetCO2)/PaCO2 ratio was a clinical variable strongly associated with weaning outcome at baseline, with area under the receiver operating characteristic curve of 0.87 (95% confidence interval [CI], 0.71-1). Similarly, the PetCO2/PaCO2 ratio was associated with weaning outcome in the clinical cohort both before the weaning trial (odds ratio, 4.14; 95% CI, 1.32-12.2; P = 0.015) and at a sweep gas flow of zero (odds ratio, 13.1; 95% CI, 4-44.4; P < 0.001). Conclusions: The primary reason for weaning failure from VV-ECMO is high effort to eliminate CO2. A higher PetCO2/PaCO2 ratio was associated with greater likelihood of weaning from VV-ECMO. [ABSTRACT FROM AUTHOR]

Rationale: Weaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) is based on oxygenation and not on carbon dioxide elimination. Objectives: To predict readiness to wean from VV-ECMO. Methods: In this multicenter study of mechanically ventilated adults with severe acute respiratory distress syndrome receiving VV-ECMO, we investigated a variable based on CO 2 elimination. The study included a prospective interventional study of a physiological cohort ( n  = 26) and a retrospective clinical cohort ( n  = 638). Measurements and Main Results: Weaning failure in the clinical and physiological cohorts were 37% and 42%, respectively. The main cause of failure in the physiological cohort was high inspiratory effort or respiratory rate. All patients exhaled similar amounts of CO 2 , but in patients who failed the weaning trial, [Formula: see text]e was higher to maintain the Pa CO 2 unchanged. The effort to eliminate one unit-volume of CO 2 , was double in patients who failed (68.9 [42.4-123] vs. 39 [20.1-57] cm H 2 O/[L/min]; P  = 0.007), owing to the higher physiological Vd (68 [58.73] % vs. 54 [41.64] %; P  = 0.012). End-tidal partial carbon dioxide pressure (Pet CO 2 )/Pa CO 2 ratio was a clinical variable strongly associated with weaning outcome at baseline, with area under the receiver operating characteristic curve of 0.87 (95% confidence interval [CI], 0.71-1). Similarly, the Pet CO 2 /Pa CO 2 ratio was associated with weaning outcome in the clinical cohort both before the weaning trial (odds ratio, 4.14; 95% CI, 1.32-12.2; P  = 0.015) and at a sweep gas flow of zero (odds ratio, 13.1; 95% CI, 4-44.4; P  < 0.001). Conclusions: The primary reason for weaning failure from VV-ECMO is high effort to eliminate CO 2 . A higher Pet CO 2 /Pa CO 2 ratio was associated with greater likelihood of weaning from VV-ECMO.