Abstract
BackgroundThere is a paucity of data concerning the optimal ventilator management in patients with COVID-19 pneumonia; particularly, the optimal levels of positive-end expiratory pressure (PEEP) are unknown. We aimed to investigate the effects of two levels of PEEP on alveolar recruitment in critically ill patients with severe COVID-19 pneumonia.MethodsA single-center cohort study was conducted in a 39-bed intensive care unit at a university-affiliated hospital in Genoa, Italy. Chest computed tomography (CT) was performed to quantify aeration at 8 and 16 cmH2O PEEP. The primary endpoint was the amount of alveolar recruitment, defined as the change in the non-aerated compartment at the two PEEP levels on CT scan.ResultsForty-two patients were included in this analysis. Alveolar recruitment was median [interquartile range] 2.7 [0.7–4.5] % of lung weight and was not associated with excess lung weight, PaO2/FiO2 ratio, respiratory system compliance, inflammatory and thrombophilia markers. Patients in the upper quartile of recruitment (recruiters), compared to non-recruiters, had comparable clinical characteristics, lung weight and gas volume. Alveolar recruitment was not different in patients with lower versus higher respiratory system compliance. In a subgroup of 20 patients with available gas exchange data, increasing PEEP decreased respiratory system compliance (median difference, MD − 9 ml/cmH2O, 95% CI from − 12 to − 6 ml/cmH2O, p < 0.001) and the ventilatory ratio (MD − 0.1, 95% CI from − 0.3 to − 0.1, p = 0.003), increased PaO2 with FiO2 = 0.5 (MD 24 mmHg, 95% CI from 12 to 51 mmHg, p < 0.001), but did not change PaO2 with FiO2 = 1.0 (MD 7 mmHg, 95% CI from − 12 to 49 mmHg, p = 0.313). Moreover, alveolar recruitment was not correlated with improvement of oxygenation or venous admixture.ConclusionsIn patients with severe COVID-19 pneumonia, higher PEEP resulted in limited alveolar recruitment. These findings suggest limiting PEEP strictly to the values necessary to maintain oxygenation, thus avoiding the use of higher PEEP levels.
Highlights
Over the last months, the global pandemic from coronavirus disease 2019 (COVID-19) has posed important challenges to intensive care unit (ICU) physicians [1, 2]
COVID-19 meets the clinical criteria for acute respiratory distress syndrome (ARDS) [4], peculiar pathophysiological features [5] and phenotypes have been identified in this disease [6]
In COVID-19 patients with high respiratory system compliance and low ventilation-perfusion ratio (VA/Q ), hypoxemia is primarily due to the VA/Qmismatch, which is more related to lung perfusion regulation impairment than to an increase in non-aerated tissue; lung recruitability is probably low [8, 9]
Summary
The global pandemic from coronavirus disease 2019 (COVID-19) has posed important challenges to intensive care unit (ICU) physicians [1, 2]. In COVID-19 patients, chest computed tomography (CT) findings typically include ground glass opacities overlapping with areas of lung consolidation, not always reflecting the severity of gas-exchange impairment [7]. In this context, severe hypoxemia might be related to loss of aeration, and to highly perfused groundglass areas [8, 9]. In COVID-19 patients with high respiratory system compliance and low ventilation-perfusion ratio (VA/Q ), hypoxemia is primarily due to the VA/Qmismatch, which is more related to lung perfusion regulation impairment than to an increase in non-aerated tissue; lung recruitability is probably low [8, 9]. We aimed to investigate the effects of two levels of PEEP on alveolar recruitment in critically ill patients with severe COVID-19 pneumonia
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