BACKGROUND: Data on microcirculatory pattern of COVID-19 critically ill patients are scarce . The objective was to compare sublingual microcirculation parameters of critically ill patients according to the severity of the disease .

METHODS: The study is a single-center prospective study with critically ill COVID-19 patients admitted in ICU . Sublingual microcirculation was assessed by IDF microscopy within 48 hours of ICU admission . Microcirculatory flow index (MFI), proportion of perfused vessel (PPV), total vessel density (TVD), De Backer score (DBS), perfused vessel density (PVD) and heterogeneity index (HI) were assessed . Patients were divided in 2 groups (severe and critical) according to the World health organization definition . FINDINGS: From 19th of March to 7th of April 2020, 43 patients were included . Fourteen patients (33 %) were in the severe group and twenty-nine patients (67 %) in the critical group . Patients in the critical group were all mechanically ventilated . The critical group had significantly higher values of MFI, DBS and PVD in comparison to severe group (respectively, PaCO2 : 49 [44-45] vs 36 [33-37] mmHg; p <0,0001, MFI : 2.8 ± 0.2 vs 2.5 ± 0.3; p = 0.001, DBS : 12.7 ± 2.6 vs 10.8 ± 2.0 vessels mm-2; p = 0.033, PVD : 12.5 ± 3.0 vs 10.1 ± 2.4 mm.mm-2; p = 0.020). PPV, HI and TVD were similar between groups Correlation was found between microcirculatory parameters and PaCO2 levels .

CONCLUSION: Critical COVID-19 patients under mechanical ventilation seem to have higher red blood cell velocity than severe non-ventilated patients.