BACKGROUND: Controversies exist on the nature of COVID-19 related acute respiratory distress syndrome (ARDS) in particular on the static compliance of the respiratory system (Crs). We aimed to analyze the association of Crs with outcome in COVID-19-associated ARDS, to ascertain its determinants and to describe its evolution at day-14 .

METHODS: In this observational multicenter cohort of patients with moderate to severe Covid-19 ARDS, Crs was measured at day-1 and day-14 . Association between Crs or Crs/ideal body weight (IBW) and breathing without assistance at day-28 was analyzed with multivariable logistic regression . Determinants were ascertained by multivariable linear regression . Day-14 Crs was compared to day-1 Crs with paired t-test in patients still under controlled mechanical ventilation .

RESULTS: The mean Crs in 372 patients was 37.6 ± 13 mL/cmH 2 O, similar to as in ARDS of other causes . Multivariate linear regression identified chronic hypertension, low PaO 2 /FiO 2 ratio, low PEEP, and low tidal volume as associated with lower Crs/IBW . After adjustment on confounders, nor Crs [OR 1.0 (CI 95% 0.98-1.02) ] neither Crs/IBW [OR 0.63 (CI 95% 0.13-3.1) ] were associated with the chance of breathing without assistance at day-28 whereas plateau pressure was [OR 0.93 (CI 95% 0.88-0.99) ]. In a subset of 108 patients, day-14 Crs decreased compared to day-1 Crs (31.2 ± 14.4 mL/cmH 2 O vs 37.8 ± 11.4 mL/cmH 2 O, p <0.001). The decrease in Crs was not associated with day-28 outcome .

CONCLUSION: In a large multicenter cohort of moderate to severe COVID-19 ARDS, mean Crs was decreased below 40 mL/cmH 2 O and was not associated with day-28 outcome . Crs decreased between day-1 and day-14 but the decrease was not associated with day-28 outcome.