Respiratory failure associated with Covid-19 can be expressed as acute respiratory distress syndrome (ARDS), which is an acute inflammatory lung injury,which generally requires the use of invasive mechanical ventilation (MV). There are inconclusive results regarding the potential lung recruitment in ARDS. At the lung level, the relationship between lung volume and pressure can be graphed through a pressure/volume (P/V) curve. In this curve, hysteresis (H) can be evaluated, which is the amount of energy generated during inspiration that is not recovered during expiration. H is related to recruitment, assuming that the greater H the greater the alveolar recruitment. For this reason, the objective of this study is the measurement of H as a way to assess the lung recruitment capacity, in patients with ARDS and in patients with Covid-19 who develop ARDS (ARDS- Covid)