 Effect of RM is evaluated from ventilator measurement of compliance C, arterial oxygenation and PF-ratio from the arterial blood gas ABG, and electrical impedance tomography EIT. EIT measures the impedance of a thoracic sagittal section by emitting and sampling electrical currents between 16 electrodes fixed on a submamillar belt. Radiology report from routine chest X-ray and ultrasonography of the lungs and pleura will be added. 