Mechanical ventilation in acute respiratory distress syndrome (ARDS) aims at delivering protective tidal volume within lungs that are characterised both by collapsed and hyperinflated tissue, and gravity plays a key role in the distribution of aeration [1]. Therefore, mechanical factors exterior to the lungs influence ventilation–perfusion relationships. For instance, prone positioning affects lung and chest wall geometry leading to beneficial physiological changes [2], whereas chest wall restriction is known to decrease lung resting volume [3]; applying negative pressure on the abdomen may generate a regional reopening of the lung [4]. Furthermore, sequential lateral positioning has been recently proposed as a potential manoeuvre to redistribute lung resting volume and promote alveolar recruitment [5].