In mechanically ventilated patients during supine position, alveolar collapse usually distributes in dependent lung region. High positive end expiratory pressure (PEEP) has been applied to improve the homogeneous distribution of ventilation by increasing the end expiratory lung ventilation (EELV) and alveolar recruitment. However, for patients who increasing PEEP in some extent still existed poor aeration in the dependent region, further elevating PEEP seems to be unreasonable that perhaps lead to overdistension. Decreasing trigger sensitivity might further evoke inspiratory efforts to improve the ventilation for this type of patients.The Electrical impedance tomography (EIT) was applied in monitoring the regional ventilation distribution at the bedside.