The indications for mechanical ventilation (MV) include excessive work of breathing, with or without evidence of respiratory muscle fatigue. The setting of the MV is still a challenge because it is based on criteria understudied, often subjective and observer-dependent. Despite several studies, to our knowledge has never been done before is the precise definition of the optimal range of ventilatory support. Novel and recognizable diagnostic techniques will be applied. No single parameter of the breathing pattern has good accuracy for the adjustment of ventilatory support. Non-invasive measures such as P0.1 and rate of muscle relaxation may have good accuracy for the adjustment of ventilatory support.