This system is characterized in that includes: means (20) for acquiring information relating to the respiratory state of the patient (1) over a breathing cycle, means (21) for acquiring information relating to the operating state of the assistance device (2) over a mechanical cycle, means for filtering (22) and for processing (23) this information in order to detect and localize the changes in states of the patient over a breathing cycle and of the device over a mechanical cycle, means (24) for calculating a piece of information on desynchronization between the patient and the device from these changes in states, and means (25) forming a man/machine interface for returning this piece of desynchronization information to an operator.
