A breathable gas supply regulation device of gas supplied by a respiratory assistance apparatus in breath assistance comprising a first input receiving a leakage signal produced by a detection member. The device regulates the supply of breathable gas to the patient in response to a received leakage signal, comprises a second input receiving a patient mouth movement measurement signal. The device comprises a processing unit provided for generating a synchronisation signal between the movement signal and the leakage signal. The processing unit generates a modification amount indicating the modification to be applied to the supply of breathable gas.
