The invention relates to a breathing assistance device for a patient, the device including: a source of respiratory pressurised gas a gas transmission duct comprising a distal end coupled to said source and a proximal end coupled to the patient a gas regulating valve interposed in the gas transmission duct at a proximal location, comprising a leakage orifice and an obstruction means capable of varying the opening of the leakage orifice upon signal of controlling means and allowing a bidirectional gas flow through the leakage orifice in both expiration and inspiration phases.
