An ambulatory assist ventilation (AA V) apparatus and system are disclosed for the delivery of a respiratory gas to assist the spontaneous breathing effort of a patient with a breathing disorder. The AA V system includes a compressed respiratory gas source, a respiratory assist device for controlling respiratory gas flow to the patient, a patient circuit tubing and a low profile nasal interface device, which does not have a dead space or hollow area where CO2 can collect, for delivering the respiratory gas to the patient, wherein the nasal interface device is fluidly connected to the respiratory assist device via tubing for receiving the respiratory gas therefrom.