A continuous positive airway pressure nasal device for use in a CPAP system to aid the patient's breathing, the device comprising: a generating body (30) that forms: an inlet (40) for fluid connection to a source of pressurized gas, a chamber (42) fluidly connected to the inlet, and first (44a) and second (44b) flow circuits fluidly connected to the chamber (42), including each of the flow circuits (44a , 44b): a corresponding nozzle (70) defining an inlet end (80) and an outlet end (82), the inlet end (80) being fluidly connected to the chamber (42) and having the end outlet (82) a diameter smaller than a diameter of the inlet end (80), and a corresponding channel (72) in which each of the channels of each of the first and second flow circuits defines: a nozzle side (92) fluidly connected to the outlet end (82) of the nozzle ( 70), a patient side (76) opposite the nozzle side (92) and configured to direct the gas to and from a patient nostril, a first ramp region (110) between the nozzle sides (92) and of patient (76), decreasing in diameter the first ramp region (110) towards the patient side (76), a second ramp region (112) between the first ramp region (110) and the patient side (76) , the second ramp region (112) increasing in diameter towards the patient's side (76), and an open port (74) fluidly connected to the channel (72) at a location between the side of the nozzle (92) and the patient side (76), the device further comprising a patient interface piece (32) fluidly connected to the patient's side of the channels (72), in which the nozzle (70) of each flow circuit is configured to create a jet stream from the pressurized gas in the chamber (42) in corresponding channel (72), in which the The second channel ramp region of each flow circuit is configured to direct the air from the patient side to divert the jet stream to the open port (74), in which in longitudinal cross-section, the channel (72) of each of the flow circuits (44a, 44b) is defined by a lower w
