A breathing device for assisting patients to breath by maintaining positive airway pressure during the breathing cycle comprises a breathing channel in fluid communication with an exhaust channel extending from a junction therebetween. A gas inlet is arranged so as to introduce gas into the breathing channel. A positive pressure may be maintained in the breathing channel wherein the axis of the gas inlet channel is laterally offset at the point at which the gas inlet channel introduces the gas into the breathing channel from the axis of the narrowest part of the breathing channel.