Abstract: Ventilator for use with a source of gas under pressure for supplying such gas to the airway of a patient having an inlet adapted to be connected to the source of gas, and an outlet adapted to be connected to the airway of the patient. A pneumatic oscillator is connected to the inlet for supplying pulsatile gas in the form of successive small volumes of gas to the airway of the patient during a breath of the patient to cause diffusive ventilation of the airway to the patient. An exhalation valve assembly is connected to the patient airway for permitting the patient to exhale gases introduced into the patient airway.