A portable medical ventilator using pulse flow from an oxygen concentrator to gain higher oxygen concentration includes a positive pressure source to deliver pressurized air to the patient and a negative pressure source to trigger the oxygen concentrator. A patient circuit attached to a patient interface mask connects the ventilator to the patient. The ventilator includes a controller module that is configured to generate a signal to the negative pressure device to trigger the concentrator to initiate one or more pulses of oxygen from the oxygen concentrator. The oxygen pulses are delivered to the patient interface directly through multi-tube or a multi lumen patient circuit. The oxygen does not mix with air in the ventilator or in the patient circuit and bypasses the leaks in the patient circuit and/or patient interface.
