A cardiopulmonary resuscitation, CPR, device (100, 200, 400) for delivering intrathoracic pressure pulses to a subject (290), the device comprising an air pressure generator (110, 310, 410) for delivering air to the airways of the subject (290), wherein the air pressure generator (110, 310, 410) is configured to: operate a first mode, wherein in the first mode the air pressure generator (110, 310, 410) generates a first output (412, 770a, 770b) comprising a first plurality of positive pressure pulses (771) for temporally increasing the subject's intrathoracic pressure to induce compressions of the heart of the subject (290) by increasing the volume of the subject's lungs； operate a second mode, wherein in the second mode the air pressure generator (110, 310, 410) generates a second output (414, 880) comprising a second plurality of positive pressure pulses for providing an assured airflow to the lungs of the subject (290)； and deliver a resulting output (425, 986, 1086) to the airways of the subject (290), the resulting output being the superposition of the first output (412, 770a, 770b) and of the second output (414, 880)； wherein said first plurality of positive pressure pulses (771) have an amplitude greater than 30 mbar and a frequency in a range of 40-240 beats per minute； and wherein said second plurality of positive pressure pulses have an amplitude smaller than 30 mbar and a frequency in a range of 3 to 20 cycles per minute.
