Apparatus for automatic delivery of chest compressions and ventilation to a patient, the apparatus including: a chest compressing device configured to deliver compression phases during which pressure is applied to compress the chest and decompression phases during which approximately zero pressure is applied to the chest a ventilator configured to deliver positive, negative, or approximately zero pressure to the airway； control circuitry and processor, wherein the circuitry and processor are configured to cause the chest compressing device to repeatedly deliver a set containing a plurality of systolic flow cycles, each systolic flow cycle comprising a systolic decompression phase and a systolic compression phase, and at least one diastolic flow cycle interspersed between sets of systolic flow cycles, each diastolic flow cycle comprising a diastolic decompression phase and a diastolic compression phase, wherein the diastolic decompression phase is substantially longer than the systolic decompression phase.
