Apparatus for automatic delivery of chest compressions and ventilation to a patient, the apparatus including: a chest compressing device (12) 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 (15) configured to deliver positive, negative, or approximately zero pressure to the airway； control circuitry and processor (14), wherein the circuitry and processor are configured to cause the chest compressing device to repeatedly deliver a set containing a plurality of first type flow cycles, each first type flow cycle comprising a first type decompression phase and a first type compression phase, and at least one second type flow cycle interspersed between sets of first type flow cycles, each second type flow cycle comprising a second type decompression phase and a second type compression phase, wherein the second type decompression phase is substantially longer than the first type decompression phase.
