Abstract: A vest system for generating cyclic fluctuations in intrathoracic pressure for use in cardiopulmonary resuscitation and non-invasive circulatory assistance. The vest is preferably provided with a two bladder inflation system. A high pressure bladder contacts the chest wall while a bias bladder is disposed between the high pressure bladder and the vest material. The bias bladder is pressurized to press the high-pressure bladder tightly against the chest wall so that cyclic inflation of the high-pressure bladder can generate large changes in intrathoracic pressure. The bias bladder is released periodically to allow the chest to expand for adequate ventilation. Air flow into and out of each bladder is controlled by sequencing large bore 3-way and 2-way solenoid valves and the rate of air flow into the high-pressure bladder is controlled by a variable resistor.