A TIME-CYCLED EXTERNAL CARDIAC COMPRESSOR
HARRY DIAMOND LABS ADELPHI MD ADELPHI United States
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During cardiac arrest, the flow of oxygenated blood to the brain becomes insufficient to support life. With new methods of cardiopulmonary resuscitation, blood circulation can be maintained, the heart restarted, normal circulation resumed, and the patients life saved. One method of maintaining circulation during this critical resuscitative period consists of rhythmically depressing the chest, thereby squeezing the heart and forcing blood to circulate. This method is known as external cardiac compression. A simple pneumatically powered external cardiac compressor was developed. This machine is time cycled and is controlled by a fluid-amplifier-driven oscillator. The device can also be synchronized with an EKG signal. Using the two controls on the machine, the operator may select ram forces up to 0.62 kN 140 lb and frequencies from 30 to 85 cpm. Chest deflection cannot exceed 7.5 cm 3 in.. The ratio of compression to total period is approximately 0.45 on the present model, but ratios from 0.21 to 0.73 could be obtained by modifying the oscillator. Performance characteristics were obtained from tests in which springs were used as physical models of the chest.