Clinical experiences with mechanized cardiac massage

The important requisites for a mechanical pump for external cardiac massage have been described and are incorporated in a unit which has been evaluated during the past two and a half years. This instrument is portable, weighs only 31 pounds and is powered by oxygen or any other gas source. The ambulance model differs from the hospital model in that the exhaust oxygen is collected in a reservoir and then used to ventilate the lungs. Also, this model does not contain the optional feature of performing synchronized massage, which may be indicated when resuscitation is performed in the hospital. Both models permit the effective performance of external cardiopulmonary resuscitation by one person without incurring fatigue. The pump has been applied to many persons who sustained cardiac arrest. It produced adequate artificial circulation in each instance as manifested by a palpable peripheral pulse, a decrease in the size of the pupils, and the allowance of electrical conversion of ventricular fibrillation to a conducted beat. The most favorable cardiorespiratory factors appear to be a rate of 40 compressions/min., with a duration of systole one-third the cycle time, and with artificial ventilation being instituted between every other compression. It is most important that the artificial circulation not be interrupted for ventilatory or any other reasons. Clinical evidence could not be obtained to indicate that faster massage rates were better. Since the mechanical pump was never found to be less effective or more traumatic than manual massage, the many obvious advantages of mechanization warrant the substitution of the pump for the individual massager as soon as it is brought to the treatment area. The ultimate rate of salvage possible among patients sustaining cardiac arrest outside the operating room is not known. The solution of several questions currently apparent will undoubtedly influence the results; e.g., (1) should open-chest massage be used when the closed method appears unsuccessful, and when should it be instituted, (2) is it necessary to synchronize mechanical compression with electrical systole, and (3) is any advantage to be obtained by using adjunct supportive measures such as balloon occlusion of the abdominal aorta and internal diastolic pumping?