Automatic External Cardiac Massage: A Portable Pneumatic External Cardiac Compression Machine

Abstract

Massage or manual compression of the heart is accepted as a useful procedure when heart action has ceased because of accident or temporarily disordered function. Experience in the operating theatre has shown that manual massage through the open chest should be maintained for over an hour before being abandoned, but the procedure is tiring, and the operator must be relieved at frequent intervals.Because of the resistance of the chest wall in adults, the power required to produce effective compression of the heart through the unopened chest is far greater and is estimated at between a quarter and a half horsepower. This power output cannot be maintained for more than ten minutes by any one person. If it is accepted that external cardiac massage produces a limited but effective circulation and that one hour is the minimum period of treatment, it is obviously desirable that mechanical assistance should be available to take over after the initial emergency manual compression. The procedure lends itself to mechanical substitution and the more precise control available should extend its use and possibly reduce the visceral damage due to uncontrolled violent chest compression. This paper describes a cardiac massage machine and reports a series of experiments on dogs whose hearts had been stopped and whose circulations were then maintained for prolonged periods by it. The apparatus is small, light, portable, and safe, and its action is easy to control. Compressed air or oxygen was considered the most suitable power source as it is convenient for artificial ventilation, and its use is understood by those concerned with the operation of resuscitation apparatus. Electric batteries have not been used because they cannot supply the large power demands of this type of apparatus and might be found to be discharged when required in emergency, especially if stored for prolonged periods in adverse conditions. Mains electric power is rarely available on an accident site and could be dangerous in some situations, and the electro-pneumatic valves available must be controlled by electronic circuits fed by dry batteries which offer another source of failure in an emergency.The machine was accordingly designed so that the timing circuits and the chest compression ram were operated solely by compressed gas. The ram can apply any weight from a few pounds to over a hundred in variable steps by operation of a single control without stopping the machine. The pressure applied can be observed on a simple gauge and the exact degree of chest depression seen by the operator. The machine can stop at suitable intervals to allow inflation of the chest and, if necessary, it can carry this out automatically.As the timing circuits controlling heart compression, rate, and the pause for lung inflation, can be set in advance, the machine is no more difficult to operate than any other mechanical resuscitation apparatus designed for use by semi-skilled persons.

Automated mechanical cardiopulmonary resuscitation devices versus manual chest compressions in the treatment of cardiac arrest: protocol of a systematic review and meta-analysis comparing machine to human

“…The first automated CPR systems have been developed just shortly after the description of manual chest compression in the 1960s. 79 Therefore, studies of over half a century will have to be assessed, and guideline revisions will have to be considered in the meantime. On the other hand, it is yet to determine to what extent study designs comply with particular recommendations.…”