THE BIPHASIC MECHANISM OF BLOOD-FLOW DURING CARDIOPULMONARY-RESUSCITATION - A PHYSIOLOGICAL COMPARISON OF ACTIVE COMPRESSION-DECOMPRESSION AND HIGH-IMPULSE MANUAL EXTERNAL CARDIAC MASSAGE

Study objective: Dismal survival in patients receiving standard manual CPR provided the rationale for the investigation of alternate methods of closed-chest circulatory support. Active compression-decompression (ACD) and high-impulse CPR are alternatives to standard manual CPR. T his study was designed to test the hypothesis that ACD CPR provides su perior cardiopulmonary hemodynamics due to an active decompression pha se when compared with high-impulse manual CPR. Participants: Hemodynam ics were studied during ACD and high-impulse CPR in eight adult beagle s. Design: Four animals were chronically instrumented and four were st udied acutely. In an additional four animals, ACD was compared with sh am ACD CPR. Each CPR technique was performed sequentially for 2 minute s, in random order, at a rate of 120, 50% duty cycle, and 1.5 to 2.0 i n of compression depth. Measurements obtained included aortic, right a trial, left ventricular, and coronary perfusion pressures (in mm Hg); pulmonary artery flow; and left ventricular dimension. Results: ACD ma ximized cardiopulmonary hemodynamics, including coronary perfusion pre ssure and stroke volume, compared with both high-impulse manual and sh am ACD CPR. ACD CPR also increased left ventricular pressure change pe r unit time during decompression, and these changes correlated well wi th left ventricular volume changes. Conclusion: In the intact dog, ACD CPR generates physiologically and statistically superior hemodynamics when compared with high-impulse manual CPR. Improved blood flow seems to be related to more efficient ventricular filling and emptying. The se findings emphasize the biphasic nature of CPR and the importance of active decompression.