CARDIOPULMONARY RESUSCITATION Coronary blood flow during cardiopulmonary resuscitation in swine RONALD

Recent papers have raised doubt as to the magnitude of coronary blood flow during closed-chest cardiopulmonary resuscitation. We will describe experiments that concern the methods of coronary flow measurement during cardiopulmonary resuscitation. Nine anesthetized swine were instrumented to allow simultaneous measurements of coronary blood flow by both electromagnetic cuff flow probes and by the radiomicrosphere technique. Cardiac arrest was caused by electrical fibrillation and closed-chest massage was performed by a Thumper (Dixie Medical Inc., Houston). The chest was compressed transversely at a rate of 66 strokes/min. Compression occupied one-half of the massage cycle. Three different Thumper piston strokes were studied: 1.5, 2, and 2.5 inches. Mean aortic pressure and total systemic blood flow measured by the radiomicrosphere technique increased as Thumper piston stroke was lengthened (mean ± SD): 1.5 inch stroke, 23 + 4 mm Hg, 525 + 195 ml/ min; 2 inch stroke, 33 + 5 mm Hg, 692 + 202 ml/min; 2.5 inch stroke, 40 + 6 mm Hg, 817 ± 321 ml/min. Both methods of coronary flow measurement (electromagnetic [EMF] and radiomicrosphere [RMS]) gave similar results in technically successful preparations (data expressed as percent prearrest flow mean + 1 SD): 1.5 inch stroke, EMF 12 + 5%, RMS 16 + 5%; 2 inch stroke, EMF 30 ± 6%, RMS 26 ± 11%; 2.5 inch stroke, EMF 50 + 12%, RMS 40 + 20%. The phasic coronary flow signal during closed-chest compression indicated that all perfusion occurred during the relaxation phase of the massage cycle. We concluded that coronary blood flow is demonstrable during closed-chest massage, but that the magnitude is unlikely to be more than a fraction of normal. Circulation 69, No. 1, 174-180, 1984. SINCE a deficiency of coronary blood flow is probably an etiologic factor in many instances of cardiac arrest, it would be important to perform cardiopulmonary resuscitation in a manner that would optimize myocardial perfusion. The validity of the method used to measure coronary flow is a crucial factor in evaluating studies of experimental cardiopulmonary resuscitation, which are directed toward developing techniques to optimize myocardial perfusion. It is by no means certain that the techniques that have been used with such success to measure coronary blood flow in the beating heart electromagnetic flow probes and the radiomicrosphere technique will be equally satisfactory during cardiac massage. We describe experiments in which these techniques can be simultaneously used to ascertain their effectiveness in measuring coronary blood flow during cardiopulmonary resuscitation. From the Division of Combat Casualty Care, Letterman Army Institute of Research, Presidio of San Francisco. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. Address for correspondence: Ronald F. Bellamy, M.D., Chief, Division of Combat Casualty Care, Letterman Army Institute of Research, Presidio of San Francisco, CA 94129. Received February 21, 1983; revision accepted September 22, 1983.