Correlation of end tidal carbon dioxide, amplitude spectrum area, and coronary perfusion pressure in a porcine model of cardiac arrest

Amplitude Spectrum Area ( AMSA ) values during ventricular fibrillation ( VF ) correlate with myocardial energy stores and predict defibrillation success. By contrast, end tidal CO 2 ( ETCO 2) values provide a noninvasive assessment of coronary perfusion pressure and myocardial perfusion during cardiopulmonary resuscitation ( CPR ). Given the importance of the timing of defibrillation shock delivery on clinical outcome, we tested the hypothesis that AMSA and ETCO 2 correlate with each other and can be used interchangably to correlate with myocardial perfusion in an animal laboratory preclinical, randomized, prospective investigation. After 6 min of untreated VF , 12 female pigs (32 ± 1 Kg), isoflurane anesthetized pigs received sequentially 3 min periods of standard (S) CPR , S‐ CPR + an impedance threshold device ( ITD ), and then active compression decompression ( ACD ) +  ITD CPR . Hemodynamic, AMSA , and ETCO 2 measurements were made with each method of CPR . The Spearman correlation and Friedman tests were used to compare hemodynamic parameters. ETCO 2, AMSA , coronary perfusion pressure, cerebral perfusion pressure were lowest with STD CPR , increased with STD CPR  +  ITD and highest with ACD CPR + ITD . Further analysis demonstrated a positive correlation between AMSA and ETCO 2 ( r  = 0.37, P  = 0.025) and between AMSA and key hemodynamic parameters ( P  < 0.05). This study established a moderate positive correlation between ETCO 2 and AMSA . These findings provide the physiological basis for developing and testing a novel noninvasive method that utilizes either ETCO 2 alone or the combination of ETCO 2 and AMSA to predict when defibrillation might be successful.