Time-Dependent Association Between Agonal Respirations and Cardiopulmonary Resuscitation Hemodynamics in a Porcine Model of Cardiac Arrest

Objective: Agonal respirations (AR) are common in patients with cardiac arrest (CA) and are associated with a higher likelihood of successful return of spontaneous circulation (ROSC). Prior preclinical studies suggest that the favorable effects of AR may be mediated by improved coronary perfusion pressure (CPP) during subsequent cardiopulmonary resuscitation (CPR) efforts, but whether this relationship is influenced by the duration of CA has yet to be studied. Accordingly, we measured CPR hemodynamics in swine following 7 minutes or 10 minutes of untreated ventricular fibrillation (VF) to determine if the frequency of AR is associated with CPP after prolonged CA. Methods: Swine (n=71) were subjected to either 7 minutes (n=50) or 10 minutes (n=21) of electrically-induced VF CA, during which the frequency of AR was recorded before the initiation of CPR with chest compressions (100/minute) and mechanical ventilation (16-20 breaths/minute). CPP was assessed during CPR by calculating the difference between aortic pressure and right atrial pressure during decompression. Animals were retrospectively stratified into two groups (high and low frequency of AR) based on the median number of AR in each cohort (7-minute CA median = 6 AR; 10-minute CA median = 9 AR).>Results: In the 7-minute CA cohort, the high AR group (9.7±2.9 AR; n=28) had a significantly longer time from first to last AR (102±6 vs. 34±6 seconds; p<0.001), shorter time from final AR to CPR initiation (208±8 vs. 280±15 seconds; p<0.001), and higher CPP during CPR (14.4±1.0 vs. 9.3±0.6 mmHg; p<0.001) than the low AR group (2.9±0.4 AR; n=22). In contrast, following 10 minutes of CA, the high AR group (12.0±0.4 AR; n=11) did not have a significantly different CPP during CPR (8.7±1.8 vs. 10.4±1.5 mmHg; p=0.48) when compared to the low AR group (6.2±0.5 AR; n=10). A greater number of defibrillation attempts were required to terminate VF after 10 minutes of CA (3.0±0.6) vs. 7 minutes of CA (1.2±0.1; p<0.001), but this was not impacted by the frequency of AR in either cohort. Conclusion: Consistent with prior studies in swine subjected to 5 minutes of untreated CA, a high frequency of AR during a 7-minute episode of CA was associated with higher CPP upon initiation of CPR. However, the favorable effects of AR frequency on CPP during CPR were no longer apparent when the duration of untreated CA was extended to 10 minutes. These results demonstrate that the beneficial effects of AR on CPR hemodynamics are time-dependent and highlight the importance of early initiation of CPR following CA. Supported by funding from the NIH and US Department of Veteran's Affairs. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.