BACKGROUND: The optimal targets for diastolic blood pressure (DBP) and end-tidal carbon dioxide (ETCO2) during cardiopulmonary resuscitation (CPR) and their association with outcomes remain unclear. This study aimed to evaluate the association between DBP and ETCO2 and the return of spontaneous circulation (ROSC) during CPR. METHODS: This study was a preplanned sub-analysis of the Augmented Medication CardioPulmonary Resuscitation (AMCPR) trial. We extracted initial (within 5 minutes), follow-up (around 10 minutes), and delta (follow-up minus initial) values of DBP and ETCO2 from the registry. The primary outcome was sustained ROSC (≥20 minutes). RESULTS: The study included 264 patients, mostly male (69.3%) and with a median age of 74 years old. Of these patients, 101 (38.3%) achieved sustained ROSC. Patients with sustained ROSC had statistically higher initial, follow-up, and delta values of DBP compared to those without ROSC. However, the levels of ETCO2 were similar between the two groups, except for follow-up values. Follow-up DBP above 26.5 and delta DBP above 6.5 were independently associated with sustained ROSC (adjusted odds ratio, aOR = 10.03, 95% confidence interval, CI = 3.64 - 27.66, p <
0.01, and aOR = 4.83, 95% CI = 1.90 - 12.26, p <
0.01). CONCLUSION: Monitoring DBP during resuscitation in patients with cardiac arrest may provide additional information about successful initial resuscitation. Improving certain levels of DBP may influence outcomes.