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Abstract

Introduction: The American Heart Association (AHA) recommends monitoring cardiopulmonary resuscitation (CPR) quality with arterial blood pressure or end tidal carbon dioxide (ETCO2). The objective of this study was to evaluate the ability of diastolic blood pressure (DBP) and ETCO2 obtained during late CPR to discriminate between survivors and non-survivors in porcine models of hypoxic and normoxic ventricular fibrillation (VF). Methods: In both models, 3-month old swine (~30kg) were randomized to receive one of two CPR strategies: 1) Hemodynamic Directed Care (CPP-20): CC depth titrated to a systolic blood pressure of 100 mmHg and titration of vasopressors to maintain coronary perfusion pressure (CPP) > 20 mmHg or 2) Depth 51mm (D51 – AHA optimal care): CC depth of 51mm with AHA epinephrine dosing (0.02 mg/kg IV every 4 minutes). In CPP-20, IV vasopressin (0.4 U/kg) was given if two doses of epinephrine failed to achieve CPP goal. In the hypoxic model, 7 minutes of endotracheal tube clamping preceded VF induction and CPR start; in the normoxic model, 7 minutes of untreated VF preceded the start of CPR. First shock was attempted after 10 minutes of CPR. CPR continued for an additional 10 minutes or until return of spontaneous circulation (ROSC). In the primary analysis, mean DBP and max ETCO2 during the last 2 minutes prior to first shock were compared using receiver operating characteristic curves (area under curve (AUC)). In a secondary analysis, chest compression (CC) depth was compared to both DBP and ETCO2. Results: Survival was 19/30 (63%) animals (CPP20: 14/15 (93%); D51 5/15 (33%); p<0.01. hypoxic: 6/10 (60%); normoxic: 13/20 (65%); p=0.99). The optimal ROSC cut points were: DBP ≥ 26 mmHg (89% sensitive / 60% specific); ETCO2 ≥ 21 mmHg (89% sensitive / 27% specific). By AUC, mean DBP was superior to max ETCO2 (overall cohort: 0.86 vs. 0.37, p<0.01; hypoxic: 0.88 vs. 0.38, p<0.044; normoxic: 0.86 vs. 0.35, p<0.01), and both mean DBP (p<0.01) and ETCO2 (p=0.038) were superior to CC depth. Conclusions: In both hypoxic and normoxic models of VF, DBP was superior to ETCO2 in discriminating survivors from non-survivors, and both DBP and ETCO2 were superior to CC depth.