Abstract 2640: Ventilation Rate and Use of the Impedance Threshold Device Are Correlated With Hemodynamics During CPR in Humans
Introduction: In an animal model, excessive ventilation rates have been shown to increase mean intrathoracic pressure, impeding venous return to the heart and decreasing hemodynamics during CPR. By generating negative intrathoracic pressure on the upstroke of CPR, the Impedance Threshold Device (ITD) has been shown to increase systolic blood pressure during CPR.
Hypothesis: We tested the hypothesis that excessive ventilation rates would be inversely proportional and use of the ITD would be directly proportional with hemodynamics during CPR in humans.
Methods: Data was retrospectively reviewed from a prospective, randomized, double-blind intention-to-treat clinical trial conducted in the Milwaukee Emergency Medical Services (EMS) System. EMS personnel placed an active or sham ITD on the endotracheal tube of adults in cardiac arrest. Care between groups was similar except for ITD type. Femoral arterial BP (mmHg) was invasively measured every 10 seconds during CPR. Ventilation rate/minute was electronically recorded. All Institutions Research Committees in Milwaukee approved the study under Federal Regulation 21 CFR 50.24.
Results: There were 23 patients entered in the study. The median age was 65 and 14/23 (60.8%) were male. Four of 23 (17%) had ventricular fibrillation as the initial cardiac arrest rhythm, 8/23 (35%) pulseless electrical activity, and 11/23 (48%) asystole. The median ventilation rate was 11 breaths/minute (range: 1–30). A total of 143 minutes of CPR with 706 femoral arterial blood pressure recordings were captured. Ventilation rate was inversely correlated with systolic blood pressure (Pearson Coefficient, −0.14457, P=0.0002) and End Tidal CO2 (Pearson Coefficient, −0.12862, P=0.0019). Use of the functional ITD during CPR had a mean blood pressure effect of 32.7 mmHg (CI: 12.3, 53.0, P=0.0037) compared with the non-functional ITD.
Conclusion: For the first time, ventilation rate has been demonstrated to be significantly and inversely correlated to systolic blood pressure during CPR in humans. The ITD had a mean blood pressure effect of 32.7 mmHg. These findings have implications for CPR guidelines, education, clinical practice, EMS and hospital-based quality assurance, and interpretation of resuscitation research.