Delayed high-quality CPR does not improve outcomes.

Objective: The quality of cardiopulmonary resuscitation (CPR) is an important factor in the outcome of cardiac arrest. Our objective was to compare outcomes following either immediate low-quality (LQ) CPR or delayed high-quality (HQ) CPR. We hypothesized that delayed HQ CPR will improve the outcomes of CPR in comparison to immediately performing LQ CPR.

Methods: Eighteen Sprague-Dawley rats were randomized into two groups: (1) Delayed HQ CPR (HQ group, n = 9). (2) Immediate LQ CPR (LQ group, n = 9). Ventricular fibrillation (VF) was induced and untreated for 8 mins. CPR was immediately performed in LQ group for 5 mins. Compression depth was set at 70% of the "optimal compression depth". VF was untreated for an additional 5 mins in HQ group. HQ CPR was started together with ventilation (100% oxygen) and external hypothermia for 8 mins in both groups. The "optimal compression depth" was approximately 30% of the anteroposterior chest diameter. Epinephrine was administrated 3 mins prior to defibrillation attempt. Restoration of spontaneous circulation, postresuscitation myocardial function and survival time were monitored.

Results: All animals in the LQ group and 7 of 9 animals in the HQ group were resuscitated. Myocardial function, including ejection fraction and cardiac output was better in the LQ group than in the HQ group (p < 0.05) and survival time was longer in the LQ group (p < 0.05).

Conclusions: The outcomes after immediate LQ CPR, were better than those after delayed HQ CPR in this rat model of cardiac arrest and resuscitation.