Influence of compression rate on initial success of resuscitation and 24 hour survival after prolonged manual cardiopulmonary resuscitation in dogs.

The influence of chest compression rate on initial resuscitation success and 24 hr survival after prolonged manual cardiopulmonary resuscitation (CPR) was investigated in 26 morphine-anesthetized dogs (17 to 30 kg). After placement of aortic and right atrial micromanometers and induction of ventricular fibrillation, manual CPR was commenced immediately and continued for 30 min. One group of 13 dogs underwent manual CPR at a compression rate of 60/min, and the other group at a rate of 120/min. The compression durations in the two groups were not significantly different (51.7 +/- 1.8% at 60/min vs 51.6 +/- 1.9% at 120/min). No drugs other than sodium bicarbonate were administered during CPR. A maximum of three attempts was permitted to defibrillate the heart. Successfully defibrillated animals were followed for 24 hr, during which time no treatment, other than naloxone, was given to reverse the effects of morphine. Arterial blood pH, PCO2, and PO2 were not significantly different in the two groups throughout the CPR period. When compared with the compression rate of 60/min, the compression rate of 120/min produced more successfully defibrillated animals (12/13 at 120/min vs 2/13 at 60/min, p less than .002) and more 24 hr survivors (8/13 at 120/min vs 2/13 at 60/min, p less than .03). All 24 hr survivors were conscious and able to sit, stand, and drink normally. One 24 hr survivor in each group had difficulty walking. Improved survival with the high-rate compression technique was consistent with the significantly higher mean aortic (systolic and diastolic) and coronary perfusion pressures attained with high-rate compressions (all p less than .002). Although the clinical applicability of these findings has yet to be demonstrated, they provide empirical support for the recent decision to increase the chest compression rate for manual CPR recommended by the American Heart Association, and indicate that the hemodynamic and survival benefits of faster compression rates in this experimental preparation were not dependent on covariant alterations in compression duration.