Experimental design for study of cardiopulmonary resuscitation in dogs

Many different designs for studies of various aspects of cardiopulmonary resuscitation (CPR) in dogs are described in the literature. No single technique is generally accepted. We present a systematized approach to the study of CPR in the canine model. Cardiac output, arterial blood pressure, and electrocardiogram were recorded for three different methods. The methods studied were closed chest compression, closed chest compression with an automatic gas-powered chest compressor, and open chest manual cardiac massage. Cardiac output for both types of external chest compression were less than 17% of control in all cases. With open chest cardiac massage, systemic arterial blood pressures were in the 50 mm Hg to 100 mm Hg range and cardiac output of up to 70% of control was achieved. Using a metronome to obtain compression rate and the arterial blood pressure to guide the efficacy of compression, consistent levels of cardiac output could be achieved for up to 30 minutes using open chest cardiac massage. Closed chest massage in man results in a cardiac output of 25% to 30% of normal when performed under optimal conditions. A cardiac output of 25% to 30% of control cannot be achieved in large dogs with external chest compression, and hence is not a good model to stimulate CPR in man.