COMPARISON OF CONVENTIONAL AND SIMULTANEOUS COMPRESSION-VENTILATION CARDIOPULMONARY RESUSCITATION IN PIGLETS

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To determine the mechanism of cardiac output and hemodynamic changes during cardiopulmonary resuscitation (CPR), we performed 60 min of CPR using a mechanical resuscitator ("Thumper", MII USA) in 20 piglets (13.7±1.2 kg) following cardiac arrest induced by intravenous injection of KCl. Conventional CPR (C-CPR), i.e., 60 external chest compressions (60 psi force, 3 cm deep, and 50% duration) and 12 ventilations (following every 5th compression, with peak airway pressure of 30 cmH₂O) per minute, was performed in 10 piglets; and simultaneous compression and ventilation CPR (SCV-CPR), i.e., 60 external chest compressions of the same magnitude, simultaneously with 60 ventilations (with peak airway pressure of 60 cmH₂O) per minute, was performed in the 10 other piglets. Cardiac output in C-CPR and SCV-CPR was maintained near 70% or more of baseline throughout the CPR. Systemic vascular resistance dropped to below 50% of baseline. Systolic, mean and diastolic arterial pressures were maintained above 70, 40, and around 20 mmHg, respectively, during the first 30 min of CPR. Central venous pressure rose after arrest and subsequent CPR to above 25 mmHg, and remained high in SCV-CPR, but declined thereafter in C-CPR. Aortic diastolic minus right atrial diastolic pressure was around 15 mmHg early in CPR and dropped to almost zero thereafter. Serial arterial blood gas analyses showed a significant deterioration after 20 min of SCV-CPR. All but one piglet in the SCV-CPR group died after 60 min of CPR. Postmortem examination revealed that pulmonary barotrauma was more extensive and severe in SCV-CPR than in C-CPR. These results suggest that cardiac pumping is the primary mechanism of cardiac output during CPR in piglets. The mechanical resuscitator consistently achieved adequate cardiac output and systolic arterial pressure. Pulmonary barotrauma may have a negative impact on CPR results.