Study objective: Abdominal compressions can be interposed between the thoracic compressions of standard CPR (SCPR). The resulting interposed abdominal compression CPR (IAC-CPR) may increase blood pressures and patient survival, particularly if applied as a primary technique after in-hospital cardiac arrest. We used a predominant cardiac compression canine model to study the effects of IAC-CPR on blood pressures and total and vital organ perfusion as a function of time after cardiac arrest and efficacy of SCPR. Design: In a crossover design, we measured blood pressures and total and regional blood flow (radioactive microspheres) during 6-minute episodes of mechanical SCPR and IAC-CPR, both early (4 to 16 minutes) and late (18 to 30 minutes) after induction of ventricular fibrillation in eight dogs (weight, 25 to 33 kg) under neuroleptanalgesia/anesthesia. Results: During IAC-CPR, the ascending aorticright atrial pressure gradient increased (P<.05), and retrograde pressure pulses contributed to the rise of ascending aortic pressure. Within 2 minutes after the start of IAC-CPR, end-tidal CO 2 fraction increased by 0.6±0.4 vol% (P<.05), suggesting enhanced venous return. IAC-CPR enhanced (P<.05) total forward blood flow (574±406 versus 394±266 mL/minute during SCPR for the early phase) and vital organ perfusion (including myocardium), in both early and late phases. The IAC-CPR-induced augmentation of blood flow was greater if perfusion was relatively high during SCPR. Conclusion: Compared with predominant cardiac compressions alone (SCPR), the addition of interposed abdominal compressions (IAC-CPR) improves total and vital organ oxygen delivery through enhanced venous return and perfusion pressures. [Hoekstra OS, van Lambalgen AA, Groeneveld ABJ, van den Bos GC, Thijs LG: Abdominal compressions increase vital organ perfusion during CPR in dogs: Relation with efficacy of thoracic compressions. Ann Emerg Med March1995;25:375-385.].