Effects of various degrees of compression and active decompression on haemodynamics, end-tidal CO2, and ventilation during cardiopulmonary resuscitation of pigs

The effects of various degrees of compression and active decompression during cardiopulmonary resuscitation were tested in a randomized cross-over-design during ventricular fibrillation in eight pigs using an automatic hydraulic chest compression device. Compared with 4/0 (compression/decompression in cm), mean carotid arterial blood flow rose by 60% with 5/0, by 90% with 4/2 and 4/3, and by 105% with 5/2. Two cm active decompression increased mean brain and myocardial blood flow by 53% and 37%, respectively, as compared with 4/0, Increasing standard compression from 4 to 5 cm caused no further increase in brain or heart tissue blood flow whether or not combined with active decompression, Tissue blood flow remained unchanged or decreased when active decompression (4/3) caused that 50% of the pigs were lifted from the table due to the force required. Myocardial blood flow was reduced with 5/0 vs, 4/0 despite no reduction in end decompression coronary perfusion pressure ((aortic-right atrial pressure) (CPP), (7 +/- 8 mmHg with 4/0, 14 +/- 11 mmHg with 5/0)(Ns)). End decompression CPP increased by 186% with 4/2 vs. 4/0, by 200% with 4/3, and by 300% with 5/2. Endo-tracheal partial pressure of CO2 was significantly increased during the compression phase of active decompression CPR compared with standard CPR, Active decompression CPR generated an significantly increased ventilation compared with standard CPR, Conclusion: Carotid and tissue blood flow, ventilation, and CPP increase with 2 cm of active decompression. An attempt to further increase the level of active decompression or increasing the compression depth from 4 to 5 cm did not improve organ blood flow.