Effect of different compression–decompression cycles on haemodynamics during ACD–CPR in pigs

Abstract

The haemodynamic effects of variations in the relative duration of the compression and active decompression (4 cm/2 cm) during active compression–decompression cardiopulmonary resuscitation (ACD–CPR), 30/70, 50/50 and 70/30, were tested in a randomized cross-over design during ventricular fibrillation in seven anaesthetized pigs (17–23 kg) using an automatic hydraulic chest compression–decompression device. Duty cycles of 50/50 and 70/30 gave significantly higher values than 30/70 for mean carotid blood flow (32 and 36 vs. 21 ml min −1, transit time flow probe), cerebral blood flow (30 and 34 vs. 19 , radionuclide microspheres), mean aortic pressure (35 and 41 vs. 29 mmHg) and mean right atrial pressure (24 and 33 vs. 16 mmHg). A higher mean aortic, mean right atrial and mean left ventricular pressure for 70/30 were the only significant differences between 50/50 and 70/30. There were no differences in myocardial blood flow (radionuclide microspheres) or coronary perfusion pressure (CPP, aortic-right atrial pressure) between the three different duty cycles. CPP was positive in both the early and late compression period and during the whole decompression period. The expired CO 2 was significantly higher with 70/30 than 30/70 during the compression phase of ACD–CPR. Beyond that no significant differences in the expired CO 2 levels was observed. In conclusion a reduction of the compression period to 30% during ACD–CPR reduced the cerebral circulation, the mean aortic and right atrial pressures with no effect on the myocardial blood flow of varying the compression–decompression cycle.