Hemodynamics of Interposed Abdominal Compression during Human Cardiopulmonary Resuscitation

Objective: Clinical studies of interposed abdominal compression CPR (IAC-CPR) have had diverse outcomes. This study compared the hemodynamics of standard CPR and IAC-CPR in humans.
Methods: A 24-month prospective nonrandomized analysis of hemo-dynamic parameters was performed in a convenience cohort of 20 adults who had had out-of-hospital, nontraumatic, normothermic cardiac arrests. The study took place in the resuscitation unit of a large urban hospital. Thoracic aortic and right atrial catheters were inserted and pressures were recorded during standard CPR and IAC-CPR. Coronary perfusion pressures (CPPs) were determined during standard CPR and IAC-CPR. The patients were separated into two groups based upon their responses to IAC-CPR. Responders had increases in CPP during IAC-CPR; nonresponders had decreases or no change in CPP during IAC-CPR. Aortic relaxation, right atrial relaxation, aortic compression, and right atrial compression phase pressures were compared between the two groups.
Results: CPPs increased in 13 patients and decreased in seven patients. The mean change in CPP with IAC-CPR was an increase of 5.8 ± 15.1 torr. An elevated right atrial compression phase pressure (RaComp) during standard CPR was predictive of an increase in CPP during IAC-CPR (p = 0.047). In those patients who showed improvements in CPP during IAC-CPR, mean aortic relaxation phase pressures (AoRelax) increased by 9.5 ± 14.2 torr (p = 0.026) and mean right atrial relaxation phase pressures (RaRelax) decreased by 2.6 ± 6.2 torr (p = 0.099) during IAC-CPR.
Conclusions: The variable effects of IAC-CPR on CPP appear to be multifactorial. The improvement in CPP that occurred in responders to IAC-CPR was secondary to an increase in AoRelax as well as a decrease in RaRelax.