Experimental paperHemodynamic improvement of a LUCAS 2 automated device by addition of an impedance threshold device in a pig model of cardiac arrest☆
Introduction
Quality of cardiopulmonary resuscitation (CPR) is critical to improving survival rates with favorable neurological function.1 Even when optimally performed, blood flow generated by manual chest compressions is, at best, less than 25% of normal.2, 3 Mechanical chest compression devices have been developed to improve the quality of CPR by replacing manual compressions. The LUCAS device consistently compresses the chest at a rate of 100/min and a depth of 5 cm and provides three pounds of upward force with each decompression. Animal studies with the Lund University Cardiopulmonary Assist System (LUCAS) have shown improved organ perfusion pressures, enhanced cerebral blood flow, and higher end-tidal CO2 during CPR compared with the use of manual compressions.4, 5, 6
Similarly, the impedance threshold device (ITD) has also been shown to improve overall CPR hemodynamics including cerebral and coronary perfusion pressure. It works by impeding inflow of respiratory gases during the decompression phase of CPR, thereby generating a greater negative intrathoracic pressure with each chest recoil. This, in turn, enhances venous return and lowers intracranial pressure thereby enhancing cardiac and cerebral perfusion7, 8.
As in the case of standard manual CPR, we hypothesize that when an active ITD is added on L-CPR, cerebral and coronary perfusion pressures will improve.
Section snippets
Methods
This study was approved by the Institutional Animal Care Committee of the Minneapolis Medical Research Foundation of Hennepin County Medical Center. All animal care was compliant with the National Research Council's 1996 Guidelines for the Care and Use of Laboratory Animals. All studies were performed by a qualified, experienced research team in Yorkshire female farm bred pigs weighing 39 ± 2 kg. A certified and licensed veterinarian assured the protocols were performed in accordance with the
Results
There were no statistical differences in baseline characteristics, regardless of the randomization order. Further, there was no evidence of a carryover effect based on the randomization order for the primary study endpoints (mean CPP of the 1st period vs. the 2nd was 29 ± 8 vs. 27 ± 8, p = 0.71 and CePP was 23 ± 11 vs. 22 ± 14, p = 0.48).
Discussion
The results demonstrated that the application of negative intrathoracic pressure during CPR with the combination of an ITD and the LUCAS 2 mechanical CPR device increased vital organ perfusion pressures during cardiac arrest resuscitation. The beneficial effect of the ITD was consistent over the duration of L-CPR. To our knowledge this study is the first to assess the beneficial effect on hemodynamics with this device combination.
In animal and human studies, the addition of an ITD to standard
Conclusion
In pigs undergoing L-CPR the addition of the ITD significantly reduced intrathoracic pressure and improved both coronary and cerebral perfusion pressures. This hemodynamic benefit warrants further study in longer term outcomes.
Funding
This study was funded by an internal grant of the Cardiovascular Division of the University of Minnesota.
Conflict of interest statement
The authors have no financial conflicts of interest.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.09.013.