Abstract
Objective
Optimising the depth and rate of applied chest compressions following out of hospital
cardiac arrest is crucial in maintaining end organ perfusion and improving survival.
The impedance cardiogram (ICG) measured via defibrillator pads produces a characteristic
waveform during chest compressions with the potential to provide feedback on cardiopulmonary
resuscitation (CPR) and enhance performance. The objective of this pre-clinical study
was to investigate the relationship between mechanical and physiological markers of
CPR efficacy in a porcine model and examine the strength of correlation between the
ICG amplitude, compression depth and end-tidal CO2 (ETCO2).
Methods
Two experiments were performed using 24 swine (12 per experiment). For experiment
1, ventricular fibrillation (VF) was induced and mechanical CPR commenced at varying
thrusts (0–60 kg) for 2 min intervals. Chest compression depth was recorded using a Philips QCPR device with
additional recording of invasive physiological parameters: systolic blood pressure,
ETCO2, cardiac output and carotid flow. For experiment 2, VF was induced and mechanical
CPR commenced at varying depths (0–5 cm) for 2 min intervals. The ICG was recorded via defibrillator pads attached to the animal's
sternum and connected to a Heartsine 500P defibrillator. ICG amplitude, chest compression
depth, systolic blood pressure and ETCO2 were recorded during each cycle. In both experiments the within-animal correlation
between the measured parameters was assessed using a mixed effect model.
Results
In experiment 1 moderate within-animal correlations were observed between physiological
parameters and compression depth (r = 0.69–0.77) and thrust (r = 0.66–0.82). A moderate correlation was observed between compression depth and thrust
(r = 0.75). In experiment 2 a strong within-animal correlation and moderate overall correlations
were observed between ICG amplitude and compression depth (r = 0.89, r = 0.79) and ETCO2 (r = 0.85, r = 0.64).
Conclusion
In this porcine model of induced cardiac arrest moderate within animal correlations
were observed between mechanical and physiological markers of chest compression efficacy
demonstrating the challenge in utilising a single mechanical metric to quantify chest
compression efficacy. ICG amplitude demonstrated strong within animal correlations
with compression depth and ETCO2 suggesting its potential utility to provide CPR feedback in the out of hospital setting
to improve performance.
Keywords
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Article info
Publication history
Published online: July 30, 2015
Accepted:
July 22,
2015
Received in revised form:
July 20,
2015
Received:
March 13,
2015
Footnotes
☆A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2015.07.020.
Identification
Copyright
© 2015 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.