Abstract
Background Effective cardiopulmonary resuscitation is a critical component of the pre-hospital treatment of cardiac arrest victims. Mechanical chest compression (MCC) devices enable the delivery of MCC waveforms that could not be delivered effectively by hand. While chest compression generated blood flow has been studied for more than 50 years, the relation between sternum kinematics (depth over time) and the resulting blood flow have not been well described. Using a five parameter MCC model, we studied the effect of MCC depth, MCC release time, and their interaction on MCC generated blood flow in a highly instrumented swine model of cardiac arrest.MethodsMCC hemodynamics were studied in 17 domestic swine (~30 kg) using multiple extra-vascular flow probes and standard physiological monitoring. After 10 min of untreated ventricular fibrillation, mechanical MCC were started. MCC varied such that sternal release occurred over 100, 200, or 300 ms. MCC were delivered at a rate of 100 per min and at a depth of 1.25″ (n = 9) or at a depth of 1.9″ (n = 8) for a total of 18 min. Transitions between release times occurred every 2 min and were randomized. Linear Mixed Models were used to estimate the effect of MCC depth, MCC release time, and the interaction between MCC depth and release time on physiological outcomes.ResultsBlood pressures were optimized by a 200 ms release. End tidal carbon dioxide (EtCO2) was optimized by a 100 ms release. Blood flows were significantly lower at a 300 ms release than at either a 100 or 200 ms release (p < 0.05). 1.9″ deep MCC improved EtCO2, right atrial pressure, coronary perfusion pressure, inferior vena cava blood flow, carotid blood flow, and renal vein blood flow relative to 1.25″ MCC.ConclusionsDeeper MCC improved several hemodynamic parameters. Chest compressions with a 300 ms release time generated less blood flow than chest compressions with faster release times. MCC release time is an important quantitative metric of MCC quality and, if optimized, could improve MCC generated blood flows and pressures.Electronic supplementary materialThe online version of this article (doi:10.1186/s12938-015-0095-4) contains supplementary material, which is available to authorized users.
Highlights
Effective cardiopulmonary resuscitation is a critical component of the pre-hospital treatment of cardiac arrest victims
Other studies use trans-vascular Doppler ultrasound measurement of blood flow in a single vessel, usually the common carotid artery [9, 15, 16]. While this measurement provides significantly better time resolution, data from a single blood vessel is not sufficient to relate sternum kinematics to chest compression generated blood flow. In this manuscript we report blood flows from a novel high-fidelity swine model in which we studied the impact of changes in sternum kinematics, via changes in chest compression depth and chest compression release time, on blood flow generated in six blood vessels with perivascular Doppler ultrasound measurements during ongoing cardiac arrest
This model may be a useful platform from which to study questions related to the impact of time on chest compression generated blood flow
Summary
Effective cardiopulmonary resuscitation is a critical component of the pre-hospital treatment of cardiac arrest victims. The thoracic pump model was proposed wherein the chest compression increases the intra-thoracic pressure, expelling blood from the heart and the blood vessels in the chest with extra-thoracic venous valves enforcing physiologically forward directionality on the resulting blood flow [2,3,4]. While these models enable mechanistic interpretations of chest compression generated blood flow, the connection between sternum kinematics (position, velocity, acceleration, and time) and intra-thoracic pressure or ventricular compression remains poorly described. The advent of mechanical chest compression devices, which make it possible to prescribe sternum kinematics with a high degree of precision and accuracy, requires a kinematic understanding of chest compression generated blood flow to enable the development of optimal chest compression waveforms
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