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The Optimization Study on Time Sequence of Enhanced External CounterPulsation in AEI-CPR
Abstract
To improve the aortic pressure and myocardial perfusion pressure during cardiac arrest, this study is designed to optimize sequence of Enhanced External Counter-Pulsation (EECP) for a cardiopulmonary resuscitation (CPR) technique - Active Compression-Decompression CPR coupled with EECP and Inspiratory Impedance Threshold Valve (AEI-CPR). EECP is lower-limbs compression equipment for AEI-CPR that enhanced blood regurgitation during chest decompression. Different occasion for EECP performance would bring different hemodynamic effect. A mathematical model of human circulatory system used to research AEI-CPR has been established. And then the AEI-CPR hemodynamic effect to the blood circulatory system is performed on the model. A genetic algorithm (GA) that used to find optimum sequence of the EECP is performed on the model when other parameters of external force for AEI-CPR are definite. At first, set the maximum strength of chest compression, chest decompression and lower-limbs compression at 400Nt, 160Nt and 300mmHg, respectively. Set the frequency of CPR at 100min-1 and the ratio of chest compression compared to LLCP at 1:1. Then, after genetic algorithm is performed on the established model, fifty groups of optimal results are obtained. The maximum coronary perfusion pressure (CPP) takes place when the EECP begin its compression at 0.2s and the interval among crural, femoral and iliac compression is 0.05s. By applying the optimization algorithm on the CPR mathematical model, the optimum sequence of the EECP could be found. And the experiment results indicate that obvious hemodynamic effect is attained when the EECP began compression at the end of chest compression.
... In addition to these two fundamental groups, third-generation devices, which combine different working mechanisms and different CPR techniques, have been used in recent years, aiming to increase the hemodynamic effects of S-CPR. These are as follows: 3. Active compression-decompression CPR devices (ACD-CPR), 4. Simultaneous sterno-thoracic cardiopulmonary resuscitation devices (SST-CPR/S-CPR/X -CPR), 5. Inspiratory impedance threshold valve/devices and ResQCPR (ACD + ITD CPR), 6. Phased thoracic-abdominal active compression-decompression CPR devices (PTACD-CPR), and 7. Active compression-decompression CPR with enhanced external counterpulsation and the inspiratory impedance threshold valve (AEI-CPR) (2,6,13,(25)(26)(27)(28)(29). The devices in these groups and their working principles have been discussed below. ...
... It has a ventilator that is meant to be used in conjunction with chest compression (Figure 1a) (Michigan Instruments, USA). Mechanical piston-driven devices that are operated manually work with a lever system and are marketed under brand names such as the "Animax Mono" (Figure 1b) (AAT Alber Antriebstechnik GmbH, Albstadt, Germany) and the "CPR RsQAssist, " which employs an audio-visual metronome (10,13,24,26,29). ...
The standard treatment of cardiac arrest is cardiopulmonary resuscitation (CPR), performed with effective manual chest compressions. Although current CPR was developed 50 years ago, cardiac arrest still has a high mortality rate and manual chest compressions have some potential limitations. Because of these limitations, mechanical chest compression devices were developed to improve the efficiency of CPR. This CPR technology includes devices such as the mechanical piston load-distributing band, active compression–decompression CPR, simultaneous sterno-thoracic CPR, impedance threshold valve, phased thoracic-abdominal active compression–decompression CPR and active compression-decompression CPR with enhanced external counterpulsation, and the impedance threshold valve. The purpose of this manuscript was to draw attention to developments in this medical area and to examine studies on the effectiveness of these devices.
Nowadays the outcome of Cardiopulmonary Resusciation (CPR) is dismal. There has been some research showing that if lower extremity counterpulsation is applied during CPR, it might augment coronary perfusion pressure, which is the most important hemodynamic merit of CPR. But lower extremity counterpulsation has not been widely recognized and used during CPR yet. In this paper, a computer model was constructed to simulate hemodynamics of CPR. Based on this computer model and under two simple restrictions, computer simulated evolution was performed to get evolved waveforms for external pressures applied during CPR from randomly chosen waveforms. The results show that the pattern of lower extremity counterpulsation is embodied in the evolved waveforms, thus validating the use of lower extremity counterpulsation during CPR. Our simulation studies show that lower extremity counterpulsation might improve hemodynamics of CPR and deserves further research.
Cardiopulmonary resuscitation is a simple and effective medical treatment for sudden cardiac arrest patients. Most research on CPR is animal experiments and human trials. Because there are many confounding factors present in experiments, conflicting conclusions are often drawn. In this paper, we follow the line of theoretical research on CPR. We adapt previous CPR models, simulate five CPR techniques using the adapted model, and compare their hemodynamics in the same test system. Comparison with experimental data shows that our simulation results agree quite well with experimental data. Our simulation results show that when external counter pulsation is applied during CPR, it may improve cardiac output and increase diastolic aortic pressure. Yet external counter pulsation is not widely used during CPR. We suppose that it deserves further research. Given the benefits of models and simulations, our adapted model may be a useful tool in CPR research.
Research on cardiopulmonary resuscitation (CPR) has always been important and thus focused on by the medical community. The hemodynamic effects of CPR have a direct impact on the survival rate of and prognosis for patients. Research shows that performing Enhanced External Counter-Pulsation (EECP) on lower limbs during the recoil phase of chest compression improves hemodynamic effects. AEI-CPR is an Active Compression-Decompression CPR coupled with EECP and an Impedance Threshold Valve (ITV). Because EECP is important during AEI-CPR, this paper examines the hemodynamic effects of EECP during AEI-CPR based on basic principles of hemodynamics. First, this paper summarizes relevant works that team collaborators have done. The linear model can be used to quantitatively analyze hemodynamic effects. The paper focuses on the nonlinear mechanism of vascular compliance of the lower limb arteries during CPR, and brings up a solution that fits the simulation of the hemodynamic effects of EECP. Running the new model, simulation results can better match the characteristics of an ascending aortic pressure curve obtained from animal experiments. So it is better than the original one.
Optimal control techniques are applied here for the first time to a validated blood circulation model of cardiopulmonary resuscitation (CPR), consisting of a system of seven difference equations. In this system, the non-homogeneous forcing term is the externally applied chest pressure acting as the “control”. The optimal control technique seeks to maximize the blood flow as measured by the pressure differences between the thoracic aorta and the right head superior vena cava. As a result, we provide a new CPR strategy, with increased blood flow. The optimal control is characterized in terms of the solutions of the circulation model and of the corresponding adjoint system. The calculated optimal control gives the pattern of the external pressure to be applied on the chest to obtain optimal blood flow and higher resuscitation rates.
Electro ventilation double pump cardiopulmonary resuscitation (EDCPR) was a cardiopulmonary resuscitation (CPR) technique
that chest compression was coupled with Lower limbs compression to improve the aortic pressure and myocardial perfusion pressure.
The paper was to study the hemodynamic effects during human cardiac arrest and find the optimum value of lower limbs compression
pressure (LLCP) when chest compression pressure was definite. First the computer model of human circulation was developed,
second the effects of EDCPR to the model were performed, third the comression schemes were performed by computer simulation
and the optimum value was found. The results were that EDCPR got the good hemodynamic effects. The proper value of the LLCP
was found. And they were in accordance with the results of parallel animal experiments and the data published before. The
developed model can successfully describe the effects of different CPR techniques and different compression schemes to the
circulation system during cardiac arrest.
This study was designed to assess whether a new method of cardiopulmonary resuscitation (CPR), termed active compression-decompression CPR, or ACD-CPR, improves organ perfusion when compared with standard (S) CPR in a dog model of ventricular fibrillation.
ACD-CPR has recently been shown to improve hemodynamic and respiratory parameters during cardiac arrest when compared with standard CPR. However, to our knowledge, the effects of ACD-CPR on tissue perfusion have not been investigated.
Ventricular fibrillation was induced in eight anesthetized, intubated animals. ACD-CPR and standard CPR were each performed twice in alternating order. All interventions were preceded by 1 min of ventricular fibrillation, in which no CPR was performed, and consisted of 6 min of CPR with either technique during which tissue perfusion was measured. Compressions were performed at 80/min with a 50 percent duty cycle and 175 to 200 N downward force applied to the chest wall for both techniques. Epinephrine was administered at the beginning of each 6-min CPR interval. Hemodynamic monitoring of aortic and right atrial pressure was performed continuously and myocardial, cerebral, and renal blood flows were measured using the radiolabeled microsphere technique at baseline and during all interventions.
Baseline organ perfusion and hemodynamics were similar for all dogs. Baseline left ventricular, brain, and renal blood flows were 62.0 +/- 5.5, 14.1 +/- 2.1, and 476.3 +/- 55.5 ml/min/100 g, respectively (mean +/- SEM). Compared with standard CPR, ACD-CPR resulted in higher global left ventricular (22.5 +/- 6.2 vs 14.1 +/- 4.0 ml/min/100 g, p < 0.01), cerebral (12.0 +/- 2.4 vs 8.5 +/- 2.3 ml/min/100 g, p < 0.01), and renal cortical (27.8 +/- 5.0 vs 17.5 +/- 5.0 ml/min/100 g, p < 0.05) blood flows. Regional flows to the epicardium, endocardium, and midmyocardium as well as to the frontal, parietal, and occipital lobes of the brain were all significantly improved by ACD-CPR. Aortic systolic (61.7 +/- 4.1 vs 49.5 +/- 3.1 mm Hg, p < 0.01), aortic mean (31.6 +/- 2.8 vs 27.2 +/- 2.2 mm Hg, p = 0.001), and myocardial perfusion pressure (12.9 +/- 3.4 vs 10.4 +/- 3.4 mm Hg, ACD-CPR vs standard CPR, p < 0.01) were all higher during ACD-CPR than during standard CPR.
We conclude that ACD-CPR improves tissue perfusion and systemic hemodynamics compared with standard CPR.
Use of an inspiratory impedance threshold device (ITD) significantly increases coronary perfusion pressures and survival in patients ventilated with an endotracheal tube (ETT) during active compression-decompression cardiopulmonary resuscitation. We tested the hypothesis that the ITD could lower intratracheal pressures when attached to either a facemask or ETT.
An active and sham ITD were randomly applied first to a facemask and then to an ETT during active compression-decompression cardiopulmonary resuscitation in 13 out-of-hospital cardiac arrest patients in a randomized, double-blinded, prospective clinical trial. The compression-to-bag-valve ventilation ratio was 15:2. Airway pressures (surrogate for intrathoracic pressure) were measured with a pressure transducer. A sham and an active ITD were used for 1 min each in a randomized order, first on a facemask and then on an ETT. Statistical analyses were made using Friedman's and Wilcoxon's rank-sum tests.
For the primary end point, mean +/- sd maximum negative intrathoracic pressures (mm Hg) during the decompression phase of cardiopulmonary resuscitation were -1.0 +/- 0.73 mm Hg with a sham vs. -4.6 +/- 3.7 mm Hg with an active ITD on the facemask (p = .003) and -1.3 +/- 1.3 mm Hg with a sham ITD vs. -7.3 +/- 4.5 mm Hg with an active ITD on an ETT (p = .0009). Decompression phase airway pressures with the facemask and ETT were not statistically different.
Use of an active ITD attached to a facemask or an ETT resulted in a significantly lower negative intratracheal pressure during the decompression phase of active compression-decompression cardiopulmonary resuscitation when compared with controls. Airway pressures with an ITD on either a facemask or ETT were similar. The ITD-facemask combination was practical and enables rapid deployment of this life-saving technology.
Interposed abdominal compression, IAC-CPR incorporates alternating chest and abdominal compressions to generate enhanced artificial circulation during cardiac arrest. The technique has been generally successful in improving blood flow and survival compared to standard CPR; however, some questions remain.
To determine "why does IAC-CPR produce more apparent benefit in some subjects than in others?" and "what is the proper compression rate, given that there are actually two compressions (chest and abdomen) in each cycle?"
Computer models provide a means to search for subtle effects in complex systems. The present study employs a validated 12-compartment mathematical model of the human circulation to explore the effects upon systemic perfusion pressure of changes in 35 different variables, including vascular resistances, vascular compliances, and rescuer technique. CPR with and without IAC was modeled.
Computed results show that the effect of 100 mmHg abdominal compressions on systemic perfusion pressure is relatively constant (about 16 mmHg augmentation). However, the effect of chest compression depends strongly upon chest compression frequency and technique. When chest compression is less effective, as is often true in adults, the addition of IAC produces relatively dramatic augmentation (e.g. from 24 to 40 mmHg). When chest compression is more effective, the apparent augmentation with IAC is relatively less (e.g. from 60 to 76 mmHg). The optimal frequency for uninterrupted IAC-CPR is near 50 complete cycles/min with very little change in efficacy over 20-100 cycles/min. In theory, the modest increase in systemic perfusion pressure produced by IAC can make up in part for poor or ineffective chest compressions in CPR. IAC appears relatively less effective in circumstances when chest pump output is high.
An impedance threshold valve (ITV) is a new airway adjunct for resuscitation that permits generation of a small vacuum in the chest during the recoil phase of chest compression.
To explore in detail the expected magnitude and the hemodynamic mechanisms of circulatory augmentation by an ITV in Standard CPR.
A 14-compartment mathematical model of the human cardiopulmonary system--upgraded to include applied chest compression force, elastic recoil of the chest wall, anatomic details of the heart and lungs, and the biomechanics of mediastinal compression--is exercised to explore the conditions required for circulatory augmentation by an ITV during various modes of CPR.
The ITV augments systemic perfusion pressure by about 5 mmHg compared to any particular baseline perfusion pressure without the ITV. When baseline perfusion is low, owing to either diminished chest compression force, the existence of a thoracic pump mechanism of blood flow, or the presence of an effective compression threshold, then the relative improvement produced by an ITV is significant. With an ITV the heart expands into soft pericardiac tissue, which makes the heart easier to compress.
An ITV can augment perfusion during CPR. The observed effectiveness of ITVs in the laboratory and in the clinic suggests a thoracic pump mechanism for Standard CPR, and perhaps also an effective compression threshold that must be exceeded to generate blood flow by external chest compression.
Objective:
To discover design principles underlying the optimal waveforms for external chest and abdominal compression and decompression during cardiac arrest and cardiopulmonary resuscitation (CPR).
Method:
A 14-compartment mathematical model of the human cardiopulmonary system is used to test successive generations of randomly mutated external compression waveforms during cardiac arrest and resuscitation. Mutated waveforms that produced superior mean perfusion pressure became parents for the next generation. Selection was based upon either systemic perfusion pressure (SPP = thoracic aortic minus right atrial pressure) or upon coronary perfusion pressure (CPP = thoracic aortic pressure minus myocardial wall pressure). After simulations of 64,414 individual CPR episodes, 40 highly evolved waveforms were characterized in terms of frequency, duty cycle, and phase. A simple, practical compression technique was then designed by combining evolved features with a constant rate of 80 min(-1) and duty cycle of 50%.
Results:
All ultimate surviving waveforms included reciprocal compression and decompression of the chest and the abdomen to the maximum allowable extent. The evolved waveforms produced 1.5-3 times the mean perfusion pressure of standard CPR and greater perfusion pressure than other forms of modified CPR reported heretofore, including active compression-decompression (ACD)+ITV and interposed abdominal compression (IAC)-CPR. When SPP was maximized by evolution, the chest compression/abdominal decompression phase was near 70% of cycle time. When CPP was maximized, the abdominal compression/chest decompression phase was near 30% of cycle time. Near-maximal SPP/CPP of 60/21 mmHg (forward flow 3.8 L/min) occurred at a compromise compression frequency of 80 min(-1) and duty cycle for chest compression of 50%.
Conclusions:
Optimized waveforms for thoraco-abdominal compression and decompression include previously discovered features of active decompression and interposed abdominal compression. These waveforms can be used by manual (Lifestick-like) and mechanical (vest-like) devices to achieve short periods of near normal blood perfusion non-invasively during cardiac arrest.