Design of near-optimal waveforms for chest and abdominal compression and decompression in CPR using computer-simulated evolution

Abstract

Objective: To discover design principles underlying the optimal waveforms for external chest and abdominal compression and decompression during cardiac arrest and 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 and a constant rate of 80/min 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 to 3 times the mean perfusion pressure of standard CPR and greater perfusion pressure than other forms of modified CPR reported heretofore, including ACD+ITV and 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 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 utilized by manual (Lifestick-like) and mechanical (vestlike) devices to achieve short periods of near normal blood perfusion noninvasively during cardiac arrest.

Mechanical chest compressions with trapezoidal waveform improve haemodynamics during cardiac arrest

“…A mathematical model that used computersimulated evolution of compression waveforms tended to result in rectangular waveforms when both chest and abdominal compressions were modelled. 11,12 In humans chest compression force and rate have been shown to influence cardiac output as measured by excreted CO 2 , 23,24 and increased average chest compression depth improved short time survival in a logistic regression. 9 Our study confirms experimentally that the waveform of the chest compressions also influences blood flow.…”

“…25 Coronary blood flow was found to be optimal with a compression rate of ∼120 min −1 in dogs, 8 and Sunde et al found that myocardial blood flow in pigs was best with the compression part of duty cycle of 50/50 4 which corresponded to the best compromise waveform found in a mathematical evolution model. 11 Myocardial blood flow occurs during decompression, as does refilling of the heart and thoracic capacitance vessels, which affects stroke volume. In our study chest compression rate and compression part of duty cycle were kept constant, but a trend towards improved CPP was seen with trapezoidal chest compressions.…”

“…We hypothesised that blood flow would be higher with more rapid onset-offset, trapezoidal compression waveforms than with the sinusoidal waveforms of manual chest compressions. Except for mathematical models 11,12 the haemodynamic effects of different chest compressions waveforms have to our knowledge been only partially explored, and such knowledge can influence the design of future mechanical chest compression devices.…”

Methods for Calculating Coronary Perfusion Pressure During CPR

“…6 The diastolic mean method, as described by Fenely et al 1988, Cohen et al 1992, and Wik et al 1996 Fig . 7 The true mean method, as described by Geddes et al 2007, Niemann et al 1985, Babbs 2006, and Jung et al 2006 Results Table 1 displays the CPP for the normally beating heart immediately before the episode of VF and the CPP provided by standard CPR (performed according to the 2005 AHA guidelines) during VF, as calculated by each of the CPP methods.…”

Closed-loop controller for chest compressions based on coronary perfusion pressure: a computer simulation study

“…The model is based on hemodynamic principles and reveals the rules of body blood circulation during CPR. Charles then proposed a 14-vascular organ module of blood circulation and the concept of the thoracic pump factor f tp to further improve the original model based on the characteristics of real human circulation and the mechanism of CCs [3,4]. CCs are a combined result of the mechanisms of the chest pump and the cardiac pump, and f tp of humans and animals ranges from 0 to 1.…”