The American Heart Association's resuscitation guidelines clearly state, "Although in operating A defibrillator, the medical practitioner chooses the defibrillator energy (joules, J), it is the electrical current (amps, A) that actually depolarizes the heart muscle." While the term energy is entrenched in current industry parlance, energy is actually a non-physiological description of the defibrillation process.
That is to say, in the process of defibrillation, what really determines whether it is successful is the "average current" intensity of the defibrillation process, and due to the existence of impedance in the human body, the current will inevitably generate heat conversion in the process of action, and this part of the energy will cause a certain degree of loss to the myocardium, which should be minimized. In order to achieve this goal, the waveform used should have the maximum average current, the lowest peak current, and the appropriate discharge duration.
The early defibrillators used single-phase attenuated sine wave (MDS) to discharge. Due to its high peak current and fast current attenuation, the defibrillation effect was poor for all kinds of patients, especially those with high impedance, and the myocardial damage was more serious.
The second generation of defibrillation waveform is biphase truncated exponential wave (BTE), which is also the most common defibrillation waveform in the market at present. This waveform improves the attenuation of defibrillation current to a certain extent, but the discharge time needs to be extended when defibrillation is performed on patients with high impedance, and this discharge time exceeding 10ms May induce secondary ventricular fibrillation in patients, resulting in adverse consequences.
In 1999, the United States ZOLL company creatively invented the third generation of defibrillation waveform: low energy biphase square wave (RBW), the waveform through a constant positive phase current to achieve the highest average current, the lowest peak current, while the discharge time fixed 10ms, to avoid too long discharge time, improve the success rate of defibrillation.
The RCD-600 uses a defibrillation waveform independently developed by Rescond, which has the same defibrillation performance as the ZOLL waveform through consistency demonstration.
Compared with the previous two generations of waveforms, the biphase square wave has the following advantages:
1. After retrospective study of clinical data, the success rate of defibrillation of RBW waveform, especially in patients with high impedance, is better than MDS waveform; In addition, in pediatric model tests, RBW waveforms were superior to BTE waveforms in terms of defibrillation per unit body weight and unit heart weight.
2.RBW waveforms perform better in out-of-hospital cardiac arrest events: In a large-scale data study, RBW waveforms had a higher probability of relapse compared to other waveforms for cardiac arrest patients on advanced life support (ALS).
3. The study also found that defibrillation with the RBW waveform was associated with better survival for patients who had just experienced cardiac arrest. For patients whose cardiac arrest occurred within 4 minutes, the survival rate was nearly doubled compared to the MDS waveform.
4. Compared with BTE waveform, RBW waveform has a higher defibrillation success rate for patients with high impedance. Compared with the defibrillation method of extending the time, the defibrillation method of increasing the average current is more effective. For defibrillation in obese patients (weighing more than 135kg), the RBW waveform can achieve a higher average current at a smaller discharge energy for a higher defibrillation success rate.
For the relationship between energy and current in the defibrillation process, we should pay particular attention to the following two points:
1. The increase in the success rate of defibrillation is not due to the increase in energy, but to the increase in current. The current provided by the 200J BTE is comparable to the 120J energy of the RBW waveform.
2. The term "low energy" is often misunderstood, equating it with "inefficiency" and creating suspicion. However, in fact "low energy" corresponds to "high current" and "high efficiency".
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