DC Described There are considerations that the biomed needs to be aware of when it comes to delivery of the Defib energy. First the amount of energy is variable. The user can select the energy to be delivered from a range of available energy provided by the manufacturer. Also, the method of delivery is important as well. Remember we want to minimize the potential danger to the patient and delivering a reduced level of energy while getting results is most desirable. In order to address this, defibs will deliver energy in different ways. Monophasic defibrillators will deliver energy in the way shown on the first waveform below. As you will note most of the energy is delivered above the baseline.
To reduce the risk of damage due to potentially high peak voltages some defibrillators will use another method of energy delivery. This method is referred to as Biphasic delivery. By utilizing some additional circuitry to change the time duration of the positive and negative waveforms the energy delivered to the patient can be further controlled. Changes in the patients’ impedance will change the shape of the wave form as seen in wave two of our waveforms above. The biphasic waveform delivers the same amount of energy to the patient, but the peak current depends on the patients’ impedance. Triphasic waveforms as seen in the third waveform may also be used. The first wave may ‘precondition’ the heart, the second ‘defibrillates’ and the third is a ‘healing’ post pulse.
Basic Circuit
