Energy adjustment method based on transthoracic impedance for a biphasic defibrillator

With the use of the biphasic truncated exponential waveform (BTE) for high energy discharges, a new concept was introduced for dealing with defibrillation: compensation (or adjustment) of the discharge voltage and time duration, as a function of transthoracic impedance. Transthoracic impedance is one of the parameters that determine the intensity and wave shape characteristics employed for the external defibrillation of a patient. A method for impedance compensation based on the impedance values measured both just before the discharge takes place and during the discharge across the patient's thorax is proposed. The algorithm was tested by producing discharges in resistors simulating the patient and measuring the delivered energy. Results are presented and discussed, concluding that an excellent impedance compensation can be achieved.