Evolution Of Defibrillators

Sudden cardiac arrest (SCA) has always been a major cause of concern worldwide; the keyword here is that it comes without warning. Statistically over 80 percent of unexplained sudden death is attributed to SCA. And if that is not enough, more than 60 percent of the coronary artery disease cases reported worldwide are from South Asia. Defibrillators form the front line of defense against SCA.

The evolution of defibrillators has seen two topologies. The older mono-phasic designs were based on an energy storage device that applies a very high voltage across the heart. Electrical current would then flow from one electrode to the other through the heart. The drawback of this topology was its inability to maintain a relatively constant current flow for a significant amount of time so that a critical mass of the heart could be driven into refractory period. It is now understood that it is current which actually performs defibrillation while energy is just an indicator that the industry is familiar with. This is where the newer topology, the bi-phasic defibrillators come in. Employing sophisticated control mechanisms, they maintain a predefined amount of current during the entire phase of defibrillation while reversing the direction in between for better coverage. For doing this it uses closed loop control systems to monitor the patient’s transthoracic impedance and control the drive strength. Clinical studies have proven that bi-phasic defibrillators have better success rates compared to monophasic defibrillators and are backed up by AHA circulations.

ECG monitoring is a default option available in defibrillators. With the addition of pulse oximetry and capnography, these devices are all that is needed to confirm Return of Spontaneous Circulation. With the addition of transcutaneous pacing it is possible to address any post recovery symptomatic bradycardia events; all using a single device.