Thoracic Electrical Bioimpedance — Alternative or Complement in Cardio-pulmonary Exercise Testing?

The noninvasive determination of hemodynamic parameters at rest and during physical stress is increasingly gaining importance, since invasive measurements for the observation of large patient collectives, particularly follow-ups, are very expensive technically and furthermore not ethically justifiable. Various existing clinically utilized methods, such as e.g. echocardiography, have methodological limits. Thoracic beat-to-beat electrical impedance cardiography (IG) is an indirect, noninvasive method for the determination of stroke volume and cardiac output. The examination is quickly and easily performed, without danger to the patient, and is repeatable as often as desired; it requires only the passive participation of the patient. The ICG is based upon the measurement of thoracic electrical resistance change synchronous with the cardiac rhythm. Using the derived base impedance and the resistance changes resulting from intrathoracic volume shifts during systole and diastole, one can calculate the stroke volume of the left ventricle. The impedance fluctuations are derived simply by means of attached ECG electrodes (Ag/AgC1).