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QCO


qCO (quantium Medical Cardiac Output) uses impedance cardiography in a simple, continuous, and non-invasive way to estimate the Cardiac output (CO) and other hemodynamic parameters such as the Stroke Volume (SV) and Cardiac index (CI). The CO estimated by the qCO monitor is referred to as the “qCO”. The impedance plethysmography allows determining changes in volume of the body tissues based on the measurement of the electric impedance at the body surface.

The assessment of Cardiac Output (CO) is important because it reveals the main cardiac function: the supply of blood to tissues. CO reflects the hemodynamic flow and hence the transport of oxygen; its clinical applications by non-invasive continuous hemodynamic monitoring are especially useful for some medical specialties like anaesthesiology, emergency care and cardiology, for example to prevent hypoperfusion and to guide fluid administration.

Several authors advocate the high reliability and good correlation of cardiography impedance compared to others techniques more established. Nevertheless, some detractors complain about the sensitivity of the technique to artefacts such as the electromyography or breathing movements.

The Impedance Cardiography (ICG or Ztot) signal represents the changes of the thoracic impedance due to variations in the blood flow. In practice, the raw Ztot signal (in O) is transformed to the –dZ/dt waveform (filtered negative first derivative, in O x s-1) by using the first derivative to remark the inflection points of the raw Ztot signal. The most important characteristics points of the –dZ/dt waveform are B, C and X points (see figure 2). All these points are associated to distinct physiological events within the systolic part of the cardiac cycle, i.e., located after the QRS complex onset. In that sense, the R wave from the ECG signal can be an important reference for detecting such events.


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