Whole-body Bio-impedance Technology, utilised in NICaSTM, is unique and propriety to Ni Medical. The NiCaSTM algorithms were developed by Ni Medical scientists over more thant twenty years of research and validated by extensive clinical testing. our products are FDA cleared and CE marked.
How Whole-body Bio-impedance works:
Nicas transmits a small electrical signal through the body (an alternating current of 30 kHz, 1.4mA) through two electrical sensors arranged in a wrist-to-ankle configuration as illustrated in the video below. This electrical signal is imperceptable to the patient. The resistance or impedance to flow of this signal (resistivity, R) is measured.
Because the electrical signal seeks the path of least resistance (Kirchov's las) the majority of the signal flows through the plasma and blood. Resistivity values of various body components are shown below:
- Blood - 150 ohm/cm
- Cardiac muscle - 750 ohm/cm
- Lungs - 1250 ohm/cm
- Fat - 2500 ohm/cm
When an alternating current of 30 Hz is applied to the body, it is primarily distributed via the extracellular fluid and the blood. With each heart beat, the volume of blood in the arterial system changes and this results in a change in the body resistivity (∆R) over time (milliseconds) as illustrated in figure 2.
Thus, stroke volume (the amount of blood pumped each beat by the left ventricle into the aorta) is calculated by a proprietary algorithm using the impedance change and physiological data (age, gender, weight, height, hematocrit, electrolytes) that are entered into the machine at the start of monitoring. Cardiac output is calculated by multiplying stroke volume by the heart rate.
In addition, NICaSTM utilizes a standard three-lead ECG connection for measuring the pulse rate.
Figure 1: Wrist-to-Ankle configuration of the electrodes
Figure 2: Interrelation between left ventricular contraction, blood pressure, arteries cross section and electrical conductivity variations
More than 1200 comparisons demonstrated a very good correlation with gold standard Swan-Genz catheter (Thermodilution).
The NICaS meets FDA Requirements doe claiming statistical bioequivolence to Thermdilution Cardiac Output.
Figure 3: NICaSTM Accuracy
Related Clinical Studies
NICaS Study Review 2014
Chest 2004 Accurate NI Continuous Monitoring Of CO By Nicas
Circulation Journal 2006 Impedance Cardiography For CO Estimation
Euro J Of Cardio 1998 NI Measurement Of CO During Coronary Bypass Grafting
Euro J Of HF WB Bio Impedance Is Accurate In NI CO
Physiological Measurement 2006 Impedance Cardiography Revisited