Unlike other Thoracic based impedance technology, NICaS Whole-body Impedance Technology use the peripheral impedance signal for calculation of the Stroke Volume. This results in an improved accuracy. In fact, NICaS is the only Bio Impedance device that meets FDA guidelines for statistical bioequivalent to thermodilution Cardiac Output.
How Whole-body Bio-impedance works:
NICaS transmits a small electrical signal (1.4 mA @ 30 kHz) through the body through two sensors arranged in a wrist-to-ankle configuration. The majority of the signal flows through the blood in the arterial system. With each heartbeat, the volume of blood in the arterial system changes and this results in a change in the body electrical resistance. These changes are being measured by the NICaS. Cardiac Output as well as other hemodynamic and respiratory parameters are calculated by proprietary algorithms. In addition, NICaS measures a 1 channel ECG. The wrist-to-ankle configuration makes the device quick and easy to use because it does not require the patient to undress. See Figure 1 for NICaS ECG and ICG (Impedance Cardiography) waveforms.
Figure 1: Whole-body Impedance Waveform
Hundreds of comparisons demonstrated a very good correlation with Pulmonary Artery Catheter (PAC) as well as Fick and Echo Doppler. See Figure 2 for NICaS validation studies.
The advantage of the Whole-body over Thoracic Impedance
The Whole-body Impedance peripheral volumetric signal in borne throughout the length of the arterial tree beginning with the left ventricular stroke volume ejection.
In contrast, the Thoracic impedance waveform is generated by multiple sources, including the aorta, lungs, atria, vena cava and artifacts due to heart movements (Wang et al 2001, Kauppinen et al 1998, Wtorek 2000). In normal people, some studies have shown that Thoracic impedance gives reasonable reliable CO results (Raaijmakers et al 1999), but in the presence of cardiac conditions, distortions of the Thoracic waveforms were observed (Kubicek et al 1974). This is contrary to the Whole-body impedance, where we see very few changes, if any, in the waveform shape incurred by the different cardiac conditions. See Figure 3 for comparison between Whole-Body and Thoracic Impedance technologies.