How It Works


CHEETAH NICOM® provides continuous, accurate, non-invasive hemodynamic monitoring and empowers fluid management in virtually any clinical setting.

It is based on Bioreactance®, a technology that was developed by Cheetah Medical's scientists over years of research and development and followed by extensive testing and validation. The basis behind CHEETAH NICOM is the use of time delay, or phase shifts, which occur when an alternating electrical current (AC) is passed through the thorax. 

The CHEETAH NICOM’s unique, patented Bioreactance® technology takes measurements continuously and with extreme precision. And it requires only four sensors, easily placed on the chest. The sensors can be placed anywhere on the chest or back as long as two are positioned above and two are positioned below the heart.

It's important to note CHEETAH NICOM bioreactance technology should not be confused with bioimpedance, an older technology that has certain limitations when used for assessing fluid responsiveness.

Detailed Explanation

Download the bioreactance technology paper.

To learn more about the phase shift, click here.


Bioreactance technology begins by placing 4 dual sensors on the patient. The CHEETAH NICOM puts in a signal at a frequency of 75 kHz into the thorax via the outer portion of the sensors.  The known frequency is then received via the inner portion of the sensors from which the CHEETAH NICOM compares to the original signal. It will then observe to what extent a time delay, or phase shift, has occurred helping to determine patient fluid responsiveness.

An advantage of bioreactance technology is the signal is only affected by pulsatile flow. The signal is reflected from the base of the aorta back to the sensors. 

Pressure, volumetric flow, resistance, capacitance, compliance, velocity, and viscosity are some of the things that contribute to flow.  Ultimately there is a relationship to “time” with all of these factors.  In short, these factors of pulsatile flow cause a shift in the signal called “phase shift”, but is better understood as a “time delay”

CHEETAH NICOM’s received signal is compared to what was put into the thorax.  It determines how much blood had to have been coming out of the left ventricle and into the base of the aorta to cause that specific time delay; this becomes the stroke volume.  Because there are ECG leads built into the unique CHEETAH NICOM sensors, heart rate can be detected.  This allows one to obtain Cardiac Output, or HR X SV = CO.