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The system continuously tracks the shift in phase between the current injected to the chest and the outgoing current. The resulting signal, which is quite similar in shape to an arterial pulse wave or doppler waveform, is then analyzed stroke by stroke. The peak rate of change in the phase is corollary to the point of peak flow.
Bioreactance and bioimpedance are non-invasive technologies which measure cardiac output, and other hemodynamic variables such as stroke volume and cardiac index.
Bioimpedance measurements detect electrical changes occurring with altering fluid levels in the thorax. Levels change as the left ventricular contracts and blood flows into the thoracic aorta. This causes a corresponding change in resistance within the thorax because the fluid level in the aorta increases. This change in impedance can be measured as a change in voltage passing between electrodes placed on a patient’s chest. Bioimpedance measures the amplitude of the voltage change across the thorax.
Bioreactance, by contrast, tracks the phase of the electrical currents traversing the chest. The underlying scientific phenomenon is that the higher the cardiac stroke volume, the more significant these phase shifts become.
The technological advancement is similar in concept to that of an AM vs. FM radio or amplitude modulation (AM) vs. frequency modulation (FM). Because FM radio detects and analyzes radio signals based on their frequency rather than amplitude difference in the wave form, greater fidelity is achieved with respect to noise cancellation. In monitoring, a high signal to noise ratio can lead to greater accuracy and ability to provide precise information during challenging day to day clinical scenarios such as unstable hemodynamics, motion, and variations on electrode location, thoracic fluids and the like.
You can read more about Bioreactance in the following publication: Evaluation of a Noninvasive Continuous Cardiac Output Monitoring System Based on Thoracic Bioreactance
Learn more about the differences between Bioreactance and bioimpedance
The TFC parameter, which stands for Thoracic Fluid Content, is useful to track changes in thoracic fluid levels over time. It is not intended to measure absolute fluid levels. In other words, TFC changes reflect directional changes in thoracic fluids, whether increasing or decreasing. TFC is measured by reading the impedance to electrical conductivity through the chest wall. It is calculated as the inverse of the impedance (1/Zo) across the thorax. This qualitative measure may be used as a relative indicator of total thoracic fluid volume. TFC is one tool by which doctors assess treatment options in hemodialysis where estimation of fluid balances are critical (Kossari et al., 2009). In another study it was shown the TFC levels, along with Cardiac Index response to an orthostatic challenge, help in differential diagnosis of heart failure vs. COPD in patients presenting to the emergency department for shortness of breath (Engineer et al., 2010). It may also be useful to track response to treatment of volume overload in heart failure patients and treatment of ARDS or Acute Lung Injury where thoracic fluids are often abnormally high.
- Is the device approved for commercial use?
- How do you know whether you have a good NICOM signal?
- What are the system’s indications for use?
- Is the NICOM device cleared by US FDA?
- How do we clean and disinfect the patient cables and connectors?
- If there is interference on one or two NICOM waveforms, does that mean that the readings are wrong?
- Is it important to do skin prep when placing the sensors on the patient?
- Is there a top and a bottom to the sensor and does it matter which way it is placed?
- Can the NICOM unit be used during a stress test?
- Is the NICOM system impacted by electrocautery (Bovie) during surgery?
- Can the NICOM work during surgery?
- What is the importance of hemodynamic monitoring?
- Why do we use dual sensors?
Yes. The Cheetah NICOM® has been used commercially in an increasing amount of hospitals worldwide, since 2008. It has been cleared by the FDA on January 2008 and is CE marked. NICOM is approved for marketing in many other countries. To check availability in your country please refer to Distributors.
The NICOM has a signal indicator. In order to ensure data integrity in case the system determines that signal quality is poor the system will discard of unacceptable signals so that they are not included in the hemodynamic parameter derivation process. The reported parameters are only based on the good quality signal. However, in rare cases when the signal quality is suboptimal for a significant part of a given minute, that minute parameter is excluded and not reported, so as to prevent the reporting of suboptimal information.
The following is taken from the FDA clearance: Cheetah NICOM with NIBP functionality is a portable, non-invasive Cardiac Output monitoring device that monitors and displays a patient’s Cardiac Output (CO) in Ltr/Min with a non-invasive blood pressure function that non-invasively measures and displays blood pressure (diastolic, systolic, and mean) and heart rate. In addition, the device measures and displays associated hemodynamic parameters based on calculations of measurements already incorporated into the Cheetah NICOM. These parameters are: Cardiac Index (CI), Ventricular Ejection Time (VET), Total Peripheral Resistance Index (TPRI), Stroke Volume Index (SVI), Stroke Volume Variation (SVV), Cardiac Power (CP), Cardiac Power Index (CPI), electrical impedance of the chest cavity (Zo) and Thoracic Fluid Content (TFC). The Cheetah NICOM with NIBP functionality is intended for use within hospitals and other healthcare facilities (e.g., outpatient clinics) that provide patient care.
Yes. The device is FDA cleared. The predicate for FDA clearance was the“Vigilance Continuous Cardiac Output” system made by Edwards Life Sciences, which is based on the pulmonary artery catheter (“Swan Ganz” catheter). The regulatory process involved comparing simultaneous measurements of both devices in critical care patients which were analyzed for inter-device agreement.
Clean all Non disposable parts, such as: Patient cable and clips with 75% medical grade alcohol.
No. The system will automatically discount degraded waveforms to ensure proper readings.
Yes, the NICOM sensors are highly accurate and similar to other monitoring device requires good skin prep. The area of skin where the NICOM Sensor is to be placed should be shaved if it is hairy; and should be roughed with the sand paper to remove any dead skin cells.
The tab is the top. It is recommended that you place the sensor with the tab up. It makes it easier to remove the sensor with less stress to the patient.
Yes because we measure a frequency shift instead of impedance. Muscle artifact does not affect the accuracy of the reading.
The NICOM system filters out interference from electrocautery and may be used in cases with significant use of electrocautery. Please note that during cautery interruptions might appear on the screen, however those interruptions are filtered out by the NICOM®.
Yes. Note that it's recommended to cover the sensors with water repellent materials such as Tegaderm™.
Advanced hemodynamic monitoring is an important part of treatment in clinical situations where aggressive, yet guided hemodynamic interventions are required in order to stabilize the patient and optimize outcome. Cardiac Output (CO) and other hemodynamic parameters play an important role in differential diagnosis, establishing the right treatment plan and monitoring and refining it in real-time. Typical clinical situations that call for advanced hemodynamic monitoring include: Hemodynamic compromise: Shock due to hypovolemia, sepsis, trauma, heart failure, neurogenic shock, acute MI with cardiogenic shock Increased metabolic demands, requiring increased blood-flow and perfusion: Sepsis, burns, major surgery (pre, intra, and post-operative)
Each sensor has 2 conductive pads on them, one pad of the sensor sends signal and one pad receives signal. Therefore, each sensor has a dual purpose of both sending and receiving a signal to and from the body.
Since precise location of the sensors is not required, the sensors may be placed away from the pacemaker zone: above/behind the shoulders of the patient.
Yes, there is no technical reason or physiologic reason why NICOM would not be accurate in hypertensive patients. NICOM validation studies and published articles are based on testing of populations which include hypertensive patients.
Yes, Body mass does not impact the NICOM results.
Examples of conditions that can overestimate reported CO, influence monitor accuracy, or result in suboptimal signal quality.
1. Severe aortic insufficiency
The regurgitation fraction associated with severe cases of aortic insufficiency may result in overestimation of the net forward CO.
2. Severe anatomic abnormalities of the thoracic aorta
Severe anatomic abnormalities of the thoracic aorta, such as a large synthetic aortic graft, large aortic aneurysm or large aortic dissection can impact the accuracy or performance of hemodynamic parameters. The abnormality has to be large in order to have a meaningful impact on monitor accuracy.
3. External pacemakers - Use caution in monitoring patients with external pacemakers in these cases the NICOM sensors should be at least 2.5 inches away from the percutanneous lead. Some external pacemakers acan add electrical artifact to the NICOM BIOREACTANCE signal. In most, but not all cases, the monitor user interface will alert the user of suboptimal signal quality.
Comparing continuous cardiac output monitoring methods requires much more than single snapshots of cardiac output values. An effective comparison requires taking into account several parameters; accuracy, precision, directional changes, and time responsiveness. Cheetah NICOM was first validated in clinical studies where the device was compared continuously to an invasive Swan Ganz catheter. Both continuous cardiac output and bolus thermodilution methods were employed as references. Further studies involved simultaneous comparisons of the NICOM system to Swan Ganz and other devices based on pulse contour analysis. The main endpoints evaluated for accuracy were absolute bias compared to the reference method, precision, sensitivity and specificity to detect directional changes in CO and time responsiveness. A recent landmark paper published in Intensive Care Medicine by several European leaders of the critical care specialty outlines the state of the art method to validate a continuous CO monitor. Of note, the aforementioned NICOM studies uniquely adhered to this protocol as was highlighted in the article. Recently, NICOM’s accuracy in determining fluid responsiveness was evaluated by assessing response to passive leg raising. These studies demonstrate NICOM’s excellent responsiveness and it’s marked sensitivity to detect changes in CO.
The Cheetah NICOM was first validated in clinical studies where the device was compared continuously to an invasive Swan Ganz catheter. Both continuous cardiac output and bolus thermodilution methods were employed as references (1-2). Further studies involved simultaneous comparisons of the NICOM system to Swan Ganz and other devices based on pulse contour analysis (3-4). The main endpoints evaluated for accuracy were absolute bias compared to the reference method, precision, sensitivity and specificity to detect directional changes in CO and time responsiveness. A recent landmark paper published in Intensive Care Medicine by several European leaders of the critical care specialty outlines the state of the art method to validate a continuous CO monitor(5). Of note, the aforementioned NICOM studies uniquely adhered to this protocol as was highlighted in the article. Recently, NICOM’s accuracy in determining fluid responsiveness was evaluated by assessing response to passive leg raising. These studies demonstrate NICOM’s excellent responsiveness and it’s marked sensitivity to detect changes in CO (1-2) References: 1. Hemodynamic Changes as a Diagnostic Tool in Acute Heart Failure – A Pilot Study, Engineer et al, AJEM 2010 2. Fluid responsiveness predicted by non-invasive Bioreactance based passive leg raise test. Benomar B et al, Inten Care Med- in Press