Frequently Asked Questions
EQUANOX™ Regional Oximetry System
Technology
What are we measuring?
We measure regional tissue oxygen saturation (rSO2), the percent of oxygenated blood within a targeted tissue
bed under our sensor.
How do we measure rSO2?
We use three or four wavelengths of light (depending on the sensor) to measure both oxygenated and
deoxygenated hemoglobin, adjusting for potential confounding effects of light scatter and other extraneous
chromophores (light absorbing substances) in the tissue bed.
Different spacing of the light emitting diodes/detectors creates different light path depths which allow us to
isolate the signal from deep tissue beds while eliminating the impact of signal from the shallow, superficial
tissues (referred to as Spatial Resolution). In addition, we further enhance this target tissue focus through a
patent-protected, dual light emitter design which doubles the number of light paths analyzed by our algorithm.
Finally, our proprietary algorithm combines the information from all wavelengths and light paths in fractions
of a second and converts it to a percent oxygenated hemoglobin value for the targeted deep tissue. The
measurement is completely independent of pulsatile flow.
Why do 3 or 4 wavelengths work better than 2?
Two-wavelength NIRS configurations allow a very basic assessment of the hemoglobin oxygen saturation
status under the sensor but are documented and claimed to only provide an accurate trend in that saturation
status. With only two wavelengths, the ability to adjust for scatter, other tissue chromophores, and individual
subject variability is limited. A third wavelength allows a more robust measurement algorithm, and accuracy
significantly improves as a result.
Adding a fourth wavelength increases accuracy beyond trending levels to “absolute” levels where you
are confidently reporting the actual percent of oxygenated hemoglobin in the targeted tissue. The fourth
wavelength also allows the algorithm to do the best job of removing inter-subject variability.
What is the difference between absolute, trending, and “real-time” accuracy?
Absolute and trending accuracy refer to the methodology of how accuracy is assessed in testing. Absolute
accuracy is when individual samples are compared to a “gold standard.” In trending accuracy a series of
samples are compared to a “gold standard” and the accuracy refers to how the changes in a series of samples
“trend” with the gold standard. In regional oximetry the device is normally compared to jugular bulb and
arterial blood samples as measured by a co-oximeter (the “gold standard”). Signal processing capable of
absolute accuracy generally has half of the plus/minus variation from “truth” exhibited by signal processing only
capable of trending accuracy.
There is no scientific basis for the term “real-time” as applied to accuracy. While Covidien refers to its INVOS
technology as having “real-time accuracy”, they have not released or published any accuracy studies to define
or support this statement. The term “Real-time accuracy” does not appear in the FDA 510(k) clearance for
this device.1
Frequently Asked Questions
EQUANOX™ Regional Oximetry System
I use cerebral oximetry as a trending monitor. Why is absolute accuracy important?
The significantly greater accuracy of an absolute monitor helps eliminate the non-physiologic fluctuations, lost
or no readings, and unusual readings frequently seen on your most difficult patients. Absolute regional oximetry
accuracy gives you the confidence that your second-to-second readings are accurate, thereby helping you avoid
the potential to over-treat or under-treat your patient. 1-3
EQUANOX sensors have two light emitters. Do I only need to use a single sensor?
The sensor still interrogates only the tissue beneath the sensor. Since physiologic differences can result in
unequal left and right perfusion it is best to monitor bilaterally with two sensors.
I already utilize a brain monitor (e.g., BIS or Sedline). Why do I need to use regional oximetry?
The Bispectral Index (BIS) and Sedline monitors measure EEG waves and through algorithmic calculation display
a number related to depth of anesthesia. Regional oximetry assesses the supply and demand of oxygen in
tissues being monitored. The two sets of information provided by these technologies are very different.
What is your update speed? Why is this important?
The Nonin EQUANOX updates measurements every 1.4 seconds. Our competitors update every 2
seconds(CASMED) or 6 seconds (INVOS). Our rapid update speed is important for noting desaturation events
quickly and responding quickly. Within our 1.4 second data update, our algorithm recalculates rSO2 26 times.
What are your data output capabilities?
The Nonin 7600 features real-time data output via Bluetooth® connectivity or RS232 port. Data from the device
are sent once per second. Data output includes all measured regional oximetry parameters and alarms, as well
as all alarm settings. Data transfer can occur in one of five available data output formats for compatibility with
legacy regional oximetry systems. All data output occurs in ASCII format.4-5
Can the Nonin EQUANOX 7600 system interface with electronic medical records systems?
The EQUANOX Model 7600 can populate EMR data fields via a Capsule™ interface into:
•Epic Systems EpicCare
•Cerner Millennium®
•Dräger Medical Systems and Siemens Innovian® Critical Care
•GE Healthcare (via Aware and Carescape® gateways in compatibility mode)
•McKesson Anesthesia Care (MAC)
•MEDITECH Client\Server & MAGIC (through Forward Advantage, MEDITECH’s approved
third party implementer)
•SAFERsleep®
In addition, Cerner has created a driver for interfacing the EQUANOX System into its EMR. The driver number is
Cerner 61032.
Frequently Asked Questions
EQUANOX™ Regional Oximetry System
Can the Nonin EQUANOX Model 7600 System interface with patient monitoring systems such as
Philips and GE?
The EQUANOX Model 7600 will also interface to the Philips IntelliVue MX50-90 series patient monitors via the
Philips VueLink or Philips IntelliBridge modules. At this time the VueLink and IntelliBridge modules allow display
of key data values.
At this time there is no released interface to GE Monitoring systems. We suggest facilities contact GE directly
to request interface of the EQUANOX System to their GE monitoring system, such as through their Unity
interface module.
Are EQUANOX Sensors latex free?
Yes. All components of the EQUANOX System and sensors are “not made with natural rubber,” in
accordance with the language used per FDA guidance documents. A letterhead statement to this effect
is available upon request.
How many times can adhesive sensors be removed and re-applied?
A sensor may be removed and reapplied several times before the adhesive does not allow proper application
without additional assistance such as tape or a wrap. Of course, the patient skin condition variability can greatly
affect the adhesive’s reapplication effectiveness.
How long are the sensors good for once I apply them to the patient?
There is no specific limit to the length of time a sensor can be used before needing replacement. We
recommend that the sensor application site be inspected 15 minutes after application and every 2-4 hours
thereafter to ensure correct sensor alignment and skin integrity. The practice of inspecting and changing sensor
position and placement should be conducted in accordance with your institution’s standard of care. 6,7
Some hospitals think that regional oximetry is too expensive. What studies have been published that
document cost savings?
There are several studies that have documented cost savings for hospitals as a result of utilizing regional
oximetry in certain areas. 8-11
Monitoring Patients
What alarm settings are used for cerebral oximetry?
Most literature describes the use of regional oximetry for a cerebral application. The bulk of this evidence
recommends the establishment of a pre-intervention baseline, with alarms set 20-25% below this baseline, or
an absolute value of 50.
When using a four-wavelength, absolute accuracy sensor (Model 8004CA) capturing the patient’s pre-induction
baseline is not a necessity to achieve parameter accuracy, but is still clinically useful since;
1) baseline settings are needed to auto-set low alarm limits,
2) beginning oxygen saturations can vary between patients, and
3) published literature demonstrates that in cardiac surgery, low baselines can be associated with
poor outcome.8-13
Frequently Asked Questions
EQUANOX™ Regional Oximetry System
Can I just set a single alarm limit for everybody?
The EQUANOX Model 7600 regional oximetry system allows a configuration that defaults to a single alarm
value independent of a pre-intervention baseline value.
I have a patient with unusual baseline values (low). What can cause that?
Physiological reasons for low baseline values in an adult patient include conditions causing poor cardiac
output such as valve disease or heart failure. Other physiological causes can include carotid disease and
cerebral vascular accidents as well as physiological malformations causing reduced perfusion to the monitored
tissue. Unusually low, and not necessarily valid, baselines are often reported by users of the competitive
2-wavelength system.13
I have a patient with unusual baseline values. Should I treat based upon what I am seeing?
Regional saturation monitors remain an adjunct monitor of regional hemoglobin oxygen saturation of tissue
under the sensor. Readings should be used in conjunction with other methods of assessing a patient’s clinical
condition including experienced clinical judgment.4
References:
1. Somanetics 5100C 510(k) market clearance K082327; United Stated Food and Drug Administration; April 3rd, 2009
2. MacLeod DA, Ikeda K, Vacchiano C, et al. Development and Validation of a Cerebral Oximeter Capable of Absolute Accuracy. J Cardiothorac Vasc
Anesth 2012;26(6):1007-14.
3. Kreeger RN, Ramamoorthy C, Nicolson SC, et al. Evaluation of Pediatric Near-Infrared Cerebral Oximeter for Cardiac Disease. Annals Thoracic Surgery
2012;94:1527-33.
4. Model 7600 Operators Manual, part no. 7839-001-02_7600
5. Model 7600 Interface Guide, part no. 8060-000-002
6. Model 8004CA Sensor Information for Use, part no. 7727-001-04
7. Model 8004CB Sensor Series Information for Use, part nos. 8924-001-01 and 8924-101-01
8. Murkin JM, Arango M. Near-infrared spectroscopy as an index of brain and tissue oxygenation. Br J Anaesth 2009.103 (Suppl1): i3 – i13.
9. Casati A MD, Fanelli G MD, Pietropaoli P MD, et al. Continuous monitoring of cerebral oxygen saturation in elderly patients undergoing major
abdominal surgery minimized brain exposure to potential hypoxia. Anesthesia & Analgesia 2005;101:740-7.
10. Goldman S MD, Sutter F DO, Ferdinand F MD, et al. Optimizing intraoperative cerebral oxygen delivery using noninvasive cerebral oximetry decreases
the incidence of stroke for cardiac surgical patients. Heart Surg Forum 2004;7(5):E376-81.
11. Fischer GW, Lin HM, Krol M, et al; Noninvasive cerebral oxygenation may predict outcome in patients undergoing aortic arch surgery. J Thoracic and
Cardiovascular Surgery 2010;141;1-7.
12. Slater JP MD, Guarino T RN, Stack J BS, et al. Cerebral oxygen desaturation predicts cognitive decline and longer hospital stay after cardiac surgery.
Annals of Thoracic Surgery 2009; 87:36-45.
13. Denault A, Deschamps A, Murken JM. A proposed Algorithm for the Intraoperative Use of Cerebral Near-Infrared Spectroscopy; Seminars in
Cardiothoracic & Vascular Anesthesia 2007; 11;274-281
14. Heringlake M et al; Preoperative Cerebral Saturation and Clinical Outcomes in Cardiac Surgery. Anesthesiology 2011;114:58-69.
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