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Juerg Feldmann

Fortiori Design LLC
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Posts: 1,530
 #1 
I get  like  so often in this cases many mails asking for Validation of MOXY and literature  on MOXY and its use.
 Simple short answer from my side followed by some more professional  info and  ideas.
 1. MOXY is the only  NIRS type Who test the way it does . It tests SmO2  ( muscle oxygenation.
 Other equipments test StO2 ( Tissue oxygen saturation  and so on. Different great equipment test different way but  all use the same wavelength.
 MOXY uses the same wavelength  like all the very expensive and incredible great equipments used for research and other  incredible ideas.. What we look for  in practical application is :
 Can we repeat the test and the information. This way we can see actual change   from  withing one individual person.
 Comparing absolute values with  different  people is interesting but the main goal is to see how SmO2 can change intraindividual due to change in training stimuli ( fatigue ) recovered and so on.)
 2. The question of validation is better answered by professionals  working in that field.
 The same holds true to  the question.
 How do you validate an equipment with what ? What is the golden standard.
 MOXY is for what we do the golden standard.
 Here  an other answer.
 

NIRS validation

Near Infrared Spectroscopy (NIRS)

C. Dean Kurth MD

Anesthesiologist-In-Chief

Cincinnati Children’s Hospital

Professor of Anesthesia and Pediatrics

University of Cincinnati College of Medicine

 

 

Determination of the accuracy of the NIRS devices has been problematic. In order to determine accuracy, the device must be compared with a gold standard. Because there is no gold standard for NIRS (ie, no other device measures O2 saturation in the tissue circulation), determination of accuracy remains an estimate. There is currently one FDA approved device, made by Somanetics. Its accuracy on the FDA application was compared relative to a weighted average (SwO2) of arterial and jugular bulb O2 saturation. In adults and children, the device is not that accurate (+10-15%) on an absolute level of oxygenation (rSO2 vs SwO2), but is fairly accurate (+5%) on a change in oxygenation ( rSO2 vs SwO2). In other words, the device indicates a change in oxygenation accurately but does not indicate accurately what the oxygenation actually is.

Other devices purport greater accuracy than the Somanetics device. However, these devices are not FDA approved, not commercially available, and have not been subject to accuracy testing on large scale. Nevertheless, several of these devices have been tested in animal models and have been found to be accurate +3% on an absolute.

Roger

Moderator
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Posts: 245
 #2 
Here's a paper that describes 2 techniques that have been attempted to create a "Gold Standard" for tissue oxygenation measurements.

http://www.coeurscientific.com/Pdf%20Files/Validation%20Of%20NIRS%20In%20Measuring%20Tissue%20Hemoglobin%20Concentration%20And.pdf

The problems with these methods become apparent when comparing Figures 8 and 12 in the paper. When the Instrument was calibrated to read correctly on one "Gold Standard" it was off (on an absolute scale) on the other one.

The fundamental limitation of methods like these is that it is very difficult to simultaneously mimic the optical and fluidic properties of living tissue and devise a method to be able to know the oxygen levels at the capillary level.

We've decided that validation studies with ex Vivo and Animal methods described in the paper aren't very useful, plus they're costly.

A much more practical method is simply to apply an arterial occlusion upstream from a test site on a real test subject and verify that the oxygenation eventually reaches 0.  Then, when the occlusion is released, the oxygenation should approach the arterial saturation 
(oxygen consumption does not stop, but the blood vessels are highly dilated).  An example of this with Moxy is shown in the following graph.






Juerg Feldmann

Fortiori Design LLC
Registered:
Posts: 1,530
 #3 
The  questions on "validation"  get more and more and I like to give some ideas from this side here.
 1. How did you Validated  your  device you use now as the " golden standard"
2. If you would have bought  first the MOXY  would you than as well  ask how you validate the device you bought first.
 3. Is the device we  buy first always the golden standard. How about Douglas bag as the golden standard this days ?

As mentioned before it is great to be critical but just arguing  whether it is validated with an existing first bought first served equipment seems an interesting scientific approach  ( Smile )
 Here what I did when comparing MOXY to otter  existing and first bought NIRS devices.
 
a) I  used both at the same muscle same time same load same situation and I showed many times  how they overlap .
 b) perhaps another less " biased" idea is as I did  with both NIRS a occlusion test and tested the time it needed  to get TSI % % and SmO2 %  down to zero as this is a very objective way as the  activity and the O2 use under occlusion  would be the same  so zero should show up in the same +- sec time  frame.  .
 Try this and sent us the info back as we  have fun not " educating " people here but discussing and use each others brain.
 Remember  that education is the ability to repeat what you have to repeat to pass the test and not the ability to use a brain.

Juerg Feldmann

Fortiori Design LLC
Registered:
Posts: 1,530
 #4 
An ongoing  mail question  to this question.
 Here  another  paper  worth while to read.
 

A brief review of the use of near infrared spectroscopy with particular interest in resistance exercise.

Author information

  • 1Departmento de Educação Física, Universidade Gama Filho, Rio de Janeiro, Brazil.

Abstract

There is growing interest in resistance training, but many aspects related to this type of exercise are still not fully understood. Performance varies substantially depending on how resistance training variables are manipulated. Fatigue is a complex phenomenon usually attributed to central (neuronal) and/or peripheral (muscular) origin. Cerebral oxygenation may be associated with the decision to stop exercise, and muscle oxygenation may be related to resistance training responses. Near infrared spectroscopy (NIRS) is a non-invasive optical technique used to monitor cerebral and muscle oxygenation levels. The purpose of this review is to briefly describe the NIRS technique, validation and reliability, and its application in resistance exercise. NIRS-measured oxygenation in cerebral tissue has been validated against magnetic resonance imaging during motor tasks. In muscle tissue, NIRS-measured oxygenation was shown to be highly related to venous oxygen saturation and muscle oxidative rate was closely related to phosphocreatine resynthesis, measured by (31)P-magnetic resonance spectroscopy after exercise. The test-retest reliability of cerebral and muscle NIRS measurements have been established under a variety of experimental conditions, including static and dynamic exercise. Although NIRS has been used extensively to evaluate muscle oxygenation levels during aerobic exercise, only four studies have used this technique to examine these changes during typical resistance training exercises. Muscle oxygenation was influenced by different resistance exercise protocols depending on the load or duration of exercise, the number of sets and the muscle being monitored. NIRS is a promising, non-invasive technique that can be used to evaluate cerebral and muscle oxygenation levels simultaneously during exercise, thereby improving our understanding of the mechanisms influencing performance and fatigue.

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