Muscle oxygenation [as assessed by NIRS - Near Infra-Red Spectroscopy]

I'm noting your description of the method not involving anything 'invasive' for the muscle and to me that seems like it could be a potentially significant thing if it can be something which could be used as a measure where perhaps other methods which might involve biopsy or something invasive might normally be used?

And also, whilst we are looking at V02 max then is there a possible of that being measured for those who are less severe, and if there were more replications finding that there is an indicator regarding oxygen at that point it could be calibrated to include those more severe with the very tiny exertions that might trigger the equivalent for them? ie just lifting a leg, arm or a small walk if that might be what causes 'PEM'?

 

I've purchased a Moxy monitor (https://www.moxymonitor.com/). It's a commercial system aimed at athletes. It's expensive (USD 900) but I purchased one and have been trialling it for 24 hours. On very early indications I think this could prove very interesting. I've posted some more papers under the moxy tag.




This is a pilot observation and I may be doing things wrong. But... it appears that I am not at all normal, with a very unstable trace. By this I don't mean there's a technical problem with sensing — instead my SmO2 level falls with minimal exertion and does not recover properly. I benchmarked against my wife, measuring left vastus lateralis. At rest she had a stable reading around 85% (females tend to be a bit higher I believe). With 20 rapid gym squats, her SmO2 did not move. She's lost a bit of fitness after a back injury last year, but will also try out more intense exercise on her static trainer over Easter.

I had been resting, reading in a chair for an hour and had a higher baseline - high 80s with an apparently stable trace, where I would expect low 70s as a male (if healthy).

Standing up led to a prompt drop of a few % points, reducing to ~70% with a few steps to the kitchen. I then took a few more steps to the deck and did 3 slow and creaky gym squats. After <1 minute delay the reading dropped quite steeply to 30% and stayed there for over 6 hours (during mostly desk work). If I moved to stand, make a coffee etc it could drop to the low 20s. At 8 hours post it's in the low 50s and varies between 40s and 60s with standing and a few paces in the house.

By comparison an athlete would expect to start at 70% and bottom out at 10-30% after 10 mins of intense exertion and maintain that until exhaustion. See The use of muscle near-infrared spectroscopy NIRS to assess the aerobic training loads of world-class rowers (2021, Biology of Sport)

The key question is what would a sedentary control look like. I'm looking for data on this but my suspicion is that a completely unfit person doing what I did might drop 10-20% and recover within minutes, at most. A reasonable approximation is probably Muscle oxygenation of the paretic and nonparetic legs during and after exercise in chronic stroke: Implications for mobility (2023, PM&R)

I'll post more findings in this thread in time. Early days obvs, but if anyone is in the position to access/purchase one of these devices, please do and post independent observations here. It just might be that this is a useful way to look at mild, moderate and even more severely affected ME (non-invasively) that might correlate with historical and recent muscle spectroscopy and biopsy findings.

 

Thanks for sharing @SNT Gatchaman! If things hold up well it might be possible to motivate an organisation to buy a handful of devices that can be tested and then sent around to different people to reduce costs.

 

So it's 12 hours since my "exercise session" (reminder this was just 3 slow squats and total step count for the day is currently a mere 458). I'm now back to SmO2 80%, having been sitting on the couch for a couple of hours after dinner. Tomorrow I will not do any additional "exercise" to check that it's not due simply to some diurnal variation. I have the POTS crazy HR situation that has me at my best at the end of the day.

 

Interesting @Hutan and @SNT Gatchaman. Trying to get my head around what you're both saying correct me if I'm misunderstanding.

[O2HbMb]-[HHbMb] is measuring roughly the same thing as SmO2 which is [O2Hb]/([O2Hb]+[HHB])x100.

@SNT Gatchaman you are maybe suggesting you are having a more extreme reduction in SmO2 than you would expect for a healthy person.

The y axis in the plot @Hutan shows is the change in [O2HbMb]-[HHbMb] as a proportion the maximum negative change in [O2HbMb]-[HHbMb] measured under ischaemic conditions. It's argued that in long covid there is less of a reduction as a proportion of the maximum reduction at the ventilatory threshold.

So what @SNT Gatchaman is seeing is sort of the opposite of what you'd expect if that's the case right? Unless the maximum reduction in ischaemic conditions is much lower in pwME, such that despite the absolute decrease in SmO2 being more extreme, as a percentage of it's ischaemic minimum it's lower. Either way that would not suggest a problem with oxygen extraction.

What do you guys think? I admit I'm out of my depth in this area

 

I cannot make head nor tail of this. It is time these physiologists explained things more clearly and stopped using impenetrable jargon. I strongly suspect that you cannot deduce much from NIR spectroscopy because so many parameters may shift - much as others have suggested.

 

@chillier I'm going to have to gather a bit more data to make sure this isn't spurious in me; and compare with both @Kiwipom and a healthy sedentary who has kindly volunteered (matched age/sex/BMI). I think the machine can't distinguish between Hb and Mb, and gives SmO2 as the percentage according to the formula exactly as you gave.

From Near-infrared spectroscopy-derived muscle oxygen saturation on a 0% to 100% scale: reliability and validity of the Moxy Monitor (2019, Journal of Biomedical Optics) —

I'll defer the rest of your questions until I've done more reading and got more understanding. The machine gives tHb in g/dL which I presume is total Hb and Mb, whether oxy- or deoxy- for both. Concentration in muscle Mb shouldn't change (albeit oxy- <-> deoxy) so I'm guessing any change indicates the component of Hb in capillaries?

 

A question @SNT Gatchaman : Could stomach muscles be affected by the same mechanism as the vastus lateralis is in the very severe patients?
Could NIRS/Moxy measure that or would it be too deep down to measure?

 

Interesting question. It's unlikely to be too deep down as vsME are typically pretty low BMI. Eg you see pictures of Whitney with a scaphoid abdomen. However, I don't think the stomach or intestine would be easy to interrogate at all, for a few reasons. Their walls are thin and quite irregular, and immediately next to that is gas and food content, and with peristalsis (assuming that's still happening) it's moving in an unpredictable way, in both space and time, in relation to the skin surface mount point. I think it would be quite different to the thigh where even at high cadence on a bike or on a rower the device-skin and skin-muscle movement would be relatively modest, and uniform.

I haven't done much more with this personally as I wanted to hand the idea over to exercise physiology experts, who can also look at n>1! (With luck this might be underway locally). I remain very interested in the idea and also wonder if it's something they might be looking at elsewhere, eg David Putrino at Mt. Sinai.

I was googling around just now and saw that someone posted this thread as a comment on a recent HealthRising article.

 

Thank you for your clear answer.

Your vastus lateralis is world famous now, going through at least 3 continents. Now let's hope researchers are paying attention too. Nice to see that local exercise physiology experts might get involved. Maybe they can come up with some ideas.
s4me is on google's list too. My message to you on Russian muscle research in space also came high up on the first page, when looking for that scientsist again.
You are becomin quite a go to resource, great job!

 

What's left of it! Though thankfully @ME/CFS Skeptic has published an excellent blog today addressing deconditioning, particularly in the context of spaceflight studies

 

So how is the experiment going @SNT Gatchaman? Have you done it on some controls? You hinted at a study. Is it a go-er?

 

In theory, but I don't know if logistics will work out in actual practice. I might hear back with an update by the end of the year (I've been happy to support, but don't wish to get in the way). It may prove unworkable in the field/domicillary, in which case a separate in-lab protocol might be a consideration.

I'm assuming overseas researchers that look at both athletes and ME/LC have thought of using this too. Perhaps they've looked and it didn't amount to anything worth reporting on.

 

[QUOTE="SNT Gatchaman, post: 548867, member: 7967

I'm assuming overseas researchers that look at both athletes and ME/LC have thought of using this too. Perhaps they've looked and it didn't amount to anything worth reporting on.[/QUOTE]


You are a special guy, but do you really think you are an exception on the measurements you made with moxy?
If others looked at this I can't imagine that they didn't find anything worth reporting.
I could feel your squads half a world away and also have muscle waste even with moving in and around the house or cycling a bit.
There is a very small line between building up and damaging muscles.
And what if more muscles all over the body "loose" much of the oxygen/blood supply when exerted just a little?

The two astronauts that are stuck in space just now show visible puffed faces, specially the male, because their body fluids are going up.
When the astronauts have metabolic changes like ME/LC aren't they exercising too much? Two hours a day may be better to get their fluids down, but when their metabolism works like ours, would they get more muscle waste than necessary?

 

No idea! I might have been doing any number of things wrong to get spurious results, so I thought best to hand on to those with expertise and able to carefully look at patients and controls.