I suggest you communicate with Lumen support again and ask how to recalibrate the device. Then do it the way I did. 10+ hour fast for the initial sample, then do not carb up at all for the samples during the day and post supper. If you do that, maybe it will help us determine whether or not your diabetes is confounding the samples.
@Don_Q I think an interesting experiment is in order. That is try to test the validity of the range I’ve estimated above. I’m off Thursday and Friday of next week again, and finish work at 2:30pm on Wednesday. I could fast from post meal Wednesday (about 11am) then see if and how long it takes me to blow consistent 1s on the Lumen. If I can accomplish that, then I’d be very confident that ~.42 is the low RER value of my range. From blowing a series of 1s, the next step would be to break the fast with something like 10 grams of ginger root (1.8 grams of carbs) to see if the reading goes up. If not, eat 10 grams more. At some point the measurement will go up. Maybe? What do you think?
You’ve been keto for so long that your current glucose metabolism might play a confounding role. You most likely have glucose sparing physiological insulin resistance at the moment, so it can’t be taken for granted that your cells will accept the glucose normally. Blood sugar could remain elevated while it does continuous loops looking for a home for a while rather than being metabolized. Ergo your RER won’t be elevated until blood sugar drops (post-spike). You’ll feel the hyperglycemia immediately, but the cessation of hyperglycemia is more subtle.
Do you have a blood glucose monitor and/or a blood ketone meter? Measuring blood glucose will tell you whether the glucose gets stuck doing loops through your bloodstream.
My suggestion would be to avoid ginger, and just eat pure dextrose, which is the simplest and fastest metabolized sugar. Smarties candies are basically 100% dextrose. Each package is 5g if I recall. I’ve used it for experiments in the past. Fair warning, it will feel a bit like eating a jar of lightning for a little while. If you can’t find Smarties at Walmart or elsewhere, just do 5g of pure table sugar. Ginger may have some other effect that further confuses the results.
That’d be my two cents. I know so little about this stuff though, it might only be a penny…
They said I can’t calibrate it… I just blew a 4
I’m presuming you mean ‘recalibrate’, and that’s unfortunate. I can think of multiple reasons to recalibrate the device periodically. So I think it’s definitely lacking a necessary feature. I mean, I can recalibrate my digital food scale as often as I like. Maybe if enough customers communicate that they pooched the initial calibration and would like to redo, we’ll see this function added. I think this would be a software mod, not a hardware mod. And probably trivial.
Before deciding conclusively that the device is not working for you and won’t work for you, I think you ought to try what I’ve been doing the past several days. That is simply take many samples during the day to see how the results change. They should, since I’ve already determined that in my case even very small changes affect apparent RER. Especially over a very small range of values. Maybe you’re already doing this? In your circumstance, I would fast for a day or two to see if that drives down the numbers. It should and if it doesn’t then I would suspect that your glucose metabolism and its idosyncracies are the problem. Do you have a glucose meter? You might be able to correlate the Lumen results with simultaneous glucose tests.
If it ends up that the Lumen is just not sophisticated enough to deal with T2D, at least you would have given it a good shot demonstrated that fact.
They basically give up with T2D. They say it likely cannot be calibrated properly on my zero-carb diet
It can’t be calibrated to 0 carb diets?
Or it can’t be calibrated for T2 diabetics on 0 carb diets?
Have these people even bothered to define what they claim to be measuring? That seems like an important feature of a measurement device.
My bathroom scale measures weight in pounds
My thermometer measures temp in degrees F
My clock measures time in seconds
What does a lumen claim to measure for $300?
I think @amwassil theory is an interesting one, that it’s measuring RER between 70 and 75 for him based on his calibration, but that’s just a theory. Why should anybody need to do experiments to try to figure out what hell this thing measures? Shouldn’t they just tell you wtf it measures?
Are there other theories from other users as to what thing does?
That’s too bad. I think the hardware is giving them raw RER values. So I think they could offer a software option just to display the calculated RER. If they thought they needed legal protection they could simply include a disclaimer that what you do with the RER info is your decision. I think it would be a trivial programming project to modify the app to display the RER value. I guess they may figure that doing so would undercut their ‘weight management & healthy living’ consulting services. Who knows why businesses decide to do something and not something else?
The only thing all indirect calorimeters in the world have in common is an O2 sensor and a CO2 sensor with a short lifespan that needs to be recalibrated against pristine samples of pure CO2 and O2. Does this have replaceable sensors?
That’s a very good question! It has a CO2 sensor. Don’t know about O2. I have yet to find any reference to an O2 sensor. If it does not, then I may have to retract everything I’ve said previously about calculating RER. Here’s what they say about calibration:
Yes, there is a personal learning process during the first day of usage - Calibration day. On this day you are required to take a morning breath after a 10 hour fast and the application will specify what you should eat that day and when to take additional breath measurements. By doing so, the Lumen system is able to use advanced machine learning capabilities to build your individual CO2 scale and subsequently personalize itself to you.
The ‘smart’ software may make an assumption about O2 based on your lung volume, which it determines before the calibration. If it then simply measures CO2 out and bases the result on assumed O2 input, that would mean a pretty rough and ready RER calc. That might explain why they don’t ‘show users that metric’.
Lumen uses RER as the core data point to bring the same measurement to a home environment by measuring the CO2 in your breath through the sensor and flow meter, based on the RER metric.
This reinforces my suspicion that O2 input is being estimated rather than measured.
They display this graph to support the accuracy of their ‘RER metric’:
The Lumen device works by measuring the concentration of CO2 in your breath to identify the type of metabolic fuel your body uses for energy and subsequently your Lumen Level.
Extracting RQ from breath is Lumen’s core innovation. Over the past 4 years, our team of scientists and engineers have been working to develop and validate Lumen’s science at top universities and hospitals around the world.
Using patent-pending algorithms, CO2 sensors, flow meters, barometric pressure and temperature sensing technology, Lumen has the ability to calculate a metric directly comparable to that of gold standard RQ measurement equipment.
Well, in my case because I didn’t follow instructions to carb up for the max RER value.
Bingo. So if it’s a rainy day it would assume you’re in Denver, and adjust the O2 calc down? Why else would a barometer be useful other than estimating altitude (and therefore ambient O2)?
Even if you had, and you blew a perfect 1.0, it still wouldn’t be clear what the machine is measuring. They haven’t said what a 1 or a 3 or a 6 means. It’s speculation that it’s equal increments between max RER and min RER. What if someone calibrated it while on a high carb diet, and then went keto? Or vice versa? The calibration sounds a bit like voodoo.
The other weird thing about the device is that it does it in one breath. Why does every other device at 100x the price require 15 mins hooked up to a respirator? If it’s sensor is that exquisitely sensitive, why is ambient CO2 not fouling up the sensor in days rather than months? It doesn’t make sense.
Both. They said the machine isn’t for those with T2DM and that it would also have problems if you don’t do the carb calibration
This is interesting.
… EE derived from VCO2 alone was suggested already 25 years ago , using estimates of the energy equivalents of CO2 (energy expended/CO2 produced; EeqCO2). Taking into account the variations in CO2 related to starvation or artificial enteral feeding, tracer techniques demonstrated that the calculation of resting energy expenditure (REE) from CO2 production should not employ a universal value for VCO2. Nevertheless, measurement of VCO2 and the replacement of VO2 by VCO2/0.84 have been proposed to calculate EE . This general value of 0.84 is the result of the arithmetic mean of the respiratory quotient (RQ) of the three main macronutrients: (1 + 0.809 + 0.707)/3 = 0.84. Since the measurement of VCO2 is available in many ventilator devices, it was suggested that this may be an easy and inexpensive way to calculate EE. Mehta et al.  used VCO2 alone in critically ill children to calculate EE and suggested that the REE may be obtained by measuring VCO2 through integrated devices in the ventilator or by a stand-alone monitor. The modified Weir equation (REE, kcal/day = 5.5 × VCO2 (L/min) × 1440 using a fixed RQ of 0.89) was compared with predictive equations and found to be much more accurate . However, there was an inherent inaccuracy due to the fixed RQ. When a RQ macro (based on the ratio of carbohydrate to fat in the diet) was used based on the ratio between carbohydrates to fat in the diet, a closer agreement was obtained between measured and REE derived from VCO2 alone, reaching a mean bias for agreement between measured REE and VCO2-derived REE of −2.0 %, but with wide limits.
BTW, since blowing a Lumen 1 at 11:40am yesterday, I’ve blown only 2s and 3s and one 4 at 11:40 pm yesterday (none today). My BrAce has been generally lower. The lowest BrAce measurement today was 7.8 ppm at 4pm after getting home from work. I’m tracking both measurements on a spreadsheet to see if any pattern emerges and if so I intend to graph it. I’m wondering how testing for CO2 indoors compares to testing outdoors, presumably less ambient CO2. I’l do some outdoor samples to see what happens.
I just took a Lumen sample on the balcony and it was 4! BrAce was 12.6 ppm. Since Feb 18, I have blown only four 4s. Three were in the late evenings (after 9:30pm) and one at 8am. Would it be reasonable to lump late evening and early morning as a single time segment? If so, all four 4s were in that segment.
I was wondering what your blood glucose looks like after a high carbohydrate intake in numbers?
I have been doing keto around 6 or 7 years now and I’m extremely flexible metabolically and can switch fuels quick through semi-disciplined eating widows.
I use to be paranoid of carbohydrates but after a great deal of time I’m noticing strange things like the less fat and protein I eat and the more carbohydrates I eat, the more body fat I loose.
I don’t eat three meals a day or I only eat when I’m hungry and not until fully satisfied most of the time, but I do eat anything I want some times; mostly junk food and then I switch back to fatty proteins and whole food carbs and right back into ketosis 0.1, 0.2 ect. those numbers to me indicate improved mitochondrial functioning.
What this tells me, if I take off the blind fold of technological limitations is that I’m metabolically fit and that I’m in-fact going into ketosis naturally when I sleep even when extremely high carb.
When I eat carbohydrates, I intuitively know they are being burned immediately like throwing objects into a molecular disassembling incinerator or like throwing table sugar directly on a burning flame and not being stored as lipids unless needed.
The experience of high blood sugar I was describing was the first time eating carbs 6 months or so. I ate 100+ g of carbs for 3 days. When I tried the experiment again a couple weeks later, the experience was totally different, and even 200g/day was no problem.
No idea. I got my first blood sugar meter when I was a teenager, but I after keto got me below 100 every day, I threw it in the trash. I’ll not be buying a new one. I have a few decades of experience with hyperglycemia however, and this was as high as anything I had ever experienced in my life.
I can’t get away from this: