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Originally Posted by Bintang
After starting to use the ketonix I began wondering how the ketonix readings might relate to total blood ketone levels rather than just to breath acetone (which is the only correlation provided in the ketonix manual) and what a ketonix reading of 100 would mean if such a reading could be obtained.
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That's awesome. I suspect that the ketonix was created for hospitals to test for ketoacidosis and that applying it to keto diet monitoring was a mistake. Especially given the fact that Acetone is the last and most variable ketone produced by the body. The mean lags way behind a dietary change and over reacts to small perturbations in lifestyle.
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I didn't manage to find an existing correlation between the ketonix and blood ketones
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You won't find one. There are some good studies that show the blood concentrations of Acetone, acetoacetate and beta-hydroxybutyrate as patients continue a starvartion diet. Funny but when I looked up the ketone names, wiki called acetone "their spontaneous breakdown product". Ha!
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but for what it is worth I have derived one myself using two correlations from the literature for breath acetone vs plasma acetoacetate (AcAc) and for breath acetone vs plasma beta-hydroxybutyrate (b-HBA)– see Figures 3 & 4 in the following reference
"Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals" http://ajcn.nutrition.org/content/76/1/65.full
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Good for you.
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I will spare everyone the mathematics but the procedure I have used is as follows:
1. Convert the ketonix reading (0 to 100) to breath acetone in ppm.
2. Convert the estimated breath acetone in ppm to units of nano-mol/liter
3. Estimate plasma AcAc and plasma b-HBA in mmol/liter from the correlations
4. Add AcAc and b-HBA to get an estimate of total blood ketones in mmol/liter
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Spare me not my friend. Two cautions. Concentrations are not conserved. Mass is. So a word to the wise, keep track of mass. Real honest to goodness mass, i.e. grams. Now breath acetone should be converted into a partial pressure which should be maintained across the gas to liquid interface. Someone smart might mention fugacity here. If so, hurt them to the point that they never do that again. Now at that point you should have a liquid concentration, i.e. blood.
The drawback is that I'm not sure if the assumption that the concentration at the surface, where the mass transfer occurs, is in thermodynamics equilibrium. Dunno. Octave is still alive. Maybe he would help. He is the father of this type of analysis and likes to figure out prehistoric concentrations of O2 from the size of dinosaurs.
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The results of these calculations are shown in the following chart:
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Too many dragons there. I would have to see the details. Then again who am I kidding. I would run out of interest before confirming them anyway.
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For additional interest I have included in the above chart the blood ketone level thresholds for the start of nutritional ketosis, optimal ketosis and starvation ketosis as per the following Volek and Phinney chart from chapter 10 of their book “The Art & Science of Low Carbohydrate Performance”:
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Unfortunately I have an opinion on that cartoon. Snoopy should mount it and chase the Red Barron for all it's worth.
Here is the paper P&V SAY that cartoon is based on. Not only hasn't that cartoon ever been reviewed, the data needed to draw that cartoon is NOT in the paper. That cartoon is a fraud and needs to be pulled from the internet.