Friday, November 18, 2016

FreeStyle Libre Patterns - non T1D (part1)

Just a quick dump of some FreeStyle Libre Sensor running on a non T1D, non T2D person. I will post interesting situations as soon as they arise. Please note that, even in normal individuals, the glycemic response to different aliments may vary. See this ground-breaking article in Cell for an in depth look at the issue:

Personalized Nutrition by Prediction of Glycemic Responses

That being said, testing foods and meals on a non T1D person offers useful insights for my son's management as the 'net' effect they have is more or less isolated from perturbations. Something that is harder to control for a non T1D person is likely to have amplified effects in T1Ds

Libre startup sequence and some fun



Post insertion, we start tickling the temperature compensation a bit (that part was done in the context of another, more tech oriented, experiment). The sensor is cooled with ice around midnight and warmed against a radiator around 2 AM. It is then left alone so it can proceed with its usual slightly noisy lowish start.

Stable sensor, some food and a bath

Sensor has stabilized: 2 eggs at 13:30, no effect, as expected. Warm bath - not hot - at 14:30. Now this gets interesting! Spot check at 146 mg/dL while there is absolutely no real reason to climb. History rewritten post-facto (through a well known... map simplification algorithm). This is again a clear example of the Libre's temperature compensation issues. As soon as the sensor cools, it resumes cruising around 100 mg/dL and some chicken breast at 16:00 have, as expected, zero effect.

Let's think about that for a minute: a warm bath (sensor fully immersed for 5-6 minutes) leads, in this case, to an almost 50% error on spot checks in a stable non T1D person. It does, however, corrects itself quickly.

Meals and exercise



Pre-made Greek salad consisting of lettuce, feta, olives, oil and some breadcrumbs at 18h20. Slow rise (as expected, way more fat than carbs) and the return to baseline has already begun at 20:45 when subject climbs on ergometric bike for a relatively intense 30 minutes spin. Hitting near hypoglycemia level at 21h20. A bit surprising as as test subject expects better counter regulation (but maybe not enough time for it to kick in). Double checked by strip tests - seems correct.  Time for two slices of gluten free bread with cheese. Response as expected.

The banana

A medium sized banana at 12:30. That single fruit does indeed have a major impact! While - according to its own strip tester - the Libre may have overestimated the impact, that single banana was much worse than the Greek salad three times the weight...

Greek salad again and an apple

Going from the Greek Salad again - based on specs (pre-made fresh food bowl), identical to the first one but let's add a medium sized apple as dessert. Impact remains lower than the banana effect.

Steak and chocolate

Steak at 18h45 has no impact as expected. Mild bump from around 30 grams of 90% cocoa chocolate.

More soon.

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