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A Metaphor of the Life with Type 1 Diabetes

Stefan Du Rietz  (e-mail: sdr (at) this domain)


Imagine yourself trying to steer a boat, floating down stream on a river. The river is flowing in a loop and is therefore, contrary to ordinary rivers, partially repeating its course. During each round, however, the loop is changed by new bends into different patterns in a seemingly random way. Moreover, the gearing of the wheel, as well as the slowness of the boat's response, is also continually changing in a seemingly random way. Consequently, you cannot but roughly know the effect of your manoeuvres.

Towards the left shore, the fresh air on the river is gradually changing into a gas that initially makes you dizzy and, closer to the shore, eventually unconscious. Towards the right shore, on the other hand, the air is gradually changing into a poisonous gas, which you cannot smell until it gets extremely concentrated. If you breathe this gas for a while in too high a concentration, your body will in due course become injured.

Complete darkness reigns all the time, so you can never see anything whatever of your surroundings. Neither can you ever hear any sounds to guide you between the shores.

You have been told to obtain one type of information only: now and then, you are able to trigger a flashgun that for a moment illuminates a spot on the shore on each side. This gives you a rough measure of your position sideways between the shores, but you cannot tell whether you are approaching either of them. You make notes of these positions and their times. You may also make notes of your manoeuvres at the wheel.

For important reasons you will not use the flashgun too often, so you miss the rapid changes of your position sideways. Note that you can neither see anything when looking forwards nor even when looking backwards! Consequently, you can get no direct information about the future course and your only direct information about previous courses is in your notes from those moments when you used the flashgun.

If you have made your notes during numerous rounds on the river, and you are trained and clever enough, you may scrutinise your notes trying to make estimations of average courses and probabilities of separate events. However, you can never be certain regarding any single future event!

The boat, designed by Evolution, is normally equipped with an automatic steering system. This system continuously measures the distance to the shores as well as a multitude of states, influencing the course of the boat. The collected information is processed and fed back to turn the wheel so that the boat remains almost on course. As a result, there is never any risk of getting too close to the shores.

Unfortunately, in your boat, this feedback is not working, so you have to turn the wheel yourself.

Control Theory (CT) is the accumulated knowledge about how to make the steering optimal with regard to different criteria and limitations. The more complicated and irregular the system to be controlled, the less knowledge you have about its properties and the more accurately it should be controlled, the more difficult it is. Much of CT is difficult to comprehend and has little in common with normal human intuition.

Most of those involved in the research and maintenance of the boat possess a very limited knowledge of CT. Despite that, they almost never collaborate with experts on CT, although the boat's steering system is extremely complicated. Therefore, the ultimate blend of knowledge – both of the physical details and of how to obtain, analyse and interpret measured data – is rarely achieved.

Postscript

This text was written in 1993 and published here in 2000 when it was not common with technical papers about diabetes control. Today it is much more common and there are even particular journals for it. However, a profound understanding about how chaotic life with type 1 diabetes is, still seems to be uncommon, both among doctors (who often don't understand any mathematics or physics) and engineers (who often don't understand the complexity of the human body). It is probably not possible to get a complete image of it without an own experience of it. So my remarks about collaboration for new progress are still relevant.

You may also want to read my more technical text about statistical measures of blood glucose.


du Rietz | Type 1 Diabetes

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