Low blood sugar, called hypoglycaemia, is a frequent complication in insulin-treated diabetes and is caused by a misbalance between the insulin need and the insulin dosed. We have two distinct mechanisms to avoid events of severe hypoglycaemia. The first is the sensation of hypoglycaemia which often includes shivering and sweating, symptoms that are familiar to most people with diabetes. The awareness of these symptoms allows us to correct the blood glucose by immediate ingestion of carbs. The second defense is the releases of the “counter regulatory hormones”, of which the most important is glucagon which makes the blood sugar rise. However, with long duration of diabetes both mechanisms may fail. Consequently as a diabetes patient you will be at increased risk for events of severe hypoglycaemia.
In 1988 scientists from Hillerød Hospital proved that the brainwaves, the so called EEG (=electroencephalogram), change when the blood sugar gets low. Figure 1 shows how the EEG looks when the blood sugar is normal (A) and low (B). It is clear that the brainwaves get both slower and larger when the blood sugar is low. We want to apply this knowledge to the development of a hypoglycaemia alarm.
While an ordinary EEG device requires several electrodes placed on the scalp, we have developed a miniaturized EEG device which can detect hypoglycaemia from only one electrode which is implanted under the skin behind the ear. The EEG is transmitted to a hearing-aid like receiver, where the data is analyzed for signs of hypoglycemia. The device is implanted by a minor operation which is performed under local anesthesia and the operation takes about 12 minutes.
We have tested the alarm in many people with diabetes who have been exposed to excess of insulin and accordingly developed low blood sugar. We have found that all patients develop the characteristic brain waves irrespective of their awareness to low blood sugar and to their duration of diabetes. Not only have we tested the alarm during daytime, – we have also tested the alarm in diabetic people which were exposed to low blood sugar during sleep. The results were similar, which is very important inasmuch as almost half of all event of low blood sugar takes place during sleep.
We are now planning larger scale evaluations of the device. This will include clinical testing in people with diabetes who are exposed to low blood sugar in the hospital and who will use the alarm device at home during everyday activities in a three month period. These clinical studies will take place in several hospitals in Denmark, and will learn us about the sensitivity of the alarm and about the users’ experiences with the alarm.