WO2005081173A1

WO2005081173A1 - Diabetes slide ruler for blood glucose control

Info

Publication number: WO2005081173A1
Application number: PCT/ZA2005/000044
Authority: WO
Inventors: Edward Henry Mathews
Original assignee: Edward Henry Mathews
Priority date: 2004-02-19
Filing date: 2005-02-18
Publication date: 2005-09-01

Abstract

This invention relates to a device to help patients with IDDM to improve their blood glucose control. The device consists of a slide ruler predicting corrective action needed to control blood glucose levels within a safe range. Said device uses the ets (Equivalent Teaspoons Sugar) concept to predict blood glucose levels and corrective measures needed (bolus insulin dosage or food intake) by the diabetic user. Device takes current blood glucose level, immediate food intake quantified in ets and exercise to be done within six hours quantified in ets into account. Individual patient sensitivity to ets (food), exercise and insulin is also considered by the device. This patent also includes the procedure to characterize said diabetic patient as well as a method of operation of such a slide ruler device. Said device therefore includes scales depicting blood glucose, food, exercise and insulin scales on which selections can be made with the input means to select current blood glucose level, food being ingested and exercises to be performed. On the insulin scale an appropriate short acting insulin dosage suggestion will then be indicated.

Description

DIABETES SLIDE RULER FOR BLOOD GLUCOSE CONTROL

This invention relates to the fields of diabetes management. It relates in particular to a system to calculate the type and magnitude of action necessary to control blood glucose levels. It also relates to a method of operation of such a system.

In this specification, the term Equivalent Teaspoon Sugar (ets) means an energy unit used for quantifying energy in food and energy usage in exercise.

Furthermore ets can also be used to quantify energy being expended during exercise by relating the energy to the effective energy available in a teaspoon sugar, ets can also be used to express any quantity of energy e.g. the blood glucose energy in the blood or the amount of glycogen energy stored in the liver. Furthermore, in this specification, the term insulin includes within its scope any blood sugar regulatory substance.

Furthermore, in this specification, the term diabetes or diabetic refers to Type 1 diabetes or Type 1 diabetic respectively unless otherwise stated.

DESCRIPTION OF PRIOR ART

IDDM (Insulin Dependant Diabetes Mellitus) or Type I Diabetes is the condition where the islets of Langerhans can no longer supply the body with the hormone Insulin. Insulin is needed by the human body to help control blood glucose levels. When consuming food containing carbohydrates (CHO) the blood glucose levels will rise. Insulin is then needed to lower the blood glucose level back to an acceptable level again by storing glucose as glycogen. Insulin is also needed by the cells to utilize the energy of the sugar in the blood. It is therefore necessary for patients with IDDM to monitor and control their blood glucose levels by administering insulin. This will help keep their blood glucose levels under a safe range preventing hypoglycemia and hyperglycemia.

Hypoglycemia occurs when the blood glucose level falls too low while hyperglycemia is the result of high blood glucose levels. Hypoglycemia has a more immediate or short-term threat to the diabetic, which can cause comas, seizures or even death. Hyperglycemia's effects become evident after a longer term of elevated blood glucose levels.

A common need therefore exists among diabetics to simplify the control of their disease. Currently many diabetics are following rigid daily schedules concerning their meals, exercises and insulin administrations. This makes it difficult for IDDM diabetics to calculate their insulin requirements when eating different meals or doing irregular extra exercises.

Although several other insulin prediction devices are patented and manufactured, the methods (e.g. carbohydrate counting) used so far have not been very accurate. This invention is unique because the insulin prediction is done using the ets concept discussed in the discussion. Blood glucose prediction for the individual can be done with high accuracy. Using the ets blood glucose prediction model the required insulin dose can be calculated for the individual. OBJECTS AND ADVANTAGES OF THE INVENTION

The main objective of this invention will be to calculate the type and measure of the corrective action needed at a given time to control the diabetic's blood glucose level within a safe range. The device will take into account the current blood glucose level, immediate food intake, exercise within 6 hours and several parameters measured on the individual patient. The main advantages of the implementation are the very low cost of the device and also the high accuracy of the prediction algorithm discussed in the description. The diabetic slide ruler will also be a great educational tool to teach diabetics the dynamics involved in their blood glucose control. Further objectives and advantages will be mentioned in the description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view representation of the diabetic slide ruler system showing the three main parts of the system.

FIG. 2 is a rear view representation of the diabetic slide ruler system showing the three main parts of the system.

FIG. 3 is a front view representation of the main center ruler part of the device. The scale shown is the current blood glucose scale shown in mmol/T.

FIG. 4 is a rear view representation of the main center ruler of the device. Two options are shown both showing corrective action suggestion scales.

FIG. 5 shows both the front and rear view of the large slider. It has scales for ets food intake and ets exercise.

FIG 6 shows the front and rear view of the small slider.

FIG. 7 is a diagrammatic illustration of how the corrective action calculation is performed by the slide ruler. ^r

FIG. 8 shows the typical blood glucose response of a Type 1 diabetic after consuming a meal containing carbohydrates.

FIG. 9 shows the typical blood glucose response of a Type 1 diabetic after administering short acting insulin.

FIG. 10 shows the increase in blood glucose (for Type 1 diabetics) to ets intake as piecewise linear function with two sections. DETAILED DESCRIPTION

This present invention is a system using a new method to help patients with IDDM to calculate the type and measure of corrective action needed to control their blood glucose levels within a safe range. Before the functionality of the slide ruler can be explained, the ets concept first has to be explained.

The ets concept is the fundamental principal used by the device for calculating the corrective action needed, ets is a new generic energy unit, ets is the abbreviation for Equivalent Teaspoons Sugar. This energy unit can be used to quantify energy in food and energy usage in exercise. Quantifying food in ets, the effect that food intake will have on blood glucose levels for a specific person, can be predicted. The blood sugar response after a meal will be predicted by using the amount of ets in the meal. Exercises can also be quantified in ets for the individual. This is very useful in calculating appropriate insulin doses for Type I diabetics. In general the blood glucose level rise for a type 1 diabetic is dependent upon the ets intake as shown in Figure 10. The gradient or sensitivity to ets is a person specific factor and can easily be measured.

The characterisation method used by the invention is based on the ets concepts. Characterisation is necessary in order to customize these products for the individual diabetic user. The effect that ets intake has on the increase of blood glucose concentration for the diabetic is approximated by a linear function.

Increase in blood sugar level = EC . Ets consu_med 0 )

The ets sensitivity value EC can be calculated performing the simple test procedure to determine the individuals blood glucose increase per unit ets consumed- At high levels of ets i_{nta e}, the ets sensitivity (EC) decreases. The blood glucose response for ets intake can generally be approximated by two piecewise linear continuous functions shown in FIG. 10. Typical patients eating healthy will normally stay within the first part of the approximation function therefore simplifying blood glucose response prediction with a single linear function.

FIG. 8 shows a typical blood glucose response of a Type I diabetic after eating a meal containing carbohydrates. The meal is ingested after fasting for six hours or longer. The time of the meal is taken as 0 minutes (36). The ets sensitivity test is performed after a six hour fast to eliminate the effects of the previous meal and previous short acting insulin injection. By this time the blood glucose level is stable. The test should not be performed if the patient is stressed or has an illness that can have an effect on the blood glucose levels. The meal that the patient eats during the test should be carefully quantified in ets. This can be done using ets tables published in literature, databases available on the Internet or other products available. The patient's blood glucose level is measured every 30 minutes after the meal for the next 3 hours using a blood glucose monitor. The maximum value of these blood glucose level measurements will be used to calculate the rise in blood glucose level 34 caused by the meal. The level rise 34 is the difference between the maximum level 33 and the blood glucose level prior to the meal 35. ets sensitivity (EC) can then be calculated. _Fr _ Increase in bloodsugar level ,^ ets in meal

ets sensitivity (EC) for higher values of ets intake can also be calculated by eating more ets after the blood sugar stabilized after the meal. Equation (2) can then be used to calculate ets sensitivity (EC) at higher levels of ets intake.

The effect that insulin has on the decrease of blood glucose concentration for the diabetic can also be approximated by a linear function. Decrease in blood sugar level = IC . (Λ»uiin injected (³)

The sensitivity of insulin value IC can be calculated performing the second part of the test procedure. The insulin sensitivity value (IC) gives a good indication of how resistant the patient is to insulin. Better insulin sensitivity values imply low insulin resistance and vice versa.

FIG. 9 shows a typical blood glucose response of a Type I diabetic after administering short acting insulin. This response illustrates an initial high blood glucose level being lowered by the administering short acting insulin. For purpose of the test insulin is only injected after the blood glucose level has stabilized after the meal. The time of the short acting insulin injection is taken at 0 minutes (40). The insulin dosage or units to be injected should be sufficient to lower blood glucose level back to an acceptable value. The patient's blood glucose level is measured right before the injection and every 30 minutes thereafter. The minimum value where the blood glucose level stabilizes is used to calculate the decrease in blood glucose level. This is merely the difference 38 between the stabilized blood glucose level after the meal 37 and the stabilized blood glucose level after the insulin injection 39. The insulin sensitivity can then be calculated. _Jr _ Decrease in bloodsugar level resulting from insulin injection , _* number of units insulin injected

To calculate the corrective action needed to control blood glucose level becomes a simple task. The predicted blood sugar level can be calculated using Equation 5. oOpredicted ⁼ o current ⁺ EC. eϊS consumed '~ IC. Ujnsulin injected

If we want to control the blood sugar level in a safe range, we specify the ^βSpredicted value as the desire blood glucose level BSdesi_red and calculate the Uι_nsuiin needed.

D wanted ⁼ βS_Current ⁺ EC. ets consumed- IC. (Λιsulin needed (6)

Therefore the

needed can be calculated by manipulating equation 6.

^insulin needed ⁼ ( BS_Current ^_ βSwanted ⁺ EC. ets consumed) / IC. (7)

The effect of exercise can also be introduced in a similar way by quantifying exercise in terms of ets e e_r is_ed. This will result in a reduction in blood glucose level per unit exercise performed. Different exercises can be quantified in terms of ets exercised. The sensitivity E_XC will be determined by the decrease in blood glucose level per unit ETS_exerc/se . If exercise is to be considered Equation 7 can be altered. 'insulin needed ⁼ ( βS_current - BSwanted ⁺ EC. ets consumed "E_XC. θtS exercised) IC. (8)

If Unsuiin needed provides a positive value, the value indicates the number of short acting insulin units to inject. If l/_lnsU|_{in needed} provides a negative value, this means that the blood glucose level will already be too low without injecting any insulin. This means that some food containing a certain amount of ets should be eaten. To calculate the amount of efs to be eaten to restore normal blood glucose levels equation 9 can be used.

etS to be eaten = (E_XC. etS exercised ' SScurrent + BSwanted ) / EC (9)

In short if the diabetic knows what the effect of a certain amount of food and exercise will be on his/her blood sugar, and the diabetic knows what effect one unit of insulin will have on his/her blood glucose level, it becomes an easy task to calculate the required insulin dosage. Therefore it is important to calculate the ets and insulin sensitivity values accurately using the device.

FIG. 1 and FIG. 2 merely shows the layout of the slide ruler without showing all the detail on the three main parts^' 1,2 and 3.

Referring to FIG. 1 , the slide ruler of the system consists of three parts. A main center ruler 1, a large slider 2 and also a small slider 3. The large slider slides over the main ruler, while the small slider slides over the large slider. The three parts 1,2 and 3 is manufactured of plastic, paper or any other synthetic material or a combination thereof. All three parts are dual sided with printing of scales and instructions done on both sides. Parts 2 and 3 are folded in a tubular fashion so that they can slide over each other and over part 1. Referring to FIG. 2, the rear view of the slide ruler of the system is shown. The rear view of the main center ruler 4, the rear view of the large slider 5 and also the rear view of the small slider 6 are shown.

FIG. 3 shows the front view of the main center ruler 1. A blood glucose scale 7 is printed on the front of the center main ruler 1. In FIG. 3 the scale can be calibrated in mmol/l but also in any other unit used for blood glucose measurement. The scale 7 ranges from 1 mmol/l to 15 mmol/l but can be extended further from 0 mmol/l to any other possible value of blood glucose level. There are also some instructions 8 on the front side of the device.

FIG. 4 shows two possible configurations A and B for the rear layout of the main center ruler 1. Printed on both options A and B are corrective action suggestions. The scales above the "Do nothing" block 13 indicate insulin doses. The scales are arranged accommodating the most insulin resistant patients on the left 9 while the scales increase to accommodate the least insulin resistant patients on the right hand side 11. In the presentation insulin doses are indicated by integers but they can also be expressed by fractions, real values or a combination thereof. Block 15 is the food suggestion block. There are instructions 16 printed in this^, block on how to calculate the amount of ets required. The arrow 14 in the food suggestion block is used to point to the amount of ets needed to rectify a low blood glucose level.

FIG. 5 shows both the front and rear view of the large slider. The large slider is folded on lines 17 and 18. Strip 25 is pasted to the edge of part 23, creating a flat tubular slider. Scale 19 is the food intake scale calibrated in ets eaten. Scale 20 is the ets to be exercised away scale calibrated in ets exercise. Pointer 22 is used to point to the current blood glucose level on the main center ruler. The numbers in block 21 is food suggestions and is used to show how many ets should be eaten if blood glucose level is too low. Parts 23, 24 and 25 are transparent so that the main center ruler can be seen below the main slider. The scales 19, 20 and pointer 22 are not transparent.

FIG. 6 shows the small slider 3. The right halve 30 of figure 6 shows the front side of the small slider while the left halve 31 shows the rear view of the small slider 3. Section 32 is a transparent window through which the main center ruler 1 can be seen. Instructions 29 for the operation of the slider ruler device are printed on the front section 30 of the small slider 3. Arrow 28 is a pointer that will be used to point to the ets eaten and ets exercise scale. Triangle 27 is a movable part that can initially be placed in the correct positions on the scale 26 and then fixed to the small outer slider 3. Scale 26 is a measure of insulin resistance. The exact placement of triangle 27 will play an important role in the insulin dosage calculation.

FIG. 7 is an illustration of the corrective measure calculation performed with the slide ruler. The slide ruler is an implementation of equation 15. The first step is to align the large slider's arrow 22 with the current blood glucose level (BS_CUrrent) on scale 7 on the main center ruler 1. The second step is to move the small slider 3 up from the pointer 22 on the large slider 2 by the number of ets to be eaten (ETStø be eaten) directly after the insulin injection. The steps to move the small slider up are calibrated in ets eaten on scale 19. The third step is too move the small slider 3 down by the number of ets to be exercised within 6 hours (ETS_exercsed). The steps to move the small slider 3 down are calibrated in ets exercise on scale 20. The blood glucose level on scale 7 directly below the small slider 3 after the previous three steps mentioned are performed is the predicted blood glucose level. The first three steps are graphically illustrated in FIG. 7 A, B and C.

The desired blood glucose value used for the slide ruler shown in figures 1 to 7 is 5mmol/l (SS_wanted) but can be altered to a different value should the diabetic patient prefer it. This will allow an additional safety range to prevent hypoglycemia.

The last step is to turn the slide ruler over on it's back. Here one of three types of corrective actions may be identified: insulin dosage to inject, do nothing (do not inject or eat anything) or a eat food suggestion. The corrective type and measure shown directly below the small slider 3 is the measure needed to reach the desired blood glucose level, again. Triangle.27 6n the small slider 3 will be placed on a position on scale 26. The position of the triangle 27 on the scale 26 is a measure of the insulin resistance of the diabetic user with most insulin resistance on the left and least insulin resistance on the right. Arrow 28 will indicate either Unsuiin needed calculated or ets to be eaten calculated.

The system will also consist of a small booklet or paper with tables listing the ets values for some popular foodstuffs and exercises.

The magnitude of the scales used for the ets -exercise, ets -food intake and insulin and food suggestion will be calibrated to suit the individual diabetic. The step sizes used in_. these scaies will be determined for the diabetic using insulin sensitivity and ets sensitivity tests discussed in the description.

Operation of the slide ruler is defined in four steps. By shifting the three main parts of the slide ruler, the corrective action is calculated. The steps in sequential order of calculation are: selecting current blood glucose values, setting food intake, setting exercise and seeing the suggestion made.

This invention predicting the corrective actions needed to correct blood glucose levels for IDDM diabetics will allow more freedom to diabetics to change their lifestyles dynamically concerning food intake and exercise.

Claims

1. A calculating device for indicating an amount of insulin to be administered to - or ets to be consumed by a person, including a first set of parameters for indicating a measured blood sugar level of such person, a second set of parameters adjustable relative to the first set, for indicating ets being ingested by the person and/or exercise ets being expended by the said person, and a third set of parameters for indicating the amount of insulin to be administered or ets to be consumed, dependant on the first and second sets of parameters.

2. A calculating device according to claim 1 , which is in the form of a slide ruler type device.

3. A calculating device according to claim 2 wherein the slide ruler type device includes a center main ruler for depicting either one of the first or second sets of parameters, a sleeve for depicting the other set, with the main ruler received in the sleeve and movable relative thereto to adjust the first set of parameters relative to the second set; and an indicating means movable relative to the main ruler and sleeve for indicating a value on the said third set of parameters.

4. A device according to any one of the preceding claims wherein the third set of parameters is a primary set of parameters divided into two secondary sets of parameters, a first being indicative of ets to be consumed and the second indicating the insulin to be administered.

5. A device according to any one of the preceding claims wherein the second set of secondary parameters is divided into a plurality of tertiary parameters which are dependant on the insulin sensitivity of the said person.

6. A device according to any one of the preceding claims including a parameter indicative of a normal blood sugar status.

7. A device according to any one of the preceding claims wherein the scale of second set of parameters is dependent on the ets sensitivity of the particular person using the device.

8. A method of calculating an amount of insulin to be administered to - or ets to be consumed by a person, including the steps of selecting a measured blood sugar level value of the person on a first set of parameters, adjusting relative to the first set a second set of parameters indicating ets being ingested by the person and/or exercise ets being expended by the said person, adjusting relative to the second set, in accordance with a value of ets being ingested by the person and/or exercise ets being expended by the said person an indicating means, and relating the said value to a third set of parameters indicating the amount of insulin to be administered or ets to be consumed.