The continuous recording of subcutaneous glucose levels (continuous glucose monitoring, CGM) using special sensors in a unique way can contribute to improve the treatment of diabetes mellitus (DM), especially in people who use insulin for metabolic control of diabetes. In particular, in recent years, a technological development has become more and more frequent due to the construction of models, which are more accurate in measurements, but also to simplify their use.
It can provide useful information about fluctuations in glucose levels over the full 24 hours (those days are particularly useful in the problem of hypoglycemic episodes, as will be discussed below) and help make appropriate decisions about food intake, exercise, and treatment that must be followed.
What is a Glucose Sensor and How Does it Work?
The definition of this type of glucose sensor can be as follows: a device placed on the body of a person with diabetes, which automatically and repeatedly (at regular intervals) determines glucose levels in real time and accurately from space surrounding. , which is located within it and specifically from the subcutaneous tissue fluid. The sensor consists of three parts: 1) the part placed on the body (electrode), 2) a wireless measurement transmitter, 3) a device that receives the measurements and transmits them through a monitor to the patient. It takes 24-hour glucose measurements at regular intervals ranging from 5 to 15 minutes.
In sensors, the enzymatic method is used, whereby the glucose contained in the fluid in the subcutaneous extracellular space reacts with glucose oxidase, which is located in the electrode placed under the skin and from this reaction produces an electron, which corresponds to a glucose molecule. In this way, an electrical current is generated, proportional to the concentration of glucose in the interstitial space, which is then transmitted to the transporter. The latter transmits information wirelessly to the device, which transmits the measurements via a screen to the patient.
Types of Glucose Sensors
CGM glucose measurements show a time lag from blood glucose values of 5 to 15 minutes, especially when blood glucose levels change very quickly. The time delay is due to: 1) blood flow to the skin. 2) at the time necessary for the enzymatic reaction with interstitial glucose and 3) at the time of signal processing. Most CGMs require calibration using twice daily capillary blood glucose measurements. Calibration is necessary to confirm the accuracy of measurements made on extracellular fluid. However, if the titration is performed during a period of time when there are very rapid changes in blood glucose levels (>2 mg/dL/min), such as after a meal or after exercise, the readings may be incorrect.
There is also a system on the Greek market that uses flash technology and does not require calibration. For this reason, whether in hyperglycemia or hypoglycemia, when there is a need for therapeutic intervention, capillary or venous blood glucose should be checked.
Other types of long-acting implantable CGMs are under investigation that use other enzymatic methods for measuring glucose in interstitial fluid or an optical or osmotic technique. Other researchers are studying the possibility of non-invasively measuring the glucose in tears.
Indications for Use of Glucose Sensors
CGM technology can be applied to a wide range of patients with T1DM, but also T2DM, who are on insulin therapy. One of the main indicators of glucose sensors is those situations where you need to check for large fluctuations in glucose levels. This possibility is not provided by the usual self-test as usually 4-7 measurements / 24 hours are taken, while 288 measurements / 24 hours are taken using the glucose sensor. Additionally, sensors can be used to prevent nighttime episodes of hypoglycemia, check for unrecognized hypoglycemia, and make treatment decisions related to better metabolic control in people using continuous subcutaneous insulin pumps or injection systems.
In particular, for hypoglycemia, there is an insulin pump model on the Greek market which, in combination with CGM, can offer the following: blood, automatically stopping insulin delivery at low glucose levels. Further improvements to glucose sensors in the future will likely create a so-called “closed loop” of insulin delivery, or simply an artificial pancreas. This is a device that measures glucose levels and delivers the required amount of insulin. In fact, with the model equipped with automatic basal rate regulation technology, excellent regulation of blood sugar is achieved, especially during the 24-hour night hours (option of automatic mode).
However, in particular, for people with TDM1, who enjoy playing sports or working in challenging occupations, and who need to avoid hypoglycemia, the use of sensors is a key indication. It can also be used in cases where capillary blood glucose measurements do not match HbA1c (glycosylated hemoglobin) values. Also, patients whose HbA1c is greater than the target. Even in patients who take frequent and regular measurements of the finger, the use of the sensor can be particularly helpful.
In our recent study, CGM was used in diabetic patients with end-stage renal disease on dialysis to discover new markers of glycemic control in these patients. In diabetic patients on hemodialysis, the measurement of HbA1c is not accurate and the search for new indicators of glycemic regulation is essential. Furthermore, a continuous diabetes monitoring system can help these patients as they are prone to frequent and unrecognized hypoglycemia.
Glucose Sensor Receiver
In the near future, this is expected to be achieved with studies currently testing new types of sensors that will not need to be calibrated or run less often, will be more accurate, will be smaller in size, will last longer, and will be combined more effectively with pumps. insulin to create a ‘pancreas’. artificial”.
Conclusions
In the last two decades, the technological development of sensors has taken great leaps with their increasingly frequent use. They can be of great help with distinct functions that self-monitoring of blood cannot provide. They help to achieve better metabolic control, reduce hypoglycemia and better food and exercise planning. In combination with the new type of insulin pumps, today they can offer the so-called “open” circuit of insulin delivery, suspending the administration of insulin with low glucose values and, in the near future, they will make a significant contribution to the creation of the “closed” circuit, that is, an “artificial pancreas”.
