Blood Sugar Monitoring: Using Infrared Instead of Invasive Techniques

Over six million people in Germany have diabetes. It is estimated that almost 400 million people are affected by this disease worldwide. Diabetes sufferers must prick their fingers several times a day to monitor their blood sugar. Now a doctoral candidate at the Interdisciplinary Center for Life Sciences in Iserlohn, Germany, is researching a modern, non-invasive monitoring method that’s designed to measure blood sugar without finger pricks. The tool: laser spectroscopy.

In this MEDICA-tradefair.com interview, Sven Delbeck talks about the importance of large volumes of data in diabetology, describes the role the new method could play in other medical specialties and reveals where there is still room for improvement.

What new opportunities does a world where the healthcare industry is becoming increasingly digital offer diabetes sufferers?

Sven Delbeck: We are now able to analyze large datasets in real-time, which facilitates optimized and personalized treatment approaches for diabetes patients. Smartphones (mhealth in the catalogue of MEDICA 2018) and apps (medical apps and app stores in the catalogue of MEDICA 2018) are some of the tools that assist a breakdown and analysis of data generated by self-monitoring of blood glucose (glucose testing in the catalogue of MEDICA 2018). A new generation of biosensor technology makes it possible to collect and analyze continuous glucose data, thus providing an improved quality in intensified insulin therapy. What’s more, apps can track and count carbohydrates and calculate the insulin dose for the patient.

Many continuous glucose monitoring systems feature warning systems that predict imminent hypoglycemic (low level of blood sugar) and hyperglycemic (high level of blood sugar) events via sounds or trend arrows. Thanks to app permission, physicians or authorized persons can use the datasets to perform remote diagnostics and provide assistance, which is especially important for parents of children with diabetes or caregivers of diabetic patients.

So far, hypoglycemia or hyperglycemia is detected by using invasive methods. You are in the process of developing a new approach. What makes it new?

Delbeck: This is not a brand-new approach. For many years, my doctoral advisor Professor Herbert Michael Heise has already been very successful in his research at the ISAS Research Institute in Dortmund (now Leibniz Institute for Analytical Sciences - ISAS eV), and prior to that by collaborating with associates of the South Westphalia University of Applied Sciences in Iserlohn.

The fundamental innovation of the current development is the use of a non-invasive, continuously measuring system based on optical technology to monitor blood sugar. Unlike studied or even established minimally or non-invasive optical methods, which usually represent a mix of integral glucose-specific measurement signals from interstitial fluid, intracellular space and blood, our approach determines the target blood glucose levels, which is considered to be the gold standard in medicine for diagnosing diabetes. The major drawback of tissue-integrated measurement methods is the individually varying time delay of glucose moving between blood and tissue, which renders current, non-invasive optical systems unable to deliver accurate readings pertaining to the patient’s arterial blood glucose concentration.

How exactly are blood glucose levels measured?

Delbeck: We use a vibrational spectroscopy setup with a near infrared light source (with longer wavelengths than visible light) and specifically designed diffuse reflection, resulting in excellent signal-to-noise ratios. The contact of well-perfused skin on the flat side of a half ball (hemispherical) lens enables the recording of skin spectra by collecting backscattered photons from the top layers of skin, focusing them on a detector and subsequently analyzing them. The top skin layers contain glucose in the capillaries, which absorbs the radiation of some specific wavelengths. To differentiate between interstitial fluid and blood glucose, changes in blood volume caused by the heartbeat are meant to be managed by pulse plethysmography trigger pulse and used to subsequently filter the glucose-specific signals using special multivariate data analysis.

What are the advantages of this new blood sugar monitoring method for diabetic patients and patients in intensive care?

Delbeck: It eliminates pain and decreases the risk of infection as it relates to multiple finger pricks per day with a lancet, which is currently the state-of-the-art technology. Even minimally invasive patch-based glucose monitoring devices that take measurements at the same site for up to two weeks have drawbacks compared to non-invasive methods because they can cause skin irritation from the adhesive or the tissue has an inflammatory response to the temporary implanted sensor. Continuous blood glucose monitoring has also been shown to improve HbA1c levels (average level of blood sugar over a longer period of time) in diabetics and reduce long-term effects such as diabetic foot ulcers, diabetic retinopathy, and kidney damage. Personalized treatments thanks to "online measurements" of the actual amount of glucose in the blood, as well as another step towards an "artificial pancreas” are added benefits of this method. This also facilitates continuous patient monitoring in the intensive care unit because it eliminates the need for staff to check blood sugar levels intermittently several times a day.

The procedure can be used in diabetology, but could it also benefit other medical specialties? Which ones and why?

Delbeck: It is conceivable to monitor various medically important blood parameters that are vital in intensive care medicine. Continuous blood glucose monitoring allows many conclusions about the patient’s metabolism. The temperature, water content or the analysis of body fluids on the skin surface - such as sweat - are also measurement parameters that play an important role in endurance sports. So-called fitness trackers (or bracelets) have been on the market for several years now. Their application range would broaden if you combine them with wearable, adhesive patch spectrometers. Clinical chemistry is yet another medical application where non-invasive monitoring of blood alcohol content can provide important information about a person’s ability to drive for example.

This method is not market-ready yet. What are some areas of improvement?

Delbeck: At the moment, we still have to characterize disturbances whose results are included in the data analysis so that we can build a robust predictive model. This includes the skin age or characteristics of tissue perfusion. Sensor patches must take skin changes prompted by the sensor cover into account (moisture content, scattering of light). These are just a few parameters that must be sufficiently known and implemented so that all patients can use a blood glucose meter every day, while the device must simultaneously deliver the same quality readings produced under laboratory conditions and standards.

Another challenge is to miniaturize the blood glucose meter while maintaining the same spectral signal-to-noise ratio performance. Newly developed and miniaturized optical and electronic components are aiding this process. In addition, electronic data processing and telemedicine solutions must also be integrated. This type of monitoring device is portable and gives patients flexibility - in the best-case scenario, it can be worn right on the body without restricting the wearer’s mobility.