Contactless ECG system for emergencies
Faster and better diagnosis of heart problems:
With a new system, doctors and paramedics can diagnose heart diseases faster and better. The multi-channel electrocardiography system, developed by researchers at the Institute of Electrical Measurements and Fundamental Electrical Engineering, offers significant advantages over conventional electrocardiography. An electrocardiogram can, almost in passing, be recorded through the clothes without contact. Since the new system can be carried similar to a notebook, it can make the quick diagnosis in the field easier in emergency cases and, in particular cases, it can even save lives.
Electrocardiography is a medical routine procedure for diagnosing heart diseases. An electrocardiogram (ECG) is made, which records the heart activity in form of electric impulses. The intensity and the time structure allow conclusions about possible heart diseases. The new method is also based on this technology. Other than the conventional ECG, the electrodes do not have to be applied laboriously with conductive gel or held by vacuum to the skin. The contactless ECG system only has to be held on the body surface to measure the heart signals.
At the same time, the recordings are much more detailed than the previous separate curves. The new machine thus acts as a “window to the heart”. It can record films of the electrical heart activity with up to 80 images per second. The measurement results are represented two-dimensionally, similar to a map. Such an illustration is called Body Surface Potential Mapping, where the measured voltages are colored (s. figure). Due to the special array of the electrodes, the doctor can immediately identify the signals spatially and assign them to the appropriate body regions. Hence, the heart activity is directly shown above the body surface. This method thus reveals additional, medically relevant information at a glance.
The integrated tablet PC is used for data acquisition. The devices can therefore be immediately available for rescue operations.
How does the new ECG work?
The method uses the effect that the heart activity also causes charge displacement on the body surface. If the charge in the body changes, it can in turn influence the charge on a metal plate close to the body. This plate does not require direct electrical contact to the skin. Measurement is therefore possible through layers of clothing. A supersensitive signal amplifier is connected to the plate which amplifies the body signal and processes it, so it can be displayed on the screen later on. Plate, amplifier and further signal processing electronic systems are integrated in the compact electrodes (30 mm in diameter, approx. the size of a 2 euro coin). The electrodes are only slightly larger than standard ECG electrodes. These new, intelligent electrodes contain essential parts of signal processing electronic systems. They are called capacitive electrodes, from which the term capacitive ECG (cECG) is derived. Researchers at the Institut für Elektrische Messtechnik und Grundlagen der Elektrotechnik developed them in cooperation with Prof. G. Curio of the Charité in Berlin and Prof. K.-R. Müller of the Fraunhofer Institute FIRST, Berlin.