QRS Morphology-Based EDR Signal—Factors Determining its Properties

Abstract

Respiration-induced signals contain a clinically significant information. It could be obtained utilizing both direct and indirect methods. ECG-Derived Respiration (EDR) method is the latter one. However, in this case, two approaches could be distinguished. First one is based on determining changes in the morphology of QRS complexes while the second one is based on the Respiratory Sinus Arrhythmia (RSA) mechanism. The former approach is discussed in the paper. The basic properties of QRS morphology-based EDR signal were evaluated by means of simulations performed using a developed FEM model and appropriate experiments. In effect, basing on changes of the leads' voltages induced by a heart translation or rotation, or by both mechanisms undergoing simultaneously, the sensitivity-like surfaces and the synthetic EDR signals were obtained. A very good agreement of the experimental and simulation results was achieved. The QRS morphology-based signal's properties strongly depend on geometrical relation of the used lead to dominating direction of the heart translation, its rotation, and on personal relation between these two mechanisms. The conclusions presented should be taken into account especially when developing or using QRS morphology-based approach in respiratory monitoring systems.INDEX TERMS Electrocardiography (ECG), ECG-derived respiration (EDR), respiration monitoring.

Non-Contact Monitoring of ECG in the Home Environment—Selecting Optimal Electrode Configuration

“…The potential distribution associated with electrical heart activity was modeled using an equivalent dipole approach [ 22 ]. The value of the dipole moment was A · m. This value was in agreement with the data available elsewhere, e.g., [ 38 ].…”

“…The conductivity value assigned to each tissue included in the model was selected according to the frequency spectrum of the ECG. Thus, the conductivity of the heart muscle, the thoracic wall, the blood, and the abdominal part of the body (the part below the diaphragm) were, respectively, equal to 0.2 S/m, 0.1 S/m, 0.5 S/m, and 0.1 S/m [ 22 , 39 ]. The lungs’ conductivity was fixed and equal to 0.05 S/m.…”

“…The analysis of ECG forward problems can be found in [ 27 ] while general considerations are described in [ 28 ]. According to the above-mentioned papers, the electric potential distribution, , shortly assigned as in the thorax, can be calculated using the partial differential equation [ 22 , 29 ]: where: and denotes the cardiac source (so-called active currents). The current density that is normal to the thorax surface, S, also has to fulfill a boundary condition: where n is a unit vector normal to S.…”

“…Aside from the measurement properties of the capacitive electrode, the lead configuration used is also important. When considering the application of the method with systems built into furniture, e.g., an armchair or a chair, the most commonly used is a lead analogous to the first Eindhoven one, but with electrodes placed in the area of the back and at different heights below the shoulders [ 22 , 23 ]. On the other hand, the ECG lead referred to as monitoring is widely used in many applications.…”