6.3 Signals of the Cardiovascular System

|

241

scatter(adj_time([idx_a1 idx_a2]), value_angle([idx_a1 idx_a2]),...

100, 'kv')

ylabel('Angle \alpha/deg', 'Color','k')

ax = gca;

ax.YColor = 'k';

axis([0 10 40 300])

yyaxis left

scatter(time_force([idx_f1 idx_f2]), value_force([idx_f1 idx_f2]),...

100, 'k^')

xlabel('Time t/s')

ylabel('Force F/N')

axis([0 10 260 500])

title('Synchronised Force and Angle Data')

legend('Force', 'Force Trigger Point', 'Angle', 'Angle Trigger Point')

6.3 Signals of the Cardiovascular System

The analysis of signals of the cardiovascular system includes, in addition to the

already discussed electrocardiogram, the evaluation of the phonocardiogram, i.e. the

heart sounds and the evaluation of the photoplethysmogram to determine the oxygen

saturation of the blood. As already indicated in section 2.2, these signals contain dif-

ferent information of the cardiovascular system and accordingly also lead to different

results in the evaluation. The ECG allows conclusions about the conduction system

of the heart, the phonocardiogram about the valve activity and the blood flow in the

heart, and the photoplethysmogram contains information about the propagation of

the pulse waves and the oxygen saturation of the blood. On the other hand, all the

above signals contain, for example, information on the heart repetition rate and can

be analysed in different ways in this respect. However, their determination from the

ECG sequence is much more accurate than their determination from the other two

signals due to the distinctive QRS complex. For diagnostic purposes, the robustness

of an analysis method with regard to the interpersonal variability of signals is also of

great importance, since a reliable statement is to be made for all patients.

6.3.1 Electrocardiogram

The section 3.2 on electrophysiology of the heart describes the origin and propaga-

tion of electromagnetic fields, which can also be measured outside the body. Since the

measurement outside the body is more patient-friendly and less time-consuming, the

standard examination consists of the measurement on the surface of the body, the time