6.3 Signals of the Cardiovascular System

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molar extinction coefficient / l mol-1 cm-1

HbO2 - Oxyhemoglobin

Hb - Hemoglobin

Fig. 6.46: Molar extinction coefficient of hemoglobin and oxyhemoglobin as a function of

wavelength [40].

about the absolute oxygen supply of the organism. In the case of blood anemia, the

hemoglobin concentration is reduced with the consequence of an oxygen deficiency.

However, the SpO2 value could be inconspicuous at the same time because the de-

creased Hb fraction is well oxygenated. Furthermore, there is a risk of misinterpreta-

tion in carbon monoxide poisoning. Then CO binds to Hb instead of O2. Since the molar

extinction coefficient εHbCO differs from εHb and is similar at some wavelengths εHbO2,

a statement about the remaining oxygen saturation with this method is no longer pos-

sible in the situation.

6.3.4 Signal Classification of Multichannel Photoplethysmography

Author of Subsection: Urs Hackstein

In the previous subsection 6.3.3 photoplethysmography (PPG) signals were used to

quantifiy the oxygen saturation of blood. Due to their simple acquisition, PPG signals

are used in an increasing number of areas for diagnostic purposes, e.g. for the de-

termination of vascular age via the arterial stiffness or the blood pressure by the pulse

transit time. Furthermore, PPG signals are used for the diagnosis of diseases [43], as

an example the case of aneurysms and stenoses detection using machine learning

techniques and classification is considered.

Cardiovascular diseases are the leading cause of death worldwide. Particularly

aortic aneurysms, i.e. abnormal aortic bulges, are problematic and underdiagnosed:

According to [10], they affect 12-14% of the population. An aortic aneurysm can be dan-

gerous if it is not spotted early on. It can get bigger over time and could burst, causing

life-threatening bleeding. However, the asymptomatic course of the diseases in most

patients and the misinterpretation of the initial symptoms in about one third of the