2
V. Blazek
to be pumped in one hour. It appeared logical to him that such a large amount of blood
could not be regenerated in any way within our body—an idea based on the erroneous
theories of blood circulation proposed by Galen of Pergamon (physician/philosopher
c. AD 129 to c. 201) that were popular at that time. Nevertheless, he forged ahead and
gained valuable insight into the closed human circulatory system based on simple
quantitative examination. Today, we know that the driving force of our blood circulation is based on the difference in pressure between the arteries and veins. The pulsed
high pressure in the arteries funnels the blood until the blood pressure in the veins
reaches a steady-state low pressure. The human vascular system (with an integral
length of hundreds of kilometers or more) circulates about 6 L of blood through
our body in just one minute, powered by our heart (weighing only 350 g) acting
as a pump and impulse generator. The transportation capacity of such an extensive
vascular network (without losses) is about 10,000 L per day. The phenomenon of
rhythmic fluctuation due to arterial blood pressure was experimentally discovered
in the eighteenth century. In 1726, the Reverend Stephen Hales (1677–1761), an
English clergyman who pioneered quantitative experimentation in plant and animal
physiology was the first to observe the magnitude of arterial blood pressure and its
pulsation in an invasive manner. Figure 1.1 illustrates the experiment he conducted
to determine the arterial blood pressure of a horse.
After the first continuous recording of blood pressure, an extensive series of investigations have taken place, all dealing with the problem of how to explain the rhythmic
fluctuation of blood flow. However, even until now, a complete understanding of the
underlying mechanisms that control the formation of such rhythms is still lacking.
A practical, non-invasive way to acquire information on peripheral venous and/or
arterial hemodynamics is by use of optoelectronics paired with quantitative photoplethysmography (PPG). An optoelectronic biosensor concept is introduced that is
capable of identifying rhythms from several sensors in combination with acquisition
of data on, for example, respiration, ECG and body movement. Depending on the
area measured and the purpose of measurement, the optoelectronic sensor can be
used in either reflection or transmission mode. The data can then be analyzed using
high-time resolution and displayed in time and frequency domains [3].
This chapter presents various possibilities related to the PPG measuring concept
by means of examples and perfusion protocols. Current research focuses not only
on the so-called central rhythms and their correlation with heartbeat and respiratory
rate, but also on the perfusion frequency range around 0.1 Hz. However, assessment
and interpretation of these perfusion rhythms are often hindered by the fact that these
patterns have a very strong spatial variability and are highly transient [4].
Nowadays, new information about the rhythmic phenomena in skin perfusion is
available based on the relationship between blood volume rhythms and respiratory
dynamics, evaluation of the hemodynamic-related effect of autogenous training, analysis of the pulse waveform parameters, and/or pulse wave transient time. Using new
camera-based sensor and signal processing strategies, a recently developed photoplethysmographic setup allows contactless measurements of cutaneous perfusion
with spatial resolution.
V. Blazek
to be pumped in one hour. It appeared logical to him that such a large amount of blood
could not be regenerated in any way within our body—an idea based on the erroneous
theories of blood circulation proposed by Galen of Pergamon (physician/philosopher
c. AD 129 to c. 201) that were popular at that time. Nevertheless, he forged ahead and
gained valuable insight into the closed human circulatory system based on simple
quantitative examination. Today, we know that the driving force of our blood circulation is based on the difference in pressure between the arteries and veins. The pulsed
high pressure in the arteries funnels the blood until the blood pressure in the veins
reaches a steady-state low pressure. The human vascular system (with an integral
length of hundreds of kilometers or more) circulates about 6 L of blood through
our body in just one minute, powered by our heart (weighing only 350 g) acting
as a pump and impulse generator. The transportation capacity of such an extensive
vascular network (without losses) is about 10,000 L per day. The phenomenon of
rhythmic fluctuation due to arterial blood pressure was experimentally discovered
in the eighteenth century. In 1726, the Reverend Stephen Hales (1677–1761), an
English clergyman who pioneered quantitative experimentation in plant and animal
physiology was the first to observe the magnitude of arterial blood pressure and its
pulsation in an invasive manner. Figure 1.1 illustrates the experiment he conducted
to determine the arterial blood pressure of a horse.
After the first continuous recording of blood pressure, an extensive series of investigations have taken place, all dealing with the problem of how to explain the rhythmic
fluctuation of blood flow. However, even until now, a complete understanding of the
underlying mechanisms that control the formation of such rhythms is still lacking.
A practical, non-invasive way to acquire information on peripheral venous and/or
arterial hemodynamics is by use of optoelectronics paired with quantitative photoplethysmography (PPG). An optoelectronic biosensor concept is introduced that is
capable of identifying rhythms from several sensors in combination with acquisition
of data on, for example, respiration, ECG and body movement. Depending on the
area measured and the purpose of measurement, the optoelectronic sensor can be
used in either reflection or transmission mode. The data can then be analyzed using
high-time resolution and displayed in time and frequency domains [3].
This chapter presents various possibilities related to the PPG measuring concept
by means of examples and perfusion protocols. Current research focuses not only
on the so-called central rhythms and their correlation with heartbeat and respiratory
rate, but also on the perfusion frequency range around 0.1 Hz. However, assessment
and interpretation of these perfusion rhythms are often hindered by the fact that these
patterns have a very strong spatial variability and are highly transient [4].
Nowadays, new information about the rhythmic phenomena in skin perfusion is
available based on the relationship between blood volume rhythms and respiratory
dynamics, evaluation of the hemodynamic-related effect of autogenous training, analysis of the pulse waveform parameters, and/or pulse wave transient time. Using new
camera-based sensor and signal processing strategies, a recently developed photoplethysmographic setup allows contactless measurements of cutaneous perfusion
with spatial resolution.