1 Skin Perfusion Studies: Historical Notes and Modern Measuring …
5
influenced by the form of respiration. One distinguishes between thoracic breathing,
diaphragmatic breathing, and mixed forms of both.
Another important factor is that through the respiration-induced effect known as
respiratory sinus arrhythmia (RSA), occasional phase jumps in the heart rate are
noticed, which always have a certain phase relationship with the respiration rate.
The exact sequence is unclear, but there seems to be a synchronization mechanism
between respiration and heart activity. Finally, there exist vasomotor effects (vascular
muscle movements) synchronous to breathing, which are driven by synchronized
neuronal activity. It would therefore be conceivable that the vasomotor centre in the
brain is connected through the respiration centre. However, it is not yet clear if both
these alleged centres could be driven by nerve impulses from the same region of the
brain stem. The respiratory rate at rest is usually at 0.2 Hz to 0.4 Hz (in the frequency
range of the middle PPG spectrum (see) in the logarithmic scale).
1.2.3 Vasomotor Rhythms
The investigation of the vasomotor system really began with the work of French
physiologist Claude Bernard (1813–1878), who demonstrated that a section of the
sympathetic nervous system in a rabbit caused dilatation of the vessels of ear and
that simulation of the peripheral cut end of the nerve caused constriction [6, 7]. His
famous quotation may be worth noting in this context:
I consider the hospital the antechamber of medicine; it is the first place where the physician
makes his observations. But the laboratory is the temple of the science of medicine
Each human organ is perfused with oxygenated blood through a capillary vascular
network. This takes care of the nutrient intake, the residual material dissipation and
temperature regulation. The structure is as follows: branching off from the arteries are
the arterioles (diameter see). From this point on, one speaks of “microcirculation”.
The venules collect the blood at the opposite ends of the microcirculation system and
pass it back into the veins. Between arterioles and venules are two types of connections: the arteriovenous anastomosis, a short circuit which is closed when required,
and the metarteriole, the main blood-flow path through the capillary network. At
the junctions are ring muscles (sphincter precapillaris), which regulate blood flow
through the capillaries. The walls of the capillaries consist of a single cell-layer
separating the blood vessel (intravascular layer) from the cell gap (interstitium). The
pressure decreases about 50% in the arterioles.
The vessel diameter is therefore well-regulated. According to Hagen-Poiseuille’s
law, the resistance R of a tube like an artery is defined as [17]:
R =
8 · v · l
π · r 4 , with: v = viscosity, l = length and r = radius of the artery. (1.1)
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influenced by the form of respiration. One distinguishes between thoracic breathing,
diaphragmatic breathing, and mixed forms of both.
Another important factor is that through the respiration-induced effect known as
respiratory sinus arrhythmia (RSA), occasional phase jumps in the heart rate are
noticed, which always have a certain phase relationship with the respiration rate.
The exact sequence is unclear, but there seems to be a synchronization mechanism
between respiration and heart activity. Finally, there exist vasomotor effects (vascular
muscle movements) synchronous to breathing, which are driven by synchronized
neuronal activity. It would therefore be conceivable that the vasomotor centre in the
brain is connected through the respiration centre. However, it is not yet clear if both
these alleged centres could be driven by nerve impulses from the same region of the
brain stem. The respiratory rate at rest is usually at 0.2 Hz to 0.4 Hz (in the frequency
range of the middle PPG spectrum (see) in the logarithmic scale).
1.2.3 Vasomotor Rhythms
The investigation of the vasomotor system really began with the work of French
physiologist Claude Bernard (1813–1878), who demonstrated that a section of the
sympathetic nervous system in a rabbit caused dilatation of the vessels of ear and
that simulation of the peripheral cut end of the nerve caused constriction [6, 7]. His
famous quotation may be worth noting in this context:
I consider the hospital the antechamber of medicine; it is the first place where the physician
makes his observations. But the laboratory is the temple of the science of medicine
Each human organ is perfused with oxygenated blood through a capillary vascular
network. This takes care of the nutrient intake, the residual material dissipation and
temperature regulation. The structure is as follows: branching off from the arteries are
the arterioles (diameter see). From this point on, one speaks of “microcirculation”.
The venules collect the blood at the opposite ends of the microcirculation system and
pass it back into the veins. Between arterioles and venules are two types of connections: the arteriovenous anastomosis, a short circuit which is closed when required,
and the metarteriole, the main blood-flow path through the capillary network. At
the junctions are ring muscles (sphincter precapillaris), which regulate blood flow
through the capillaries. The walls of the capillaries consist of a single cell-layer
separating the blood vessel (intravascular layer) from the cell gap (interstitium). The
pressure decreases about 50% in the arterioles.
The vessel diameter is therefore well-regulated. According to Hagen-Poiseuille’s
law, the resistance R of a tube like an artery is defined as [17]:
R =
8 · v · l
π · r 4 , with: v = viscosity, l = length and r = radius of the artery. (1.1)