294
M. Thanaj et al.
comprehensively reviewed [24, 68, 69] and the signalling pathways underlying the
responses described elsewhere [68].
19.3 Analysis of Microvascular Blood Flow Signals
in the Spectral Domain
The LDF technique has been extended to explore microvascular control mechanisms
within the skin through the analysis of the component frequencies of the laser Doppler
signal [21, 38, 48]. Time series analysis of LDF signals shows spontaneous, local,
rhythmic oscillatory fluctuations of the blood flux in the microvascular network.
These periodic oscillations have been shown to reflect the influence of myogenic
(~0.05–0.15 Hz) [45], neurogenic (~0.02–0.05 Hz) [78] and both endothelial nitric
oxide (NO)-dependent (~0.0095–0.02 Hz) and -independent (<0.0095 Hz) [47, 49,
66] activity on vascular tone. Additionally, the haemodynamic effects of the heart
beat (~0.6–2.0 Hz) and respiratory activity (~0.15–0.6 Hz) [10] may be detected in
the LDF signal (Table 19.1).
The two main methods of spectral analysis that have been used to extract these
oscillatory signals are based on the Fast Fourier Transform (FFT) algorithm and on
a generalized wavelet transform (WT) [2].
Table 19.1 Periodic activity of the laser Doppler blood flux signal and its potential origins (From
[19])
Periodic activity
Time constant (s) Frequency (Hz) Origin
Endothelial NO-independent >105
<0.0095
Mechanisms other than
NO-mediated originating
from endothelial cells, e.g.
endothelial derived
hyperpolarizing factor
(EDHF)
Endothelial NO-dependent
48–105
0.0095–0.02
NO production by
endothelial cells
Neurogenic
19–48
0.02–0.05
Sympathetic nervous
system
Myogenic
7–19
0.05–0.15
Vascular smooth muscle
(VSM) cells
Respiratory
1.6–7
0.15–0.620
Breathing
Cardiac
0.5–1.6
0.60–2.00
Heartbeat
M. Thanaj et al.
comprehensively reviewed [24, 68, 69] and the signalling pathways underlying the
responses described elsewhere [68].
19.3 Analysis of Microvascular Blood Flow Signals
in the Spectral Domain
The LDF technique has been extended to explore microvascular control mechanisms
within the skin through the analysis of the component frequencies of the laser Doppler
signal [21, 38, 48]. Time series analysis of LDF signals shows spontaneous, local,
rhythmic oscillatory fluctuations of the blood flux in the microvascular network.
These periodic oscillations have been shown to reflect the influence of myogenic
(~0.05–0.15 Hz) [45], neurogenic (~0.02–0.05 Hz) [78] and both endothelial nitric
oxide (NO)-dependent (~0.0095–0.02 Hz) and -independent (<0.0095 Hz) [47, 49,
66] activity on vascular tone. Additionally, the haemodynamic effects of the heart
beat (~0.6–2.0 Hz) and respiratory activity (~0.15–0.6 Hz) [10] may be detected in
the LDF signal (Table 19.1).
The two main methods of spectral analysis that have been used to extract these
oscillatory signals are based on the Fast Fourier Transform (FFT) algorithm and on
a generalized wavelet transform (WT) [2].
Table 19.1 Periodic activity of the laser Doppler blood flux signal and its potential origins (From
[19])
Periodic activity
Time constant (s) Frequency (Hz) Origin
Endothelial NO-independent >105
<0.0095
Mechanisms other than
NO-mediated originating
from endothelial cells, e.g.
endothelial derived
hyperpolarizing factor
(EDHF)
Endothelial NO-dependent
48–105
0.0095–0.02
NO production by
endothelial cells
Neurogenic
19–48
0.02–0.05
Sympathetic nervous
system
Myogenic
7–19
0.05–0.15
Vascular smooth muscle
(VSM) cells
Respiratory
1.6–7
0.15–0.620
Breathing
Cardiac
0.5–1.6
0.60–2.00
Heartbeat