Synchronous and baroceptor-sensitive oscillations in skin microcirculation: evidence for central autonomic control

Abstract

To determine whether skin blood flow is local or takes part in general regulatory mechanisms, we recorded laser-Doppler flowmetry (LDF; left and right index fingers), blood pressure, muscle sympathetic nerve activity (MSNA), R-R interval, and respiration in 10 healthy volunteers and 3 subjects after sympathectomy. We evaluated 1) the synchronism of LDF fluctuations in two index fingers, 2) the relationship with autonomically mediated fluctuations in other signals, and 3) the LDF ability to respond to arterial baroreflex stimulation (by neck suction at frequencies from 0.02 to 0.20 Hz), using spectral analysis (autoregressive uni- and bivariate, time-variant algorithms). Synchronous LDF fluctuations were observed in the index fingers of healthy subjects but not in sympathectomized patients. LDF fluctuations were coherent with those obtained for blood pressure, MSNA, and R-R interval. LDF fluctuations were leading blood pressure in the low-frequency (LF; 0.1 Hz) band and lagging in the respiratory, high-frequency (HF; ∼0.25 Hz) band, suggesting passive “downstream” transmission only for HF and “upstream” transmission for LF from the microvessels. LDF fluctuations were responsive to sinusoidal neck suction up to 0.1 Hz, indicating response to sympathetic modulation. Skin blood flow thus reflects modifications determined by autonomic activity, detectable by frequency analysis of spontaneous fluctuations.

Autonomic Blockade During Sinusoidal Baroreflex Activation Proves Sympathetic Modulation of Cerebral Blood Flow Velocity

“…The results reconfirm that 0.1 Hz NS is suited to activate sympathetic outflow to vasomotor nerves, 30 and show that 25 mg of the α-and β-adrenoreceptor blocker was sufficient to significantly reduce sympathetic BP modulation. 31,32 Still, the question arises whether (1) the 0.1 Hz NS-induced increases and carvedilol-induced decreases in CBFV and in 0.1 Hz CBFV modulation also reflect an increase, respectively decrease, in sympathetic outflow in sympathetic outflow onto the cerebral vasculature; or whether (2) these changes in CBFV and 0.1 Hz CBFV powers are secondary to, and passively driven by the increases, respectively decreases, in BP and in sympathetic 0.1 Hz BP modulation.…”

“…4,5,29 Moreover, the significantly lower BP values and lower sympathetically mediated 0.1 Hz BP-powers after than before carvedilol confirm that 25 mg of the α-and β-receptor blocker are sufficient to reduce sympathetic outflow at rest, as well as during 0.1 Hz NS-induced sympathetic activation. 30 Effects of carvedilol on CBFV and 0.1 Hz CBFV oscillations were similar to effects on BP and sympathetic 0.1 Hz BP oscillations: the sympathetic blockade lowered CBFV values at baseline and during 0.1 Hz NS-induced sympathetic activation, and also reduced 0.1 Hz CBFV spectral powers at baseline and during sympathetic activation (P<0.05).…”

Method of estimation of synchronization strength between low-frequency oscillations in heart rate variability and photoplethysmographic waveform variability

“…However, it is important to consider that PPG signal contains information about both peripheral blood flow (including microcirculatory bloodstream) and distal arterial bed [29]. It could explain showings of central neural regulation in peripheral blood flow detected by some authors [30]. Systolic oscillations of blood filling analyzed using PPG signals are similar, but not identical, to the oscillations in BPV in large arteries and to the HRV oscillations [31].…”

Effects of antihypertensive treatment on cardiovascular autonomic control: a prospective study

“…These rhythms are observed in heart rate (HR) (4-7), blood pressure (BP) (1,2,4,5,8) and photoplethysmogram (PPG) signals (1,2,(9)(10)(11)(12). It is evident that they have both the central (3,9,13,14) and baroreflex (15,16) origin. The 0.1-Hz rhythm in HR is an estimate of combined vagal and β-sympathetic activity (17), whereas the 0.1-Hz rhythm in peripheral BP is an estimate of α-sympathetic activity (18).…”