Effect of sympathetic nerve blockade on low‐frequency oscillations of forearm and leg skin blood flow in healthy humans

Abstract

Our data support that the frequency band (0.021-0.052 Hz) associated with neurogenic activity appears to be correct having a large sympathetic component.

Cutaneous vasomotor responses in boys and men

“…Additionally, wavelet analysis may be unable to delineate local and reflex sympathetic activity. While previous work has clearly demonstrated that the neural frequency band (0.02-0.05 Hz) is mostly sympathetic (Hodges et al 2017a), there is also likely to be some sensory nerve involvement. Thus, categorical statement of what the neural influences are and whether the observed effects are of local or reflex origin on cutaneous vascular control are not possible at the present time with this approach.…”

“…This method characterizes the dynamics of signals over a wide frequency D r a f t range, from 0.005 to 1.6 Hz. The six frequency intervals and associated physiological functions were as follows: 0.005-0.01 Hz (endothelial: NO-independent) and 0.01-0.02 Hz (endothelial: NO-dependent) (Kvandal et al 2006); 0.02-0.05 Hz (neurogenic) (Söderström et al 2003, Hodges et al 2017a; 0.05-0.15 Hz (myogenic) (Johnson 1989, Söderström et al 2003; 0.15-0.40 Hz (respiratory); 0.40-1.6 Hz (cardiac).…”

“…We ran the wavelet transform on a minimum of 80 min of data. While we have chosen short time windows for certain phases to extract median amplitudes of the vasodilator responses (handgrip, PORH), the fact that the wavelet was run on the entire data laser-Doppler signal ensured that even these smaller extracted portions had appropriate resolution and power to examine the low-frequency bands (Hodges et al 2017b(Hodges et al , 2017a…”

“…Data supporting the vascular oscillation centred around 0.1 Hz and termed myogenic activity is still equivocal. A sympathetic origin of these oscillations has been suggested (Stauss et al 1998, Cevese et al 2001; however, studies employing anaesthesia and skin flaps (Söderström et al 2003) and with localized sympathetic blockade (Hodges et al 2017a) have been able to uncouple the systems and distinguish separate oscillations. However, it is important to note that there has been no direct confirmation of the role of myogenic activity due to the difficulties in manipulating and measuring microvascular pressure and obtaining a flow measure simultaneously in vivo in human skin.…”

“…However, it is important to note that there has been no direct confirmation of the role of myogenic activity due to the difficulties in manipulating and measuring microvascular pressure and obtaining a flow measure simultaneously in vivo in human skin. That is why we have focused mostly on oscillations associated with D r a f t endothelial and neural activities, as these have the most evidence to support their function (Kvandal et al 2003, 2006, Hodges et al 2017a. Also, it is important to note that the frequency bins are not completely independent and caution must be exercised in making definitive statements regarding the underlying mechanisms of action.…”