Novel, high-amplitude blood-flow oscillations in vasodilating human skin

Cassandra D. Haley, Annerieke Zeyl, Nigel A.S. Taylor, Arthur B. Jenkins
2004 Journal of Thermal Biology  
Regulation of skin blood flow (Q s k) is vital to homeostasis, with adjustments to flow in response to important sympathetic thermal and non-thermal reflexes and by other factors which remain to be fully determined, but include local regulatory mechanisms (i.e. axon reflexes, release of endothelial vasoactive substances etc.). Laser-Doppler flowmetry is a well-known technique, used for assessing microvascular function, with raw Q S k traces displaying marked variability, which is in part due to
more » ... the above mechanisms, but also results from passive influences (i.e. oscillations in pressure resulting from cardiac frequency (f c ) or respiration (/"-,), alterations to local transmural pressure and turbulences in flow due to vessel structure and or the viscosity of blood). The central focus of this dissertation was an investigation and characterisation of an apparently hidden, novel Qsk phenomenon, which has not been previously reported in the literature, possibly due to traditional data processing techniques. This phenomenon encompasses high-amplitude oscillations in Q S k which were detected using laser-Doppler flowmetry in human and rat Q S k, which have a characteristic frequency of -0.4 H z , spanning -1000 ms, and consist of high-amplitude peaks, accounting for up to a seven-fold increase of basal Q S k-Experiments presented within this thesis confirm the biological nature of these oscillations, which are present in both acral and non-acral skin regions. These oscillations, increase significantly with increases in local and mean skin temperature (T S k; humans and rats Qsk; P<0.05) and m a y occur independently of core temperature. Further, these oscillations appear to be unaffected by global changes in mean arterial pressure within the normotensive range (P>0.05). Local application of anaesthetic (i.e. to remove vessel tone) attenuated these oscillations in response to whole-body heating. However, propranolol treatment (80mg; orally) produced no significant differences in the characteristics of these oscillations (P>0.05), despite producing a significant reduction in/ c (~ 10 b-min" 1 ; P<0.05). Differences in baroreceptor loading between a supine and seated posture (as reflected by a significant increase in f c of -10 b-min" 1 in the seated posture; P<0.05) produced no differences in the frequency of the high-amplitude oscillations at the forearm when recorded at heart level (~ 0.4 Hz). However, measurements at the thigh in the seated posture, displayed a significant decrease in the frequency of these oscillations (reduction of iii PUBLICATIONS ARISING FROM THIS THESIS . Investigating high-amplitude oscillations in rat tail skin blood flow during core heating and cooling. Journal of Thermal Biology. 29(7-8): 779-783. v ACKNOWLEDGMENTS Foremost I would like to thank m y supervisors Arthur Jenkins and Nigel Taylor for giving m e the chance to complete m y P h D and for the other valuable opportunities provided to me. I a m grateful to Arthur and Nigel for their help, guidance, tolerance, and generosity but mostly for their unique senses of humour, that made this process all the more pleasant. Also I a m greatly appreciative of Arthur for creating the macro that allowed m e to analyse m y data, without which I m a y never have finished this work. I would like to acknowledge Chris Gordon, Jo Caldwell, Annerieke Zeyl and Efjee Manders for their assistance, patience and friendship during the hours of data collection. Additionally, thanks to Avraham Schitzer, for his guidance with experimental analysis. A special thanks also goes to all the subjects that have endured hours of discomfort, to participate in m y studies. This work would not have been completed without the endless encouragement, support, tolerance and love of m y family and friends. T o m y friends (you know w h o you are), thanks for the runs, the dancing and all the other distractions that reminded m e that there is life and fun to be had outside of this thesis. Thanks to m y m u m Dale, for always believing in me. T o m y sisters and brothers, Rochelle, Bryce, G e m m a and Aaron, thanks for being you and always brightening m y day. Finally, a very special thank-you goes to Ben, your support, understanding and love during this time is something I will never forget.
doi:10.1016/j.jtherbio.2004.08.045 fatcat:vhznqy7nqncl5eyhkhyusyqtwe