Cutaneous venoarteriolar reflex alters 0.1 Hz fluctuations in skin blood flow

Skin blood flow (SkBF) fluctuations around 0.1 Hz are thought to be indicative of autonomic control of the cutaneous vasculature. The purpose of this study was to identify whether these fluctuations can be altered by the cutaneous venoarteriolar reflex. This reflex causes vasoconstriction via local mechanisms secondary to venous congestion. In 9 subjects SkBF was monitored on both forearms using laser-Doppler flowmetry [expressed in perfusion units (PU)]. While supine, and with both arms at heart level, each subject breathed at a rate of 0.25 Hz for 6 minutes. The venoarteriolar reflex was then engaged by lowering one arm (experimental) such that the laser-Doppler flow probe was 35±2 cm below heart level. The other arm (control) remained at heart level throughout the test. The aforementioned breathing protocol was repeated. The spectral power surrounding the low frequency peak (0.03 to 0.15 Hz) was not different between sites when both arms were at heart level (control: 652±146 PU²; experimental: 623±211 PU², P>0.05), nor was there a difference in SkBF (control: 13.3±1.7 PU; experimental: 12.5±1.4 PU, P>0.05). Engagement of the venoarteriolar reflex in the experimental arm significantly reduced SkBF (control: 11.1±1.6 PU; experimental: 5.0±0.3 PU, P<0.05) and spectral power (control: 737±173 PU²; experimental: 73±71 PU², P<0.05) in that arm. Reduced power of 0.1 Hz fluctuations in SkBF are likely due to increased vasomotor tone associated with the venoarteriolar reflex, thereby demonstrating that these fluctuations can be modified locally.