PRESSURE SENSITIVITY OF FLOW OSCILLATIONS IN POSTOCCLUSIVE REACTIVE SKIN HYPEREMIA

Skin blood flow was monitored using a laser-Doppler (LD) flowmeter in 21 healthy volunteers after an occlusion of the digital arteries. The peripheral vascular bed was exposed to occlusion ischemia of varying d uration (1, 4, or 8 min) and to a change in digital arterial pressure produced by different positions of the arm above heart level to charac terize the pattern of LD flow oscillations in postocclusive reactive h yperemia (PRH) and to elucidate the relevance of metabolic and myogeni c mechanisms in governing its fundamental frequency. The descending pa rt of the hyperemic flow was characterized by the appearance of conspi cuous periodic oscillations with a mean fundamental frequency of 7.2 /- 1.5 cycles/min (SD, n = 9), as assessed by a Fourier transform freq uency analysis of 50-s sections of flow. The mean respiratory frequenc y during the periods of flow frequency analysis was 17.0 +/- 2.2 (SD, n = 9), and the PRH oscillations remained during apnea in all tested s ubjects. The area under the maximum flow curve increased significantly with prolongation of the occlusion (paired t test, P < 0.001; n = 9), but showed no dependence on the estimated blood pressure in the digit al arteries, which suggests the predominant role of a metabolic compon ent in this part of the PRH response. In contrast, the fundamental fre quency of PRH oscillations exhibited a significant decrease with a red uction in the estimated digital arterial pressure (linear regression, b = 0.08, P < 0.001; n = 12), but did not change with the prolongation of arterial occlusion despite a significant increase in mean LD flow (paired t test, P < 0.001; n = 9). These results are consistent with t he hypothesis that PRH oscillations reflect pressure-dependent vasomot ion.