Abstract
BackgroundCold-induced vasodilation (CIVD) is known to be influenced by the ambient temperature. Frequency analysis of blood flow provides information on physiological regulation of the cardiovascular system, such as myogenic, neurogenic, endothelial nitric oxide (NO) dependent, and NO-independent activities. In this study, we hypothesized that the major origin of CIVD occurs prior to the CIVD event and investigated finger skin blood flow during the initial stage of CIVD at different ambient temperatures using frequency analysis.MethodsEighteen healthy volunteers immersed their fingers in 5 °C water at air temperatures of 20 °C and 25 °C. Finger skin blood flow was measured using laser Doppler flowmetry and analyzed using Morlet mother wavelet. We defined the time when the rate of blood flow increased dramatically as the onset of CIVD, and defined three phases as the periods from the onset of cooling to minimum blood flow (vasoconstriction), from minimum blood flow to the onset of CIVD (prior to CIVD), and from the onset of CIVD to maximum blood flow (CIVD).ResultsThe increment ratio of blood flow at CIVD was significantly higher at 20 °C air temperature. In particular, at 20 °C air temperature, arteriovenous anastomoses (AVAs) might be closed at baseline, as finger skin temperature was much lower than at 25 °C air temperature, and endothelial NO-independent activity was significantly higher and neurogenic activity significantly lower during vasoconstriction than at baseline. Additionally, the differences in both activities between vasoconstriction and prior to CIVD were significant. On the other hand, there were no significant differences in endothelial NO-dependent activity between baseline and all phases at both air temperatures.ConclusionsOur results indicated that the increase of endothelial NO-independent activity and the decrease of neurogenic activity may contribute to the high increment ratio of blood flow at CIVD at 20 °C air temperature.
Highlights
Cold-induced vasodilation (CIVD) is known to be influenced by the ambient temperature
There were no significant differences in endothelial nitric oxide (NO)-dependent activity between baseline and all phases at both air temperatures, suggesting that this activity may not be implicated in CIVD
In this study, we focused on the initial stage of CIVD of finger skin blood flow at air temperatures of 20 °C and 25 °C through wavelet analysis
Summary
Cold-induced vasodilation (CIVD) is known to be influenced by the ambient temperature. We hypothesized that the major origin of CIVD occurs prior to the CIVD event and investigated finger skin blood flow during the initial stage of CIVD at different ambient temperatures using frequency analysis. After several minutes of vasoconstriction, finger skin blood flow increases and decreases cyclically despite continuous local cooling. This behavior of the blood flow during local cooling is known as coldinduced vasodilation (CIVD) and was first reported as the “hunting response” [1]. Arteriovenous anastomoses (AVAs) may be implicated in CIVD because CIVD mainly occurs where AVAs are abundant [4], and relaxation of AVAs leads to an increase in local blood flow and tissue temperature [5]. Some reviews of several potential mechanisms and models have been published [5, 14,15,16]
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