Spontaneous rhythmic fluctuations of the cutanous blood flow in man.

Using the reflection photoelectric plethysmograph, rhythmic fluctuations of the blood flow were investigated in the human skin. Frequency and amplitude of the rhythmic fluctuations were not synchronous with those in other skin areas. They increased with increase in ambient temperature as well as local heating of the skin. On the contrary they decreased with decrease in ambient temperature as well as local cooling of the skin. A rise in the local venous pressure caused an increase in frequency. The rhythm was suppressed by a cutaneous nerve block, though the suppression was not persistent. Intravenous injection of a large amount of chlorpromazine caused a marked increase in frequency. Rhy· thmic fluctuations of the blood flow through the fingers and toes of some patients were also investigated. The results suggest that the myogenic automaticity of the vessels may be mainly involved in the rhythmic fluctuations of the blood flow through the skin, and that it may be under the influence of sympathetic nerve activity, perhaps organized at the spinal level. Spontaneous small fluctuations of the cutaneous blood flow in man have been supposed to contribute to a fine adjustment of the regional blood flow1>. However, little has been investigated on the mechanism involving the fluctuations. Intrinsic myogenic contractions of the vascular smooth muscles were confirmed by direct observations in animals by using the transparent chamber technique2>5>. It may be, therefore, worthwhile to consider the fluctuations with relation to the intrinsic myogenic contractions of the vessels. The reflection photoelectric plethysmograph is a useful device to detect blood flow change in the human skin and by using the instrument the authors found the rhythmic fluctuations of the cutanecus blood flow of the ear lobe to be not synchronous with those in the opposite ear lobe'>. This suggests that although the cutaneous blood vessels are highly innervated organs contraction of the vascular smooth muscles is not wholly dependent on the integrated nerve discharges to the vessels. The present work, hence, was undertaken to study the features of the rhythm and to determine whether the nerve impulses could have an im:JK m ~:X. l~*~:.t:!l!B Recieved for publication November 14, 1966.