Simultaneous assessment of blood flow in UVB-inflamed human skin by laser Doppler flowmetry and the 133-xenon cashout technique

The purpose of the study was to compare skin bloood flow by laser Doppler flowmetry (LDF) and the 133-Xenon washout technique in UVB-inflamed human skin. Six healthy subjects participated in the study. Forearm skin blood flow was measured prior to irradiation and then 8, 24, 48 and 72 h the exposure to twice the minimal erythema dose of UVB. Baseline blood flow as measured by the 133-Xenon washout metod was 5,2(range 3,0 to 10,4) ml/100g/min and LDF flux was 3,1 (range 2,7 to 5,7) arbitrary units. Following irradiation, maximum blood flow increase as evaluated by the 133-Xenonwashout was 10,8 (95% confidence interval 3,7 to 11,3) time baseline blood flow, corresponding to an absolute blood flow of 47,5 (range 33,8 to 56,3) ml/100g/min. Maximum increase after induction of inflammation as assessed by LDF was 34,6 (95% confidence interval 24,6 to 56,5) times baseline flux. The two metods showed comparable time courses in al subjects. A significant correlation between the two methods was found, Spearman's rho = 0,54, p = 0,006. The relative LDF blood flow increase was 4,2-fold (95% confidence interval 2,7 to 5,0) greater than the increase measured by the 133-Xenon washout method. These results are at variance with previous comparative studies of the two methods. Som explanations are discussed.