A comparison between 133Xenon washout technique and Laser Doppler flowmetry in the measurement of local vasoconstrictor effects on the microcirculation in subcutaneous tissue and skin

Changes in skin blood flow measured by Laser Doppler flowmetry and changes in subcutaneous blood flow measured by 133Xenon washout technique were compared during activation of the local sympathetic mediated veno-arteriolar vasoconstrictor reflex by lowering the area of investigation below heart level. The measurements were performed in tissue with and without sympathetic innervation. In five subjects, who all had been cervically sympathectomized for manual hyperhidrosis, the Laser Doppler and 133Xenon blood flow measurements were performed simultaneously on the sympathetically denervated forearm, and on the calf with preserved sympathetic nerve supply. The Laser Doppler method registered a 23% reduction in skin blood flow during lowering of the extremities independently of the sympathetic nerve supply to the skin. The 133Xenon method recorded a 44% decrease in blood flow in innervated and unchanged blood flow in denervated subcutaneous tissue during lowering of the extremities. Our results indicate that the Laser Doppler method and 133Xenon method are not comparable, and that the Laser Doppler method is not useful in measuring local sympathetic mediated blood flow changes.