[Diagnostically relevant effect and disturbance factors in Doppler ultrasound studies of the arterial system]

For the clinical use of the Doppler-sonography besides the knowledge of evident criteria of judgment also the consideration of important sources of error and factors of influence is necessary. Functional effects of obstructions of the arterial system depend on the actual flow time volume, the elasticity of the arteries and on the peripheral flow resistance. The derivation and registration of the Doppler-signals must be performed under standardized conditions. Particularly important are multifactorial changes of the width of the vessels and of the resistance in the regions of the arterioles which influence the poststenotic pressure-flow-behaviour and the results of Doppler-sonographic measurements. Apart from the central haemodynamics the functional changes depending on age concern the elasticity of the vessels and the degree of efficacy of the muscular blood supply. Patients with hypertension react on stimuli increasing the blood supply with a smaller increase of their functionally effective cross-section of the vessels. Disturbances of the peripheral haemodynamics in diabetics are to be referred to a deficit of the tonus of sympathetic vasoconstrictors due to an autonomous and may, moreover, be regarded as vasomotor compensation mechanisms in primarily haemorheologically conditioned disturbance of the microcirculation.