Normal blood flow in the arteries of the lower limb
Last reviewed: 23.04.2024
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The picture of normal blood flow at rest
After identifying the vessels in the B-mode, examine them in the mode of color duplex sonography about the longitudinal axis and, if necessary, along the transverse. The color regime is initially used only in the region of the shin and forearm, because it allows to determine the localization and the course of the vessels. Choose pulse repetition frequency before measuring blood flow velocity. For longitudinal scanning, change the beam and select the angle of the sensor to improve the angle between the beam and the vessel and optimize the color image. Due to the high peripheral resistance, the spectra from the peripheral arteries show a typical three-phase picture of the blood flow, consisting of a steep systolic rise , a systolic peak, an inverse blood flow component ("immersion") in early diastole, direct flow to the late diastole, and presystolic zero blood flow. Note the typical constant blood flow in the eponymous vein at each stage of the cardiac cycle.
The picture of normal blood flow during exercise
The physical load leads to a decrease in peripheral resistance, which normally leads to the appearance of a two-phase spectrum that differs from the spectrum at rest in the absence of reverse flow to the early diastole, a higher level of diastolic blood flow, and a higher peak systolic rate. The physical load can consist of repeated compressions of the hand or circular movements of the foot.
The wall filter should be 100 Hz or lower, and the control volume should occupy not more than 2/3 of the lumen of the vessel in order to avoid wall artefacts. An empty spectral window) under the systolic peak is the norm, indicating the absence of slow turbulent components of the blood flow. When the stenosis appears, the window is filled. Stenosis can be quantified by analyzing spectral waves that determine the ratio of peak blood flow velocities or planimetrically on true transverse images. It is necessary to reduce the transverse region by at least 30% to determine the detected spectral changes. The indices of pulsation and resistance give little information, since they vary along with the peripheral resistance of the vessels (for example, the ripple index can vary from 3 to 30). The blood flow velocities are also different, but the peak systolic velocity should be about 100 cm / s in the thigh area and 50 cm / s in the calf region.
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