The mature continuous wave techniqu

The mature continuous wave technique was used to monitor blood flow velocity, direction, discharge area (csa), peak velocity, ventricular hemostasis time, flow velocity time (vti), heart rate (hr), total peripheral resistance (svr), etc., to accurately measure the hemodynamics of each heartbeat and directly reflect the blood pump function. The formula is c0xvtixcsaxhr. In continuous measurement, csa from aortic valve or lung is obtained by measuring the area of aortic valve ring or pulmonary valve ring, and vti is the blood distance of every stroke. Continuous waves use ultrasound with a frequency of 20,000Hz, which is a Doppler form of continuously emitting sound waves, especially when they emit sound waves, they receive Doppler shift sound waves reflected by each red blood cell. The accuracy of monitoring blood flow velocity, signal intensity and angle of measuring blood flow direction by continuous wave technique is closely related to the soft tissue encountered by continuous wave. It can be seen that when the beam is parallel to the blood flow direction and the angle is 0 degrees, the measured speed is the most accurate; When the beam is perpendicular to the blood flow direction, the measured velocity is zero. When the ultrasonic waves hit the air, the light beam is completely reflected on the probe and will not reach the blood vessels. If ultrasound is irradiated to the lungs, the air in the lungs will prevent the signal from passing through the lung valve and entering the blood flow from the probe. The monitor is full of noise, which makes it impossible to distinguish typical waveforms from sound signals. When ultrasonic waves hit bones, such as ribs or sternum, the beams are completely absorbed by bones, unable to penetrate, unable to reach red blood cells, unable to show spectral shapes on the display, and unable to hear classical sound signals. When ultrasound encounters thick adipose tissue, the intensity of beam signal is greatly reduced, but the reduced beam can still reach red blood cells. The monitor can see the typical frequency spectrum and hear the sound signal, but the intensity will decrease. Therefore, in practice, we should try to keep the bundle parallel to the blood flow direction, avoid the lungs, bones and excessive fat, and make the test results more accurate.