Ultrasonic Doppler fetal heart center principle;
Doppler effect is an important physical phenomenon of ultrasound. When continuous wave ultrasonic waves are emitted, when there is relative motion between the sound source and the measured object, Doppler effect will occur. When the moving target moves to the sound source, the wavelength of the reflected wave is compressed, so the frequency increases; On the contrary, when the target is far away from the sound source, the wavelength of the reflected wave becomes longer, so the frequency decreases in unit time.
Advantages of ultrasonic Doppler fetal heart rate;
Ultrasonic Doppler technology can be used in obstetrics and gynecology to check and diagnose the heartbeat of heart and valve, blood flow and fetal heart beat. Because it is safe and harmless to pregnant women and fetuses, it can be checked repeatedly, diagnosed accurately and used conveniently, so it is widely used.
How to choose an ultrasound Doppler fetal desire How to choose an ultrasound Doppler fetal desire is a quite technical problem. In addition to paying attention to brands and consulting shopping guides, everyone should also know the basic knowledge of ultrasound Doppler fetal desire in advance.
1, depending on the specifications.
The maximum comprehensive sensitivity of ultrasonic Doppler fetal heart rate is greater than 90db according to national standards, and the high-quality Doppler fetal heart rate is generally greater than 100d b, indicating the signal amplification ability. According to the national industry standard, the frequency deviation is 10%, while the high-quality Doppler fetal heart rate deviation is 5%.
2. Look at the interface quality.
If the quality of the connecting line and interface between the host computer and the probe is not well designed, it is easy to fail. Durable maintenance-free wire should be an important index for choosing Doppler fetal heart.
3. Selection of probe (i.e. sensor)
Ultrasonic Doppler fetal heart probe determines the high sensitivity detection of fetal heart sounds, pregnant women's uterine pulse sounds, umbilical blood flow sounds, placental blood flow sounds and other parameters from early pregnancy to labor. Under normal circumstances, the probe frequency is 2MHz lower and the depth sensitivity is high, which is used for pregnant women with large months; 3MHz high frequency, high surface sensitivity, used for abortion pregnant women.
4. Power supply used
The power sources used are AC and AC /DC. The latter is generally equipped with rechargeable batteries, which can work for a long time after charging once. There are two kinds of batteries, namely, Ni-MH battery with large capacity and no memory, and Ni-Cd battery with small capacity and short life with memory.
5. Display mode of fetal heart rate value
Whether the fetal heart rate can be directly displayed, if so, is convenient for doctors to diagnose quickly and improve efficiency and accuracy. Doppler fetal heart rate display includes liquid crystal display and digital display.
6. Speakers
A sound box with good sound effects can ensure that high-fidelity output effects can be extracted from the matrix.
How to use Doppler fetal heart rate How to use Doppler fetal heart rate is a question that many pregnant women will ask. In fact, the general fetal heart rate has instructions, and pregnant women can do it according to the instructions. The usage of Doppler fetal heart rate is generally as follows:
First of all, when listening to the fetal heart, expectant mothers need to find a quiet environment where they can lie flat, lift their heads slightly, straighten their legs and relax. After lying flat, the fetal heart will be closer to the abdominal wall and closer to the fetal heart probe, making it easier to listen to the fetal heart.
Then apply coupling agent, olive oil or skin care oil, because ultrasonic waves are easily lost in the air. The role of coupling agent is to squeeze out the air in the pores of the skin and make the probe closely contact with the skin.
Second, look for the location of the fetal heart. Before the first use, open the cover of the fetal heart battery and put in the battery. You can plug the earphone into the earphone hole of the host computer, or you can listen directly. Put the probe close to the abdominal wall and use a little elasticity to prevent the air between the probe and the abdomen from making noise.
Finally, listen to the fetal heart. Find the correct position of the fetal heart, after hearing the baby's steady and continuous fetal heart sound, rest for a while, and let the fetal heart probe receive the steady and continuous fetal heart signal. At this time, the displayed value is desirable. Generally, every time you listen to 1-2 minutes, the number of fetal heartbeats is calculated as 1 minute, and 120- 160 beats/minute is the normal range.
Does Doppler fetal heart rate affect the baby? Doppler fetal heart rate is mainly used as an instrument for fetal heart monitoring, mainly used for the diagnosis of heart, blood vessels, blood flow and fetal heart. General maternity hospitals provide fetal heart monitoring, so Doppler fetal heart generally does not affect the baby.
However, it should be noted that the principle of Doppler fetal heart rate is to listen to fetal heart beat through sound waves, and sound waves are a physical factor and energy, so there is a problem of safe dose. Whether ultrasound is harmful to human body or fetus depends on the dose of ultrasound, which is also called threshold safe dose. That is to say, when the ultrasonic dose used is less than this value, it is harmless, otherwise it may have harmful effects or damage. Therefore, when purchasing Doppler fetal heart rate, you must choose products with certification certificates.