What Is a Prenatal Monitor?

Chinese name: Fetal monitor
Principle: Ultrasound Doppler principle

The main structure: Fetal heart rate recorder and uterine contraction recorder
Tracing: Fetal heart activity pattern

Fetal Monitor Product Brief

A fetal monitor provides continuous monitoring, display, and recording of fetal heart rate (FHR), as well as prenatal uterine function (UA) testing and monitoring. This device may only be used by trained healthcare personnel in hospitals, clinics, clinics, and patients' homes.

Fetal Monitor Product Uses

The fetal monitor is a non-invasive prenatal monitoring system. It displays the abdomen contractions and fetal heart rate through waveforms and charts, and can record the data on a strip chart recorder. This data can be helpful in assessing the health of the fetus before the childbirth (stress test). Use of this device is restricted to trained medical personnel in hospitals, clinics, clinics, and patient homes.

Fetal Monitor Product Features

Monitoring data can be continuously or intermittently recorded on the strip chart recorder as required by the operator. The recorded information includes chart trend data and monitor software and hardware status information, time and date, patient number, operation setting changes, and patient and clinician event markers.

Fetal Monitor Details

Physical properties

Dimensions-9.6 cm high x 32.6 cm long x 27.6 cm wide

Weight-approx. 5.5 kg

Complies with EN60601-1, EN60601-1-1, En60601-2

Electrical category: Type I BF

Can work continuously

Dop / UC sensor: IPX8 [Waterproof rating]

power supply

Power consumption	Internal power
	Rechargeable Ni-MH battery
	The monitor is fully charged within 14 hours of use;
	Fully charged for 8 hours when the monitor is off;
	Battery specifications: 1.2V × 12
	Input: AC (100-240V), 50 ~ 60Hz, 1.2A
	Output: DC (18V), 2.5A
	200VA

surroundings

Operating temperature:	10 ° C to 40 ° C (50 ° F to 104 ° F)
stored temperature:	20 ° C to 60 ° C (4 ° F to 140 ° F)
Relative humidity:	20% to 90% non-condensing
Altitude:	0-3048 meters (0-10,000 feet)

Doppler ultrasound (FHR) monitor

ISATA @ Transducer Face	1.95 mW / cm ²
Entrance beam dimension	8.54865 cm ²
Center frequency	0.985 Mhz
Pulse duration	128 sec
Pulse repetition frequency	3472 Hz
Measurement uncertainty for ISATA	+/- 19%
Measurement uncertainty for ultrasonic power	+/- 19%
Measurement uncertainty for center frequency	+/- 4.5%

Basic parameters	Value
Incident wave size:	22mm
Pulse duration:	99.65625s
Pulse repetition frequency:	3.2 KHz
Heartbeat range per minute:	30 240 heartbeats per minute
Accuracy:	The fetal heart rate is within the range of 30 to 100 beats / minute, and the error is not greater than ± 2%;
	Fetal heart rate in the range of 100 to 240 beats / minute, the error is not greater than ± 2 beats / minute
Patient leakage current:	normal status	DC0.01mA
		AC0.1 mA
	Single fault state	DC0.05mA
		AC0.5 mA
	Application part screening voltage: 5mA
insulation:	> 4 KV RMS, BF type

Delivery tension / uterine function delivery monitoring

parameter
TOCO range:	0-99 relative units
Resolution:	1 Count
Accuracy:	± 1% relative unit
Leakage:	<10 A @ 264 VAC applied to transducer
insulation:	> 4 kV RMS, Type BF applied part

ECG drawings

type of packaging:	Z-folding paper
Package dimensions:	150 mm x 90 mm x 15 mm
Packaging seal:	Seal marks along the edges of the paper
Loading paper:	Open the recorder tray and slide the paper in
Paper detection:	Paper output
Paper detection:	Tray open

Paper speed

Normal: 1,2, and 3 cm / min ± 1%

High speed: 10 cm / min (only in trend mode)

Paper tracking accuracy: ± 1% (excluding paper accuracy)

Fetal monitor Doppler fetal monitor

Doppler fetal instruments are mainly used to provide continuous monitoring, display and recording of fetal heart rate (FHR), as well as prenatal uterine function (UA) testing and monitoring. General maternity hospitals provide fetal monitoring. These fetal heart rate monitors use ultrasound Doppler technology, so they are also called Doppler fetal monitors. Fetal heart rate monitoring purposes: To monitor whether the fetal movement is abnormal. Take appropriate action. Examination time: after 28 weeks of pregnancy Examination object: fetal movement abnormality / normal pregnant woman fetal heart monitoring fetal heart rate is regulated by sympathetic and parasympathetic nerves, and the signal of the monitoring pattern formed by the instantaneous fetal heart changes can be used to understand the The response of the fetal heart during contractions to speculate whether the fetus in the uterus is hypoxic. Normal pregnancy is performed weekly from the 37th week of pregnancy. If there are comorbidities or complications, it can be performed from the 28th to 30th week of pregnancy. Attention should be paid to whether the rhythm of the fetal heart sounds is fast or slow. Normal fetal heart sounds are 120 to 160 beats per minute. If the fetal heart sounds are more than 160 beats per minute or continue for 100 beats per minute, it means that the fetus is hypoxic. Treat promptly. The manifestation and cause of abnormal fetal heart rate The normal heart rate of the fetus is between 120 beats / min to 160 beats / min. If the fetal heart rate lasts for more than 10 minutes or> 160 points, it indicates that the fetal heart rate is abnormal. The application of the fetal heart rate monitor has become more popular. When the fetal heart rate is in care, it is found that the fetal heart rate is abnormal, and it is often used to indicate the abnormality of the fetal heart rate. In most cases, fetal heart abnormality indicates that the fetus has hypoxia in the uterus. The more severe the fetal heart abnormality, it usually means that the fetal hypoxia is also more severe, but not all fetal heart abnormalities are caused by hypoxia. In addition, the condition of the pregnant woman also affects the change of the fetal heart rate. For example, if the pregnant woman has a fever, the fetal heart rate often exceeds 160 beats per minute. The pregnant woman has hyperthyroidism, her own heart rate is fast, and the fetal heart rate often exceeds 160 beats per minute. If pregnant women take certain medications, such as Shuchuanning when preterm delivery is used, or atropine, it can cause the heart rate of mothers and children to increase. Slow fetal heart rate may be caused by fetal hypoxia, but sometimes pregnant women take certain drugs, such as propranolol, which affect the fetus through the placenta, causing the fetal heart rate to slow. When the fetal heart rate continues to be slow, you should pay attention to check whether the fetus has congenital heart disease. In addition, after 40 weeks of pregnancy, due to the development of the fetal nervous system, the fetal heart rate can sometimes be less than 120 times / Therefore, when there is abnormal fetal heart, it is necessary to carefully analyze the situation and make correct judgments and treatments. If there is indeed a fetal hypoxia, it should be delivered early.

Fetal monitor Doppler effect

: The wavelength of the radiation changes due to the relative movement of the light source and the observer. In front of a moving wave source, the wave is compressed and the wavelength changes

Shorter, the frequency becomes higher (blue shift). Behind the wave source of motion, the opposite effect occurs. The wavelength becomes longer and the frequency becomes lower (red shift). The higher the velocity of the wave source, the greater the effect. According to the red / blue shift of the light wave, the speed of the wave source moving in the observation direction can be calculated. The displacement of a star's spectral line shows how fast the star is moving in the direction of observation. Unless the speed of the wave source is very close to the speed of light, the degree of Doppler shift is generally small. All wave phenomena (including light waves) have a Doppler effect.

Fetal monitor ultrasound Doppler

According to the ultrasound Doppler principle and fetal cardiac current changes, the fetal heart rate recorder and uterine contraction recorder are the main structures that can be used to describe the fetal heart movement pattern measuring instrument. There are two types of monitoring: intrauterine monitoring (internal monitoring) and abdominal wall monitoring (external monitoring). When monitoring the abdominal wall, the mother takes the supine position, and the probe is placed on the abdominal wall of the mother for drawing. This method is simple, safe and widely used. Intrauterine monitoring requires the catheter or electrode plate to be placed into the uterine cavity through the cervical canal. Therefore, it must be performed when the cervix is opened or the membrane has been broken. The catheter can only be used once, the cost is higher, the operation is more complicated, and it causes The possibility of infection, but intrauterine surveillance is less affected by external interference than abdominal wall surveillance, so there are fewer false positives. Fetal monitoring is often applied before or during high-risk pregnancy. It can continuously monitor the change of fetal heart rate and its relationship with uterine contraction, understand the fetal intrauterine condition, and detect fetal distress early.

Fetal Heart Rate-Contractions (FHR-UC)

Including the following:

Baseline fetal heart rate (BFHR) The fetal heart rate recorded during or without contractions can be analyzed in terms of fetal heart rate per minute (bpm) and fetal heart rate variability. The baseline of normal fetal heart rate fluctuates between 120 and 160 bpm with small periodic fluctuations ranging from 10 to 25 bpm. This is called the baseline swing (Figure 3), which indicates that the fetus has a certain reserve capacity and is fetal health. Performance. The abnormal fetal heart rate patterns are as follows: The baseline of the fetal heart rate is flat or stationary, and the swing amplitude is below 10 bpm, which indicates that the fetal reserve capacity is low, or the fetus is hypoxic, or affected by sleep and sedative drugs. The baseline variation increased, and the swing range was 25-30 bpm or more, reflecting the imbalance of the fetal autonomic nervous system, such as blocked venous circulation, and reduced blood volume to the heart. Makes heart rate compensatory faster. It is an early manifestation of fetal distress. Accelerated heart rate, fetal heart rate> 160bpm, lasting more than 10 minutes, is an early manifestation of fetal distress. Bradycardia, fetal heart rate <120bpm, is a sign of fetal distress, and severe bradycardia is often a manifestation of fetal death.

Periodic change in fetal heart rate with contractions (PFHR)

There are the following: Acceleration refers to the acceleration of fetal heart rate caused by fetal movement or contractions. The range of fetal heart rate increase after normal uterine contraction is 15-20 bpm for more than 15 seconds. This indicates that the fetus has a good sympathetic response to the cardiovascular system. The acceleration that occurs during childbirth often has no pathological significance. Deceleration, divided into early, variable and late deceleration. Early deceleration means that the slowing of the fetal heart rate occurs at the same time as the contraction of the fetus, the lowest point of the decline of the fetal heart rate is the peak of the contraction, and the fetal heart rate returns to normal at the end of the contraction, with a change of <40bpm. Mostly due to fetal head compression, temporary reduction in cerebral blood flow, no pathological significance (Figure 4). If the fetal heart rate drops <80bpm and recurs, it may be related to umbilical cord complications (around the neck). Variable deceleration means that there is no consistent relationship between deceleration and contractions, and the fetal heart rate drops significantly, often <100bpm, with a large amplitude (60-80bpm), long duration, and rapid recovery. Most people think that the compression of the umbilical cord excites the vagus nerve. Late deceleration means that the fetal heart rate begins to decrease slowly after the peak of contraction, lasts for a long time, and the recovery is also slow, which is the manifestation of fetal hypoxia.

Fetal Monitor Application

The application of fetal monitor in predicting the fetal reserve capacity includes the following:

The non-excitation (load) test (NST) uses a monitor to record changes in the fetal heart rate during fetal movement without contractions to understand the fetal intrauterine reserve capacity. It is generally believed that at least three or more fetal movements in 20 minutes are accompanied by an increase in fetal heart rate (more than 15 bpm for 15 seconds), which is called NST response, indicating that the fetal condition is good. If there is no fetal movement or fetal movement during this period and insufficient fetal heart rate acceleration after fetal movement, the above values are NST non-response, and the cause should be found.

Oxytocin challenge test (OCT)

Also called contraction irritation test (CST). Monitor changes in fetal heart rate with oxytocin-induced uterine contractions. If late deceleration occurs after multiple uterine contractions, fetal heart rate variability decreases, and no fetal heart rate increases after fetal movement, which is OCT positive, indicating placental dysfunction . If fetal heart rate variability exists, fetal heart rate increases after fetal movement, and there is no late deceleration after uterine contraction, which is OCT negative, indicating that the placenta function is still good.

The above two tests can be performed in some high-risk pregnancy cases after 30 to 32 weeks. Do NST first, once a week. If there is no response, you need to find the reason to exclude factors such as fetal physiological sleep or sedative effects or pregnant women hunger. If necessary, perform OCT. If OCT is positive, it indicates that the placenta is impaired, and pregnancy needs to be ended as soon as possible.

In addition, NST false positives (no response) are more common, and negative (reactive) prediction is of great significance. Therefore, multiple monitoring is often used in clinical practice to comprehensively estimate the placental function.

Automatic analysis of fetal heart rate contractions

The perfect combination of medicine and electronics, the use of the latest electronic technology, computer technology, digital image processing technology, fetal monitoring graphics analysis and diagnostic technology, after years of arduous experiments, successfully developed real-time online computer automatic analysis technology : During the monitoring process, changes in the baseline fetal heart rate at various moments, changes in various accelerations and decelerations, changes in fine variation, changes in contractions, changes in fetal movement, and changes in blood pressure, blood oxygen saturation, and pulse heart rate of pregnant women The situation is automatically monitored online in real time, and the monitoring data is automatically analyzed and diagnosed, and the results are displayed on the screen in real time. It can also comprehensively analyze all the information of the entire monitoring at any time, give the diagnosis results and fetal scores, and print out an automatic analysis report of the fetal monitoring computer. Clinical practice proves that the accuracy of automatic analysis results is more than 95%. This patent achievement completely solves the problem that it is easy for the medical staff to monitor and difficult to diagnose, so that every medical staff can make accurate and timely diagnosis of the monitoring results. Early detection and early treatment of abnormal conditions that occur in the clinic can prevent fetal hypoxia, fetal asphyxia, and even fetal death, prevent medical disputes and accidents, and greatly improve the quality of obstetrics.

Automatic analysis report of fetal heart rate contraction