In the past 20 years, research scientists have been searching for more precise methods for non-invasive measurement of blood pressure in mice or rats.  More precise non-invasive methods for measuring systolic blood pressure, diastolic blood pressure, heart rate, and other blood flow parameters in rodents are valuable for clinical research.  Invasive method for measuring blood pressure  Invasive blood pressure is the gold standard for evaluating non-invasive blood pressure. When evaluating non-invasive blood pressure, the measurement of invasive blood pressure was measured from the carotid artery of the animal.  The use of telemetry to measure blood pressure is also very reliable and accurate, and it is also used to evaluate the authenticity of non-invasive blood pressure. This method measures non-invasive blood pressure by burying the implant in the animal. The blood pressure of the animal measured by this method is highly correlated with the blood pressure measured by the direct method.  The advantage of the telemetry method is that the researchers can monitor the blood pressure of free animals for a long time in the experiment.  However, the telemetry method also has its shortcomings in measuring blood pressure: 1) When the implant is initially implanted into an animal, the surgery has an effect on the animal's physical condition. 2) The battery life of the sensor is relatively short. If it is necessary to monitor the blood pressure of the animal for a long time, it is necessary to replace the implanted battery. 3) Especially for mice, if the sensor is relatively large or of high quality, the effect on the body state of the mouse will be greater. 4) The current technology (signal emission and acceptance) needs to be implanted in the implanted mouse separately from the other mice, a mouse and a rat cage, which affects the normal social activities of the mouse, destroying its normal Living habits. 5) The telemetry method cannot perform large-scale measurements. 6) The normal maintenance costs of the instrument, whether it is a measuring instrument or a transducer, are very expensive. 7) It takes a lot of manpower and material resources to waste. 8) In this area, the price of products and services is very high due to lack of sufficient competition.  Noninvasive method for measuring blood pressure  This method of measuring blood pressure is probably such that the blood flow of the rat tail is blocked by a balloon placed at the base of the rat tail, and then the balloon is deflated a little, while a photoelectric or piezoelectric pulse sensor is placed at the end of the rat. The blood pressure was measured by the combination of the two. There are currently three non-invasive blood pressure sensors: photoelectric method, piezoelectric method and volumetric pressure recording method.  1). Photoelectric method  This is the earliest and most primitive method based on light. The purpose of the sensor is to record the first and last pulse when the cuff is deflated. He uses an incandescent lamp or LED to illuminate the rat tail to record the pulse signal.  Photoelectric measurement of non-invasive blood pressure is inaccurate because it is recorded by sensing the amplitude of the pulse and can only be used to measure systolic blood pressure and heart rate in a poor manner. This method has many limitations: 1) If the light of the environment is strong enough, the light capacity of the rat tail will be saturated. 2) Animal activity is sensitive to changes in light 3) Especially for animals with darker skin, it is more difficult to obtain pulse signals. 4) The animal will have a burning sensation because the light source is closer to the tail of the mouse or even in contact with the rat tail.  Photoelectric method is unable to measure the diastolic blood pressure of animals. Because he can only record the first pulse, his diastolic pressure is calculated by software rather than the actual measurement.  The length of the occlusion cuff is also a cause of data error or instability. The length of the occlusion cuff is inversely proportional to the accuracy of the blood pressure. In most optoelectronic methods of measuring non-invasive blood pressure, the longer the occlusion cuff, the lower the blood pressure value is than the actual value.  These limitations severely affect the accuracy, stability, and consistency of non-invasive blood pressure measurements by optoelectronic methods.  Photoelectric measurement of non-invasive blood pressure has little correlation with invasive blood pressure and is the least recommended one among non-invasive blood pressure measurements in rodents, especially mice.  2). Piezoelectric measurement of non-invasive blood pressure  The second non-invasive blood pressure measurement method is the piezoelectric method. He also obtained systolic blood pressure and heart rate by obtaining the first pulse of the animal during deflation. This is the same as the photoelectric method for measuring non-invasive blood pressure.  Like the photoelectric method, they have common limitations. The photoelectric method uses light to obtain a pulse signal, and the piezoelectric method uses a piezoelectric ceramic wafer to obtain a pulse signal. In general, the piezoelectric method has higher sensitivity than the photoelectric method because it obtains the signal by measuring the frequency of the pulse change, and the photoelectric method obtains the signal by the amplitude of the pulse. Therefore, even a mouse sensor with a very high heart rate can perceive a good signal.  The non-invasive blood pressure measured by the piezoelectric method is more accurate than the photoelectric method, but the same technical limitations make him produce the same erroneous results in the measurement process, but one of the positive aspects is that when the non-invasive blood pressure is measured by the piezoelectric method, Skin pigmentation in rodents does not affect the outcome.  Although the piezoelectric method is better than the photoelectric method, the non-invasive blood pressure measured by the two methods is less correlated than the invasive or telemetry.  3). Volumetric pressure recording  The third method is volumetric pressure recording. This volumetric pressure sensor uses a specially designed differential pressure sensor to measure blood pressure non-invasively at the end of the rat. Volumetric pressure recording method can truly measure six parameters of animal blood pressure: systolic blood pressure, diastolic blood pressure, average pressure, heart rate, rat tail blood volume and blood flow.  Because the volumetric pressure recording method uses the method of measuring volume to obtain blood volume and blood flow, the ambient light does not interfere with the measurement, and the movement interference is also minimized. Moreover, the volumetric pressure recording method does not depend on the animal's skin pigmentation, so dark-skinned animals do not have any influence on the measurement. The blood pressure of 10 g of black mice can be easily measured by volumetric pressure recording. Animal non-invasive blood pressure measurement technology  We performed an accurate calculation of the length of the blood flow occlusion ring to bring the blood pressure value closer to the true value.  Volumetric pressure recording is a reliable, consistent and accurate measurement of mice and rats from 10g to 950g.  In an independent clinical laboratory study conducted by Yale University in 2003, the volumetric pressure recording method was 99% correlated with the pressure measured by the direct method.  “The volumetric pressure recording method is very good. It is very accurate and reliable. We conducted a comparative experiment on temperature-controlled adult rats. The results show that this method has a perfect correlation with the results obtained by direct measurement methods. We are very satisfied with its results.  The accuracy, reliability and stability of this method have been confirmed in numerous research journals.  Rodent restraint  The ideal animal restraint can make the animal feel more comfortable when it restricts the behavior of the animal, the pressure on the animal is relatively small, and the researcher can continuously observe the behavior of the animal. Experience has shown that a trained mouse or rat can stay comfortably in a suitable restraint for up to several hours.  It is useful to add a black conical nosepiece to the animal restraint, which limits the animal's field of view and reduces the animal's oppression. The conical nose sleeve allows the animal's nose to extend outside the restraint so that it can breathe freely and comfortably. The animal's tail can be completely exposed through the opening in the back cover of the restraint.  In the blood pressure measurement process, the size of the animal binder is critical. Too small a restraint will cause the free space of the animal to be too small, which will limit the free breathing of the animal. The animal will stretch its body in order to breathe smoothly, and the rat tail will swing, which will affect the blood pressure measurement.  Animal body temperature control  A non-invasive blood pressure measurement system must consider the heating of the animal more comfortable, minimize the pressure on the animal, and ensure the blood flow of the rat tail.  The temperature of the animal's body is very important for accurate and continuous measurement of blood pressure. The tail of the animal to be tested must have sufficient blood flow to obtain a blood pressure signal. When the animal's body temperature is relatively high, it will release heat by increasing the blood circulation of the rat tail, thereby achieving the purpose of lowering the body temperature.  Animals have lower body temperature under anesthesia than awake, so measures must be taken to maintain the proper temperature of the animal's body. Commonly used are infrared heating or circulating water bath heating. Allow the animal to feel comfortable in the best condition when heated and not overheat.  It is not advisable to heat the animal's body temperature by heating the chamber, heating the lamp, or directly heating the heating platform of the animal's foot. These types of heating devices can cause excessive local body temperature in the animal, increase the respiratory rate of the animal, and increase the pressure on the animal. These conditions can cause the animal to develop a temperature-regulating response, resulting in an unstable, unreliable pressure record.  Ambient temperature  When measuring non-invasive blood pressure in animals, the temperature of the environment is also very important. The temperature in the laboratory should be 26 degrees or more. If the laboratory's ambient temperature is too low, say below 22 degrees, the animal's own regulation will not be able to achieve the effect, the blood flow of the rat tail will be reduced, so that the rat tail blood pressure signal is difficult to obtain, the animal is placed in the cooler Measuring blood pressure on a metal plate is not suitable.  Animal preparation  Animals should be allowed to stay in the appropriate restraint for 10 to 15 minutes before conducting the experiment. Animals familiar with the environment can get blood pressure results faster. Proper animal handling is also important to get consistent, accurate blood pressure. An animal with a nervous stress has a tail that has a smaller circulation than normal.  Most rodents are able to adapt quickly in small, black, confined, and comfortable environments. But some researchers also want to train animals before the experiment. Train for 15 minutes a day and train for three days.  During the experiment, the animal will climb into the restraint. After the animal enters, adjust the position of the nose so that the animal can not be excessively active, but keep the state more restrained. Under normal circumstances, the animal will stay in the restraint more honestly, and will not turn the head to one side or twist the body. The body temperature of the animals should be monitored during the course of the experiment.  in conclusion:  Volumetric pressure recording methods provide consistent, accurate, and reliable results for both non-invasive blood pressure measurements in conscious animals and anesthetized animals. Animal non-invasive blood pressure measurement technology  And if you need to measure a large number of animals, this system is more efficient and cheaper. It is necessary for the experiment to be able to operate the animal with a lot of practice and it is necessary for the experiment. It is very beneficial for the experiment to train the animals before the experiment or to monitor the body temperature of the animals during the experiment.  The volumetric pressure recording method has the highest correlation with the telemetry or directly measured blood pressure values, and is the most suitable rat tail measurement method.  Volumetric Pressure Recording Non-invasive blood pressure measurement system is the most valuable non-invasive blood pressure research tool, and it will play a greater role in more research fields. Its main advantages are: 1) non-invasive. 2) It is cheaper than other blood pressure measurement methods, such as compared with telemetry. 3) For most animals, changes in systolic and diastolic blood pressure can be seen during the course of the experiment. 4) In long-term studies, it provides researchers with consistent, accurate, animal blood pressure. Greenhouse Drip Irrigation System
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