实验用鼠 z-bo 2020-08-13 545

　　In the past 20 years, research scientists have been looking for more precise non-invasive methods for measuring blood pressure in mice or rats. More precise non-invasive methods to measure rodents' systolic blood pressure, diastolic blood pressure, heart rate, and other blood flow parameters are very valuable for clinical research.

　　1. Invasive method to measure 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 is measured from the carotid artery of the animal.

　　It is also very reliable and accurate to measure blood pressure using telemetry, and it is also used to evaluate the authenticity of non-invasive blood pressure. This method measures non-invasive blood pressure by burying an implant in the animal's body. The blood pressure of the animal measured by this method has a great correlation with the blood pressure measured by the direct method.

　　The advantage of the telemetry method is that researchers can monitor the blood pressure of free animals for a long time in the experiment.

　　But the telemetry method to measure blood pressure also has its disadvantages:

　　1. When the implant is initially implanted in the animal, the surgical operation will affect the animal's physical condition.

　　2. The battery life of the sensor is relatively short. If you need to monitor the blood pressure of the animal for a long time, you need to replace the implant battery.

　　3. Especially for mice, if the sensor is relatively large or heavy, it will have a greater impact on the physical state of the mice.

　　4. The current technology (signal transmission and reception) requires that the implanted mice be separated from other mice, each mouse has a squirrel cage, which affects the normal social activities of the mice and destroys their normal Life habits.

　　5. The telemetry method cannot make large-scale measurements.

　　6. The normal maintenance costs of measuring instruments, transducers and instruments are very expensive.

　　7. Need to waste a lot of manpower and material resources.

　　8. Due to the lack of sufficient competition in this field, the prices of products and services are very high.

　　2. Non-invasive method to measure blood pressure

　　This method of measuring blood pressure is roughly like this. The blood flow of the rat’s tail is blocked by an air bag placed at the base of the tail of the rat, and then the air bag is deflated a little bit. At the same time, a photoelectric or piezoelectric pulse sensor is placed on the tail of the rat, The combination of the two measures blood pressure.

　　There are currently three types of non-invasive blood pressure sensors: photoelectric method, piezoelectric method and volume pressure recording method.

　　1. Photoelectric method

　　This is the earliest and most primitive light-based method. The purpose of the sensor is to record the first and last pulse when the cuff is deflated. He uses incandescent lamps or light-emitting diodes to illuminate the tail of the rat to record pulse signals.

　　The photoelectric method is inaccurate in measuring non-invasive blood pressure because it records by sensing the amplitude of the pulse, and can only be used to roughly measure systolic blood pressure and heart rate. This method has many limitations:

　　(1) If the light in the environment is very strong and sufficient, the light capacity of the rat tail will reach saturation.

　　(2) Animal activities are more sensitive to changes in light

　　(3) Especially for animals with darker skin, it is more difficult to obtain pulse signals well.

　　(4) Since the light source is close to or even touching the tail of the rat, the animal will have a burning sensation.

　　The photoelectric method cannot measure the animal's diastolic blood pressure. Because he can only record the first pulse, his diastolic blood pressure is calculated by software instead of the actual measurement value.

　　The length of the occlusion cuff is also a cause of data errors or instability. The length of the occlusion cuff is inversely proportional to the accuracy of blood pressure. In most non-invasive blood pressure measurement devices using photoelectric methods, the longer the occlusion cuff is, the lower the blood pressure value is than the true value.

　　These limitations seriously affect the accuracy, stability and consistency of the photoelectric method for measuring non-invasive blood pressure.

　　The photoelectric method for measuring non-invasive blood pressure has little correlation with invasive blood pressure, and is the least recommended for non-invasive blood pressure measurement in rodents, especially mice.

　　2. Piezoelectric method to measure non-invasive blood pressure

　　The second non-invasive blood pressure measurement method is the piezoelectric method. He also obtained the systolic blood pressure and heart rate by obtaining the animal's first pulse 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 the pulse signal, and the piezoelectric method uses a piezoelectric ceramic chip to obtain the pulse signal. Generally speaking, the piezoelectric method has higher sensitivity than the photoelectric method, because it obtains the signal by measuring the frequency of pulse changes, while 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 limitation makes him produce wrong results during the measurement process. However, one thing is certain is that when the piezoelectric method is used to measure non-invasive blood pressure, The skin pigment of rodents does not affect the results.

　　Although the piezoelectric method is better than the photoelectric method, the non-invasive blood pressure measured by the two methods has a poorer correlation with the invasive or remote measurement.

　　3. Volume pressure recording method

　　The third method is the volume pressure recording method. This volumetric pressure sensor uses a specially designed differential pressure sensor to non-invasively measure blood pressure in the tail of the rat. The American Kent company has a utility patent for this technology. The volumetric pressure recording method can truly measure 6 parameters related to animal blood pressure: systolic blood pressure, diastolic blood pressure, mean blood pressure, heart rate, rat tail blood volume and blood flow.

　　Because the volumetric pressure recording method uses the method of measuring the volume to obtain the blood volume and blood flow, the ambient light will not interfere with the measurement, and the mobile interference will be minimized. In addition, the volumetric pressure recording method does not rely on animal skin pigments, so dark-skinned animals will not have any influence on the measurement. The blood pressure of 10g black mice can be easily measured by volume pressure recording method.

　　We have accurately calculated the length of the blood flow occlusion loop to make the blood pressure value closer to the true value.

　　The volume pressure recording method can reliably, consistently and accurately measure mice and rats from 10g to 950g.

　　An independent clinical laboratory research report conducted by Yale University in 2003 showed that the volumetric pressure recording method has a 99% correlation with the pressure measured by the direct method.

　　The volume pressure recording method can obtain consistent, accurate and reliable results whether it is to measure the non-invasive blood pressure of awake animals or anesthetized animals.

　　And if a large number of animals need to be measured, this system is more efficient and inexpensive. It is necessary for the experiment to practice more and be able to manipulate animals well and skillfully. Training the animals before the experiment or monitoring the body temperature of the animals during the experiment is very beneficial for the experiment.

　　The volume pressure recording method has the highest correlation with the blood pressure value measured by remote or direct measurement, and it is the most suitable rat tail measurement method.

　　The volume pressure recording method 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 experiment.

　　(4) In long-term research, it can provide researchers with consistent, accurate, animal blood pressure.

　　Experimental conditions for non-invasive blood pressure measurement

　　Rodent restraint

　　The ideal animal restraint can make the animal feel more comfortable when restricting the animal's behavior, cause less stress to the animal, and enable the researcher to continuously observe the animal's behavior. Experience has shown that a trained mouse or rat can stay in a suitable restraint for several hours more comfortably.

　　It is very useful to add a black tapered nose sleeve to the animal restraint, which can restrict the animal's field of vision and reduce the animal's sense of oppression. The tapered nose sleeve can make the animal's nose stick out of the restraint, so that it can breathe more freely and comfortably. The tail of the animal can be fully exposed through the opening on the back cover of the restraint.

　　In the blood pressure measurement process, the size of the animal restraint is very critical. If the restraint device is too small, the free space in which the animal is located is too small, which will restrict the animal's free breathing. The animal will stretch its body for smooth breathing, and the rat's tail will swing, which will affect the blood pressure measurement.

　　Control of animal body temperature

　　A non-invasive blood pressure measurement system must consider heating the animal more comfortably, minimize the animal's pressure, and ensure the blood flow of the rat's tail.

　　The temperature of the animal's body is very important for accurate and continuous blood pressure measurement. The tail of the tested animal 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's tail, thereby achieving the purpose of lowering the body's temperature.

　　The body temperature of the animal under anesthesia is lower than that under the awake state, so measures must be taken to maintain a proper temperature of the animal's body. Commonly used are infrared heating method or circulating water bath heating method. It is best for animals to feel comfortable when heating, and not overheating.

　　It is not advisable to raise the animal's body temperature through an air heating chamber, a heating lamp, or a heating platform that directly heats the animal's feet. These types of heating devices make the animal's local body temperature too high, increase the animal's breathing rate, and increase the animal's stress. These conditions will cause the animal to produce a temperature-regulating response, resulting in unstable and unreliable pressure records.

　　Ambient temperature

　　When measuring animal non-invasive blood pressure, the temperature of the environment is also very important. The temperature in the laboratory should be 26 degrees or above. If the ambient temperature in the laboratory is too low, for example, lower than 22 degrees, the animal's self-regulation will not be effective, and the blood flow of the rat tail will be reduced, so that the blood pressure signal of the rat tail will be difficult to obtain. Keep the animal in a cooler place. Measuring blood pressure on the metal plate is very inappropriate.

　　Animal preparation

　　The animal should be allowed to stay in a suitable restraint for 10 to 15 minutes before conducting the experiment. Animals familiar with the environment can get blood pressure results faster. Correct animal handling is also very important to obtain consistent and accurate blood pressure. A nervous and stressed animal has smaller tail circulation than normal.

　　Most rodents can adapt quickly in small, black, confined, comfortable environments. But some researchers prefer to train animals before experiments. Train for 15 minutes a day for three days.

　　During the experiment, the animal will climb into the restraint by itself. After the animal enters, adjust the position of the nose cover so that the animal cannot move excessively, but keep its state more restrained. Under normal circumstances, the animal will stay in the restraint relatively honestly, and will not turn its head to one side or twist its body. The animal's body temperature should be monitored during the experiment.