Blood Pressure Measurement Laboratory
Blood Pressure Measurement Laboratory
Blood pressure measurement is also an important part of cardiovascular disease-related research. Currently, there are 2 commonly used methods for measuring blood pressure in mice: the noninvasive tail-cuff method and the aortic invasive telemetry method. The tail-cuff method detects blood pressure in awake mice, but requires that the mice be acclimatized to the appropriate equipment for about 1 week before measurement, and the mice are acclimatized for at least 20 minutes at a fixed time each day and measured at the same time point. The invasive aortic telemetry method can measure blood pressure in mice at any time of the day, but it is more complex compared with the former method because of the higher surgical requirements and the need to take into account the effects of the post-surgical pressure-receptive reflex cycle on the activity of the autonomic nervous system in mice. The latter is the only option for the measurement of blood pressure in mice during exercise such as running or swimming.
Operation method
Tail-cuff method for measuring blood pressure in mice
Materials and Instruments
Equipment: System mainframe, inflation and deflation controller Move The basic procedure of the tail-cuff method for blood pressure measurement in mice can be divided into the following steps, using the ALC-NIBP noninvasive blood pressure measurement and analysis system as an example: For more product details, please visit Aladdin Scientific website.
Inflation and deflation control cable, animal cage, pulse sensor
Guide tubes, communication cables, power cables, ALC-NIBP software, etc. (different models may have different configurations)
Thermostat or heater, etc. (configuration may vary by model)
1. Preparation of the experiment (1) Connect the system:A. Connect the system main unit with the inflation and deflation controller: the side of the inflation and deflation controller with the ALCBIO logo on it is placed upwards. Take the inflation control cable and connect one end to the connector at the back of the inflation controller and the other end to the connector at the back of the main unit. Make sure that the connector pin core is aligned and inserted first, then tighten the retaining ring.B. System host and computer connection: Connect the host connector end of the communication cable (the squarer end) to the USB connector on the back panel of the host, and pay attention to the direction of the connector to match, otherwise it will lead to damage of the instrument. The other end of the communication cable is connected to the USB connector of the computer.C. Turn on the power.D. Connect the inflation and deflation air line: take the inflation and deflation hose and connect one end to the air hole in front of the inflation and deflation controller and the other end to the air hole of the fixer, if it is a multi-channel system, connect the inflation and deflation hose one by one.E Connecting the pulse sensor to the main unit: Connect the connector end of the pulse sensor to the signal port on the front panel of the main unit. Insert the connector into the signal port on the front panel of the main unit after aligning it and tightening the fixing ring. For multi-channel systems, connect the inflator and deflator tubes one by one.Turn on the power switch at the back of the main unit, the power light on the front panel of the main unit will be on, indicating that the system is ready to start working. The system (with sensors connected) should be warmed up for 20 minutes before conducting experiments. After warming up, you can open the application program to check the readiness of the system.(2) Calibration:Calibration is to confirm the ratio between the pressure signal and the voltage obtained after its conversion by the pressure sensor in the system mainframe, after calibration, the system can calculate the exact size of blood pressure according to this ratio. The calibration process includes:① Make the sensor unloaded and measure the signal size when the sensor is unloaded.② Accurately give a constant pressure standard value and measure the signal size at this pressure.③ The system automatically calculates and determines the signal conversion ratio to complete the calibration. The load standard value given to the sensor during calibration should be close to a frequently used blood pressure value, usually 100 mm Hg. The ALC-NIBP system is factory calibrated and can usually be used without further calibration.Due to the electronics, the sensitivity of the sensors may change slightly after a certain period of time, and should be recalibrated to ensure that accurate experimental data are obtained. The system is equipped with a calibration wizard that can be followed to complete the calibration.(3) Animal adaptation:Animal tension will lead to elevated blood pressure and large fluctuations in blood pressure. And the reduced blood circulation in its tail under tension also makes the pulse signal bad. Catch the animal gently and minimize stimulation to keep it quiet. Considering the fluctuating nature of blood pressure, try to measure the blood pressure at the same time point every day.Note: A pre-test is required before the formal experiment. Train the animal at the same time of day for at least 1 week to accustom it to the device and its operation. Keep the environment quiet during the measurement to avoid animal agitation, which may affect the results.(4) Warming:When the ambient temperature is low, the pulse in the tail artery is weak, so it is necessary to warm the animal in order to detect the pulse. When using a thermostat, the animal is placed on a fixator, and then the animal, along with the fixator, is placed all the way into the thermostat for measurement. The temperature of the thermostat is usually set at 25 to 32 °C, and the temperature to be used can be determined based on the results of the pre-test.The temperature used should be such that the animal has good tail circulation and the pulse can be easily detected with minimal effect on the rest of the animal. Use a constant temperature for the same experiment. When warming, only the tail of the rat is warmed. To use, attach the thermostat to the tail of the rat and connect it to the power supply to start warming. 2. Starting the experiment A. Start the operating system.B. Power on the mainframe.C. Run the ALC-NIBP application program.D. Place the mouse in the animal cage with the head inward and the tail exposed.E. Lift the tail holder lever, place the animal cage containing the mouse with the exposed tail side facing the air bag onto the tail holder, and press the animal cage with the lever.F. Apply soapy water to the mouse tail guide tube and guide the mouse tail through the air bag side of the tail retainer and pull it out the other end.G. Lift the pressure bar and move the animal cage as close to the immobilizer as possible while straightening the rat's tail so that the immobilizer airbag is at the root of the rat's tail.Note: The rat's tail should not be twisted and maintain the vertical upward position of the vein above it.H. Place the pulse sensor into the immobilizer, taking care to lift the tail as you do so. The ventral surface of the tail should be directly underneath the pulse sensor.CAUTION: The pulse sensor is very sensitive and should be placed carefully without squeezing the surface of the sensor.I. Tighten the lever and press down on the animal cage to ensure that the cage does not move.CAUTION: The inflation and deflation controller and the tail retainer should be placed at the same level. Be sure to apply lubricant (e.g., soapy water) to the surface of the rat tail guide tube, otherwise the air bag may be damaged. Do not place the pulse sensor in the fixator before threading the rat tail. 3. Start Measurement (1) Create a new task file and enter the name of the experiment and the number of the animal to be measured. Click the "Play" button and the signal waveform appears in each channel.(2) Gently turn the knob of the mouse tail presser and press the mouse tail gently on the pulse sensor. You can check the pressure on the tail knob and the mouse tail through the hole of the holder. Do not press the tail knob too tightly, adjust the tail knob carefully and observe the waveform of the pulse channel at the same time until a good pulse signal is detected.Good pulse signal: The pulse amplitude is ± 1 to ± 3, and the waveform is regular and stable. The waveform can be observed by zooming in and out with the zoom-in and zoom-out buttons. If the pulse signal itself is too small, it will affect the blood pressure measurement result of the system. After observing a good pulse waveform signal, the pressure measurement can be started.Note: When the temperature is low, the temperature should be increased appropriately before measurement in order to obtain a good pulse signal. However, the heating temperature should not be too high and the time should not be too long, in order to obtain a good pulse waveform.(3) Blood pressure measurement: After observing and recording the normal pulse waveform for at least 10 seconds, click "inflate" to inflate and pressurize the tailgate, the waveform of the pressure channel can be seen to rise, and at the same time, the pulse wave of the pulse channel can be seen to gradually decrease to disappear, and after the disappearance of the pulse waveform, continue to pressurize the tailgate for about 20 mm Hg, and then click the "inflate" button again, and then the button will jump up to stop inflating the tailgate, and then click "deflate" for 2-3 seconds, and the pressure will drop, and the pulse wave will reappear. The pulse wave reappears. As shown in Figure 8-5-3. 
This completes one operation. After the pulse has fully recovered for 10 seconds (must not be less than 10 seconds, wait for the pulse waveform to stabilize), you can inflate and deflate again to measure, the measurement method is the same as above.Repeat the measurement several times, preferably 4 to 6 times. Insufflation and deflation control can also be performed automatically by using the "AUTO EXPERIMENT" for cycle measurement.Precautions: Position the tail of the rat correctly; adjust the knob of the tail presser appropriately; after fixing it with the fixer, wait for the animal to calm down for 20 minutes before measuring the pressure. 4. Blood Pressure Results (1) Select the number of measurements:The system has automatically calculated the results of each measurement. The user checks the number of measurements to be included in the average according to the situation at the time of measurement. Measurement results that affect the quality of waveforms such as unstable pulse waveforms before inflation, animal agitation, disturbed pulse waveforms, or suddenly too small pulses are not checked. It is better to have 4 to 6 measurements, and then take the number of measurements in which the difference between the results is 5 to 10 mm Hg.(2) Blood pressure measurement results:The system takes the average value of the measurement results selected by the user in "Current Data Analysis" as the result of this measurement. Click "Enter Database" to enter the result (i.e., the average value) into the accumulated data.(3) Blood pressure manual value:The principle of manual calculation is based on the axial sleeve pressure SBP when the blood flow is blocked, and the pressure corresponding to the point where the pulse wave disappears is SBP, and the pressure corresponding to the point where the pulse wave begins to weaken is DBP.It should be noted that the pulse wave of an animal may have an increase in amplitude after pressurization, and then gradually decrease, therefore, the point of pulse wave onset should be compared with the pulse wave in the steady state.Note: Heart rate is taken manually in the same way as blood pressure. The data can be exported in .txt, Excel or Access format, and the image can be saved in .bmp format.