Measuring Blood Pressure in Mice using Volume Pressure Recording, a Tail-cuff Method

The word coda is Italian for tail. The Coda non-invasive blood pressure system enables blood pressure measurements in rodents, thanks to a specialized volume pressure recording sensor that measures tail blood volume changes when placed over an animal's tail. This video demonstrates how to set up the system, prepare the animals, and acquire blood pressure measurements for eight animals simultaneously.

Hi, I am Anju Bala Krishnan, working in Alan Dougherty's lab Cardiovascular Research Center, university of Kentucky, Lexington. Today we will show you a procedure how to measure blood pressure in mice using volume pressure recording a tail cuff method. We use this procedure in our laboratory to study cardiovascular system.

So let's get started. To set up the CODA system, select an area in the lab where the room temperature is a stable 20 degrees Celsius or above. Avoid locations near air conditioning vents, exposing animals to loud noise or odors, may irritate or stress.

The animal odors can include any strong perfume that you may be wearing. Turn on the Coda controller and then warming platforms which are set to level three. If the room temperature is above 25 degrees Celsius, start at levels one or two.

Perform the Controller Diagnostics test first, open the Coda software. Select the Coda device by clicking on it. Click on test selected device.

Select the cuffs and channels to test and click test. After the controller diagnostics test is complete, close the device test window. Select the code of controller to use, then click.

Use these devices to set up the software. Select tools manage personnel. Next, click on researcher one.

To change the name, click on subsequent rows to add additional researchers. Then click save data. Click on the technicians tab to modify or add technicians.

After that, click on the specimens tab to name the animals for easy identification and to select the animal type. Then click save data. Finally, click on the animals tab.

To alter the animal type and sensitivity, click save data, and then close. To begin a new experiment, select file New experiment. Enter the experiment name, select the key researcher and select a begin date.

Click next. The next step is to enter the basic session information. Start by entering the session name set acclimation cycles to five if you prefer not to include acclimation cycles set to zero.

Set number of sets to one time between sets to 30 seconds for multiple sets. Cycles per set to 20 cycles, and time between cycles to five seconds. Then click next.

To begin specimen selection, select the specimen from the specimen pool and assign it to the first available channel. And click next to set session parameters. Set maximum occlusion pressure to 250 millimeters.

Mercury deflation time to 20 seconds. For mice, minimum volume to 15 microliters and display style to one channel per graph. You may also add additional researchers and technicians.

Then click next. Review the session script and click next. Do not select finish until you complete the animal preparation section, which is described next.

And now you may retrieve the animals and set them next to the coda blood pressure sys. Before placing the animals into the holders, note the size of each animal in relation to the size of the selected holder. The animal should be able to freely enter the holder.

Place each animal in a holder by picking it up by the tail and gently placing it into the rear of the holder, which faces the open end of the nose cone. Carefully secure the rear hatch to the holder by turning the screw on the rear hatch. Be careful not to pinch the tail or any other body parts while securing the rear hatch.

Next slide. The nose cone toward the rear hatch. Limiting the movement of the animal.

The nose cone should be in a position to limit the animal from turning around. While inside the holder, place the holder onto the warming platform. In the designated position, allow the animal at least five minutes to acclimate to the holder.

Do not touch or handle the animal. While inside the holder, the increased contact could irritate the animal and never leave the animal in the holder unattended. To properly place the occlusion tail cuff, thread the tail through the occlusion cuff and place the cuff as close to the base of the tail as possible without force.

After that, thread the tail through the VPR sensor cuff, placing it within two millimeters of the occlusion cuff. Secure the tubing in the notch on the top rear of the holder. The occlusion tail cuff is inflated to impede the blood flow to the tail.

The occlusion cuff is slowly deflated and the VPR tail cuff incorporating a specially designed sensor measures the physiological characteristics of the returning blood flow as the blood returns to the tail. The VPR sensor cuff measures the tail swelling as a result of the arterial pulsations from the blood flow. Systolic blood pressure is automatically measured at the first appearance of tail swelling.

Diastolic blood pressure is automatically calculated when the increasing rate of swelling ceases in the tail. After all the animals have been placed in the holders and their tail's cuffed, allow them at least five minutes to thermal regulate. Record the temperature of the animals.

Frequently with an infrared thermometer, the animal's temperature should be between 32 and 35 degrees Celsius. Now that the animals are ready, we can begin the experiment. Click finish to begin the experiment.

The red line represents the deflation of the occlusion cuff and VPR sensor cuff. The blue line represents blood volume changes in the tail. The first inflection of the blue line, minimum rate of change, identifies the systolic blood pressure.

The second inflection of the blue line, maximum rate of change identifies the diastolic blood pressure when the experiment has ended. Remove the animals immediately from the cuffs and holder. A simple session summary report is displayed.

The data collected in the experiment is saved as an Excel file. There are several ways to process the data within the Excel file. A common practice is to obtain the average and standard deviation, delete measurements.

If the standard deviation is greater than 30. Additionally, rejected cycles may be viewed and the entire database can be easily exported to Excel. Consult the written protocol and user's manual.

For more information, I have just shown you how to measure blood pressure in mice non-invasively using volume pressure recording. It is most important to reduce animal stress by following this procedure in order to get accurate and consistent measurements. So that's it.

Thanks for watching and great success with the experiments.