Rat Blood Pressure

Measuring blood pressure in the tail of a rat is very straightforward with the right equipment. Various levels of sophistication are possible, depending on whether you want an integrated system, or to build your own system from components.

• This discussion only mentions equipment that we distribute in Australia and New Zealand; if you are in another country, please follow the provided links to the original equipment manufacturers. Of course there may be alternative manufacturers - but you can find those yourself!

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Principles

BP is measured in rat tails in much the same way as it is measured non-invasively in humans. A cuff is placed around the tail, and inflated above the systolic pressure. This causes pulsations at a more distal pulse sensor to cease. As the cuff is slowly deflated, the reappearance of pulsations is noted, and the cuff pressure at which this occurs is taken to be the systolic pressure in the tail.

There are a couple of caveats here:

1. The recorded pressure is the systolic pressure. There have been reports in the literature of a good correlation between diastolic pressure and the pressure at which the pulsations are maximal, but not all workers would agree with this and there appears to be no good physical explanation for the effect.
2. Rats seem to have pulsatile flow in the tail only when they are under mild temperature stress, and it is therefore necessary to enclose the rat in a warmed chamber. Rat-tail methods which claim not to need warming probably rely on the rats self-heating when confined.
   

Integrated Systems

We supply integrated Rat BP systems from Biopac and Panlab.

The Biopac system consists of an amplifier unit with built-in pump, plus cuff assembly, pulse sensor, animal restrainer and optional heater. The system interfaces to a Biopac Data Acquisition System (or a third-party acquisition system).

The Panlab system similarly consists of an amplifier/pump module, plus anilam restrainer/heater and cuff/sensor assembly, operating with stand-alone Windows software. Switching units are available to enable measurements to ve made from up to 12 animals without re-positioning the cuffs.

Basic DIY Equipment

• We can supply combined cuff and pulse sensors from Harvard Apparatus. These are available in various sizes to suit differeing ages of animal.

• An inflation device and pressure readout. The simplest would be a hand-held sphygmomanometer which we can supply (part no. S300).

• A readout for the pulse sensor. In the simplest case a laboratory oscilloscope would be adequate (a small power supply will also be needed). The procedure would be to inflate and then slowly deflate the cuff, watching the pulse display on the oscilloscope and noting the reading on the sphygmomanometer at the instance pulsations reappear during deflation.

• For higher accuracy and ease of use, we would recommend using a data acquisition system to record the cuff pressure and the pulsations simultaneously (as in the integrated system mentioned above).