In this VETgirl online veterinary continuing education blog, Amy Newfield, CVT, VTS (ECC) reviews how to measure a blood pressure in a dog and cat. So, if you’re looking for the 411 on how to use your Doppler blood pressure machine, read on! (And yes, VETgirl believes EVERY veterinary clinic should have one!).
Blood pressure 101, by Amy Newfield, CVT, VTS, VETgirl, LLC.
Blood pressure got your blood boiling? Never fear! This VETgirl blog provides quick steps on how to perform Doppler blood pressure.
Pick the Right Size Cuff
It is imperative that the cuff size be measured correctly. The cuff must be 40% of the circumference of the selected area. If it is too wide the reading will be falsely low and if it is too small (narrow) it will be falsely high.
I’ve never had an issue with the bladder size being too small, but it’s always good to check. The bladder on the cuff is the thing that holds air. It is always good to make sure it inflates and there is not a hole in the cuff. The bladder needs to cover a minimum of 80% of the circumference of the leg. If it is too small it will not occlude the artery enough.
There are 4 locations to obtain a blood pressure from:
• On the underside the carpus (right next to the large pad of the front of the foot)
• On the underside the metatarsus (right next to the large pad of the back of the foot)
• On the top of the medial aspect of the metatarsus. You will want to go between the long bones of digits 2 and 3 on the top of the back foot.
• On the underside base of the tail
Most veterinary professional choose on the back of the front foot so pet owners do not see the shave spot, but this is not the easiest location. The two easiest locations are the underside base of the tail and the top of the back foot. You can generally palpate the pulse on the top of the metatarsal area making is very easy to locate the pulse.
1) The machine should be turned off while ultrasound gel is applied to the curve side of the probe. Turning on the machine at this stage will cause loud screeching sounds which will upset the pet.
2) Shave the location, place the cuff on the pet with the sphygmomanometer attached.
3) Place a LOT of gel on the probe to ensure you get good contact. Place the probe on the shaved area. Once the probe is on the pet the machine should be turned on. Volume should be increased until a pulse can be heard. It is this author’s experience that the unit should be turned all the way up to allow for best sounds.
4) Locate the artery using small movements in a grid like pattern. If you move the probe sporadically all over the site you will miss the pulse.
5) Once you have obtained the pulse inflate the sphygmomanometer to a point where you no longer hear the pulse. Do not inflate the cuff all the way as this is uncomfortable and painful to the pet. Only inflate until you no longer hear the pulse.
6) Slowly deflate the cuff. It takes some practice inflating and deflating using the knob or button on the sphygmomanometer so practice without a pet until you are comfortable. Once you hear the pulse return you can deflate all the way.
What is the Sound Heard While Measuring Blood Pressure?
The short answer is likely the systolic arterial pressure (SAP). Interestingly enough when researching whether diastolic sounds could be heard using doppler ultrasound flow method many human nursing blogs and forums suggested that when having difficulty obtaining a BP in a patient it is best to reach for a Doppler machine as it is more sensitive and diastolic sound becomes more audible. There have also been several studies in human literature (using animals as models) stating that it is quite possible to obtain a diastolic sound. There have also been studies on felines stating the sound you hear first when taking a Doppler blood pressure is more closely related to mean arterial pressure and not systolic. It is important to remember that blood pressure is just one diagnostic point when looking at how the pet is doing. Obtain the reading and then decide how it correlates to the other values and what you see in the pet.