There have been great technological strides made in blood pressure testing, and although there’s a variety of equipment available, the basic tool of measurement remains the almost unpronounceable sphygmomanometer.
For starters, it’s pronounced “sfig"mO-mu-nom'i-tur” and it’s a clever tool. It uses a simple combination of pressure applied to the upper arm to temporarily halt the blood supply, while the caregiver uses a stethoscope to listen to the point at which the heart rate stops being heard, then can be heard again.
Listening to the heartbeat while pumping up the cuff, the doctor watches the mercury rise to about 180 mm Hg. Then the cuff is slowly deflated whilst the doctor listens with his stetoscope. The reading where the sound of the heartbeat becomes audible is measured and is counted as your systolic pressure. This means the pressure was just enough to release bloodflow through the brachial artery.
As the pressure in the cuff is released further, your healthcare professional notes at which reading the sound of the heartbeat disappears completely, which provides a reading of your diastolic pressure.
Your blood pressure will need to be measured several times to determine an average, as it’ll vary according to your activity level. Other factors that can affect your blood pressure include your intake of fluids and alcohol, and your exposure to tobacco smoke.
Stood the test of time
This method of measuring blood pressure has remained virtually unchanged since originally described by Dr Korotkoff in 1906. It is still regarded as one of the most effective and reliable methods of recording BP. However, a good stethoscope and correct technique is crucial. The correct cuff size must also be used.
Environmental concerns about mercury
Currently most sphygmomanometers still use a column of mercury, the height of which correlates well with the pressure in the artery. However, mercury sphygmomanometers may become a thing of the past in the near future. As a toxic and bioaccumulable substance, mercury is seen as a contributor to environmental pollution. In fact, these devices have already been banned in many countries.
Electronic measurement devices can be very user-friendly and accurate. Some also give a print-out that makes recordkeeping easy. Get professional advice before purchasing one, as the numerous devices are not all equally reliable.
(Reviewed: Dr Kathleen Coetzee, MBChB)