How to Take Blood Pressure
There are many ways to measure a blood pressure. The most simple and common way to measure a blood pressure is the brachial artery occlusion method, commonly known as ‘the Cuff.’
This is accurate, but the accuracy depends on correct cuff sizing and operator use. It can be done automatically, but once again, training is required for automatic use.
- Manual/automated systems
- Errors are associated with incorrect cuff sizing and poor technique
Blood can only be heard through a stethoscope if it is turbulent. As the cuff is inflated, the artery is compressed, making the blood flow through the artery turbulent. When the artery is completely closed, there is no blood flow and no sound. As pressure in the cuff is reduced, the point at which the artery is open just enough to let the blood pass, is the systolic blood pressure.
This is detected by turbulent blood flow heard through the stethoscope. As pressure in the cuff is further reduced, the vessel will once again be completely open and non-turbulent. At this point, no more sound is heard and diastolic blood pressure has been reached.
The arm should be raised slightly, so that it is level with the heart.
- Measurement of blood pressure above the heart level will lower the blood pressure reading
- Measurement of blood pressure below the heart level will raise the blood pressure reading
It is important to allow the client to rest for a few minutes before measurement of the blood pressure. Any activity will raise the blood pressure slightly, and pain, exertion, stress or heavy exercise may raise it quite a bit.
In regard to the preferred site for measurement, blood pressure may be obtained from different arteries, sometimes from the forearm or leg, but these are not considered as accurate as the brachial arteries as these are closer to the heart.
If there is a blockage in an artery, this will lower the blood pressure reading on that limb. There’s no way to know for sure at the bedside, but if there is a difference between the left and right arms or legs, this would suggest a blockage or stenosis in an artery. In this situation, the higher blood pressure result would be more accurate.
In truth, the most accurate way to document a patient’s blood pressure is to log the artery tested (especially if it is not the brachial artery), the position of the patient, and any other factor that may have increased or decreased the blood pressure during the measurement, such as pain.
Peripatetic and always intellectually restless, Darren has pursued varied careers in journalism, media production, academic philosophy and nursing. As a nurse, he worked in the speciality areas of critical care, community care, remote area healthcare and education. As a formally qualified academic philosopher Darren taught undergraduate units in law and ethics in healthcare, although his principle research focus revolved around logic and the philosophy of language. Darren’s media production output can be found scattered about the Ausmed website and in his long forgotten days as a word monkey, he wrote for European publications such as The Scotsman, The Great Outdoors, Country Walking and The Times. In 2014 Darren consulted to the Department of Health for the development of Consumer Directed Care policy and guidelines for remote area communities in the Northern Territory. These days he is the managing editor of a small independent publishing company based in the United Kingdom, and lives in Tasmania. In his spare time, Darren is currently studying a formal course in celestial navigation, just in case the inevitable zombie apocalypse messes with the world’s GPS satellite system.