Measuring Blood Pressure the Right Way

What is the accurate way to measure blood pressure?

After more than hundred years of measuring blood pressure with the use of a stethoscope and sphygmomanometer (yes, that is what your doctor uses in his office to check your blood pressure) you wonder why the question.

An article in the Canadian Medical Association Journal (CMAJ) makes the point that things have changed in the last 20 years as more and more automated blood pressure measuring devices have hit the market. Their reliability and accuracy have increased. You find them in people’s homes, in your local pharmacy and may be in your doctor’s office.

The blood pressure measurement by sphygmomanometer is called auscultatory method because the method uses a stethoscope to listen the pulse. The automated machine measures the blood pressure by oscillometric method; it detects and analyzes pulse waves to determine blood pressure.

Each method is an indirect way to measure the blood pressure. The accuracy and consistency of the measurement and its clinical relevance depends on the skill of the individual taking the pressure and proper functioning of the automated device.

High blood pressure is known to be a silent killer. The CMAJ article says that clinical practice guidelines set uniform standards to take the blood pressure so consistency and accuracy is maintained. This allows the clinician to predict the effect of abnormal blood pressure on the human body. The guidelines are based on the use of auscultation method using a bare arm – “roll up your sleeve so I can take your blood pressure.”

In another article in the CMAJ, the authors challenge the recommendation that blood pressure should be measured on a bare arm. In their study they found that taking a blood pressure reading over the sleeve of a shirt, blouse or light sweater was not statistically different than taking the blood pressure on a person’s bare arm.

The article also challenges the hypertension practice guidelines which require the use of different size blood pressure cuffs for different sized arms – some arms have a bigger circumference than others. The automated devices have cuffs which do not meet the clinical practice guidelines for measuring blood pressure by the traditional way.

The article says the use of automated blood pressure measuring devices in the clinic provides some real benefits. Well-working fully automated devices are:
-free of terminal digit bias,
-deflate at the correct rate,
-operate consistently over time,
– record the results,
-do not require good hearing and
-generally require less training to operate properly.

In spite of all these benefits, the automated device will not provide a correct reading if the patient or the individual is not mentally and physically relaxed. There are various human behaviours – emotional and physical – which affect a person’s blood pressure, albeit temporarily. So the reading taken may not be of much clinical use. Same problem applies when the blood pressure is taken by the traditional way.

So the jury is still out. The article says that in spite of advances in technology the accurate measurement of blood pressure depends on factors related to the patient, the equipment and the method used to take the blood pressure.

Have you had your blood pressure taken recently? If not, then better do so. Don’t forget, high blood pressure is a silent killer. You may not have any symptoms but your blood pressure may be high. See your doctor and roll up your sleeve or may be not.

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