Jul 29, 2011 at 11:19am IST

How to measure your blood pressure

HYDERABAD: For many years, we have been told that high blood pressure as measured in your doctor’s office is harmful to your heart, kidneys and brain and could lead to heart attacks, heart failure and kidney disease. Like most things in this world, there are multiple facets to everyday life and your true blood pressure level is not as simple and easy to measure as we may think.
New and novel ways of measuring a person’s blood pressure have identified different patterns of blood pressure variation. Some of these patterns of high blood pressure are bad for a person’s health, a few being potentially worse than others, while at the opposite end of the spectrum there are some which are harmless and do not need medication. Blood pressure measurement in the physician’s office has been a longstanding and usual practice.
In fact, the most common reason a patient visits a physician’s office is for management of his blood pressure. World experts in hypertension have outlined very specific guidelines for the method to be followed in measuring a person’s blood pressure. If the correct method is not utilised, then there could be inaccuracies in the blood pressure measurement.
dos and don’ts to measure blood pressure
Very briefly, the patient whose blood pressure is to be measured should avoid tobacco, coffee and tea at least for a few hours before this is done. The person should rest for five to 10 minutes in a comfortable chair with a back-rest, feet flat on the ground. The blood pressure monitor should be placed at the level of the heart and the blood pressure cuff should be of appropriate size. Blood pressure should be measured several times at intervals of at least one to two minutes between readings/measurements. Ideally, the first blood pressure reading should be discarded and then all the subsequent readings averaged to give the person’s blood pressure measurement. Blood pressure should not be measured when a patient is anxious or under stress. It is often seen that none of these basic requirements for measuring blood are followed during general visits to the doctor. Mostly, only a single reading is taken, the person may not be given time to relax and blood pressure may be measured in a rushed manner due to lack of time. This leaves scope for much inaccuracy in blood pressure measurement and often a high reading may be obtained if the patient is tired, stressed, rushed or anxious. This will result in a person being wrongly informed that he has high blood pressure and antihypertensive medications may be started when they may not actually be necessary. What is ideally required is that a true blood pressure reading be obtained first as recommended by expert guidelines.
24 hour ambulatory blood pressuremonitoring system
An important device that has been introduced recently and has grown in acceptance as being vital for accurate blood pressure measurement is the 24 hour ambulatory blood pressure monitoring system. This device is the size of a cell phone, is attached to a blood pressure cuff and is worn by a patient for a 24 hour period on a regular day when he goes about his usual activities and work. The 24-hour ambulatory monitor measures and records the person’s blood pressure automatically several times during the day and during the night while sleeping.
These serial blood pressure measurement data are then uploaded to a computer and analysed. The average value of these 70-80 readings during the 24 hour period is now considered the most accurate blood pressure measurement for that person and is considered the gold standard for blood pressure measurement.
White Coat Hypertension vs Masked Hypertension
Several patterns of blood pressure can be noted in patients who have their blood pressure measured in their doctor’s office. A patient may have elevated high blood pressure when measured in the doctor’s office but normal blood pressure readings when measured in out-of-clinic settings, such as at home. This phenomenon is termed as white coat hypertension. Studies show that this is generally a benign condition that does not require treatment. The problem with White Coat hypertension is that, if physicians rely only on office blood pressure measurements, they may add or increase antihypertensive medications based on this, which is not necessary. Such patients with white coat hypertension often end up experiencing unwanted side effects and adverse effects related to excessive antihypertensive medications, which were not necessary in the first place.
On the other hand, there are a few patients who have normal blood pressure and appear to be well controlled on treatment for hypertension, when their blood pressure is measured in the doctor’s office.
However, it is interesting to note that on 24 hour ambulatory blood pressure monitoring, these patients may actually have an elevated blood pressure average which needs to be addressed for optimal blood pressure control.
This pattern of high blood pressure has been termed as Masked Hypertension, and such patients could be missed if their doctors relied only upon usual office blood pressure measurement techniques.
Measurement of 24 hour blood pressure has recently identified a new pattern of blood pressure, now termed as nocturnal hypertension. The patients who have nocturnal hypertension are relatively well controlled, but their blood pressure levels are elevated at night. Nocturnal hypertension like masked hypertension is harmful to vital organs.
Trials are underway to see if controlling night time blood pressure offers protection and preserves these organs.Careful and thorough evaluation of a patient with hypertension is fundamental in providing optimal care to those with truly elevated blood pressure.
(The author is an American Board certified nephrologist and a leading hypertension expert at Nephrology Department at Apollo Hospitals Hyderguda. He also runs Apollo’s Center for Blood Pressure Management)