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BLOOD PRESSURE-MEASURING: FALSE BLOOD PRESSURE READINGS
Many elderly people thought to have high blood pressure (BP) may instead have false hypertension, or pseudohy-pertension, the American Family Physician (32#2:242) reports. There are a number of reasons why this could be the case.
One reason that BP readings may be falsely elevated is that the patient has hardening of the arteries. One can find out whether the arteries are hard by feeling the pulse at the wrist while a BP cuff is pumped up on the same arm. If, when the cuff pressure has been raised high enough to obliterate the pulse, the tube-like form of the artery at the wrist can still be felt, this means that it has not collapsed below the inflated cuff and must therefore be abnormally hard. The true BP in such cases can be determined only by inserting a tube directly into the artery through a needle.
Secondly, BP readings may be increased by as much as 10 percent if, while taking them with a stethoscope, one presses the instrument too hard on the arm, the Western Journal of Medicine (141:193) reports. To get a true reading it is best to apply the stethoscope with merely a slight pressure. Although increasing the pressure does not alter the systolic BP reading (the upper of the two numbers), the diastolic reading (the lower of the two numbers) can be significantly raised, and it is usually the important one in gauging the effects of anti-hypertension treatment.
Thirdly, blood pressure readings taken with a cuff that is too small for the arm may be as much as 10 mm Hg (millimeters of mercury) too high. This could easily result in a large-armed person taking medicine unnecessarily. According to correspondence in the New England Journal of Medicine (306:108), false high readings will not be made if the inflatable bladder in the cuff is long enough (when not inflated) to wrap at least three-fourths of the way round the arm. When a regular adult cuff is too small, a “large adult” or even a “thigh” cuff may be used.
Finally, many people are so nervous while their blood pressure (BP) is being taken in a doctor’s office that the readings are abnormally high. This reaction, Emergency Medicine (19#11:54) reminds us, often leads to the unwarranted diagnosis of hypertension when, in fact, the BP is perfectly normal. To avoid this problem, the reading could be taken repeatedly, at least five times over a period of five minutes or longer, until it stops falling.
All of these factors can result in people taking BP-lower-ing medication that they do not need. Not only is this wasteful, but it can make the patient feel light-headed, weak, and tired because, as a result of unnecessary medication, the BP is too low. To avoid this problem, therefore, anyone who is said to be hypertensive should learn to take his or her BPs at home, since one’s own readings are much less likely to be misleading.
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