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Why blood pressure readings can vary




 

 

DEAR DR. ROACH: I would like to comment on your column regarding blood-pressure differences between the arms.

A difference of greater than 10 mmHg between the two arms in systolic pressure is considered abnormal. We see patients not uncommonly in consultation for this reason alone, perhaps as many as one a month. Almost always, the reason for the difference is blockage of the subclavian artery. The wrist pulse on the side with lower blood pressure may be normal, diminished or absent in those patients.

From 30 years of observation, I have noticed that patients with BP differences between the arms are nearly always female smokers (or former smokers), and the left subclavian is much more likely to be affected (have a lower blood pressure) than the right. Why this sex difference should be and why the left side should predominate is not understood and, to my knowledge, has not been described in print. Additionally, the presentation is usually in a non-obese woman in her 40s or 50s who is still smoking.

The significance of the finding is that it is a red flag waving for tobacco cessation and is a marker that that person’s arteries have already been significantly altered by the habit. Fortunately, the incidence of arm symptoms associated with the lower BP on that side is quite low — perhaps 1 in 10 have any symptoms. It is important, of course, for such patients to be aware of the difference between the arms only to remember which arm (the higher arm systolic number) has the correct measurement (most often, but not always, the right). — Jerry Svoboda, MD, FACS

ANSWER: I thank Dr. Svoboda for his expertise and will add difference in arm blood pressures to my (already very long list) of reasons to quit smoking immediately.

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DEAR DR. ROACH: I’ve heard many medical providers say that they believe they get more accurate blood pressure readings from the old-fashioned manual method, rather than the automatic cuff machines. I wonder how true this can be, though, since the former is subject to human hearing ability. My excellent hearing lets me pick up on beats far beyond what someone who has average hearing can detect, so it stands to reason that there would be a difference in the reading. — C.B.

ANSWER: The very best machines are accurate at measuring blood pressure; however, a trained clinician remains the standard for blood pressure measurement. Fortunately, good, but not necessarily outstanding, hearing is required for accurate blood pressure measurement. Proper placement and inflation of the cuff, the correct slow deflation rate and, importantly, measuring both arms are as significant as good hearing. I was taught to take an average of three measurements.

Excellent hearing helps the clinician pick up on subtle heart murmurs and other noises, normal and abnormal, that the heart makes. If you decide to become a physician, consider cardiology. We physicians should take great care to protect our ears; sadly, some of us listened to music that was too loud at some points in our lives.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@ med.cornell.edu. To view and order health pamphlets, visit www.rbmamall.com, or write to Good Health, 628 Virginia Drive, Orlando, FL 32803.

©2016 North America Synd.


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