Measuring Blood Pressure

High blood pressure or hypertension is a major risk factor for heart attacks, strokes and death, so its mechanisms and control are a major area of study.  No wonder then, that I responded Duh! on this week's podcast when met with a study description concluding that multiple measurements of blood pressure were best. 

Duhs on me, though. This study in Annals of Internal Medicine taught both Rick and me something about people who are already taking one medication for blood pressure and seem to be poorly controlled.  Btw, that would be many, many people with high blood pressure.  The study followed about 450 men with hypertension for 18 months.  During that time their blood pressure was measured by three methods:  in a typical clinic visit, using a standardized protocol for blood pressure measurement we'll call the 'research method,' and using measurements subjects themselves obtained at home.  Altogether this resulted in over 110,000 data points for analysis.

In the typical clinic setting, which Rick describes as the patient being rushed in after a hectic trip to get to the place, hurriedly seated and strapped with the blood pressure cuff, only 28% of subjects had blood pressures that met the target for acceptable control.  Using measurements the patients themselves obtained at home, 47% were well controlled.  But using the research method, where people are seated for three minutes, their arm is positioned at about the level of the heart, and then a measurement is taken, almost 70% were doing just fine, thank you.

The implications of this research in managing high blood pressure are huge.  Most people with the condition will ultimately end up on more than one agent, each of which works via a different mechanism, to reach target blood pressure.  But what this study suggests is that an error in measurement may be the culprit and not recalcitrant blood vessels.  We're familiar with the concept of 'white coat hypertension,' where people routinely have higher blood pressures in the clinical setting because of the inherent stress of the situation, but this study demonstrates that that phenomenon is alive and well even among those taking blood pressure medication.  As Rick opines in the podcast, it would be great if we could avoid the all too typical scenario where the person whose blood pressure seems to be difficult to get under control goes on a second agent, then calls the office and says, "Doc, I feel like I'm going to pass out."  Or more commonly simply doesn't take the prescribed medications because the side effects are unacceptable, but won't fess up to their physician.

So as the study concludes, multiple blood pressure measurements are best.  The authors suggest five or six measurements, skewed toward those obtained at home, will provide a more trustworthy picture.  Rick cautions that people who want to do this should bring their blood pressure device into their physician's office to make sure it's properly calibrated but then offers wholehearted support for the strategy.

Other topics this week include door in door out time for people having a heart attack in JAMA, in the same journal the diabetes risk of high dose statins, and the E.coli outbreak in both NEJM and the Lancet.  Until next week, y'all live well.

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healthy December 31, 2013 at 8:40 pm

That is a good tip especially to those fresh to the blogosphere.
Short but very accurate info… Appreciate your sharing this one.

A must read post!

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Rishi Gupta April 25, 2012 at 4:41 pm

I found a nice way to practice my skills in taking blood pressure using an online blood pressure cuff: http://practicalclinicalskills.com/blood-pressure.aspx

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Taron September 5, 2011 at 1:36 pm

Your asnewr was just what I needed. It's made my day!

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