Blood Pressure Readings: Position Does Matter

Blood pressure monitoring is an essential part of routine care, yet it’s surprisingly difficult to get accurate readings. American Heart Association (AHA) guidelines advise that patients be seated with feet flat on the floor, relaxed and quiet, for 5 minutes before the measurement begins – yes, 5 full minutes. Otherwise, readings are likely to be higher than they actually are.

Further, the patient’s arm should be supported at the level of the right atrium (not hanging down or resting on lap). And, the patient should have an empty bladder and have avoided caffeine, smoking, and exercise for at least 30 minutes prior to measurement.

Getting the details right makes a bigger difference than you might think. In a paper published last year in The Lancet’s eClinical Medicine (and funded in part by the Midmark Corporation, a company that manufactures sphygmomanometers) researchers found that readings taken with the patient seated on the exam table, legs dangling, were substantially higher (7.0 mmHg greater systolic, 4.5 mmHg greater diastolic) than those taken with the patient seated in a chair.

However, when it comes to meeting these guidelines, the deck is stacked against the average medical practice. For most clinics, neither the workflow nor the examination rooms allow for the AHA-advised approach. Blood-pressure cuffs are often wall mounted, and the patient has to sit on the table to be within reach.

In addition, readings are typically taken at the beginning of the visit, when the patient has just been through a potentially stressful check-in and waiting period, explained Randell K. Wexler, MD, professor of family medicine at The Ohio State University Wexner Medical Center and senior author on the eClinical Medicine study.

Why Not Lie Down?

To complicate matters, some research has indicated that blood pressure readings taken with the patient supine might be provide better prediction of cardiovascular outcomes than those taken in the traditional seated position, although some other research has found the opposite. At last fall’s AHA’s Hypertension Scientific Sessions, Stephen Juraschek, MD, PhD, primary care physician, epidemiologist, and associate professor of medicine at Harvard Medical School, presented findings from his ongoing research in this area.

While he found that having hypertension in both the supine and seated position was consistently linked with adverse outcomes, he also found that hypertension determined only in the supine position was as bad as having hypertension in both positions. In his study, the group with high seated but normal supine blood pressure didn’t seem to have the same long-term risk as patients with supine hypertension. “What this told us,” Dr. Juraschek told MedCentral, “is that supine hypertension is a negative state, even if your blood pressure seems to be normal when you're sitting down.”

What’s a Doctor to Do?

Does this mean clinicians should be checking blood pressure with their patients supine? That’s not entirely clear, said Dr. Juraschek. Although the data was taken from a cohort study with 13,000 people and 30-year follow-up, he would like to see it replicated in other studies, and is hoping to do that soon.

Meanwhile, short of remodeling offices or investing in programmable sphygmomanometers that can take readings while the patient is waiting for you to arrive in the room, there are a few ways to consistently obtain more accurate blood pressure readings. For example, Dr. Wexler suggests letting the patient fill out paperwork in the exam room rather than the waiting room.

However, Drs. Wexler and Juraschek agree that the most accurate readings are probably those taken at home. “I think patients are really good at that,” said Dr. Wexler, who gives patients an AHA handout explaining the proper way to get an accurate reading.