Arm position during blood pressure check may lead to wrong reading, study finds

The study reveals that blood pressure reading could not be correct unless the person’s arm is in the right way positioned.

An analysis of earlier studies of how blood pressure readings changed when people held their arms in three ways — resting on a surface, on the lap, or hanging by the side of the body — showed that some positions could cause a substantial rise in systolic pressure, the higher number in a blood pressure reading, the journal JAMA Internal Medicine reported on Monday. Systolic is a measure of pressure in the arteries of a given individual when the heart executes a pulsation and pumps blood to the various body organs.

Essentially and to the extent of the findings, nearly seven points in the arm dangling position, the researchers were surprised said the studies’ senior author Dr. Tammy Brady, a pediatrician, epidemiologist, and a medical director of the pediatric hypertension program at the Johns Hopkins Children’s Centre.

The kind of result the researchers got before conducting their experiment could not be predicted. “There was a chance that arm position was not important,” she said.

“One of my hopes is that this will also help patients learn how to do this on their own but also how to tell their health care provider,” Brady said. “Patients should have their say on how that genuine blood pressure measurement can be obtained.”

The American Heart Association guidelines suggest that a patients arm should be held to get the correct measurement. The guidelines also say: 

No caffeine, and exercise and no smoking for the next 30 minutes. 

It means that the blood pressure cuff should be prevented at mid-heart level.

The patient’s feet should be placed on the floor and the back should be straight. 

Nearly half of U.S. adults have high blood pressure, which occurs when the measured force of blood flowing through blood vessels is higher than what is considered normal: lower than 120 systolic pressure and less than 80 diastolic. Diastolic is the pressure in the arteries when the heart in between beats.It often produces few signs and symptoms, but if left unchecked, hypertension can lead to stroke, heart attack, and other related cardiovascular diseases.ngs taken while people held their arms three different ways — leaning on a surface, resting on the lap or hanging by the side of the body — showed certain positions could lead to a significant increase in systolic pressure, the upper number in a blood pressure reading, according to the study published Monday in JAMA Internal Medicine. Systolic refers to the amount of pressure in a person’s arteries, when the heart sends blood throughout the body.

The size of the difference, nearly 7 points in the arm dangling position, was a surprise, said the study’s senior author, Dr. Tammy Brady, a pediatrician and epidemiologist and medical director of the pediatric hypertension program at the Johns Hopkins Children's Center.

The researchers weren’t sure what to expect prior to running their experiment. “There was a chance that arm position was not important,” she said.

“One of my hopes is that this will help inform patients as to how to do this on their own and also to tell their health care provider the right way,” Brady said. “Patients should be empowered to make sure the blood pressure measurement is accurate.”

The American Heart Association recommends that a patient’s arm should be supported to get an accurate reading. The guidelines also say: 

Avoid caffeine, exercise and smoking for 30 minutes. 

The blood pressure cuff should be positioned at mid-heart level.

The patient’s feet should be flat on the floor, with the back supported. 

Nearly half of U.S. adults have high blood pressure, which occurs when the measured force of blood flowing through blood vessels is higher than what is considered normal: less than 120 systolic pressure and less than 80 diastolic. Diastolic is the pressure in the arteries between heart beats. Hypertension often causes minimal symptoms but untreated it can increase  the risk for stroke, heart attack and other serious cardiovascular conditions.

To find out if arm position affected the blood pressure reading, Brady and her co-authors invited 133 adults, 52 percent of whom were female and 78 percent Black. The participants in the study were between the age of 18 and 80. 

As mentioned above, blood pressure was measured in all the participants in each of the three arm positions, but the order with which the positions were taken assumed a random sequence of no fixed order, Here the participants were divided in to six groups randomly and each group had a different order of positions.

The researchers discovered that the blood pressure was elevated by 6.5 points on average in terms of systolic pressure, and 4.4 points on average in terms of diastolic pressure when the arms and hands were at rest beside the body rather than on a desk during the reading. 

Also when the people had their arms resting on their laps, the systolic blood pressure was raised by 3.9 points from when the arms were on a surface, while the diastolic pressure escalated to 4 percent from the supported state.

These differences may mean that more people are diagnosed with hypertension and more patients are given drugs they do not require.

For instance, if a person is actually has blood pressure at 134 and then measured it in a dangling arm manner the reading could tally up over 140, which is stage 2 hypertension.

Misposition of a patient’s arm “unfortunately is a reality that is encountered frequently enough”, according to Dr Karyn Singer, an assistant professor of medicine at New York University, and also the assistant vice president of chronic disease and prevention at NYC Health + Hospitals. These feelings can be quite relatable to most patients and may sound like, “As a patient, I’ve been there.”

The study is a form of evidence “that is really important,” explained Singer, who didn’t participate in the new study. “Until now it has not been said which movement of the arm alters the blood pressure readings.”

Singer’s main message for patients: “They need to know the right way of having their blood pressure checked and that they too need to speak up if they feel that their blood pressure has been taken incorrectly or is higher than it should be.”    

As a patient, Dr. Megan Kamath has also seen the situation in other different health care settings and other different offices.

The arm position can result in a rather huge disparity in BP readings, according Kamath, a UCLA Health cardiologist.

“This is a great piece of work,” said Kamath, who did not participate in the study. “It seems to me that by using substantially trivial study design these researchers pointed out some real world considerations that can matter in practice, such as the decision to diagnose a patient with hypertension and start him on treatment.”

Patients get a command which may not need to lower their blood pressure and result to side effects including dizziness, fainting, tiredness and poor vision, he disclosed.

A cardiologist, Dr. Matthew Tomey from Mount Sinai Fuster Heart Hospital in New York City, said the research can make a patient demand the doctor to measure blood pressure the “right way.”  

But the variations noted by the researchers can actually change a person from one group to another of hypertension, Tomey, who was not involved in the latest study, pointed out.