Warning that simple arm-position errors can send blood pressure readings soaring

Thousands of people in Britain could be told they have high blood pressure in error because of basic mistakes made during routine NHS checks, a GP has warned.

NHS guidance says patients should be seated upright with their arm supported on a table when a reading is taken.

However, specialists say that advice is not always followed in busy clinics, increasing the chance of inaccurate results and wrong diagnoses.

“Accurate blood pressure measurement is essential if we are to correctly identify and treat people at risk of damage from high blood pressure,” Dr Dean Eggitt, an NHS GP, told the Daily Mail.

“Over-treatment and medication-induced side effects can cause real harm, particularly in vulnerable patients.

“Poor technique can ultimately result in inappropriate treatment decisions and reduce quality of life.”

The warning comes after a recent US study found that arm position can make a major difference to blood pressure readings.

Experts at Johns Hopkins Medicine found that letting an arm hang unsupported at a patient’s side raised systolic blood pressure — the top number in a reading — by nearly 7mmHg.

Resting the arm on the lap also led to that figure being overstated by almost 4mmHg.

Experts say the findings support NHS advice that a patient’s arm should be placed on a table or desk at heart level during a blood pressure check.

That is because an unsupported arm can cause muscles to contract, temporarily increasing blood pressure.

Putting the arm in the lap can also increase the distance between the arm and the heart, pushing the reading higher.

High blood pressure affects around one in three adults in England and increases the risk of stroke, heart attack, kidney disease and even dementia.

Because it often causes no symptoms, it can go unnoticed until damage has already been done.

More than four million people in England are thought to have the condition without realising it.

The findings, published in JAMA Internal Medicine, came as updated American Heart Association guidance placed greater emphasis on accurate blood pressure measurement when monitoring the problem at home.

Patients are also advised to sit quietly for at least five minutes before a reading, keep both feet flat on the floor and support their back. The middle of an adjustable cuff should sit at mid-heart level while the arm rests on a desk or table.

In the study, Johns Hopkins Medicine researchers measured blood pressure in 133 adults aged 18 to 80.

Before the readings, all participants walked for two minutes, as if arriving at a doctor’s appointment, and then sat for five minutes.

Each participant wore an upper-arm blood pressure cuff and underwent a series of measurements 30 seconds apart.

The results suggested that patients could be diagnosed with hypertension simply because of arm position, with readings highest when the arm hung by the side.

Researchers found this position overestimated systolic pressure by 6.5mmHg and diastolic pressure by 4.4mmHg.

They said the differences were large enough to change whether some patients met the threshold for a hypertension diagnosis.

According to the NHS, normal blood pressure is between 90/60mmHg and 120/80mmHg.

High blood pressure is classed as anything above 135/85mmHg when measured at home, or 140/90mmHg and above when taken by a healthcare professional at a pharmacy, GP surgery or hospital.

The warning comes after separate analysis by researchers at the University of Oxford suggested that more than half of people living with high blood pressure do not know they have it, leaving them at greater risk of early death.

The researchers also estimated that only half of those treated for the condition by their GP have it under control.

The authors said current National Institute for Health and Care Excellence (NICE) guidelines mean many people with high blood pressure are never identified, treated or brought under good control.

They argued that current diagnostic pathways can create a “leaky cascade of care”, with some patients never receiving a diagnosis or effective treatment.