How to put your arm when measuring blood pressure? It must strictly be placed on a table, because keeping it on your lap or worse still dangling can distort the results to the point of diagnosing (and treating) hypertension when there is no hypertension. Doctors and patients are warned a group of researchers from Johns Hopkins Medicine in the USA, who in a study published in ‘Jama Internal Medicine’ explain the mistakes not to be madecalculating how much they could weigh on the correctness of the values detected: by making a mistake in the position of the arm, the diastolic pressure, the so-called minimum, can be more than 4 millimeters of mercury (mmHg) higher than the real one, while the systolic pressure, i.e. the maximum, is almost higher 7 mmHg. Enough to make the difference between a ‘normotensive’ report and a ‘hypertensive’ one.
The study
The authors of the work – whose funding bodies include Bloomberg Philanthropies, Bill and Melinda Gates Foundation, Gates Philanthropy Partners and Chan Zuckerberg Foundation – underline the importance of respecting the indications on the correct measurement of blood pressure, in order not to risk obtaining data ” significantly overestimated”. The latest guidelines from the American Heart Association list the various key steps for a successful test: use an appropriately sized cuff to wear on the forearm at heart level, sit with your back resting with your feet firmly planted on the floor and legs uncrossed, place arm on a desk or table. Despite these recommendations, “too often” blood pressure is measured with the arm in the wrong position, scientists report: supported by the doctor, held in the patient’s lap, on the side without any support. Instead, “location makes a big difference,” warns Tammy Brady, lead author of the study.
The research was conducted on 133 adults aged 18 to 80, following all the recommendations for a ‘doc’ blood pressure measurement, except for the different arm positions. The authors thus observed that “measurements obtained with arm positions frequently used in clinical practice (arm in lap or unsupported) were significantly higher than those obtained when the arm was resting on a desk, the standard recommended position” . In detail, keeping the arm in the lap caused an overestimation of 3.9 mmHg for the systolic pressure and 4 mmHg for the diastolic, while leaving it dangling distorted the data of +6.5 mmHg for the systolic and +4.4 mmHg for diastolic. Almost 7 mmHg more systolic pressure “means a potential difference between a maximum of 123 and a maximum of 130, or between a maximum of 133 and a 140 which is considered stage 2 hypertension”, remarks Sherry Liu, one of the authors of the study.
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