Newer devices often underestimate blood pressure

(Reuters Health) – Automated blood pressure measuring devices are replacing old-fashioned mercury manometers in doctor’s offices and clinics around the world. But a new head-to-head comparison of the two techniques suggests that the newer version isn’t necessarily better — and could even be missing some people with high blood pressure who are in need of blood pressure-lowering treatment.

Readings were about two points lower, on average, with the automated device compared to the mercury-based technique, Drs. Robert A. Koner, Stanley H. Wishner, and Johanna Landgraf of Good Samaritan Hospital in Los Angeles found. What’s more, discrepancies were larger in people 65 and older.

The older “auscultatory” method (from the Latin word for listening) uses a stethoscope and a mercury manometer. The stethoscope placed over an artery in the patient’s arm allows a doctor or nurse to listen for when pulse sounds return (systolic blood pressure), and then disappear again (diastolic blood pressure), as a blood pressure cuff deflates and blood flows back into the artery. The mercury manometer indicates the pressure at each of these time points in millimeters of mercury (mm Hg).

The newer automated oscillometric devices calculate systolic and diastolic blood pressure based on the average pressure in the artery. Oscillometric measurement requires less skill than the older technique, and may be suitable for use by untrained staff and for automated patient home monitoring of blood pressure.

Researchers testing blood pressure medications in large clinical trials have generally used the older auscultatory technique, Kloner noted in an interview, but the mercury manometers are “sadly” being phased out in many clinics and doctor’s offices.

There’s been controversy over whether oscillometric devices are as accurate as the older technique, he added, and studies comparing the two approaches have had mixed results.

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